Patent Application
20150183737
The presently disclosed subject matter relates to compositions for inhibiting a biological activity of a cyclooxygenase (COX) polypeptide. In some embodiments, the compositions comprise derivatives of non-steroidal anti-inflammatory drugs (NSAIDs) that are COX-1-specific, COX-2-specific, or are non-specific COX inhibitors. In some embodiments, the methods comprise administering a composition comprising an inhibitor of the presently disclosed subject matter to a subject in order to modulate a COX-2 biological activity. In some embodiments, the methods comprise administering a composition comprising an inhibitor of the presently disclosed subject matter to a subject in order to modulate a subset of COX-2 biological activities including, but not limited to endocannabinoid oxygenation catalyzed by COX-2. In some embodiments, the modulation of the subset of COX-2 biological activities does not substantially affect other COX-2 biological activities including, but not limited to arachidonic acid oxygenation.
Non-steroidal anti-inflammatory drugs (NSAIDs) are a class of therapeutic agents that are widely used for their anti-inflammatory and anti-pyretic properties to treat human distress and disease. Exemplary NSAIDs include aspirin, ibuprofen, acetaminophen, indomethacin, naproxen, and others.
The anti-inflammatory and anti-pyretic activities of NSAIDs derive from the ability of these compounds to bind to and inhibit the actions of the cyclooxygenase (COX) enzymes. COX activity originates from two distinct and independently regulated enzymes, termed cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2; see DeWitt & Smith, 1988; Yokoyama & Tanabe, 1989; Hla & Neilson, 1992). COX-1 is a constitutive isoform and is mainly responsible for the synthesis of cytoprotective prostaglandins in the gastrointestinal (GI) tract and for the synthesis of thromboxane, which triggers aggregation of blood platelets (Allison et al., 1992). On the other hand, COX-2 is inducible and short-lived. Its expression is stimulated in response to endotoxins, cytokines, and mitogens (Kujubu et al., 1991; Lee et al., 1992; O'Sullivan et al., 1993). NSAIDs exhibit varying selectivity for COX-1 and COX-2 but, in general, most display inhibitory activity towards both enzymes (Meade et al., 1993).
The COX enzymes are homodimers of 70 kiloDalton (kDa) subunits that are comprised of membrane-binding and catalytic domains (Garavito et al., 2003). The cyclooxygenase active site is located deep inside the catalytic domain separated by a gate from a channel that leads through the membrane-binding domain to the exterior of the protein. The two monomers of each COX enzyme are functionally interdependent and binding of a substrate or inhibitor at one active site alters the properties of the other active site (Yuan et al., 2006). The communication between subunits occurs through the dimer interface (Yuan et al., 2009).
COX enzymes oxygenate polyunsaturated fatty acids to prostaglandin endoperoxides in the first step of a metabolic cascade that leads to the generation of prostaglandins and thromboxanes. Inhibition of COX enzymes, especially COX-2, is a major contributor to the pharmacological effects of NSAIDs. COX-2 oxygenates a range of fatty acyl substrates including fatty acids, esters, and amides. Arachidonic acid (AA) and 2-arachidonoylglycerol (2-AG) are the best acid and ester substrates and display comparable kcat/Km's for oxygenation (Kozak et al., 2000).
2-AG and arachidonoylethanolamide (AEA) are endocannabinoids that exert anxiolytic, analgesic, and anti-inflammatory effects through their actions at the cannabinoid receptors, CB1 and CB2 (Piomelli, 2003; Di Marzo et al., 2005; Kogan & Mechoulam, 2006). They are also substrates for the fatty acid oxygenases, lipoxygenases, and cyclooxygenases (COXs), as well as for certain cytochromes of the P450 family, which convert them to bioactive, oxygenated metabolites (Ueda et al., 1995; Yu et al., 1997; Kozak et al., 2000; Chen et al., 2008; Snider et al., 2010). 2-AG and AEA are oxygenated efficiently to prostaglandin glycerol esters (PG-Gs) and prostaglandin ethanolamides (PG-EAs), respectively, by COX-2, but much less so than by COX-1. PG-Gs and PG-EAs activate calcium mobilization in macrophages and tumor cells, enhance miniature excitatory and inhibitory postsynaptic currents in neurons, induce mechanical allodynia, and stimulate thermal hyperalgesia (Nirodi et al., 2004; Sang et al., 2006; Snag et al., 2007; Hu et al., 2008; Richie-Jannetta et al., 2010). 2-AG and AEA are rapidly hydrolyzed by monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), respectively, to arachidonic acid (AA), which terminates endocannabinoid signaling but produces a fatty acid that is converted to leukotrienes and prostaglandins, among others (Cravatt et al., 1996; Dinh et al., 2004). Thus, 2-AG and AEA are at the nexus of a complex network of bioactive lipid production, inactivation, and signaling (see
The importance of endocannabinoids as naturally occurring analgesic agents provides a potential mechanism for inhibition of neuropathic pain: that is, through the development of agents that prevent endocannabinoid metabolism at sites of neuroinflammation (Piomelli et al., 2000). FAAH inhibitors seem to be promising candidates in this regard, and MAGL inhibitors are also potential leads, although their broader range of cannabimimetic effects in animal models potentially limit their utility (Cravatt & Lichtman, 2003; Long et al., 2009a). What is needed, then, are additional methods and compositions for inhibiting a biological activity of a cyclooxygenase (COX) polypeptide, such as but not limited to a subset of COX-2 biological activitites including, but not limited to endocannabinoid oxygenation catalyzed by COX-2. Such methods and compositions represent a long-felt and continuing need in the art.
This Summary lists several embodiments of the presently disclosed subject matter, and in many cases lists variations and permutations of these embodiments. This Summary is merely exemplary of the numerous and varied embodiments. Mention of one or more representative features of a given embodiment is likewise exemplary. Such an embodiment can typically exist with or without the feature(s) mentioned; likewise, those features can be applied to other embodiments of the presently disclosed subject matter, whether listed in this Summary or not. To avoid excessive repetition, this Summary does not list or suggest all possible combinations of such features.
The presently disclosed subject matter provides in some embodiments methods for selectively inhibiting endocannabinoid oxygenation but not arachidonic acid oxygenation. The presently disclosed subject matter also provides in some embodiments methods for elevating a local endogenous cannabinoid concentration in a tissue, cell, organ, and/or structure in a subject.
The presently disclosed subject matter also provides in some embodiments methods for reducing depletion of an endogenous cannabinoid in a tissue, cell, organ, and/or structure in a subject.
The presently disclosed subject matter also provides in some embodiments methods for inducing analgesia in a subject.
The presently disclosed subject matter also provides in some embodiments methods for providing an anxiolytic and antidepressant therapy to a subject. In some embodiments, the presently disclosed methods comprise contacting a COX-2 polypeptide with an effective amount of a substrate-selective COX-2 inhibitor (referred to herein as an “SSCI”).
In some embodiments of the presently disclosed methods, the substrate-selective inhibitor of COX-2 (SSCI) comprises a substantially pure (R)-profen or a derivative thereof, optionally wherein the derivative thereof does not stereoisomerize in vivo to an (S)-profen. In some embodiments, the SSCI is selected from the group consisting of Compounds A-G, Compounds 3a-3e, Compounds 4a-4e, Compounds 5a-5e, Compounds 7a-7e, Compounds 101-116, an (R)-enantiomer of Compound 6a, an (R)-enantiomer of Compound 6b, an (R)-enantiomer of Compound 6c, an (R)-enantiomer of Compound 6d, an (R)-enantiomer of Compound 6e, acetaminophen (APAP), 4-aminophenol, and N-(4-hydroxyphenyl)arachidonoylamide (AM404), and combinations thereof.
In some embodiments of the presently disclosed subject matter, the COX-2 polypeptide is present in the tissue, cell, organ, and/or structure in the subject and/or is present in a distant location in the subject that under normal conditions provides an endogenous cannabinoid to the tissue, cell, organ, and/or structure in the subject. In some embodiments, the COX-2 polypeptide is present in a region of inflammation in the subject.
The presently disclosed subject matter also provides compounds. In some embodiments, the compound is selected from the group consisting of Compounds A-G, Compounds 3a-3e, Compounds 4a-4e, Compounds 5a-5e, Compounds 7a-7e, Compounds 101-116, an (R)-enantiomer of Compound 6a, an (R)-enantiomer of Compound 6b, an (R)-enantiomer of Compound 6c, an (R)-enantiomer of Compound 6d, and an (R)-enantiomer of Compound 6e.
In some embodiments, the presently disclosed subject matter provides pharmaceutical compositions comprising, consisting essentially of, or consisting of a substrate-selective inhibitor of COX-2 and a pharmaceutically acceptable carrier or excipient, optionally wherein the pharmaceutically acceptable carrier or excipient is acceptable for use in a human. In some embodiments, the substrate-selective inhibitor of COX-2 comprises a substantially pure (R)-profen or a derivative thereof, optionally wherein the derivative thereof does not stereoisomerize in vivo to an (S)-profen. In some embodiments, the (R)-profen or a derivative thereof is selected from the group consisting of Compounds A-G, Compounds 3a-3e, Compounds 4a-4e, Compounds 5a-5e, Compounds 7a-7e, Compounds 101-116, an (R)-enantiomer of Compound 6a, an (R)-enantiomer of Compound 6b, an (R)-enantiomer of Compound 6c, an (R)-enantiomer of Compound 6d, an (R)-enantiomer of Compound 6e, Compounds acetaminophen (APAP), 4-aminophenol, and N-(4-hydroxyphenyl)arachidonoylamide (AM404), and combinations thereof.
Thus, it is an object of the presently disclosed subject matter to provide compositions and methods to selectively inhibit endocannabinoid oxygenation but not arachidonic acid oxygenation by cyclooxygenases. An object of the presently disclosed subject matter having been stated hereinabove, and which is achieved in whole or in part by the presently disclosed subject matter, other objects will become evident as the description proceeds when taken in connection with the accompanying Figures as best described herein below.
Product formation was monitored following the oxygenation of arachidonic acid, 2-AG and AEA by COX-2 to form prostaglandins (solid lines), PG-Gs (dashed lines), and PG-EAs (dotted lines) in DRGs. IC50 values were calculated using a nonlinear regression. The data points represent percent inhibition with respect to a control consisting of two sets of three DRG culture plates from two independent DRG preparations for each (R)-profen. The data points (n=6) represent the mean+s.e.m.
The fatty acid concentrations (n=6) are plotted as mean+s.e.m. and statistical significance was determined using a one-way ANOVA analysis. Statistically significant increases (P<0.05) in both AEA and 2-AG are indicated by overhead brackets.
Silver-associated fatty acid ions were monitored using the following transitions: 2-AG 485→411, 2-AG-d8 493→419, AA 519→409, AA-d8 527→417. Minimal inhibition of MAGL by (R)-profens was observed while the IC50 for JZL-184 was 9 nM.
a-21n are a series of graphs demonstrating that Compound A (also referred to herein as “LM-4131”) is an in vivo bioactive substrate-selective COX-2 inhibitor (SSCI).
PG levels as a % of corresponding vehicle group.
F and p values shown for one-way ANOVA, and p values for Dunnett's post hoc analysis show in
a-23i are a series of bar graphs showing that Compound A selectively increased brain eCBs without affecting related lipids. The effects of Compound A and PF-3845 on brain NAE levels two hours after i.p. injection are shown in
a-24e are a series of bar graphs showing that Compound A selectively increased AEA in peripheral tissues. The effects of Compound A on NAE, MAG, and PG levels in the stomach, small intestine, heart, kidney, and lung two hours after injection are shown in
Multiplicity corrected p values and t-statistics by unpaired two-tailed t-tests with Holm-Sidak multiple comparisons a correction are given in each Figure. F and p values for one-way ANOVA, followed byp values from Dunnett's post hoc analysis are also given for PG analyses. n=number of mice per treatment group indicated. Error bars represent S.E.M.
a-25h are a series of graphs showing that Compound A reduces anxiety-like behaviors in the novel open field. The effects of PF-3845 (
a-26c are a series of graphs showing the effects of COX inhibitors in the novel open-field test.
a and 28b are a series of graphs showing the effects of Compound A in CB1(−/−) mice.
a-29f are a series of bar graphs showing that Compound A reduced anxiety behaviors in the light-dark box.
a-30f are a series of graphs showing the effects of Compound A and PF-3845 in an Elevated Plus Maze (EPM) test.
a-31d are a series of graphs showing that Compound A did not exert overt cannabimimetic effects in vivo.
The present subject matter will be now be described more fully hereinafter with reference to the accompanying Examples and Figures, in which representative embodiments of the presently disclosed subject matter are shown. The presently disclosed subject matter can, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the presently disclosed subject matter to those skilled in the art.
While the following terms are believed to be well understood by one of ordinary skill in the art, the following definitions are set forth to facilitate explanation of the presently disclosed subject matter.
All technical and scientific terms used herein, unless otherwise defined below, are intended to have the same meaning as commonly understood by one of ordinary skill in the art. Mention of techniques employed herein are intended to refer to the techniques as commonly understood in the art, including variations on those techniques or substitutions of equivalent techniques that would be apparent to one of skill in the art. While the following terms are believed to be well understood by one of ordinary skill in the art, the following definitions are set forth to facilitate explanation of the presently disclosed subject matter.
Following long-standing patent law convention, the terms “a”, “an”, and “the” refer to “one or more” when used in this application, including the claims. Thus, the phrase “a cell” refers to one or more cells, and can thus also refer to a tissue or an organ.
The term “about”, as used herein to refer to a measurable value such as an amount of weight, time, dose (e.g., therapeutic dose), etc., is meant to encompass in some embodiments variations of ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments ±0.1%, in some embodiments ±0.5%, and in some embodiments ±0.01% from the specified amount, as such variations are appropriate to perform the disclosed methods.
As used herein, the term “and/or” when used in the context of a list of entities, refers to the entities being present singly or in any possible combination or subcombination. Thus, for example, the phrase “A, B, C, and/or D” includes A, B, C, and D individually, but also includes any and all combinations and subcombinations of A, B, C, and D.
As used herein, the term “COX-2” refers to a cyclooxygenase-2 gene or gene product. It is also referred to as prostaglandin-endoperoxide synthase 2 (PTGS2) and prostaglandin G/H synthase. Generally, COX-2 gene products catalyze the oxygenation of arachidonic acid (AA) and the endocannabinoids, 2-arachidonoylglycerol (2-AG) and arachidonoylethanolamide (AEA), to prostaglandin endoperoxide derivatives. COX-2 gene products have been identified in several species, and biosequences corresponding thereto are present in the GENBANK® database. By way of example and not limitation, in some embodiments a COX-2 gene product comprises, consists essentially of, and/or consists of a sequence as set forth in Table 1.
Homo sapiens
Mus musculus
Rattus norvegicus
Felis catus
Sus scrofa
Canis lupus familiaris
Equus caballus
Xenopus laevis
As used herein, the term “cell” refers not only to the particular subject cell (e.g., a living biological cell), but also to the progeny or potential progeny of such a cell. Because certain modifications can occur in succeeding generations due to either mutation or environmental influences, such progeny cells might not, in fact, be identical to the parent cell, but are still included within the scope of the term as used herein.
The term “comprising”, which is synonymous with “including” “containing”, or “characterized by”, is inclusive or open-ended and does not exclude additional, unrecited elements and/or method steps. “Comprising” is a term of art that means that the named elements and/or steps are present, but that other elements and/or steps can be added and still fall within the scope of the relevant subject matter.
As used herein, the phrase “consisting of” excludes any element, step, or ingredient not specifically recited. For example, when the phrase “consists of” appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.
As used herein, the phrase “consisting essentially of” limits the scope of the related disclosure or claim to the specified materials and/or steps, plus those that do not materially affect the basic and novel characteristic(s) of the disclosed and/or claimed subject matter. For example, a therapeutic method of the presently disclosed subject matter can “consist essentially of” one or more enumerated steps as set forth herein, which means that the one or more enumerated steps produce most or substantially all of the therapeutic benefit intended to be produced by the claimed method. It is noted, however, that additional steps can be encompassed within the scope of such a therapeutic method, provided that the additional steps do not substantially contribute to the therapeutic benefit for which the therapeutic method is intended.
In some embodiments, the pharmaceutical compositions of the presently disclosed subject matter consist essentially of an SSCI and a pharmaceutically acceptable carrier or excipient. In some embodiments, the SSCI consists essentially of a substantially pure (R)-profen or a derivative thereof, optionally wherein the derivative thereof does not stereoisomerize in vivo to an (S)-profen. In some embodiments, the (R)-profen or a derivative thereof is selected from the group consisting of Compounds A-G, Compounds 3a-3e, Compounds 4a-4e, Compounds 5a-5e, Compounds 7a-7e, Compounds 101-116, an (R)-enantiomer of Compound 6a, an (R)-enantiomer of Compound 6b, an (R)-enantiomer of Compound 6c, an (R)-enantiomer of Compound 6d, an (R)-enantiomer of Compound 6e, acetaminophen (APAP), 4-aminophenol, and N-(4-hydroxyphenyl)arachidonoylamide (AM404), and combinations thereof.
With respect to the terms “comprising”, “consisting essentially of”, and “consisting of”, where one of these three terms is used herein, the presently disclosed and claimed subject matter can include the use of either of the other two terms. For example, the presently disclosed subject matter relates in some embodiments to compositions that comprise the SSCIs disclosed herein. It is understood that the presently disclosed subject matter thus also encompasses compositions that in some embodiments consist essentially of the SSCIs disclosed herein, as well as compositions that in some embodiments consist of the SSCIs disclosed herein. Similarly, it is also understood that in some embodiments the methods of the presently disclosed subject matter comprise the steps that are disclosed herein, in some embodiments the methods of the presently disclosed subject matter consist essentially of the steps that are disclosed, and in some embodiments the methods of the presently disclosed subject matter consist of the steps that are disclosed herein.
As used herein, the term “enzyme” refers to a polypeptide that catalyzes a transformation of a substrate into a product at a rate that is substantially higher than occurs in a non-enzymatic reaction.
As used herein the term “gene” refers to a hereditary unit including a sequence of DNA that occupies a specific location on a chromosome and that contains the genetic instruction for a particular characteristic or trait in an organism.
Similarly, the phrase “gene product” refers to biological molecules that are the transcription and/or translation products of genes. Exemplary gene products include, but are not limited to mRNAs and polypeptides that result from translation of mRNAs. As would be understood by those of ordinary skill, gene products can also be manipulated in vivo or in vitro using well known techniques, and the manipulated derivatives can also be gene products. For example, a cDNA is an enzymatically produced derivative of an RNA molecule (e.g., an mRNA), and a cDNA is considered a gene product. Additionally, polypeptide translation products of mRNAs can be enzymatically fragmented using techniques well known to those of skill in the art, and these peptide fragments are also considered gene products.
As used herein, the term “inhibitor” refers to a chemical substance that inactivates or decreases the biological activity of a polypeptide (e.g., an enzymatic activity). In some embodiments, the polypeptide is a cyclooxygnease (COX) polypeptide (e.g., a COX-1 polypeptide or a COX-2 polypeptide). In some embodiments, the biological activity of the COX polypeptide catalyzes the metabolism of arachidonic acid (AA) to prostaglandin H2 (PGH2). In some embodiments, the biological activity of the COX polypeptide catalyzes the oxygenation of the endocannabinoids 2-arachidonoylglycerol (2-AG) and arachidonoylethanolamide (AEA) to prostaglandin endoperoxide derivatives.
As used herein, the term “interact” includes “binding” interactions and “associations” between molecules. Interactions can be, for example, protein-protein, protein-small molecule, protein-nucleic acid, and nucleic acid-nucleic acid in nature.
As used herein, the term “modulate” refers to an increase, decrease, or other alteration of any, or all, chemical and biological activities or properties of a biochemical entity, e.g., a wild type or mutant polypeptide. As such, the term “modulate” can refer to a change in the expression level of a gene (or a level of RNA molecule or equivalent RNA molecules encoding one or more proteins or protein subunits), or of an activity of one or more proteins or protein subunits, such that expression, level, or activity is greater than or less than that observed in the absence of the modulator. For example, the term “modulate” can mean “inhibit” or “suppress”, but the use of the word “modulate” is not limited to this definition.
The term “modulation” as used herein refers to both upregulation (i.e., activation or stimulation) and downregulation (i.e., inhibition or suppression) of a response. Thus, the term “modulation”, when used in reference to a functional property or biological activity or process (e.g., enzyme activity or receptor binding), refers to the capacity to upregulate (e.g., activate or stimulate), downregulate (e.g., inhibit or suppress), or otherwise change a quality of such property, activity, or process. In certain instances, such regulation can be contingent on the occurrence of a specific event, such as activation of a signal transduction pathway, and/or can be manifest only in particular cell types.
The term “modulator” refers to a polypeptide, nucleic acid, macromolecule, complex, molecule, small molecule, compound, species, or the like (naturally occurring or non-naturally occurring) that can be capable of causing modulation. Modulators can be evaluated for potential activity as inhibitors or activators (directly or indirectly) of a functional property, biological activity or process, or a combination thereof, (e.g., agonist, partial antagonist, partial agonist, inverse agonist, antagonist, and the like) by inclusion in assays. In such assays, many modulators can be screened at one time. The activity of a modulator can be known, unknown, or partially known.
Modulators can be either selective or non-selective. As used herein, the term “selective” when used in the context of a modulator (e.g., an inhibitor) refers to a measurable or otherwise biologically relevant difference in the way the modulator interacts with one molecule (e.g., a COX-1 polypeptide) versus another similar but not identical molecule (e.g., a COX-2 polypeptide).
It must be understood that it is not required that the degree to which the interactions differ be completely opposite. Put another way, the term selective modulator encompasses not only those molecules that only bind to a given polypeptide (e.g., COX-2) and not to related family members (e.g., COX-1, or vice versa). The term is also intended to include modulators that are characterized by interactions with polypeptides of interest and from related family members that differ to a lesser degree. For example, selective modulators include modulators for which conditions can be found (such as the nature of the substituents present on the modulator) that would allow a biologically relevant difference in the binding of the modulator to the polypeptide of interest (e.g., COX-2) versus polypeptides derived from different family members (e.g., COX-1).
When a selective modulator is identified, the modulator will bind to one molecule (for example, COX-2) in a manner that is different (for example, stronger) than it binds to another molecule (for example, COX-1). As used herein, the modulator is said to display “selective binding” or “preferential binding” to the molecule to which it binds more strongly.
As used herein, “significance” or “significant” relates to a statistical analysis of the probability that there is a non-random association between two or more entities. To determine whether or not a relationship is “significant” or has “significance”, statistical manipulations of the data can be performed to calculate a probability, expressed as a “p-value”. Those p-values that fall below a user-defined cutoff point are regarded as significant. For example, a p-value less than or equal to in some embodiments 0.05, in some embodiments less than 0.01, in another example less than 0.005, and in yet another example less than 0.001, are regarded as significant.
As used herein, the term “significant increase” refers to an increase in activity (for example, enzymatic activity) that is larger than the margin of error inherent in the measurement technique, in some embodiments an increase by about 2 fold or greater over a baseline activity (for example, the activity of the wild type enzyme in the presence of an activator), in some embodiments an increase by about fold or greater, and in still some embodiments an increase by about 10 fold or greater.
With respect to the binding of one or more molecules (for example, a modulator) to one or more polypeptides (for example, a COX polypeptide), a significant increase can also refer to: (a) a biologically relevant difference in binding of two or more related compounds to the same polypeptide; and/or (b) a biologically relevant difference in binding of the same compound to two different polypeptides. In this aspect, “significant” is to be thought of in its ordinary meaning: namely, a difference between two occurrences that is important (i.e., biologically or medically relevant). By way of example, a significant increase can also refer to an increase in the amount of a derivative of an NSAID (for example, an NSAID derivative of the presently disclosed subject matter) that interacts with a particular COX polypeptide (for example, a COX-2 polypeptide) per unit dose of the derivative administered as compared to the amount of the non-derivatized NSAID that interacts with the same COX polypeptide per unit dose of the non-derivatized NSAID. In some embodiments, if a derivative binds to a particular COX enzyme less strongly than does the parent NSAID from which is was derived, on a mole-for-mole basis, more of the derivative should be available to interact with other COX polypeptides than would be available if the parent NSAID were administered.
As used herein, the terms “significantly less” and “significantly reduced” refer to a result (for example, an amount of a product of an enzymatic reaction or an extent of binding to a target such as, but not limited to a cyclooxygenase) that is reduced by more than the margin of error inherent in the measurement technique, in some embodiments a decrease by about 2 fold or greater with respect to a baseline activity (for example, the baseline activity of the enzyme in the absence of the inhibitor), in some embodiments, a decrease by about 5 fold or greater, and in still some embodiments a decrease by about 10 fold or greater.
The term “subject” as used herein refers to a member of any invertebrate or vertebrate species. Accordingly, the term “subject” is intended to encompass any member of the Kingdom Animalia including, but not limited to the phylum Chordata (i.e., members of Classes Osteichythyes (bony fish), Amphibia (amphibians), Reptilia (reptiles), Aves (birds), and Mammalia (mammals)), and all Orders and Families encompassed therein.
Similarly, all genes, gene names, and gene products disclosed herein are intended to correspond to orthologs from any species for which the compositions and methods disclosed herein are applicable. Thus, the terms include, but are not limited to genes and gene products from humans and other mammals. It is understood that when a gene or gene product from a particular species is disclosed, this disclosure is intended to be exemplary only, and is not to be interpreted as a limitation unless the context in which it appears clearly indicates. Thus, for example, the genes and/or gene products disclosed herein are intended to encompass homologous genes and gene products from other animals including, but not limited to other mammals, fish, amphibians, reptiles, and birds.
The methods and compositions of the presently disclosed subject matter are particularly useful for warm-blooded vertebrates. Thus, the presently disclosed subject matter concerns mammals (including, but not limited to humans) and birds. More particularly provided is the use of the methods and compositions of the presently disclosed subject matter on mammals such as humans and other primates, as well as those mammals of importance due to being endangered (such as Siberian tigers), of economic importance (animals raised on farms for consumption by humans) and/or social importance (animals kept as pets or in zoos) to humans, for instance, carnivores other than humans (such as cats and dogs), swine (pigs, hogs, and wild boars), ruminants (such as cattle, oxen, sheep, giraffes, deer, goats, bison, and camels), rodents (such as mice, rats, and rabbits), marsupials, and horses. Also provided is the use of the disclosed methods and compositions on birds, including those kinds of birds that are endangered, kept in zoos, as well as fowl, and more particularly domesticated fowl, e.g., poultry, such as turkeys, chickens, ducks, geese, guinea fowl, and the like, as they are also of economic importance to humans. Thus, also provided is the application of the methods and compositions of the presently disclosed subject matter to livestock, including but not limited to domesticated swine (pigs and hogs), ruminants, horses, poultry, and the like. As used herein, the phrase “substantially pure” refers to a compound or composition that is in some embodiments greater than 50% pure, in some embodiments greater than 60% pure, in some embodiments greater than 70% pure, in some embodiments greater than 80% pure, in some embodiments greater than 90% pure, in some embodiments greater than 95% pure, in some embodiments greater than 96% pure, in some embodiments greater than 97% pure, in some embodiments greater than 98% pure, and in some embodiments greater than 99% pure. In some embodiments, the purity of an enantiomeric compound in a composition is expressed as compared to the amount of the other enantiomer that is present in the composition. For example, a “substantially pure (R)-profen” is in various embodiments greater than 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% pure with respect to any (S)-profen that might be present in the composition.
As used herein, the phrases “substrate-selective COX-2 inhibitor” (SSCI) and “substrate-selective inhibitor of endocannabinoid oxygenation by COX-2” are used interchangeably to refer to a compound and/or composition that in some embodiments is a weak, competitive inhibitor of arachidonic acid oxygenation by COX-2, but in some embodiments acts as a potent non-competitive inhibitor of 2-AG and AEA oxygenation by COX-2. In some embodiments, an SSCI is selected from the group consisting of a substantially pure (R)-profen or a derivative thereof, optionally wherein the derivative thereof does not stereoisomerize in vivo to an (S)-profen. In some embodiments, the substrate-selective inhibitor of endocannabinoid oxygenation of COX-2 is selected from the group consisting of Compounds A-G, Compounds 3a-3e, Compounds 4a-4e, Compounds 5a-5e, Compounds 7a-7e, Compounds 101-116, an (R)-enantiomer of Compound 6a, an (R)-enantiomer of Compound 6b, an (R)-enantiomer of Compound 6c, an (R)-enantiomer of Compound 6d, an (R)-enantiomer of Compound 6e, acetaminophen (APAP), 4-aminophenol, and N-(4-hydroxyphenyl)arachidonoylamide (AM404), ibuprofen, naproxen, lumiracoxib, derivatives thereof, and anlogues thereof.
II.A. General Considerations
In some embodiments, the presently disclosed subject matter provides compounds that are SSCIs. In some embodiments, the SSCIs are substantially pure (R)-profens or derivatives thereof, optionally wherein the derivative thereof does not stereoisomerize in vivo to an (S)-profen. In some embodiments, the SSCI is selected from the group consisting of Compounds A-G, Compounds 3a-3e, Compounds 4a-4e, Compounds 5a-5e, Compounds 7a-7e, Compounds 101-116, an (R)-enantiomer of Compound 6a, an (R)-enantiomer of Compound 6b, an (R)-enantiomer of Compound 6c, an (R)-enantiomer of Compound 6d, an (R)-enantiomer of Compound 6e, acetaminophen (APAP), 4-aminophenol, and N-(4-hydroxyphenyl)arachidonoylamide (AM404), and combinations thereof.
Throughout the specification, Figures, and claims, some structural formulas are depicted without including certain methyl groups and/or hydrogens. In the structural formulas, solid lines represent bonds between two atoms, and unless otherwise indicated, between carbon atoms. Thus, bonds that have no atom specifically recited on one end and/or the other have a carbon atom at that and/or the other end. For example, a structural formula depicted as “—O—” represents C—O—C. Given that hydrogens are not explicitly placed in all structural formulas, implicit hydrogens are understood to exist in the structural formulas as necessary. Thus, a structural formula depicted as “—O” can represent H3C—O, as appropriate given the valences of the particular atoms.
As used herein, the term “alkyl” means in some embodiments C1-10 inclusive (i.e., carbon chains comprising 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms); in some embodiments C1-6 inclusive (i.e., carbon chains comprising 1, 2, 3, 4, 5, or 6 carbon atoms); and in some embodiments C1-4 inclusive (i.e., carbon chains comprising 1, 2, 3, or 4, carbon atoms) linear, branched, or cyclic, saturated or unsaturated (i.e., alkenyl and alkynyl) hydrocarbon chains, including for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, ethenyl, propenyl, butenyl, pentenyl, hexenyl, butadienyl, propynyl, butynyl, pentynyl, hexynyl, and allenyl groups.
The alkyl group can be optionally substituted with one or more alkyl group substituents, which can be the same or different, where “alkyl group substituent” includes alkyl, halo, arylamino, acyl, hydroxy, aryloxy, alkoxyl, alkylthio, arylthio, aralkyloxy, aralkylthio, carboxy, alkoxycarbonyl, oxo, and cycloalkyl. In this case, the alkyl can be referred to as a “substituted alkyl”. Representative substituted alkyls include, for example, benzyl, trifluoromethyl, and the like. There can be optionally inserted along the alkyl chain one or more oxygen, sulfur or substituted or unsubstituted nitrogen atoms, wherein the nitrogen substituent is hydrogen, alkyl (also referred to herein as “alkylaminoalkyl”), or aryl. Thus, the term “alkyl” can also include esters and amides. “Branched” refers to an alkyl group in which an alkyl group, such as methyl, ethyl, or propyl, is attached to a linear alkyl chain.
The term “aryl” is used herein to refer to an aromatic substituent, which can be a single aromatic ring or multiple aromatic rings that are fused together, linked covalently, or linked to a common group such as a methylene or ethylene moiety. The common linking group can also be a carbonyl as in benzophenone or oxygen as in diphenylether or nitrogen in diphenylamine. The aromatic ring(s) can include phenyl, naphthyl, biphenyl, diphenylether, diphenylamine, and benzophenone among others. In particular embodiments, the term “aryl” means a cyclic aromatic comprising about 5 to about 10 carbon atoms, including 5 and 6-membered hydrocarbon and heterocyclic aromatic rings.
An aryl group can be optionally substituted with one or more aryl group substituents which can be the same or different, where “aryl group substituent” includes alkyl, aryl, aralkyl, hydroxy, alkoxyl, aryloxy, aralkoxyl, carboxy, acyl, halo, nitro, alkoxycarbonyl, aryloxycarbonyl, aralkoxycarbonyl, acyloxyl, acylamino, aroylamino, carbamoyl, alkylcarbamoyl, dialkylcarbamoyl, arylthio, alkylthio, alkylene and —NR′R″, where R′ and R″ can be each independently hydrogen, alkyl, aryl and aralkyl. In this case, the aryl can be referred to as a “substituted aryl”. Also, the term “aryl” can also include esters and amides related to the underlying aryl group.
Specific examples of aryl groups include but are not limited to cyclopentadienyl, phenyl, furan, thiophene, pyrrole, pyran, pyridine, imidazole, isothiazole, isoxazole, pyrazole, pyrazine, pyrimidine, and the like.
The term “alkoxy” is used herein to refer to the —OZ1 radical, where Z1 is selected from the group consisting of alkyl (in some embodiments, C1 to C6 alkyl), substituted alkyl, cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substituted heterocycloalkyl, silyl groups, and combinations thereof as described herein. Suitable alkoxy radicals include, for example, methoxy, ethoxy, benzyloxy, t-butoxy, etc. A related term is “aryloxy” where Z1 is selected from the group consisting of aryl, substituted aryl, heteroaryl, substituted heteroaryl, and combinations thereof. Examples of suitable aryloxy radicals include phenoxy, substituted phenoxy, 2-pyridinoxy, 8-quinalinoxy, and the like.
The term “amino” is used herein to refer to the group —NZ1Z2, where each of Z1 and Z2 is independently selected from the group consisting of hydrogen; alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, heterocycloalkyl, substituted heterocycloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkoxy, aryloxy, silyl and combinations thereof. Additionally, the amino group can be represented as N+Z1 Z2 Z3, with the previous definitions applying and Z3 being either H or alkyl.
As used herein, the term “acyl” refers to an organic acid group wherein the —OH of the carboxyl group has been replaced with another substituent (i.e., as represented by RCO—, wherein R is an alkyl or an aryl group as defined herein). As such, the term “acyl” specifically includes arylacyl groups, such as an acetylfuran and a phenacyl group. Specific examples of acyl groups include acetyl and benzoyl.
“Aroyl” means an aryl-CO— group wherein aryl is as previously described. Exemplary aroyl groups include benzoyl and 1- and 2-naphthoyl.
“Cyclic” and “cycloalkyl” refer to a non-aromatic mono- or multicyclic ring system of about 3 to about 10 carbon atoms, e.g., 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms. The cycloalkyl group can be optionally partially unsaturated. The cycloalkyl group also can be optionally substituted with an alkyl group substituent as defined herein, oxo, and/or alkylene. There can be optionally inserted along the cyclic alkyl chain one or more oxygen, sulfur or substituted or unsubstituted nitrogen atoms, wherein the nitrogen substituent is hydrogen, lower alkyl, or aryl, thus providing a heterocyclic group. Representative monocyclic cycloalkyl rings include cyclopentyl, cyclohexyl, and cycloheptyl. Multicyclic cycloalkyl rings include adamantyl, octahydronaphthyl, decalin, camphor, camphane, and noradamantyl.
“Aralkyl” refers to an aryl-alkyl-group wherein aryl and alkyl are as previously described. Exemplary aralkyl groups include benzyl, phenylethyl, and naphthylmethyl.
“Aralkyloxyl” refers to an aralkyl-O— group wherein the aralkyl group is as previously described. An exemplary aralkyloxyl group is benzyloxyl.
“Dialkylamino” refers to an —NRR′ group wherein each of R and R′ is independently an alkyl group as previously described. Exemplary alkylamino groups include ethylmethylamino, dimethylamino, and diethylamino.
“Alkoxycarbonyl” refers to an alkyl-O—CO— group. Exemplary alkoxycarbonyl groups include methoxycarbonyl, ethoxycarbonyl, butyloxycarbonyl, and t-butyloxycarbonyl.
“Aryloxycarbonyl” refers to an aryl-O—CO— group. Exemplary aryloxycarbonyl groups include phenoxy- and naphthoxy-carbonyl.
“Aralkoxycarbonyl” refers to an aralkyl-O—CO— group. An exemplary aralkoxycarbonyl group is benzyloxycarbonyl.
“Carbamoyl” refers to an H2N—CO— group.
“Alkylcarbamoyl” refers to a R′RN—CO— group wherein one of R and R′ is hydrogen and the other of R and R′ is alkyl as previously described.
“Dialkylcarbamoyl” refers to a R′RN—CO— group wherein each of R and R′ is independently alkyl as previously described.
“Acyloxyl” refers to an acyl-O— group wherein acyl is as previously described.
“Acylamino” refers to an acyl-NH— group wherein acyl is as previously described.
“Aroylamino” refers to an aroyl-NH— group wherein aroyl is as previously described.
The term “amino” refers to the —NH2 group.
The term “carbonyl” refers to the —(C═O)— group.
The term “carboxyl” refers to the —COOH group.
The term “hydroxyl” refers to the —OH group.
The term “hydroxyalkyl” refers to an alkyl group substituted with an —OH group.
The term “mercapto” refers to the —SH group.
The term “oxo” refers to a compound described previously herein wherein a carbon atom is replaced by an oxygen atom.
The term “nitro” refers to the —NO2 group.
The term “thio” refers to a compound described herein wherein a carbon or oxygen atom is replaced by a sulfur atom.
The term “sulfate” refers to the —SO4 group.
In some embodiments, an SSCI of the presently disclosed subject matter is an (R)-profen. As used herein, the term “(R)-profen” refers to a derivative of 2-phenylpropanoic acid that has a chiral center and is capable of binding to and modulating a biological activity of a COX-2 enzyme. Exemplary, non-limiting (R)-profens are disclosed herein.
In some embodiments, the (R)-profen or (R)-profen derivative has a structure:
Ar—Z—CO2H,
wherein:
Ar is aryl, optionally substituted by one or more aryl group substituents; and
Z is methylene, mono-substituted methylene (i.e., —CH(Z′)—, wherein Z′ is an alkyl group substituent), or di-substituted methylene (i.e., —C(Z′)2—, wherein each Z′ is an alkyl group substituent or both Z′ groups together can form an alkylene group).
In some embodiments, the carboxylic acid group of the profen or profen derivative can be replaced by an ester or amide (e.g., that can be hydrolyzed in vivo or in vitro to provide the carboxylic acid group).
In some embodiments, Z is selected from methylene, alkyl-substituted methylene (e.g., —CH(CH3)—), dialkyl-substituted methylene (e.g., —C(CH3)2—), and
wherein x is an integer between 1 and 10. In some embodiments, x is an integer between 1 and 5 (i.e., 1, 2, 3, 4, or 5). In some embodiments, x is 1.
In some embodiments, Z is
wherein Z′ is alkyl. In some embodiments, Z′ is methyl.
In some embodiments, Ar is phenyl or napthyl, optionally substituted with one or more aryl group substituents (e.g., halo, aryl, alkyl, alkoxyl, aryloxy (e.g., phenoxy), and acyl (e.g., aroyl)). In some embodiments, Ar is diphenyl (e.g., phenyl-substituted phenyl, optionally substituted with one or more additional aryl group substituents). In some embodiments, Ar is selected from the group comprising:
In some embodiments, an SSCI is an indomethacin analog. In some embodiments, the indomethancin analog has the structure:
wherein R is selected from —NH2, —NHR′, and —N(R″)2, wherein R′ can be selected from alkyl, substituted alkyl (e.g., hydroxyl substituted alkyl), aralkyl, aryl, and substituted aryl; and each R″ can be independently selected from alkyl, substituted alkyl, aralkyl, aryl, or substituted aryl or wherein the two R″ groups together form an alkylene group, wherein said alkylene group can be optionally substituted or include a heteroatom (e.g., O or S) in the alkylene chain in place of a carbon atom).
In some embodiments, R is —N(R″)2.
In some embodiments, an SSCI is a Lumiracoxib or a derivative thereof. In some embodiments, the Lumiracoxib or derivative thereof has the structure:
wherein:
each of R1, R2, R3, and R4 is selected from the group comprising H, alkyl, aryl, aralkyl, alkoxyl, aryloxy, aralkoxyl, carboxy, acyl, halo (i.e., fluoro, chloro, bromo or iodo), mercapto, hydroxyl, nitro, alkoxycarbonyl, aryloxycarbonyl, aralkoxycarbonyl, acyloxyl, acylamino, aroylamino, carbamoyl, alkylcarbamoyl, dialkylcarbamoyl, arylthio, alkylthio, amino, alkylamino and dialkylamino; and Rs is selected from H, alkyl, and halo. In some embodiments, the carboxylic acid group of the Lumiracoxib or derivative thereof can be replaced by an ester or amide (e.g., that can be hydrolyzed in vivo or in vitro to provide the carboxylic acid group).
In some embodiments, R5 is H and the Lumiracoxib or derivative thereof has the structure:
In some embodiments, R1 is selected from H, alkyl, and halo. In some embodiments, R1 is selected from H and alkyl. In some embodiments, R1 is H or methyl. In some embodiments, R1 is methyl.
In some embodiments, each of R2, R3, and R4 is selected from H, alkyl, and halo. In some embodiments, each of R2, R3, and R4 is selected from H, methyl, and halo.
In some embodiments, at least one of R2, R3, and R4 is halo. In some embodiments, at least two of R2, R3, and R4 are halo. In some embodiments, at least R2 and R3 are halo.
In some embodiments, R1 is alkyl (e.g., methyl) and at least one of R2, R3, and R4 is halo.
II.B. Development and Evaluation of Achiral Profen Probes
Cyclooxygenase-2 (COX-2) oxygenates arachidonic acid and the endocannabinoids, 2-arachidonoylglycerol (2-AG) and arachidonoylethanolamide (AEA). (R)-profens selectively inhibit endocannabinoid oxygenation but not arachidonic acid oxygenation. This was evaluated by synthesizing achiral derivatives of five profen scaffolds and evaluating them for substrate-selective inhibition using in vitro and cellular assays. The size of the substituents dictated the inhibitory strength of the analogs, with smaller substituents enabling greater potency but less selectivity. Inhibitors based on the flurbiprofen scaffold possessed the greatest potency and selectivity, with desmethylflurbiprofen (Compound 3a) exhibiting an IC50 of 0.11 μM for inhibition of 2-AG oxygenation. The crystal structure of desmethylflurbiprofen complexed to mCOX-2 demonstrated a similar binding mode to other profens. Desmethylflurbiprofen exhibited a half-life in mice comparable to that of ibuprofen. The data presented suggest that achiral profens can act as lead molecules toward in vivo probes of substrate-selective COX-2 inhibition.
Cyclooxygenase-2 (COX-2) is a molecular target for non-steroidal anti-inflammatory drugs (NSAIDs). It generates prostaglandin-H2 (PGH2), PGH2-glyceryl ester (PGH2-G) and PGH2-ethanolamide (PGH2-EA) from arachidonic acid (AA) and the endocannabinoids, 2-arachidonoylglycerol (2-AG) and arachidonoylethanolamide (AEA), respectively (see
Rapid, reversible inhibitors of COX-2, such as ibuprofen and mefenamic acid, are significantly more potent inhibitors of 2-AG and AEA oxygenation than AA oxygenation. These “substrate-selective” inhibitors bind in one active site of the COX-2 homodimer and alter the structure of the second active site so that 2-AG and AEA oxygenation is inhibited, but AA oxygenation is not. Inhibition of AA oxygenation requires rapid, reversible inhibitors to bind in both active sites. Inhibitor binding in the second active site requires much higher concentrations than binding in the first active site, which gives rise to the phenomenon of substrate-selective inhibition. (R)-enantiomers of the arylpropionic acid (profen) class of NSAIDs, which were considered to be inactive as COX inhibitors, have been shown to be substrate-selective.
In some embodiments, the presently disclosed subject matter provides in vivo probes that can be employed to determine the effects of blocking 2-AG and AEA, but not AA, oxygenation by COX-2.
In some embodiments, the presently disclosed subject matter provides methods for producing SSCIs. It is noted that any suitable synthesis scheme can be employed for producing the presently disclosed SSCIs, and one of ordinary skill in the art will understand what synthesis schemes can be employed based on the exemplary compounds disclosed herein.
Representative synthesis schemes are discussed in more detail herein below in the EXAMPLES and the Figures. It is understood that the representative schemes are non-limiting, and further that the scheme depicted in Scheme 1 as being applicable for synthesizing achiral profens can also be employed with modifications that would be apparent to one of ordinary skill in the art after review of the instant specification for synthesizing additional derivatives that fall within the scope of the instant disclosure.
Also provided herein are methods for using the disclosed SSCIs to modulate COX-2 polypeptide biological activities. In some embodiments, the methods comprise contacting a COX-2 polypeptide with an effective amount of a compound as disclosed herein including, but not limited to those disclosed herein.
The presently disclosed subject matter also provides methods for selectively inhibiting endocannabinoid oxygenation but not arachidonic acid oxygenation via COX-2. In some embodiments, the methods comprising contacting a COX-2 polypeptide with an effective amount of an SSCI as disclosed herein. Exemplary, non-limiting SSCIs include substantially pure (R)-profens or derivatives thereof, optionally wherein the derivatives thereof do not stereoisomerize in vivo to (S)-profens. In some embodiments, the SSCI is selected from the group consisting of Compounds A-G, Compounds 3a-3e, Compounds 4a-4e, Compounds 5a-5e, Compounds 7a-7e, Compounds 101-116, an (R)-enantiomer of Compound 6a, an (R)-enantiomer of Compound 6b, an (R)-enantiomer of Compound 6c, an (R)-enantiomer of Compound 6d, an (R)-enantiomer of Compound 6e, acetaminophen (APAP), 4-aminophenol, and combinations thereof. The presently disclosed subject matter also provides methods for elevating local endogenous cannabinoid concentrations in tissues, cells, organs, and/or structures in a subject. In some embodiments, the methods comprise contacting a COX-2 polypeptide present in the subject with an effective amount of an SSCI as disclosed herein. Exemplary, non-limiting SSCIs include substantially pure (R)-profens or derivatives thereof, optionally wherein the derivatives thereof do not stereoisomerize in vivo to (S)-profens. In some embodiments, the SSCI is selected from the group consisting of Compounds A-G, Compounds 3a-3e, Compounds 4a-4e, Compounds 5a-5e, Compounds 7a-7e, Compounds 101-116, an (R)-enantiomer of Compound 6a, an (R)-enantiomer of Compound 6b, an (R)-enantiomer of Compound 6c, an (R)-enantiomer of Compound 6d, an (R)-enantiomer of Compound 6e, acetaminophen (APAP), 4-aminophenol, and combinations thereof.
In some embodiments, the presently disclosed subject matter also provides methods for reducing depletion of endogenous cannabinoids in tissues, cells, organs, and/or structures in subjects. In some embodiments, the methods comprise contacting a COX-2 polypeptide present in a subject with an effective amount of an SSCI as disclosed herein. In some embodiments, the COX-2 polypeptide is present in a tissue, cell, organ, and/or structure in a subject and/or is present in a distant location in the subject that under normal conditions provides an endogenous cannabinoid to the tissue, cell, organ, and/or structure in the subject. Exemplary, non-limiting SSCIs include substantially pure (R)-profens or derivatives thereof, optionally wherein the derivatives thereof do not stereoisomerize in vivo to (S)-profens. In some embodiments, the SSCI is selected from the group consisting of Compounds A-G, Compounds 3a-3e, Compounds 4a-4e, Compounds 5a-5e, Compounds 7a-7e, Compounds 101-116, an (R)-enantiomer of Compound 6a, an (R)-enantiomer of Compound 6b, an (R)-enantiomer of Compound 6c, an (R)-enantiomer of Compound 6d, an (R)-enantiomer of Compound 6e, acetaminophen (APAP), 4-aminophenol, and combinations thereof. In some embodiments, the COX-2 polypeptide is present in a region of inflammation in the subject.
The presently disclosed subject matter also provides methods for inducing analgesia in subjects. In some embodiments, the methods comprise contacting a COX-2 polypeptide present in the subject with an effective amount of a substrate-selective COX-2 inhibitor. In some embodiments, the SSCI comprises a substantially pure (R)-profen or a derivative thereof, optionally wherein the derivative thereof does not stereoisomerize in vivo to an (S)-profen. Exemplary, non-limiting SSCIs include substantially pure (R)-profens or derivatives thereof, optionally wherein the derivatives thereof do not stereoisomerize in vivo to (S)-profens. In some embodiments, the SSCI is selected from the group consisting of Compounds A-G, Compounds 3a-3e, Compounds 4a-4e, Compounds 5a-5e, Compounds 7a-7e, Compounds 101-116, an (R)-enantiomer of Compound 6a, an (R)-enantiomer of Compound 6b, an (R)-enantiomer of Compound 6c, an (R)-enantiomer of Compound 6d, an (R)-enantiomer of Compound 6e, acetaminophen (APAP), 4-aminophenol, and combinations thereof. In some embodiments, the COX-2 polypeptide is present in a region of inflammation in the subject. In some embodiments, the COX-2 polypeptide is present in a region of inflammation in the subject.
The presently disclosed subject matter also provides methods for providing an anxiolytic therapy, antidepressant therapy, or both to subjects. In some embodiments, the methods comprise contacting a COX-2 polypeptide present in the subject with an effective amount of an SSCI as disclosed herein. In some embodiments, the SSCI comprises a substantially pure (R)-profen or a derivative thereof, optionally wherein the derivative thereof does not stereoisomerize in vivo to an (S)-profen. Exemplary, non-limiting SSCIs include substantially pure (R)-profens or derivatives thereof, optionally wherein the derivatives thereof do not stereoisomerize in vivo to (S)-profens. In some embodiments, the SSCI is selected from the group consisting of Compounds A-G, Compounds 3a-3e, Compounds 4a-4e, Compounds 5a-5e, Compounds 7a-7e, Compounds 101-116, an (R)-enantiomer of Compound 6a, an (R)-enantiomer of Compound 6b, an (R)-enantiomer of Compound 6c, an (R)-enantiomer of Compound 6d, an (R)-enantiomer of Compound 6e, acetaminophen (APAP), 4-aminophenol, and combinations thereof. In some embodiments, the COX-2 polypeptide is present in a region of inflammation in the subject.
The methods disclosed herein for using the disclosed SSCIs to modulate, optionally inhibit, COX-2 polypeptide biological activities or subsets thereof including, but not limited to endocannabinoid oxygenation, can be used for in vivo, ex vivo, and/or in vitro modulation, optionally inhibition, of COX-2 polypeptide biological activities and/or subsets thereof. As such, in some embodiments the COX-2 polypeptide is present within a subject, optionally wherein the subject is a mammal, including but not limited to a human.
IV.A. Formulations
A composition that comprises, consists essentially of, or consists of an SSCI as described herein comprises in some embodiments a composition that includes a pharmaceutically acceptable carrier. Suitable formulations include aqueous and non-aqueous sterile injection solutions that can contain antioxidants, buffers, bacteriostats, bactericidal antibiotics, and solutes that render the formulation isotonic with the bodily fluids of the intended recipient; and aqueous and non-aqueous sterile suspensions, which can include suspending agents and thickening agents.
The compositions used in the methods can take such forms as suspensions, solutions, or emulsions in oily or aqueous vehicles, and can contain formulatory agents such as suspending, stabilizing, and/or dispersing agents. The compositions used in the methods can take forms including, but not limited to peroral, intravenous, intraperitoneal, inhalation, intraprostatic, and intratumoral formulations. Alternatively or in addition, the active ingredient can be in powder form for constitution with a suitable vehicle (e.g., sterile pyrogen-free water) before use.
The formulations can be presented in unit-dose or multi-dose containers, for example sealed ampules and vials, and can be stored in a frozen or freeze-dried (lyophilized) condition requiring only the addition of sterile liquid carrier immediately prior to use.
For oral administration, the compositions can take the form of, for example, tablets or capsules prepared by a conventional technique with pharmaceutically acceptable excipients such as binding agents (e.g., pregelatinized maize starch, polyvinylpyrrolidone or hydroxypropyl methylcellulose); fillers (e.g., lactose, microcrystalline cellulose or calcium hydrogen phosphate); lubricants (e.g., magnesium stearate, talc or silica); disintegrants (e.g., potato starch or sodium starch glycollate); or wetting agents (e.g., sodium lauryl sulfate). The tablets can be coated by methods known in the art. For example, a neuroactive steroid can be formulated in combination with hydrochlorothiazide, and as a pH stabilized core having an enteric or delayed-release coating which protects the neuroactive steroid until it reaches the colon.
Liquid preparations for oral administration can take the form of, for example, solutions, syrups or suspensions, or they can be presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations can be prepared by conventional techniques with pharmaceutically acceptable additives such as suspending agents (e.g., sorbitol syrup, cellulose derivatives or hydrogenated edible fats); emulsifying agents (e.g., lecithin or acacia); non-aqueous vehicles (e.g., almond oil, oily esters, ethyl alcohol or fractionated vegetable oils); and preservatives (e.g., methyl or propyl-p-hydroxybenzoates or sorbic acid). The preparations can also contain buffer salts, flavoring, coloring, and sweetening agents as appropriate. Preparations for oral administration can be suitably formulated to give controlled release of the active compound. For buccal administration the compositions can take the form of tablets or lozenges formulated in conventional manner.
The compounds can also be formulated as a preparation for implantation or injection. Thus, for example, the compounds can be formulated with suitable polymeric or hydrophobic materials (e.g., as an emulsion in an acceptable oil) or ion exchange resins, or as sparingly soluble derivatives (e.g., as a sparingly soluble salt).
The compounds can also be formulated in rectal compositions (e.g., suppositories or retention enemas containing conventional suppository bases such as cocoa butter or other glycerides), creams or lotions, or transdermal patches.
In some embodiments, the presently disclosed subject matter employs a COX inhibitor composition that is pharmaceutically acceptable for use in humans. One of ordinary skill in the art understands the nature of those components that can be present in a COX inhibitor composition that is pharmaceutically acceptable for use in humans and also what components should be excluded from a COX inhibitor composition that is pharmaceutically acceptable for use in humans.
IV.B. Doses
As used herein, the phrases “treatment effective amount”, “therapeutically effective amount”, “treatment amount”, and “effective amount” are used interchangeably and refer to an amount of a therapeutic composition sufficient to produce a measurable response (e.g., a biologically or clinically relevant response in a subject being treated). Actual dosage levels of active ingredients in the pharmaceutical compositions of the presently disclosed subject matter can be varied so as to administer an amount of the active compound(s) that is effective to achieve the desired therapeutic response for a particular subject. The selected dosage level can depend upon the activity of the therapeutic composition, the route of administration, combination with other drugs or treatments, the severity of the condition being treated, the condition and prior medical history of the subject being treated, etc. However, it is within the skill of the art to start doses of the compound at levels lower than required to achieve the desired therapeutic effect and to gradually increase the dosage until the desired effect is achieved.
The potency of a therapeutic composition can vary, and therefore a “therapeutically effective amount” can vary. However, one skilled in the art can readily assess the potency and efficacy of a candidate modulator of the presently disclosed subject matter and adjust the therapeutic regimen accordingly.
After review of the disclosure herein of the presently disclosed subject matter, one of ordinary skill in the art can tailor the dosages to an individual subject, taking into account the particular formulation, method of administration to be used with the composition, and other factors. Further calculations of dose can consider subject height and weight, severity and stage of symptoms, and the presence of additional deleterious physical conditions. Such adjustments or variations, as well as evaluation of when and how to make such adjustments or variations, are well known to those of ordinary skill in the art of medicine.
Thus, in some embodiments the term “effective amount” is used herein to refer to an amount of an SSCI, a pharmaceutically acceptable salt thereof, a derivative thereof, or a combination thereof sufficient to produce a measurable an amelioration of a symptom and/or consequence associated with undesirable COX (e.g., COX-2) biological activity. Actual dosage levels of active ingredients in an SSCI composition of the presently disclosed subject matter can be varied so as to administer an amount of the active compound(s) that is effective to achieve the desired response for a particular subject and/or application. The selected dosage level can depend upon a variety of factors including the activity of the SSCI composition, formulation, route of administration, combination with other drugs or treatments, severity of the condition being treated, and physical condition and prior medical history of the subject being treated. In some embodiments, a minimal dose is administered, and dose is escalated in the absence of dose-limiting toxicity to a minimally effective amount. Determination and adjustment of an effective dose, as well as evaluation of when and how to make such adjustments, are known to those of ordinary skill in the art.
For administration of an SSCI composition as disclosed herein, conventional methods of extrapolating human dosage based on doses administered to a murine animal model can be carried out using techniques known to one of ordinary skill in the art. Drug doses can also be given in milligrams per square meter of body surface area because this method rather than body weight achieves a good correlation to certain metabolic and excretionary functions. Moreover, body surface area can be used as a common denominator for drug dosage in adults and children as well as in different animal species as described by Freireich et al., 1966. Briefly, to express a mg/kg dose in any given species as the equivalent mg/m2 dose, multiply the dose by the appropriate km factor. In an adult human, 100 mg/kg is equivalent to 100 mg/kg 37 kg/m 2=3700 mg/m2.
For additional guidance regarding formulations and doses, see U.S. Pat. Nos. 5,326,902; 5,234,933; PCT International Publication No. WO 93/25521; Remington et al., 1975; Goodman et al., 1996; Berkow et al., 1997; Speight et al., 1997; Ebadi, 1998; Duch et al., 1998; Katzung, 2001; Gerbino, 2005.
IV.C. Routes of Administration
The presently disclosed compositions can be administered to a subject in any form and/or by any route of administration. In some embodiments, the formulation is a sustained release formulation, a controlled release formulation, or a formulation designed for both sustained and controlled release. As used herein, the term “sustained release” refers to release of an active agent such that an approximately constant amount of an active agent becomes available to the subject over time. The phrase “controlled release” is broader, referring to release of an active agent over time that might or might not be at a constant level. Particularly, “controlled release” encompasses situations and formulations where the active ingredient is not necessarily released at a constant rate, but can include increasing release over time, decreasing release over time, and/or constant release with one or more periods of increased release, decreased release, or combinations thereof. Thus, while “sustained release” is a form of “controlled release”, the latter also includes delivery modalities that employ changes in the amount of an active agent (e.g., an SSCI composition) that are delivered at different times.
In some embodiments, the sustained release formulation, the controlled release formulation, or the combination thereof is selected from the group consisting of an oral formulation, a peroral formulation, a buccal formulation, an enteral formulation, a pulmonary formulation, a rectal formulation, a vaginal formulation, a nasal formulation, a lingual formulation, a sublingual formulation, an intravenous formulation, an intraarterial formulation, an intracardial formulation, an intramuscular formulation, an intraperitoneal formulation, a transdermal formulation, an intracranial formulation, an intracutaneous formulation, a subcutaneous formulation, an aerosolized formulation, an ocular formulation, an implantable formulation, a depot injection formulation, a transdermal formulation and combinations thereof. In some embodiments, the route of administration is selected from the group consisting of oral, peroral, buccal, enteral, pulmonary, rectal, vaginal, nasal, lingual, sublingual, intravenous, intraarterial, intracardial, intramuscular, intraperitoneal, transdermal, intracranial, intracutaneous, subcutaneous, ocular, via an implant, and via a depot injection. Where applicable, continuous infusion can enhance drug accumulation at a target site (see, e.g., U.S. Pat. No. 6,180,082). See also U.S. Pat. Nos. 3,598,122; 5,016,652; 5,935,975; 6,106,856; 6,162,459; 6,495,605; and 6,582,724; and U.S. Patent Application Publication No. 2006/0188558 for transdermal formulations and methods of delivery of compositions. In some embodiments, the administering is via a route selected from the group consisting of peroral, intravenous, intraperitoneal, inhalation, intraprostatic, and intratumoral.
The particular mode of drug administration used in accordance with the methods of the presently disclosed subject matter depends on various factors, including but not limited to the vector and/or drug carrier employed, the severity of the condition to be treated, and mechanisms for metabolism or removal of the drug following administration.
IV.D. Combination Therapies
In some embodiments, a method of treatment that comprises administration of an SSCI of the presently disclosed subject matter can also comprise any other therapy known or expected to be of benefit to a subject with a condition, disease, or disorder associated with undesirable COX (e.g., COX-2) biological activity. By way of example and not limitation, anxiety and pain are conditions, diseases, or disorders associated with an undesirable COX-2 biological activity. Any standard therapy that is used to treat anxiety and/or pain or a precursor condition thereof can be employed before, concurrently with, and/or after administration of a composition of the presently disclosed subject matter.
The presently disclosed subject matter also provides methods for designing and/or identifying new SSCIs. In some embodiments, computer modeling software such as those disclosed herein are employed for designing SSCIs that interact with the COX-2 homodimer as do the SSCIs disclosed herein. For example, the (R)-profens are disclosed herein to
Alternatively or in addition, the presently disclosed subject matter provides for methods of identifying new SSCIs that employ libraries of compounds (e.g., a high-throughput screening library comprising potential SSCIs) that are tested for substrate-selective inhibitory activity. By way of example and not limitation, potential SSCIs can be incubated with a COX-2 enzyme preparation (e.g., a pure preparation or an isolate from a cell, tissue, or organ, or subject) in the presence of arachidonic acid and/or 2-arachidonoylglycerol or arachidonoylethanolamide. In some embodiments, the products are extracted and analyzed by liquid chromatography-mass spectrometry as described in herein to identify SSCIs.
The following Examples provide further illustrative embodiments. In light of the present disclosure and the general level of skill in the art, those of skill will appreciate that the following Example is intended to be exemplary only and that numerous changes, modifications, and alterations can be employed without departing from the scope of the presently disclosed subject matter.
Materials. Along with the wild type protein, mCOX-2 protein with the mutations R120Q, E524L, S530A, or Y355F were expressed in insect cells and purified as described previously in (Rowlinson et al., 1999). With respect to COX-2 amino acid mutations, the amino acid position numbers listed herein are based on the COX-1 sequence, which includes an additional 14 amino acids at the N-terminus. Hence, “R120Q” refers to a change from arginine to glutamine at the position that corresponds to R120 of COX-1. It is noted that this position actually corresponds to amino acid 106 in murine COX-2 as set forth in GENEBANK® database Accession No. NP—035328 (which shows R106, E510, S516, and Y341, for example). Similarly, the gluamtic acid referred to herein as “E524” is actually at amino acid position 510 of mCOX-2, “Y335” is a tyrosine at amino acid position 321 of mCOX-2, etc. Human MAGL was purchased from Cayman Chemical. Humanized rat FAAH was a generous gift of R. Stevens and B. Cravatt (The Scripps Research Institute, La Jolla, Calif., United States of America). Human 15-lipoxygenase-1 was a generous gift of A. Brash (Vanderbilt University School of Medicine, Nashville, Tenn., United States of America).
Various concentrations of inhibitor (or DMSO) were incubated with mCOX-2 (200 nM) for 5-15 minutes in 100 mM Tris-HCl with 0.5 mM phenol, pH 8.0. For mutant mCOX-2 experiments, the enzyme concentration was adjusted such that the turnover was approximately equal to wild type enzyme. The preincubation time was determined on the basis of previous reports regarding the time required to achieve maximal inhibition, and preincubation was performed at 25° C. except for the final 3 minutes, which took place at 37° C. (Kalgutkar et al., 1998; Prusakiewicz et al., 2009). After the preincubation of enzyme and inhibitor, arachidonic acid or 2-AG was added for 30 seconds at 37° C. The reaction was quenched with ice-cold ethyl acetate containing 0.5% (v/v) acetic acid and 1 μM PGE2-d4 and PGE2-G-d5. The solution was then vigorously mixed and cooled on ice. The organic layer was separated and evaporated to near-dryness under nitrogen. For analysis, the samples were reconstituted in 1:1 MeOH:H2O and chromatographed using a Luna C18(2) column (50 2 mm, 3 μm; Phenomenex Inc., Torrance, Calif., United States of America) with an isocratic elution method requiring 66% (v/v) 5 mM ammonium acetate, pH 3.3 (solvent A) and 34% (v/v) acetonitrile containing 6% (v/v) solvent A (solvent B) at a flow rate of 0.375 ml min−1. MS/MS was conducted on a Quantum triple-quadrupole mass spectrometer operated in positive-ion mode using a selected reaction monitoring method with the following transitions: m/z 370→317 for PGE2/D2, m/z 374→321 for PGE2-d4, m/z 444→391 for PGE2/D2-G, and m/z 449→396 for PGE2/D2-G-d5. Peak areas for analytes were normalized to the appropriate internal standard to determine the amount of product formation, and the amount of inhibition was determined by normalization to a DMSO control.
Protein crystallization was performed as described in (Duggan et al., 2010). Data sets were collected on an ADSC Quantum-315 CCD (Area Detector Systems Corp., Poway, Calif., United States of America) using the synchrotron radiation X-ray source tuned at a wavelength of 0.97929 Å with an operating temperature of 100 K at beamline 24ID-E of the Advance Photon Source at the Argonne National Laboratory (Lemont, Ill., United States of America). Diffraction data were processed with the software program HKL-2000 (HKL Research; Otwinowski & Minor, 1997). Initial phases were determined by molecular replacement using a search model (PDB 3NT1) with MOLREP (Vagin & Teplyakov, 2000). Solutions with two molecules in the asymmetric unit of (R)-naproxen and four molecules in that of (R)-flurbiprofen were obtained. The models were improved with iterative rounds of model building in Coot and with refinement in PHENIX (Adams et al., 2002; Emsley & Cowtan, 2004). Data collection and refinement statistics are reported in Table 2.
Values in pararenthese correspond to the highest resulution shells.
In the Ramachandran plot, 93.7% of all residues are in the most favored region for the (R)-naproxen/mCOX-2 structure, and 94.0% of all residues appear in the most favored region for the (R)-flurbiprofen/mCOX-2 structure. The estimated coordinate errors are 0.25 Å for (R)-naproxenlmCOX-2 and 0.29 Å for (R)-flurbiprofen/mCOX-2. Molecular graphics (see
DRG Preparation.
DRG culturing and staining for neurons and glia was performed as described in Wu et al., 2009 using a protocol approved by the Vanderbilt University Institutional Animal Care and Use Committee. Staining for COX-2 was performed as described in Uddin et al., 2010. Treatment with inflammatory stimuli was performed as described herein below. Extraction and analysis of prostaglandins, PG-Gs, and PG-EAs was performed as described in Kingsley & Marnett, 2007.
Accession Codes.
Crystal structure coordinates were deposited with the RCSB Protein Data Bank (PDB) under the codes 3Q7D and 3RR3 for (R)-naproxen/mCOX-2 and for (R)-flurbiprofen/mCOX-2, respectively.
To explore the generality of substrate-selective inhibition, the effects of different classes of NSAIDs on the COX-2-dependent oxygenation of arachidonic acid and 2-AG were compared. An assay that measured prostaglandin or PG-G formation by LC-MS/MS following a 15 minute preincubation of enzyme and inhibitor to ensure maximal inhibition of the oxygenation of both substrates was employed. Saturating concentrations of both arachidonic acid and 2-AG (50 μM) were used.
The results are summarized in Table 3. Weak, reversible inhibitors of arachidonic acid oxygenation were strong inhibitors of 2-AG oxygenation, whereas slow, tight-binding inhibitors were potent inhibitors of both 2-AG and arachidonic acid oxidation by COX-2, with comparable half-maximum inhibitory concentration (IC50) values for both substrates (see Table 3). While not wishing to be bound by any particular theory of operation, the ability of slow, tight binding inhibitors to inhibit 2-AG and arachidonic acid oxygenation at comparable concentrations might arise from the capacity of a single molecule of inhibitor to block the oxygenation of both substrates (Kulmacz & Lands, 1985; Prusakiewicz et al., 2009; Rimon, G. et al., 20101 Dong et al., 2011). Within inhibitor classes, no differences in behavior were observed between compounds that were COX-2-selective inhibitors or nonselective inhibitors of both COX enzymes (for example, celecoxib versus diclofenac).
aEnzyme and inhibitor were preincubated for 15 minutes before the addition of 50 μM substrate for 30 seconds. Reactions were quenched with organic solvent containing deuterated internal standards. Product formation was analyzed by LC-MS/MS using selected reaction monitoring and was notmalized to DMSO control values.
bSubstrate oxygenation was measured using an oxygen electrode.
cValues for ibuprofen and mefenamic acid taken from Prusakiewicz et al., 2009.
Profens showed marked enantiospecificity for inhibition of arachidonic acid oxygenation by COX enzymes. The (S) enantiomers of naproxen, ibuprofen, and flurbiprofen inhibited arachidonic acid oxygenation by COX-1 and COX-2, but the (R) enantiomers inhibited either poorly or not at all.
The ability of the (R) enantiomers of naproxen, ibuprofen, and flurbiprofen to inhibit 2-AG oxygenation by COX-2 was examined. (R)-flurbiprofen (4 or 20 μM) or (R)-naproxen (20 rM) were incubated with mCOX-2 for 0, 15, 30, 45, 60, 120, 180, 300, or 600 seconds prior to the addition of a saturating concentration of 2-AG for 30 seconds. Reactions were quenched and PG-G's were measured by LC-MS/MS as described herein above under the heading “Materials and Methods for the EXAMPLES”.
The results are shown in
aEnzyme and inhibitor were preincubated for 15 min before the addition of substrate for 30 s. Reactions were quenched with organic solvent containing deuterated internal standards. Product formation was analyzed by LC-MS/MS using selected reaction monitoring and was normalized to DMSO control.
The findings disclosed herein illustrated that the (R) enantiomers of arylpropionic acids bound to COX-2 and inhibited the oxygenation of 2-AG. This was surprising given prior results suggesting that predicted steric clashes with active site residues would be expected to prevent the binding of (R)-arylpropionic acids within the COX active site (Bhattacharyya et al., 1996). Therefore, crystallized complexes of each of the (R) enantiomers bound to mCOX-2 were produced and analyzed to identify their binding sites.
Diffraction-quality crystals were obtained with both (R)-naproxen and (R)-flurbiprofen using a methodology described in (Duggan et al., 2010). An experimental electron density map for (R)-naproxen bound to murine COX-2 (mCOX-2) was produced with a simulated annealing omit map (Fo-Fc) contoured at 30. The inhibitor was located exclusively within the cyclooxygenase active site; its carboxylate moiety was adjacent to Arg120 and Tyr355 at the mouth of the active site, and its naphthyl ring projected up into the center of the cyclooxygenase channel. This is typical of the orientation of arylpropionic acids in the COX active site as has been reported for (S)-ibuprofen complexed to COX-1, (S)-naproxen complexed to COX-2, and (S)-flurbiprofen complexed to COX-1 or COX-2 (Kurumbail et al., 1996; Selinsky et al., 2001; Duggan et al., 2010).
Previous reports based on site-directed mutagenesis and structure-activity studies had suggested that stable binding of (R)-arylpropionic acids within the active site of COX would be prevented by unfavorable steric interactions between the α-methyl group and Tyr355 at the base of the active site (see Bhattacharyya et al., 1996). Surprisingly, the α-methyl group of (R)-naproxen bound adjacent to Tyr355.
The (S)-naproxen structure was recently reported at 1.7 Å, and an overlay of (R)-naproxen and (S)-naproxen bound in the active site of mCOX-2 was generated (see Duggan et al., 2010). The p-methoxy substituents and the two naphthyl rings were nearly superimposed, and the two enantiomers seemed to participate in many of the same interactions with surrounding protein residues. These included hydrogen bonding with Arg120 and Tyr355 as well as hydrophobic interactions with Ala527, Va1349, Gly526, Trp387, Tyr385, and Leu352.
However, (R)-naproxen did appear to participate in some interactions distinct from those of (S)-naproxen. The α-methyl group of (R)-naproxen participated in van der Waals interactions with Ser530 and Ser353, but the α-methyl substituent of (S)-naproxen did not. The principal difference in protein structure between the two complexes was the repositioning of Arg120 and Tyr355 to accommodate the α-methyl group in the binding of (R)-naproxen (r.m.s. deviations of 0.47 Å and 0.45 Å, respectively). This increase in the hydrogen-bond distance between Tyr355 and the carboxylate of (R)-naproxen to 3.05 Å, which was much further compared to the distance of 2.44 Å for (S)-naproxen, could reduce the binding energy of the (R)-naproxen/COX-2 complex.
Like the naproxen enantiomers, the (R) and (S) enantiomers of flurbiprofen bound in a similar fashion within the mCOX-2 active site (see
To probe the importance of individual residues in the inhibition of 2-AG oxygenation, the inhibitory activity of (R)-flurbiprofen against a series of active site mutants was measured. The R120Q mutation, which eliminated the ability of that residue to participate in ion-pairing interactions, abolished (R)-flurbiprofen inhibition (see
(R)-Flurbiprofen has analgesic activity in humans and inhibits neuropathic pain in rodents (see Lo{umlaut over (t)}sch et al., 1995; Bishay et al., 2010). It is inefficiently converted to (S)-flurbiprofen in vivo and does not show gastrointestinal toxicity, which is typically observed with compounds that inhibit COX-dependent prostaglandin synthesis (see Jamali et al., 1988; Brune et al., 1992). Notably, (R)-flurbiprofen has been reported to elevate AEA in the dorsal horn of rats surgically treated to induce nerve injury (see Bishay et al., 2010). The mode of action by which (R)-flurbiprofen causes analgesia and AEA elevation is uncertain, although its weak inhibition of FAAH (IC50>1 mM in vitro) has been suggested as a possible explanation (see Bishay et al., 2010).
The analgesic activity of (R)-flurbiprofen could also be explained by its inhibition of the COX-2-selective metabolism of endocannabinoids. To evaluate this possibility and to test whether substrate-selective inhibition can be detected in intact cells stimulated to release physiological amounts of 2-AG and AEA, cellular experiments were performed with DRGs. DRGs were harvested from E14 mouse embryos and plated onto collagen-coated dishes. After being cultured for 3-5 days, they were treated overnight with granulocyte-macrophage colony-stimulating factor followed by lipopolysaccharide, interferon γ, and 10 μM 15(S)-hydroxy-5,8,11,13-eicosatetraenoic acid for 6 hours. This resulted in a strong induction of COX-2 but not COX-1 in the DRGs and no increase in the amounts of MAGL, ABHD6, or FAAH (see
DRGs, activated as above for 3 hours were treated with ionomycin for an additional 3 hours to stimulate substrate release. The substrates and products of COX-2-mediated oxygenation were extracted and identified by LC-MS/MS. Peaks were detected that co-eluted with prostaglandin, PG-G, and PG-EA standards. In all cases, the major products were PGF2α and PGE2, their glyceryl esters, and ethanolamide derivatives.
It is noteworthy that the stimulation of DRGs resulted in the generation of PG-EAs. This was the first time that these oxygenated metabolites of AEA had been detected in intact cells stimulated to release endogenous COX-2 substrates. The identity of the PG-EAs was verified by collision-induced dissociation and analysis of the fragment ions (see
The amounts of prostaglandin, PG-G, and PG-EA were quantified using stable-isotope dilution methods with labeled internal standards. The addition of increasing concentrations of (R)-flurbiprofen, (R)-ibuprofen, or (R)-naproxen 1 hour before the addition of ionomycin inhibited the synthesis of endocannabinoid-derived eicosanoids, PG-Gs, and PG-EAs at concentrations that did not inhibit the synthesis of prostaglandins. The concentration-dependence values for inhibition of 2-AG oxygenation and AEA oxygenation were similar (see
Thus, the substrate-selective inhibition of endocannabinoid oxygenation observed with purified COX-2 was also observed in intact DRGs stimulated with physiological agonists and endogenous substrates. The IC50 values for 2-AG and AEA oxidation in DRGs by the (R)-profens ((R)-flurbiprofen-2-AG, 5.8±2.9 μM, (R)-flurbiprofen-AEA, 6.0±2.7 μM; (R)-naproxen-2-AG, 8.9±3.2 μM, (R)-naproxen-AEA, 11.8±4.1 μM; (R)-ibuprofen-2-AG, 10.1±4.7 μM, (R)-ibuprofen-AEA, 9.4 Å-4.3 μM) were closer to those for pure COX-2 at 50 μM 2-AG than at 5 μM 2-AG (see Table 4 above). A closer correspondence to values at low substrate concentrations in vitro might have been expected, but there were many differences between the in vitro and cellular assays, including different incubation times (30 seconds versus 4 hours), the presence of serum in the cell culture medium, and the presence of multiple competing fatty acids and other lipids in the activated DRGs. These might have had the effect of increasing the IC50 values of the (R)-profens in intact DRGs relative to those in purified enzyme.
Concomitant with the inhibition of PG-G and PG-EA formation, treatment of stimulated DRGs with (R)-flurbiprofen, (R)-ibuprofen, and (R)-naproxen increased the amounts of AEA and 2-AG measured in cell extracts but did not increase the amounts of arachidonic acid (see
Notably, FAAH did not seem to be present in the DRGs. Indeed, incubation of increasing concentrations of the three (R)-profens with purified MAGL or FAAH in vitro caused no inhibition of their catalytic activities at concentrations up to 1 mM (see
Finally, the enantiomeric composition of the (R)-profens that were recovered after a 4 hour incubation with DRGs was evaluated by chiral chromatography and was shown to be >99% (R) (see
The results presented herein above expand the range of compounds capable of substrate-selective inhibition of endocannabinoid oxygenation and indicated that such inhibition was limited to compounds characterized as rapid, reversible inhibitors of COX-2. The results also illustrated that (R) enantiomers of arylpropionic acid inhibitors, which were previously not considered COX inhibitors because of their inability to inhibit arachidonic acid oxygenation, actually bound to the enzyme and potently inhibited endocannabinoid oxygenation. Crystallographic studies indicated that the binding sites of (R)-naproxen and (R)-flurbiprofen were exclusively within the COX-2 active site, and functional studies indicated that ion pairing to Arg120 was critical for (R)-flurbiprofen binding.
The potency of (R)-profen inhibition of endocannabinoid oxygenation dramatically illustrates the negative cooperativity between the two subunits of the COX-2 homodimer that results from binding of an inhibitor molecule to a single subunit (see
COX-2 oxygenation of 2-AG and AEA in intact cells produces PG-G and PG-EA derivatives that have a range of biological activities (see Nirodi et al., 2004; Rouzer & Marnett, 2005; Yang & Chen, 2008; Woodward et al., 2008; Richie-Jannetta et al., 2010). The receptors responsible for these effects have not been identified, but they seem to be distinct from classic prostaglandin receptors (see Nirodi et al., 2004; Liang, et al., 2008). Thus, COX-2-dependent endocannabinoid oxygenation might represent a new mechanism for generating lipid signaling molecules dependent on different sets of agonists and phospholipases that are responsible for COX-2- (or COX-1-) dependent prostaglandin formation.
Testing this hypothesis in cellular systems or animal models has been difficult because of the lack of specific reagents that can differentiate COX-2-dependent 2-AG and AEA oxygenation from arachidonic acid oxygenation. The high degree of substrate-selective inhibition shown by (R)-profens suggested that they could be valuable probes for dissecting the specific contributions of COX-2 to cellular physiology or pathophysiology of endocannabinoid oxygenation from those of arachidonic acid oxygenation.
The metabolism of endocannabinoids and their relationship to signaling involves a complex set of enzymes and receptors (see Piomelli; 2003; Di Marzo, 2009). Following their biosyntheses from phospholipid precursors, AEA and 2-AG bind, respectively, to the CB1 receptor and TRPV1 and to the CB1 and CB2 receptors to stimulate cellular responses. The concentrations of AEA and 2-AG are primarily controlled through hydrolysis by FAAH and MAGL, respectively, although other enzymes will also hydrolyze 2-AG (for example, ABHD6, ABHD12 and carboxyl esterase 1; see Blankman et al., 2007; Xie et al., 2010). AEA and 2-AG are also oxygenated by COX-2, lipoxygenases, and cytochromes in the P450 family, and it is conceivable that, under certain conditions, oxygenation sufficient to further lower endocannabinoid concentrations could occur.
COX-2 is a particularly attractive candidate for modulation of endocannabinoid concentrations because it is highly induced by a range of agents, including proinflammatory stimuli. COX-2 production was induced in DRGs stimulated with proinflammatory agents; in contrast, the amounts of MAGL, FAAH, and ABHD6 were not increased (see
These findings uncover a potential mechanism for the analgesic activity of (R)-flurbiprofen. The ability of (R)-flurbiprofen to selectively inhibit AEA and 2-AG oxygenation in DRGs correlates to its ability to elevate AEA concentrations at sites of neuroinflammation in the spinal cord (see Bishay et al., 2010). Although FAAH and MAGL are most likely responsible for the basal turnover of endocannabinoids in non-inflamed tissue, diurnal fluctuations lead to increases in COX-2 in regions of the brain, and induction of inflammation in the peripheral or central nervous system by nerve injury results in elevations of COX-2 concentrations in the inflamed tissue (see Guay et al., 2004; Glaser & Kaczocha, 2010). COX-2 induction might contribute to the depletion of AEA and 2-AG, and blockage of this depletion by substrate-selective inhibition of COX-2 by (R)-flurbiprofen could spare endocannabinoid concentrations and induce analgesia. Consistent with this mechanism, the analgesic effect of (R)-flurbiprofen is prevented by CB1-receptor antagonists despite the fact that (R)-flurbiprofen does not activate the CB 1 receptor (see Bishay et al., 2010). This highlights the importance of maintaining endocannabinoid tone in the analgesic action of (R)-flurbiprofen.
Described herein above are a series of experiments that demonstrated that rapid-reversible inhibitors of cyclooxygenase-2 (COX-2) are substrate-selective inhibitors, while slow, tight-binding inhibitors of COX-2 are non-substrate-selective inhibitors. In particular, it was determined that the (R)-profens, which had previously been classified as inactive toward COX-2, are actually substrate-selective inhibitors of COX-2. It was also determined that (R)-profens increased the levels of anandamide (AEA) and 2-arachidonoyl glycerol (2-AG) while decreasing the levels of prostaglandin ethanolamides (PG-EAs) and prostaglandin glycerol esters (PG-Gs) in primary murine dorsal root ganglia cells stimulated to express COX-2. In vivo, however, (R)-profens undergo a one way stereoisomerization to (S)-profens, which are non-substrate-selective inhibitors of COX-2.
Disclosed herein are additional SSCIs that in some embodiments can be employed in vivo. Through the use of site-directed mutagenesis it was determined that disruption of the hydrogen bonding and ion pairing network can cause slow, tight-binding, non-substrate-selective inhibitors to become rapid-reversible, substrate-selective inhibitors. Based on the site-directed mutagenesis data, it was determined that tertiary amides of indomethacin are potent substrate-selective inhibitors of COX-2. In particular, the morpholino amide of indomethacin, 2-[1-(4-Chloro-benzoyl)-5-methoxy-2-methyl-1H-indol-3-yl]-1-morpholin-4-yl-ethanone (referred to herein as “Compound A”; see
Cyclooxygenase-2 (COX-2) catalyzes the oxygenation of arachidonic acid (AA) and the endocannabinoids, 2-arachidonoylglycerol (2-AG) and arachidonoylethanolamide (AEA), to prostaglandin endoperoxide derivatives. Non-steroidal anti-inflammatory drugs such as ibuprofen, naproxen, and lumiracoxib, which are weak, competitive inhibitors of AA oxygenation, are potent non-competitive inhibitors of 2-AG and AEA oxygenation. These compounds are as much as 1,000-fold more potent at inhibiting endocannabinoid oxygenation than AA oxygenation. The instant co-inventors have termed this phenomenon “substrate-selective inhibition” (SSI-COX-2) and propose that it contributes to the pharmacological effects of certain NSAIDs by preventing oxidative endocannabinoid metabolism at sites of COX-2 induction.
The analgesic agent, acetaminophen (APAP), and its in vivo metabolites 4-aminophenol and N-(4-hydroxyphenyl)arachidonoylamide (AM-404), exhibit SSCI activity with IC50's of 233 μM, 71 μM, and 97 nM, respectively, for inhibition of 2-AG oxygenation. No inhibition of AA oxygenation was observed up to 1 mM for APAP or 4-aminophenol. AM-404 exhibited 700-fold selectivity for inhibition of 2-AG and AEA oxygenation compared to AA oxygenation.
APAP and AM404 selectively inhibited 2-AG oxygenation by lipopolysaccharide-activated RAW264.7 cells with IC50's of 97 μM and 46 nM, respectively. Structure-activity analysis of a series of AM404 analogs revealed that the presence of a hydroxyl group at the para-position of the phenylamide ring was important for SSI-COX-2. Dissociation of AM404 from COX-2 was slow in the absence of substrate but was rapid in the presence of AA. Inhibition of endocannabinoid oxygenation was reversed by addition of nanomolar concentrations of AA. The observations were consistent with a model for SSCIs in which APAP, 4-aminophenol, or AM404 binds to the allosteric subunit of COX-2 to inhibit endocannabinoid oxygenation in the catalytic subunit. Substrate-selective inhibition of endocannabinoid oxygenation might therefore contribute to the pharmacological actions of APAP and its metabolites.
Development of endocannabinoid (eCB) degradation inhibitors has significantly advanced the therapeutic potential of eCB signaling for a variety of pathological conditions including mood and anxiety disorders. COX-2 degrades both AEA and 2-AG, and activation of eCB signaling contributes to the analgesic effects of COX-2 inhibitors. However, therapeutic development of COX-2 inhibitors as modulators of eCB signaling is limited by the significant role that COX-2 plays in prostaglandin (PG) synthesis.
Disclosed herein are SSCIs that inhibit COX-2 activity only when 2-AG or AEA, but not arachidonic acid, are used as substrates. Also disclosed herein are tests of the hypothesis that SSI-COX-2 increases brain eCB levels via a COX-2 dependent mechanism without affecting PG formation.
The SSCI Compound A increased brain AEA levels without affecting 2-AG levels 2 hours after i.p administration. Compound A did not affect brain or lung PG levels. Indomethacin also increased brain AEA levels, but profoundly decreased PG levels. The ability of Compound A to increase brain AEA levels was absent in COX-2 knockout (KO) mice, but was present in wild type littermates.
Compound A dose-dependently increased exploratory behavior in the open field, as well as center time exploration, which was most pronounced during minutes 40-60 of the one-hour test. These effects were similar to those seen with the fatty acid amide hydrolase (FAAH) inhibitor PF-3845 (N-3-pyridinyl-4-[[3-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenyl]methyl]-1-piperidinecarboxamide; CAS Number 1196109-52-0). Importantly, the observed behavioral effects of Compound A were absent in COX-2 KO mice and CB 1 receptor KO mice. Compound A also increased the number to light compartment entries in the light-dark box test. These data indicated that use of SSI-COX-2s is a viable strategy for in vivo augmentation of eCB signaling, and that the SSI-COX-2 Compound A has anxiolytic actions in animal models.
Silica gel column chromatography was performed using Sorbent silica gel standard grade, porosity 60 Å, particle size 32-63 μm (230 ×450 mesh), surface area 500-600 m2/g, bulk density 0.4 g/mL, pH range 6.5-7.5, purchased from Sorbent Technologies (Atlanta, Ga., United States of America). Desmethylketoprofen Compound 3e was purchased from Toronto Research Chemicals. All other reagents, purchased from the Aldrich Chemical Company (Milwaukee, Wis., United States of America), were used without further purification. 1H and 13C NMR were taken on a Bruker AV-I console operating at 400 MHz. Mass spectrometric analyses were performed on a Thermo Electron Surveyor pump TSQ 7000 instrument in ESI positive or negative ion mode. HPLC was performed with a Waters 2695 Separations Module with detection by a Waters 2487 Dual 2 Absorbance Detector at 260 nm and 285 nm. Light scattering was performed on a Sedex 75.
A generalized scheme for generating SSCIs is presented in
General Procedure 1: Synthesis of Benzyl Aldehydes Compounds 2a-2d:
(Methoxymethyl)triphenylphosphonium chloride (4.0 eq) was suspended in dry THF (0.2 M) and cooled to 0° C. under an argon atmosphere. A solution of potassium tert-butoxide in THF (4.0 eq) was added slowly to the suspension and allowed to stir for 45 minutes at 0° C. The desired aryl aldehyde (e.g., Compound 1a; 3.0 mmol, 1.0 eq) was added dropwise and the solution was allowed to stir at room temperature for one hour. The reaction was quenched with saturated NH4Cl and extracted 3× with EtOAc. The organic phase was dried with MgSO4, filtered, and concentrated to yield an oil. The oil was then dissolved in a 5:2 THF:5 N HCl solution (0.2 M) and refluxed for one hour. The solution was cooled to room temperature, quenched with saturated NaHCO3 and extracted 3× with EtOAc. The organic layer was dried with MgSO4, filtered, and concentrated to yield an oil that was purified via silica gel column chromatography eluting with 30:1 hexanes:EtOAc.
General Procedure 2: Synthesis of Desmethylprofens Compounds 3a-3d:
The desired benzyl aldehyde (e.g., Compound 2a; 2.5 mmol, 1 eq) was dissolved in a 1:1 solution of H2O:t-BuOH (0.1 M). In order, 2,3-dimethyl-2-butene (20 eq), KH2PO4 (2.0 eq) and sodium chlorite (2.5 eq) were added to the solution and allowed to stir for 40 minutes at room temperature. The reaction was extracted 3× with EtOAc and the combined organic layers were washed with a saturated NaCl solution, dried with MgSO4 and concentrated to yield an off-white solid. The crude product was purified via silica gel column chromatography eluting with 9:1 hexanes:EtOAc to give a white solid.
General Procedure 3: Synthesis of Dimethyl Profen Methyl Esters:
A racemic profen (e.g., Compound 6a, 0.5 mmol, 1 eq) was dissolved in MeOH (0.2 M). A drop of concentrated H2SO4 was added and the solution was refluxed for two hours. The reaction was quenched with sat. NaHCO3, extracted 3× with EtOAc, dried with MgSO4 and concentrated to yield the methyl-ester protected racemic profen as an oil. This oil was dissolved in dry THF (0.2 M) and cooled to −78° C. under argon. A solution of LDA in THF (1.5 eq) was added slowly and allowed to stir at −78° C. for 30 minutes. The solution was warmed to 0° C. and HMPA (1.4 eq) was added slowly and allowed to stir at 0° C. for 30 minutes. Finally, 1.9 eq. of Mel was added dropwise to the solution and allowed to stir for 30 minutes at 0° C. and then thirty minutes at room temperature. The reaction was quenched with NH4Cl, extracted 3× with EtOAc, dried with MgSO4 and concentrated to yield an orange oil. The crude product was purified via silica gel column chromatography eluting with 9:1 hexanes:EtOAc to give an oil. Note: Compounds 3a-3e can be used as the starting material with this procedure as long as the equivalents of LDA, HMPA, and Mel are doubled from those described above.
General Procedure 4: Synthesis of Cyclopropyl Profen Methyl Esters:
A desmethylprofen (e.g., Compound 3a, 0.5 mmol, 1 eq) was dissolved in MeOH (0.2 M). A drop of concentrated H2SO4 was added and the solution was refluxed for two hours. The reaction was quenched with sat. NaHCO3, extracted 3× with EtOAc, dried with MgSO4 and concentrated to yield the methyl-ester protected profen as an oil. This oil was dissolved in dry THF (0.2 M) and cooled to −78° C. under argon. A solution of LDA in THF (2.5 eq) was added slowly and allowed to stir at −78° C. for 30 minutes. The solution was warmed to 0° C. and HMPA (2.0 eq) was added slowly and allowed to stir at 0° C. for 30 minutes. Finally, 1.5 eq. of 1,2-dibromoethane was added dropwise to the solution and allowed to stir for 30 minutes at 0° C. and then thirty minutes at room temperature. The reaction was quenched with NH4Cl, extracted 3× with EtOAc, dried with MgSO4 and concentrated to yield an orange oil. The crude product was purified via silica gel column chromatography eluting with 9:1 hexanes:EtOAc to give an oil.
General Procedure 5: Synthesis of Dimethyl (Compounds 4a-4e) and Cyclopropyl (Compounds 5a-5e) Profens:
A methyl-ester protected dimethyl profen or a methyl-ester protected cyclopropyl profen (0.2 mmol, 1.0 eq) was dissolved in dry THF (0.2 M). KOTMS (2.0 eq) was added to the reaction flask and refluxed for two hours. The slurry was quenched at room temperature with NH4Cl, extracted 3× with EtOAc, dried with MgSO4 and concentrated to yield an off-white solid. The crude product was purified via silica gel column chromatography eluting with 30:1 DCM:MeOH to give a dimethyl profen (e.g., Compound 4a) or a cyclopropyl profen (e.g., Compound 5a), respectively, as a white solid.
Compound 2a was prepared via general procedure 1 as a clear oil (56% yield). 1H NMR (400 MHz, CDCl3) δ 9.82 (t, 1H), 7.59 (m, 2H), 7.4-7.52 (m, 4H), 7.09 (m, 2H), 3.77 (d, 2H). MS m/z (ESI): calc. for C14H11FO [M-H]− 213.08. found 213.4.
Compound 2b was prepared via general procedure 1 as a clear oil (48% yield). 1H NMR (400 MHz, CDCl3) δ 9.84 (t, 1H), 7.72-7.78 (m, 2H), 7.64 (s, 1H), 7.28-7.32 (m, 1H), 7.15-7.20 (m, 2H), 3.95 (s, 3H), 3.83 (d, 2H). MS m/z (ESI): calc. for C13H12O2 [M-H]− 199.08. found 199.4.
Compound 2c was prepared via general procedure 1 as a clear oil (77% yield). Note: intermediate and product are volatile when heated under reduced pressure. 1H NMR (400 MHz, CDCl3) δ 9.76 (t, 1H), 7.16 (d, 2H), 7.10 (d, 2H), 3.65 (d, 2H), 2.47 (d, 2H), 1.84 (m, 1H), 0.89 (d, 6H). MS m/z (ESI): calc. for C12H16O [M-H]− 175.08. found 175.4.
Compound 2d was prepared via general procedure 1 as a clear oil (75% yield). 1H NMR (400 MHz, CDCl3) δ 9.75 (t, 1H), 7.32 (m, 3H), 7.12 (m, 1H), 6.88-7.09 (m, 4H), 3.66 (d, 2H). MS m/z (ESI): calc. for C14H12O2 [M-H]− 211.07. found 211.27.
Compound 3a was prepared via general procedure 2 as a white solid (58% yield). 1H NMR (400 MHz, CDCl3) δ 7.55 (d, 2H), 7.35-7.5 (m, 4H), 7.1-7.2 (m, 2H), 3.7 (s, 3H). 13C NMR (400 MHz, CDCl3) δ 176.1, 160.8, 159.2, 135.6, 134.7, 131.0, 129.1, 128.6, 128.2, 127.8, 125.5, 117.3, 117.1, 40.4. HRMS m/z (ESI): calc. for C14H11FO2 [2M+Na]− 481.1233. found 481.1245.
Compound 3b was prepared via general procedure 2 as a white solid (94% yield). 1H NMR (400 MHz, CD3OD) δ 7.75-7.65 (m, 3H), 7.38-7.32 (d, 1H), 7.3 (s, 1H), 7.11-7.08 (d, 1H), 3.9 (s, 3H), 3.72 (s, 2H). MS m/z (ESI): calc. for C13H12O3 [M-H]− 215.08. found 215.23.
Compound 3c was prepared via general procedure 2 as a white solid (89% yield). 1H NMR (400 MHz, CDCl3) δ 7.2 (d, 2H), 7.15 (d, 2H), 3.64 (s, 2H), 2.5 (d, 2H), 1.93-1.82 (m, 1H), 0.94-0.92 (d, 6H). MS rz/z (ESI): calc. for C12H16O2 [M-H]− 191.12. found 191.19.
Compound 3d was prepared via general procedure 2 as a white solid (99% yield). 1H NMR (400 MHz, CDCl3) δ 7.35-7.23 (m, 3H), 7.12-7.07 (m, 1H), 7.0 (m, 3H), 6.98-6.88 (m, 2H), 3.62 (s, 3H). MS m/z (ESI): calc. for C14H12O3 [M-H]− 227.08. found 227.07.
The methyl-ester protected form of Compound 4a was prepared via general procedure 3 as an oil (57% yield). 1H NMR (400 MHz, CDCl3) δ 7.54-7.50 (m, 2H), 7.47-7.3 (m, 4H), 7.17-7.1 (m, 2H), 3.7 (s, 3H), 1.61 (s, 6H). MS m/z (ESI): calc. for C17H17FO2 [M+Na]+295.12. found 295.0.
The methyl-ester protected form of Compound 4b was prepared via general procedure 3 as an oil (58% yield). 1H NMR (400 MHz, CDCl3) δ 7.54-7.50 (m, 2H), 7.47-7.3 (m, 41H), 7.17-7.1 (m, 2H), 3.7 (s, 3H), 1.61 (s, 6H). MS m/z (ESI): calc. for C16H18O3 [M+Na]+281.13. found 281.07.
The methyl-ester protected form of 4c was prepared via general procedure 3 as an oil (85% yield). 1H NMR (400 MHz, CDCl3) δ 7.25-7.2 (d, 2H), 7.1 (d, 2H), 3.68 (s, 3H), 2.47 (d, 2H), 1.9-1.8 (m, 1H), 1.6 (s, 6H), 0.93 (d, 6H). MS m/z (ESI): calc. for C15H22O2 [M+Na]+257.16. found 257.07.
The methyl-ester protected form of Compound 4d was prepared via general procedure 3 as an oil (48% yield). 1H NMR (400 MHz, CDCl3) δ 7.35-7.25 (m, 3H), 7.13-6.97 (m, 5H), 6.87-6.82 (m, 1H), 3.70 (s, 3H), 1.58 (s, 6H). MS m/z (ESI): calc. for C17H18O3 [M+Na]+ 293.13. found 293.0.
The methyl-ester protected form of Compound 4e was prepared via general procedure 3 as an oil (64% yield). 1H NMR (400 MHz, CDCl3) δ 7.8 (m, 3H), 7.68-7.4 (m, 6H), 3.7 (s, 3H), 1.64 (s, 6H). MS m/z (ESI): calc. for C18H18O3 [M+Na]+ 305.13. found 305.20.
Methyl-1-(2-fluoro-[1,1′-biphenyl]-4-yl)cyclopropanecarboxylate: The methyl-ester protected form of Compound 5a was prepared via general procedure 4 as an oil (28% yield). 1H NMR (400 MHz, CDCl3) δ 7.57-7.49 (m, 2H), 7.45-7.33 (m, 4H), 7.2-7.12 (m, 2H), 3.66 (s, 3H), 1.66-1.62 (dd, 2H), 1.25-1.20 (dd, 2H). MS m/z (ESI): calc. for C17H15FO2 [M+Na]+ 293.11. found 293.10.
The methyl-ester protected form of Compound 5b was prepared via general procedure 4 as an oil (22% yield). 1H NMR (400 MHz, CDCl3) δ 7.70-7.68 (m, 3H), 7.46-7.44 (m, 1H), 7.15-7.12 (m, 2H), 3.92 (s, 3H), 3.62 (s, 3H), 1.67-1.64 (dd, 2H), 1.28-1.24 (dd, 2H). MS m/z (ESI): calc. for C16H16O3 [M+ Na]279.11. found 279.09.
The methyl-ester protected form of Compound 5c was prepared via general procedure 4 as an oil. Note: the product could not be isolated as a pure compound after column chromatography, but the impurities did not affect the next reaction (41% crude yield). 1H NMR (400 MHz, CDCl3) δ 7.27-7.2 (d, 2H), 7.18-7.13 (d, 2H), 3.68 (s, 3H), 2.44-2.4 (d, 2H), 1.88-1.78 (m, 1H), 1.6-1.55 (dd, 211), 1.28-1.24 (dd, 2H). MS m/z (ESI): calc. for C15H20O2 [M+Na]+ 255.15. found 255.12.
The methyl-ester protected form of Compound 5d was prepared via general procedure 4 as an oil (17% yield). 1H NMR (400 MHz, CDCl3) δ 7.36-7.21 (m, 3H), 7.12-7.0 (m, 5H), 6.88-6.84 (m, 1H), 3.63 (s, 3H), 1.59-1.57 (dd, 2H), 1.19-1.16 (dd, 2H). MS m/z (ESI): calc. for C17H16O3 [M+Na]+291.11. found 291.09.
The methyl-ester protected form of Compound 5e was prepared via general procedure 4 as an oil (18% yield). 1H NMR (400 MHz, CDCl3) δ 7.82-7.78 (m, 3H), 7.7-7.66 (m, 1H), 7.61-7.54 (m, 2H), 7.52-7.39 (m, 3H), 3.64 (s, 3H), 1.67-1.63 (d, 2H), 1.25-1.21 (dd, 2H). MS m/z (ESI): calc. for C17H16O3 [M+Na]+303.11. found 303.15.
Compound 4a was prepared via general procedure 5 as a white solid (84% yield). 1H NMR (400 MHz, CDCl3) δ 7.56-7.5 (m, 2H), 7.45-7.36 (m, 4H), 7.17-7.08 (m, 2H), 1.65 (s, 6H). 13C NMR (400 MHz, CDCl3) δ 182, 161, 158, 146, 135, 131, 129, 128.5, 128, 127.8, 122, 114.3, 114, 46, 27 (two carbons). HRMS m/z (ESI): calc. for C16H15FO2 [2M+Na]-537.1859. found 537.1871.
Compound 4b was prepared via general procedure 5 as a white solid (92% yield). 1H NMR (400 MHz, CDCl3) δ 7.74-7.71 (m, 3H), 7.51-7.49 (m, 1H), 7.17-7.12 (2H), 3.93 (s, 3H), 1.70 (s, 6H). MS m/z (ESI): calc. for C15H16O3 [M-H]− 243.110 found 243.31.
Compound 4c was prepared via general procedure 5 as a white solid (92% yield). 1H NMR (400 MHz, CDCl3) δ 7.33-7.3 (d, 2H), 7.11-7.07 (d, 2H), 2.58-2.53 (d, 2H), 1.91-1.80 (m, 1H), 1.60 (s, 2H), 0.92-0.89 (d, 6H). MS m/z (ESI): calc. for C14H20O2 [M-H]− 219.15. found 219.13.
Compound 4d was prepared via general procedure 5 as a white solid (95% yield). 1H NMR (400 MHz, CDCl3) δ 7.36-7.24 (m, 3H), 7.13-6.98 (m, 5H), 6.85-6.80 (m, 1H), 1.58 (s, 6H). MS m/z (ESI): calc. for C16H16O3 [M-H]− 255.11. found 255.07.
Compound 4e was prepared via general procedure 5 as a white solid (89% yield). 1H NMR (400 MHz, CDCl3) δ 7.88-7.76 (m, 3H), 7.68-7.53 (m, 3H), 7.47-7.39 (m, 3H), 1.64 (s, 6H). MS m/z (ESI): calc. for C17H16O3 [M-H]− 267.11. found 267.13.
Compound 5a was prepared via general procedure 5 as a white solid (77% yield). 1H NMR (400 MHz, CDCl3) δ 7.54-7.52 (m, 2H), 7.45-7.36 (m, 4H), 7.23-7.15 (m, 2H), 1.74-1.71 (dd, 2H), 1.34-1.31 (dd, 2H). 13C NMR (400 MHz, CDCl3) δ 181, 161, 158, 140, 135.5, 131, 129, 128.5, 128.3, 127.7, 126.4, 118.4, 118.2, 28, 18 (two carbons). HRMS m/z (ESI): calc. for C16H13FO2 [M-H]− 255.0827, found 255.0835.
Compound 5b was prepared via general procedure 5 as a white solid (78% yield). 1H NMR (400 MHz, CDCl3) δ 7.7-7.68 (m, 3H), 7.48 (m, 1H), 7.14-7.11 (m, 2H), 3.91 (s, 3H), 1.74-1.71 (dd, 2H), 1.36-1.34 (dd, 2H). MS m/z (ESI): calc. for C15H14O3 [M-H]− 241.09. found 241.2.
Compound 5c was prepared via general procedure 5 as a white solid. 1H NMR (400 MHz, CDCl3) δ 7.27-7.24 (d, 2H), 7.07-7.03 (d, 2H), 2.47-2.41 (d, 2H), 1.89-1.8 (m, 1H), 1.66-1.62 (dd, 2H), 1.25-1.21 (dd, 2H), 0.91-0.86 (d, 6H). MS m/z (ESI): calc. for C14H18O2 [M-H]− 217.13. found 217.30.
Compound 5d was prepared via general procedure 5 as a white solid (59% yield). 1H NMR (400 MHz, CDCl3) δ 7.35-7.19 (m, 3H), 7.09-6.96 (m, 5H), 6.87-6.83 (m, 1H), 1.7-1.67 (dd, 2H), 1.3-1.28 (dd, 2H). MS m/z (ESI): calc. for C16H14O3 [M-H]− 253.09. found 253.27.
Compound 5e was prepared via general procedure 5 as a white solid (59% yield). 1H NMR (400 MHz, CDCl3) δ 7.83-7.81 (m, 3H), 7.73-7.68 (m, 1H), 7.61-7.56 (m, 2H), 7.49-7.39 (m, 3H), 1.74-1.71 (dd, 2H), 1.33-1.30 (dd, 2H). MS m/z (ESI): calc. for C17H4O3 [M-H]−265.09. found 265.29.
Separation of Compounds 7d and 7e:
A racemic profen (e.g., Compound 6d) was dissolved in a 90:10 solution of hexanes:IPA with 0.1% TFA for a final concentration of 10 mg/mL. An aliquot of 30 L was injected onto a CHIRALCEL® AD column using an isocratic gradient of 90:10 hexane:IPA with 0.1% TFA. Compound 7d eluted at 7.7 minutes and Compound 7e eluted at 14.2 minutes. Fractions were collected manually. The identities of the enantiomers were identified after separation via optical rotation (see e.g., Brebion et al., 2003; Monti et al., 2005). Enantiomeric excess was determined by re-injecting the separated enantiomers (e.g., Compound 7d) and integrating each peak (
Disclosed herein are investigations into developing an in vivo probe to determine the effects of blocking 2-AG and AEA, but not AA, oxygenation by COX-2. The (R)-profens are active in vitro and in intact cells, but undergo uni-directional inversion to the (S)-enantiomers (which inhibit AA oxygenation) in vivo.
This enantiomerization is an enzymatic process proceeding through an acyl coenzyme A thioester intermediate (Woodman et al., 2011). One approach to eliminate this complication is to synthesize profen derivatives that are unable to invert in vivo. Described herein is the synthesis and in vitro evaluation of achiral NSAIDs based on five profen scaffolds that exhibit substrate-selective behavior (i.e., flurbiprofen, naproxen, ketoprofen, fenoprofen, and ibuprofen), with the most potent and substrate-selective inhibitors being further examined in activated RAW264.7 cells and evaluated for stability in animal models (Davie et al., 1092; Ossipov et al., 2000; Duggan et al., 2011).
Three achiral derivatives of each profen scaffold were synthesized by altering the substitution pattern at the methyl-bearing stereocenter to contain a desmethyl (two hydrogens), dimethyl (two methyls), or cyclopropyl (two methylenes) group. The synthetic route is outlined in
Compounds 3a-e, 4a-e, and 5a-e were tested for their ability to inhibit the COX-2-dependent oxygenation of 2-AG and AA in vitro using the method described in Duggan et al., 2011. The IC50 value for 2-AG oxygenation was determined for each compound. Since none of the compounds potently inhibited AA oxygenation, percent inhibition was determined at the highest concentration employed. The data are presented in Table 5.
aIC50 values were determined by incubating five concentrations of inhibitor and a solvent control in DMSO with purified murine COX-2 (40 nM) for three min followed by addition of 2-AG or AA (5 μM) at 37° C. for 30 s.
bMean ± standard deviation (n = 6); dash (—) indicates <50% inhibition of 2-AG oxygenation at 10 μM inhibitor. Numbers in parentheses indicate maximum inhibition (when not equal to 100%) at 10 μM inhibitor.
c% inhibition of AA oxygenation measured at 10 μM inhibitor.
Several interesting observations were made. First, it appeared that inhibition of 2-AG oxygenation was dependent on the size of the substituents on the α-carbon, with smaller groups exhibiting higher potency. In general, desmethylprofen Compounds 3a-e had lower 2-AG IC50 values than the dimethyl and cyclopropyl profens, Compounds 4a-e and 5a-e, respectively. Profens, 4a-e and 5a-e, possessed approximately equivalent IC50 values against 2-AG, reflecting their similar steric bulk.
Second, regardless of the substitution on the α-carbon, flurbiprofen derivatives exhibited the lowest 2-AG IC50 values compared to the other profen scaffolds in the same class. Flurbiprofen derivative Compound 3a has a 2-AG IC50 value of 0.11 μM, significantly lower than the next best achiral inhibitor, Compound 3e (0.5 μM). The ketoprofen scaffold was the next most potent, followed by the naproxen and then fenoprofen scaffolds. The achiral ibuprofen derivatives were the weakest inhibitors of 2-AG oxygenation, with the best ibuprofen-based inhibitor, Compound 3c, possessing a relatively weak 2-AG IC50 value of 5.5 μM.
Third, the flurbiprofen scaffold offers the best substrate selectivity of the scaffolds evaluated. Each flurbiprofen derivative had lower or equal inhibition of AA oxygenation than the other derivatives in each class while also having a lower IC50 for 2-AG.
Finally, while every achiral compound besides Compound 5a showed some inhibition of AA oxygenation, the desmethyl class of compounds was the only class where each inhibitor displayed greater than 5% AA inhibition. Within this class it appears that the gains in potency of 2-AG inhibition come at a cost of substrate selectivity.
The enantiomers of racemic fenoprofen and ketoprofen were also resolved to determine their ability to act as substrate-selective inhibitors in an in vitro assay. (R)-Fenoprofen (Compound 7d) and (R)-ketoprofen (Compound 7e) possessed weak inhibitory effects on both 2-AG and AA oxygenation (Table 6). (S)-Fenoprofen and (S)-ketoprofen exhibited 2-AG IC50 and percent AA inhibition values similar to those of racemic fenoprofen (Compound 6d) and ketoprofen (Compound 6e), respectively. These data suggest that the activity of the racemates originate from their (S)-enantiomers and demonstrate that a (R)-profen scaffold does not guarantee substrate selectivity.
Flurbiprofen derivatives, Compounds 3a, 4a, 5a, and 7a were evaluated for their ability to selectively inhibit COX-2 dependent oxygenation of 2-AG over AA in intact cells (
The pharmacokinetic properties of the two most potent and selective profens screened to date, Compounds 3a and 7a, were also evaluated in C57BL/6 mice. Animals (n=4) received intraperitoneal (i.p.) injections of 10 mg/kg Compound 3a or Compound 7a in 4% DMSO/2% Tween 80 in saline at 0, 8, 24, 32, 48 and 56 hr, with blood collected at 72 hr. Plasma was analyzed for the dosed compound and, in the case of Compound 7a, its stereoinversion product (S-flurbiprofen). When compared to Compound 7a, Compound 3a appeared to exhibit less metabolic stability. Sixteen hr after the last injection, Compound 3a was not detected in mouse plasma, whereas Compound 7a gave an average plasma concentration of 20 μM. The concentration of the stereoinversion product was 31 μM.
Mice underwent acute dosing of Compound 3a at shorter time points to better estimate the compound's half-life in mouse plasma. Blood samples were collected at 1, 2 and 4 hr after a single injection. Analysis of the resultant plasma levels revealed that the 1 hr time point had an average Compound 3a plasma concentration of 68 μM (n=3) followed by concentrations of 50 (n=2) and 6 μM (n=3) at the 2 and 4 hr time points, respectively. These data suggested that Compound 3a possessed a half-life similar to ibuprofen (t1/2≈2-3 hr).
X-ray crystallography was used to study the interaction between achiral profens and COX-2. A complex of mCOX-2 and Compound 3a, using a previously described crystallization procedure, diffracted to 2.81 Å. The carboxylic acid of the ligand forms salt bridges with Arg-120 and Tyr-355. The biphenyl moiety of Compound 3a is deeply buried into the hydrophobic channel and interacts with several residues, such as Val-349, Phe-381, Trp-387, Phe-518, Met-522, Val-523, and Leu-531.
When the crystal structures of (R)-flurbiprofen and Compound 3a bound to mCOX-2 are overlaid, the two profens have the same general binding orientation in the mCOX-2 active site (0.24 Å RMSD). This orientation allows for the formation of a salt bridge with Arg-120, an interaction crucial for binding. Establishing the salt bridge with Arg-120 requires the carboxylic acid and α-carbon stereocenter of flurbiprofen to bind near the constriction site of the COX-2 binding pocket, a sterically congested region. Relief of this congestion is likely responsible for the increased inhibition of 2-AG oxygenation upon introduction of smaller substituents at the flurbiprofen α-carbon. Yet, there is a trade-off between potency and selectivity. Comparing the RAW cell data of Compounds 3a and 7a suggests that reducing the steric bulk at the α-carbon (i.e., converting the α-methyl group of Compound 7a into the hydrogen present in Compound 3a) increases potency for 2-AG and AA inhibition, resulting in less substrate selectivity. While not wishing to be bound by any particular theory of operation, there appear to be favorable interactions promoting substrate selectivity that the more sterically demanding Compound 7a can utilize, but are unavailable to the smaller Compound 3a.
The data presented here led to several conclusions about achiral profen COX-2 inhibitors. First, achiral profens demonstrated substrate-selective behavior in vitro and in a cellular setting. Second, smaller α-carbon substituents (i.e., hydrogens) resulted in more potent, but less selective inhibitors than more sterically demanding groups (i.e., dimethyl, cyclopropyl). Finally, inhibitor potency and selectivity were dependent on the profen's aryl scaffold, with some scaffolds (e.g. flurbiprofen) offering superior behavior relative to others (e.g., ibuprofen). In addition, the most potent compound, desmethylflurbiprofen (Compound 3a), possessed metabolic stability on par with ibuprofen. These results indicated that achiral profens can act as in vivo probes of substrate-selective COX-2 inhibition.
General Procedure for In Vitro Assay:
Desired concentrations of inhibitor in DMSO or blank (DMSO) were incubated with mCOX-2 (40 nM) for 3 minutes in 100 mM Tris-HCl with 0.5 mM phenol, pH 8.0 at 37° C. After pre-incubation of enzyme and inhibitor, 5 μM of AA or 2-AG was added at 37° C. Thirty seconds later, the reaction was quenched with 200 μL of ice-cold ethyl acetate containing 0.5% acetic acid (v/v) and 1 μM PGE2-d4 and PGE2-G-d5. The solution was then vortexed and the aqueous layer frozen. The organic layer was removed and evaporated to near-dryness under nitrogen. The samples were reconstituted in 1:1 MeOH:H2O and chromatographed using a LUNA® C18(2) column (50 2 mm, 3 μm; Phenomenex, Torrance, Calif., United States of America). The elution method was run at a flow rate of 0.4 mL/min and consisted of a linear gradient 20-95% Solvent B over five minutes, followed by a one minute linear gradient 95-20% Solvent B and a thirty second isocratic gradient at 20% Solvent B. Solvent A contained 5 mM ammonium acetate pH=3.5 and Solvent B was 6% Solvent A in ACN. MS/MS was conducted on a Quantum triple quadrupole mass spectrometer operated in positive ion mode utilizing a selected reaction monitoring method with the following transitions: m/z 370-+317 for PGE2/D2, m/z 374-321 for PGE2-d4, m/z 444-+391 for PGE2/D2-G and m/z 449-396 for PGE2/D2-G-d5. Analyte peak areas were normalized to the appropriate internal standard to determine the amount of product formation, and inhibition was determined by normalization to a DMSO control. Results are presented in Table 6.
aIC50 values were determined by incubating five concentrations of inhibitor and a solvent control in DMSO with purified murine COX-2 (40 nM) for three min followed by addition of 2-AG or AA (5 μM) at 37° C. for 30 seconds.
bMean ± standard deviation (n = 6); dash (—) indicates <50% inhibition of 2-AG oxygenation at 10 μM inhibitor. Numbers in parentheses indicate maximum inhibition (when not equal to 100%) at 10 μM inhibitor.
c% inhibition of AA oxygenation measured at 10 μM inhibitor.
dData taken from reference 10.
en = 3.
General Procedure for RAW Cells Assay:
RAW 264.7 macrophages were plated onto 60×15 mm collagen coated dishes at 2 million cells per dish in DMEM with GLUTAMAX® tissue culture medium supplement with 10% HI-FBS. The cells were then stimulated overnight with 20 ng/ml of granulocyte-macrophage colony-stimulating factor. The media was replaced in the morning with DMEM with GLUTAMAX® and the cells were stimulated with 100 ng/ml lipopolysaccharide and 20 units/ml interferon γ. Two hours after stimulation varying doses of inhibitor were added to the cell media and 6 hours after stimulation the media was collected and extracted in acidified ethyl acetate spiked with deuterated internal standards. The organic layer was dried down under a stream of nitrogen gas and reconstituted in 1:1 water:methanol and analyzed by LC-MS/MS for prostaglandin levels using the same instrumentation, column, solvents and conditions as described for the in vitro assay above.
General Procedure for In Vivo Mouse Assay:
The following animal protocol was approved by the Vanderbilt University Institutional Animal Care and Use Committee, and all procedures were performed in accordance with national guidelines and regulations. Male C57BL/6 mice were dosed by intraperitoneal (i.p.) injection with 10 mg/kg of compound. For Compound 3a at the designated time points of one hour, two hours, and four hours, mice were euthanized. Separately, mice were dosed with either Compound 3a or Compound 7a i.p. with 10 mg/kg at 0, 8, 24, 32, 48 and 56 hours. Blood was collected from the mice at 72 hours. All blood samples were immediately collected into heparinized syringes by cardiac puncture. The 16 hour time points for Compounds 7a, 3a, and (S)-flurbiprofen were extracted from murine plasma as follows: 200 μL plasma was diluted 5:1 (v.v) with 1% acetic acid (aqueous) then 100 μL acetonitrile and 1.2 mL hexane were added. The plasma samples were mixed well and centrifuged to promote phase separation. The upper, organic layer was removed and dried. The samples were reconstituted in 9:1 isopropyl alcohol:hexane (v:v) immediately prior to analysis on an isocratic system where the mobile phase was 98:2 isopropyl alcohol:hexane with 0.1% acetic acid. Chiral separation occurred on a CHIRALCEL® OD column (25×0.46 cm) and fluorescence detection was employed (λex=248 nm, λem=312 nm). The one, two and four hr timepoints for Compound 3a were extracted from murine plasma as follows: 200 L murine plasma was spiked with flurbiprofen (internal standard) and diluted with 1 mL 1% acetic acid (aqueous) and loaded onto a pre-conditioned OASIS HLB solid phase extraction column. The OASIS HLB cartridge had been conditioned with 3 mL methanol and 2 mL of 1% acetic acid (aq). The loaded cartridge was washed with 3 mL of 1% acetic acid (aq) and 1.5 mL of 1% acetic acid (aq) with 20% methanol. The cartridge was eluted with 2 mL methanol and the eluant was dried. The samples were reconstituted in 100 μL methanol and 50 μL water immediately prior to analysis on a gradient of 30% B to 75% B over 11 min, where A=water and B=1:1 methanol:acetonitrile (v:v), each with 0.1% acetic acid. Separation occurred on a Zorbax C18 column (15×0.21 cm) and fluorescence detection was employed (λex=285 nm, λem=340 nm).
General Procedure for Crystallization, X-Ray Data Collection, Structure Determination and Refinement:
Crystallization was performed as described in Duggan et al., 2011 with modest modification. Purified mCOX-2 (10 mg/mL) was reconstituted with a 2-fold molar excess of Fe3+-protoprophyrin IX. After dialysis against 20 mM sodium phosphate buffer pH 6.7, 100 mM NaCl, 0.01% NaN3, 0.6% (w/v) β-OG, β-OG concentration was adjusted to 1.2% and 10-fold molar excess of Compound 3a was added prior to setup. Crystallization was performed using hanging drop vapor diffusion method by combining 3.5 μL of the protein solution with 3.5 μL 50 mM EPPS pH 8.0, 80-120 mM MgCl2, 20-25% (v/v) PEG MME-550 equilibrating over reservoir solution containing 0.5 mL of 50 mM EPPS pH 8.0, 100-120 mM MgCl2, 20-25% (v/v) PEG MME-550 at 291 K. Crystals were mounted after about 3 weeks growth and transferred to the stabilization solution[50 mM EEPS, 28% (v/v) PEG MME 550, 100 mM MgCl2] for about 10 seconds and flash frozen for crystal transportation.
Data sets were collected on an ADSC Quantum-315 CCD using the synchrotron radiation X-ray source at a wavelength of 0.97929 Å with 100 K liquid nitrogen streaming at beamline 24-ID-E of the Advance Photon Source at the Argonne National Laboratory. Diffraction data were collected and processed with HKL-2000 (Otwinowski et al., 1997). Initial phases were determined by molecular replacement using a search model (PDB 3NT1) with Phaser software. Solution with four molecules in the asymmetric unit was obtained. The models were improved with several rounds of model building in COOT software (Emsley et al., 2010) and CCP4 suite (Patterton et al., 2003). There were no significant structural differences evident among the monomers. Global non-crystallographic symmetry was applied during the refinement. The ligand was built using SMILE and waters were adding from COOT (Emsley et al., 2010). The final model has Rwork and Rfree 0.240 and 0.289, respectively. The potential of phase bias was excluded by simulated annealing using Phenix software (Adams et al., 2010). The values of the Ramachandran plot for the final refinement of the structure were obtained with PROCHECK software (Laskowski et al. 1993). Data collection and refinement statistics are reported in Table 7. The atomic coordinates and structure factor have been deposited in the Protein Data Bank under the access id 4FM5 (see the website of the RCSB PDB on the World Wide Web; www[dot]rcsb[dot]org). The illustrations were prepared using the coordinates of monomer A with Pymol (Schrodinger, LLC).
The values in parentheses are for the highest resolution shell;
where Fo and Fe are the observed and calculated structure factors, Rfree=test set 5.0%.
This crystal structure has been deposited in the Protein Data Bank (PDB: 4FM5).
Materials.
Indomethacin was purchased from Sigma Aldrich Chemical (St. Louis, Mo., United States of America). NS-398, SC-560, JZL-184, PF-3845, URB597, PGE2-d4, AA-d5, 2-AG-d5, and AEA-d5 were purchased from Cayman Chemical (Ann Arbor, Mich., United States of America). Compound A (2-[1-(4-Chloro-benzoyl)-5-methoxy-2-methyl-1H-indol-3-yl]-1-morpholin-4-yl-ethanone) was synthesized as described in Kalgutkar et al., 2000b.
In Vitro Enzyme Purification and Activity Assays.
Wildtype, R120Q, and Y355F COX-2 were expressed in insect cells and purified as described in Rowlinson et al., 1999. In vitro COX-2 inhibition assays were performed as described in Duggan et al., 2011. The RAW 264.7 macrophage inhibition assay was performed as described in Rouzer & Marnett, 2006. MAGL was purified using BL21(DE3) pLysS E. coli transformed with pET-45b(+) plasmid containing human MGL-His.
Cells were grown at 37° C. to a density of 0.7 OD and then protein expression induced with IPTG (1 mM). Cells were harvested 4 hr later and proteins purified using Ni-NTA Agarose (Qiagen) as described in Blankman et al., 2007. After purification, the protein was dialyzed overnight at 4° C. into buffer containing 0 mM HEPES and 0.01% Triton X-100. MAGL inhibition was assessed as described in Blankman et al., 2007. Humanized rat FAAH was a generous gift of R. Stevens and B. Cravatt (The Scripps Research Institute). FAAH inhibition was assessed as described in Ahn et al., 2009. Human DAGLα in pcDNA3.1D was expressed in HEK293T cells for 24 hours then harvested and membranes prepared as described in Pedicord et al., 2011. DAGLα activity was assessed using 5 μg of membrane protein in a 50 μL reaction of assay buffer containing 50 mM MES (pH 6.5) and 2.5 mM CaCl2. 1-steroyl-2-arachidonoyl glycerol (SAG) was added directly from a 100% methanol stock for a final concentration of 250 μM (5% final concentration of methanol in reaction). The reaction was terminated after 15 minutes by the addition of 200 μl methanol containing 125 pmol 2-AG-d8. The samples were spun down at 2000×g and the soluble material injected directly for LC/MS/MS analysis.
Animals.
5-7 week old male ICR mice were used for all experiments with the exception of knockout animals (Harlan, Indianapolis, Ind., United States of America). Mice were housed 5 per age. All behavioral tests were conducted during the light cycle between 0900 and 1700. KO and WT littermate controls for FAAH(−/−) and COX-2(−/−) mice were derived from heterozygote breeding pairs, bred and genotyped as described in Uddin et al., 2011. CB1(−/−) mice were bred from homozygote breeding pairs and genotyped as described in Pan et al., 2008. Mice were group-housed on a 12:12 light-dark cycle (lights on at 06:00), with food and water available ad libitum. All animal studies were approved by the Vanderbilt Institutional Animal Care and Use Committee and conducted in accordance with the Guide for the Care and Use of Laboratory Animals of the United States National Institutes of Health.
Tissue Preparation and Lipid Extraction.
Mice were sacrificed by cervical dislocation and decapitation. The brain, lungs, liver, stomach, small intestines, and kidneys were then rapidly removed and frozen on a metal block in dry ice. The tissue was then placed in a tube and stored at −80° C. until extraction, usually one day after harvesting. For PG and eCB analysis, lipid extraction from tissue was carried out as described in Patel et al., 2009.
Open Field Test.
Animals were tested for open-field activity in a novel environment one hour after i.p. injection of compound as described in Sumislawski et al., 2011. Briefly, one-hour sessions were performed using automated experimental chambers (27.9 27.9 cm; MEDOFA-510; MED Associates, Ga., Vermont, United States of America) under constant illumination within a sound-attenuated room. Analysis of open field activity was performed using Activity Monitor v5.10 (MED Associates).
Light-Dark Box.
Anxiety responses were assessed in a plastic light-dark chamber measuring 20×20 cm. Half of the chamber was opaque with a black Plexiglas insert; the other half remained transparent. Photocells recorded the movement of the mice between compartments. Mice were placed individually into the dark compartment at the beginning of the session. Total time spent in the light and dark compartments, the number of light to dark transitions, and total distance travelled during the 20 minute session were measured.
Elevated Plus-Maze (EPM).
EPM analysis was conducted using ANY-MAZE™ video tracking software as described in Sumislawski et al., 2011.
Rectal Temperature, Catalepsy, and Antinociception.
Mice were treated with either Compound A (10 mg/kg) or (R)-(+)-[2,3-Dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone (WIN-55,212-2; 10 mg/kg), or corresponding vehicle by i.p. injection. Every 15 minutes, the rectal temperature of the mice was taken using a lubricated rectal thermometer for a total of 1 hour post drug injection. To test catalepsy every 15 minutes the hindpaws of the mice were rested on a table and the front paws of the mouse were placed on a metal ring attached to a stand elevated 16 cm above the table. The time for the mouse to place its front paws on the table was recorded. For the hot plate antinociception test, mice were placed on a flat surface that was electrically-heated to 55° C. within an open Plexiglas tube, which was cleaned in between testing each mouse with Vimoba, a chlorine dioxide solution. The latency of the mice to respond upon placement on the hot plate apparatus by shaking, hindpaw licking, jumping, or tucking of the forepaws or hindpaws was recorded.
Novel Object Recognition.
Mice were handled 4 days prior to training for at least 1 min per day. During pre-training, mice were placed in an open Plexiglas rectangular chamber for 10 minutes in order for the mice to become familiar with the testing environment. Twenty-four hours later, the mice were placed into the same rectangular chamber with two identical sample objects, yellow rubber ducks, for 10 minutes in order for the mice to become familiar with the objects. During training, the sample objects were placed in opposite corners in the back of the chamber 5 cm from each wall and secured by weight to the floor of the chamber. Twenty-four hours later, the mice were placed into the chamber again with one sample or familiar object and a novel object, a white leaf statue, for 5 minutes. During testing, the objects were placed in opposite corners in the back of the chamber 5 cm from each wall and secured by weight to the floor of the chamber.
Two hours prior to testing, the mice were treated either with vehicle or Compound A (10 mg/kg), by i.p. injection. To determine exploration time with the sample and novel objects, each mouse was timed when interacting with the sample or novel object when the nose of the mouse was in contact with the object or directed toward the object within a 2 cm distance of the object. The time the mouse spent on top of the objects was not included in the exploration time analyses. In addition, a discrimination ratio (e.g., ratio of a mouse's interaction with a novel object to that mouse's total interaction with both sample and novel objects) was determined. If the discrimination ratio was above 0.5, it was considered that the mouse interacted more with the novel object than with the sample or familiar object.
Mass Spectrometry Analysis.
Analytes were quantified using LC-MS/MS on a Quantum triple-quadrupole mass spectrometer in positive-ion mode using selected reaction monitoring. Detection of eicosanoids was performed as described in Kingsley & Marnett, 2007. For fatty acid analysis the mobile phases used were 80 μM AgOAc with 0.1% (v/v) acetic acid in H2O (solvent A) and 120 μM AgOAc with 0.1% (v/v) acetic acid in MeOH (solvent B). The analytes were eluted using a gradient from 20% A to 99% B over 5 minutes. The transitions used were m/z 300→282 for PEA, m/z 328→310 for SEA, m/z 434→416 for OEA, m/z 456→438 for AEA, m/z 464→446 for AEA-d8, m/z 331→257 for 2-PG, m/z 359→285 for 2-SG, m/z 463→389 for 2-OG, m/z 485→411 for 2-AG, m/z 493→419 for 2-AG-d8, m/z 519→409 for AA, and m/z 527→417 for AA-d8. Peak areas for the analytes were normalized to the appropriate internal standard and then normalized to tissue mass for in vivo samples.
Statistical Analysis.
Statistical analysis was performed using GRAPHPAD PRISM® Version 6.0c. For determining statistical significance between groups a two-tailed t-test, one-way ANOVA, or two-way ANOVA with a Sidak's post-test analysis, or multiple t-tests with Holm-Sidak a correction for multiple comparisons was used throughout. F and P values shown correspond to the value obtained from the test used. Error bars represent S.E.M. throughout. No treatment blinding was conducted. Sample sized were based on previous studies (see Patel et al., 2009). N for each group represents number of mice, i.e., independent biological replicate. Mice were arbitrarily assigned to treatment group in a manner that resulted in approximately equal sample sized per treatment group. Each treatment group was represented at least once per cage of mice.
It has been shown that (R)-flurbiprofen, but not (S)-flurbiprofen, selectively inhibits eCB oxygenation by COX-2 in vitro without affecting AA oxygenation to PGs. This phenomenon was termed “substrate-selective COX-2 inhibition” (SSCI). However, (R)-flurbiprofen isomerizes to (S)-flurbiprofen in vivo (see Knihinicki et al., 1990) which limits its utility to probe the in vivo regulation of eCB signaling by SSCI.
To develop novel in vivo biologically active SSCIs, site-directed mutagenesis of COX-2 active site residues was employed to identify the key molecular interactions required for SSCI. Previous studies had established that mutations of Arg-120 and Tyr-355 of COX-2 drastically reduce the ability of the COX inhibitor indomethacin to inhibit AA oxygenation by eliminating its ability to ion-pair and hydrogen bond with COX-2 (Kalgutkar et al., 2000a). As expected, mutation of these key residues dramatically reduced the ability of indomethacin to inhibit AA oxygenation. However, it was determined that indomethacin still potently inhibited eCB oxygenation by the COX-2 R120Q and Y355F mutants. This indicated that, although ion-pairing and hydrogen-bonding with Arg-120 and Tyr-355 were critical for indomethacin inhibition of AA oxidation to PGs, they were much less important for inhibition of eCB oxygenation.
Whether structural modifications that reduced the ability of indomethacin to ion-pair with Arg-120 and Tyr-355 would lead to SSCI was also tested. A small library of tertiary amide derivatives of indomethacin, which are less polar and thus have reduced ion-pairing and hydrogen bonding capacity, was synthesized and screened. Each of the tertiary amides inhibited eCB oxygenation by COX-2 but did not inhibit AA oxygenation (Table 8).
Compound A (
To assess the ability of Compound A to modulate eCB levels in vivo, Compound A was adminstered to male ICR mice via intraperitoneal (i.p.) injection, and levels of eCBs, PGs, and AA were assayed two hours after administration. It was determined that Compound A significantly increased whole brain AEA levels at 3 mg/kg (p<0.01) and 10 mg/kg (p<0.0001) with a non-significant trend to increase 2-AG levels at the highest dose (
To more reliably quantify the magnitude of the increase in brain eCBs induced by Compound A treatment, a subsequent meta-analysis of data obtained from 12 cohorts of animals was conducted, normalizing eCB levels in each animal to mean eCB levels in the respective vehicle control group. This analysis revealed that, on average, Compound A at 10 mg/kg significantly increased AEA to 139% of vehicle (p<0.0001), and increased 2-AG levels to 109% of vehicle (p<0.01;
COX-2 was then confirmed as the in vivo molecular target mediating the increase in brain eCBs observed after Compound A treatment using COX-2 knockout (ptgs-2(−/−); COX-2(−/−)) mice. Compound A (10 mg/kg) significantly increased AEA (p<0.01) and 2-AG (p<0.05) levels in wild type, but not COX-2(−/−) littermates (
One major limitation of currently available eCB degradation inhibitors is their lack of selectivity for eCBs over related non-eCB lipids. For example, FAAH inhibition increases AEA levels, but also increases levels of a class of N-acylethanolamides (NAEs; oleoylethanolamide (OEA), palmitoylethanolamide (PEA), and stearoylethanolamide (SEA)). Similarly MAGL inhibition increases 2-AG levels, but also a class of related monoacylglycerols (MAGs) including 2-oleoylglycerol (2-OG), 2-palmitoylglycerol (2-PG), and 2-stearoylglycerol (2-SG).
Given the selectivity of COX-2 for AA-containing lipids, whether Compound A would be more selective for the AA containing NAE, AEA, and the AA containing MAG, 2-AG, relative to other non-eCB members of the NAE and MAG lipid classes was examined. Targeted lipid profiling of NAEs and MAGs after Compound A treatment was employed. As expected, Compound A significantly increased brain AEA (p<0.0001;
To further exclude FAAH inhibition as contributing to the AEA elevating effects of Compound A, several additional experiments were conducted. First, it was determined that Compound A caused a significant additional increase in AEA levels (p<0.01) when combined with the FAAH inhibitor PF-3 845, compared to PF-3845 treatment alone (
Second, if Compound A increased AEA via FAAH inhibition, one would expect an increase in NAEs in tissues with very high FAAH expression such as the liver. However, it was determined that Compound A did not affect levels of any NAE in the liver, while PF-3845 caused robust increases in levels of all NAEs in this FAAH rich tissue (
Lastly, it was determined that Compound A increased brain AEA levels in WT and FAAH KO mice to a similar extent (
The selectivity of Compound A for 2-AG over other MAGs as compared to the MAGL inhibitor JZL-184 (40 mg/kg) was also tested. While Compound A (10 mg/kg) significantly increased brain 2-AG levels (p<0.05), it did not affect levels of any other MAG (
Additionally, the selectivity of the regulation of basal brain eCBs by COX-2 over related non-eCB NAEs was also determined. To that end, the effect of Compound A on brain NAEs in WT and COX-2(−/−) mice was examined. It was again found that Compound A significantly increased brain AEA (p<0.001), but no other NAE (
Like other eCB degrading enzymes including FAAH and MAGL, COX-2 is expressed in many tissues. The effects of Compound A on eCB, NAE, MAG, and PG levels in a variety of peripheral tissues was tested. Compound A (10 mg/kg) significantly increased AEA levels in the stomach (p<0.05), small intestine (p<0.05), kidney (p<0.0001), and lung (p<0.001) but not heart (
To confirm that Compound A retained substrate-selective pharmacology outside the CNS, levels of PGs in each tissue after Compound A and indomethacin treatment was tested. As expected, indomethacin robustly decreased PGs in all tissues examined (p<0.0001 for stomach, heart, kidney and lung; p<0.001 for intestine), while Compound A had no effect on PGs levels in any tissue examined (
Since eCB augmentation via FAAH inhibition has been suggested to represent a novel approach to the treatment of mood and anxiety disorders (Kathuria et al., 2003; Piomelli, 2005)), the behavioral effects of Compound A in pre-clinical models of anxiety were tested. FAAH inhibitors had been reported to have anxiolytic activity in the novel open-field arena (Rossi et al., 2010), and in agreement with this, it was determined that the FAAH inhibitor PF-3 845 (10 mg/kg) increased center distance travelled and center time in the open-field arena (
To test the hypothesis that all COX inhibitors that increase brain AEA exert a similar behavioral profile to Compound A, the effect of indomethacin (10 mg/kg), NS-398 (10 mg/kg), and SC-560 (10 mg/kg) were also tested in the open-field arena (Supplemental
To determine if the behavioral effects of Compound A were mediated by substrate-selective inhibition of COX-2, the behavioral effects of Compound A were tested in COX-2(−/−) mice and wild type littermates. While exhibiting a normal anxiolytic-like response in wild type littermates (
Since the anxiolytic effects of FAAH inhibition are mediated via AEA acting on CB1 cannabinoid receptors (Kathuria et al., 2003; Moreira et al., 2008), the role of CB1 receptors in the anxiolytic-like behavioral effects of Compound A in the open field arena was tested. While again exerting anxiolytic actions in vehicle-pretreated mice, Compound A had no significant behavioral effect in mice treated with the CB1 receptor antagonist Rimonabant (5-(4-Chlorophenyl)-1-(2,4-dichloro-phenyl)-4-methyl-N-(piperidin-1-yl)-1H-pyrazole-3-carboxamide) at 3 mg/kg (
To verify that Compound A actually increased eCB levels in CB1(−/−) mice, the eCB levels and PG levels in CB1(−/−) mice after Compound A treatment was analzyed, and it was determined that Compound A increased AEA and 2-AG levels in the brains of the CB1(−/−) mice while again having no effect on PG levels (
To further assess the anxiolytic-like effects of eCB augmentation by Compound A, the effects of Compound A and the FAAH inhibitor PF-3845 in the light-dark box and the elevated plus-maze were analyzed. In the light-dark box test, it was determined that the FAAH inhibitor PF-3845 (10 mg/kg) and Compound A (10 mg/kg) both significantly increased light-zone time (p<0.05 for both drugs) and the number of light-zone entries (p<0.001 PF-3845, and p<0.01 Compound A) without significantly affecting overall locomotor activity, further validating the anxiolytic-like actions of Compound A (
In the elevated plus-maze both PF-3845 (10 mg/kg) and Compound A (10 mg/kg) significantly reduced open arm latency (p<0.01 for PF-3845 and p<0.0001 for Compound A;
Finally, the relative cannabimimetic effects of Compound A was examined in vivo. Exogenous activation of CB1 receptors produces a classical “tetrad” of behavioral effects characterized by hypolocomotion, analgesia, catalepsy, and hypothermia (Fride et al., 2006). The open field data indicated that Compound A did not cause hypolocomotion, and additional studies revealed that Compound A did not cause hypothermia, catalepsy, or antinociception in the hot plate test (
Pharmacological approaches to augment eCB signaling have thus far focused on inhibition of FAAH and MAGL. Both approaches have been validated to robustly augment eCB levels in vivo (Kathuria et al., 2003; Long et al., 2009b), and exert preclinical therapeutic effects in a variety of pathological conditions. However, both approaches increase non-eCB lipids (NAEs for FAAH inhibition and MAGs for MAGL inhibition) that have biological actions at targets other than cannabinoid receptors (O'Sullivan, 2007). Disclosed herein are investigations that demonstrated that COX-2 is a key regulator of eCB levels in vivo, and that substrate-selective inhibition of COX-2 represents a viable alternative approach to augment eCB levels with a high degree of selectivity (
These data validated the in vivo substrate-selectivity of Compound A and provide a novel and effective pharmacological strategy to selectively augment central eCB signaling via COX-2 inhibition. The larger effects of COX-2 inhibition on AEA over 2-AG might be related to the closer proximity between COX-2 and the site of AEA biosynthesis, and might explain its relative lack of overt cannabimimetic effects (Long et al., 2009a). In support of this notion, FAAH, which is the primary metabolic regulator of AEA, is localized to the same postsynaptic cellular compartment as COX-2 (Cristino et al., 2008).
Furthermore, Compound A did not affect levels of non-eCB NAEs or MAGs in the brain or periphery, providing enhanced selectivity over FAAH and MAGL inhibition for eCB augmentation. That Compound A was able to increase AEA in several peripheral tissues tested suggested that COX-2 plays a widespread role in the regulation of AEA signaling. Although the precise mechanisms regulating tissue specificity of Compound A remain to be determined, they likely relate to relative levels of COX-2 and FAAH, and rates of tonic AEA biosynthesis in each tissue.
Consistent with studies demonstrating that elevating AEA levels via FAAH inhibition exerts anxiolytic-like actions in preclinical models (Kathuria, et al., 2003; Patel & Hillard, 2006; Moreira et al., 2008; Rossi et al., 2010), it was also determined that Compound A decreased anxiety-like behaviors using multiple validated assays. These data suggested that SSCIs could represent a viable approach to the treatment of mood and anxiety disorders. Interestingly, COX-2 inhibition has demonstrated clinical antidepressant efficacy as an adjunct to traditional antidepressants (Muller & Schwarz, 2008). The data presented herein raised the intriguing possibility that these effects could be in part due to augmentation of brain eCB signaling.
In addition to having beneficial effects in the brain, the substrate-selectivity of Compound A could potentially be employed to reduce some common side effects mediated by inhibition of PG synthesis by traditional NSAIDs. Gastrointestinal PG production is essential for stimulation of mucosal bicarbonate and mucus secretion as well as increasing mucosal blood flow (Patrignani et al., 2011). As such, traditional NSAIDs are associated with serious gastrointestinal complications. The data presented herein indicated that an exemplary SSCI, Compound A, did not cause overt gastrointestinal hemorrhage as seen with indomethacin.
Furthermore, cardiovascular toxicity problems of COX inhibitors are well-established, and have been suggested to be mediated by inhibition of PG synthesis (Yu et al., 2012). As such, SSCI might be devoid of such toxicity since they do not affect PG levels in the heart or lung.
Disclosed herein are experiments demonstrating that COX-2 is a key regulator of brain eCB signaling in vivo and that substrate-selective inhibition of COX-2 could represent a novel pharmacological approach to the treatment of anxiety disorders. Moreover, given the numerous pathological processes in which dysregulation of eCB signaling has been demonstrated coupled with the high degree of selectivity of SSCIs for eCBs over related lipids, SSCIs represent a novel class of pharmaceutical agents with broad therapeutic potential.
Lumiracoxib and certain derivatives thereof were synthesized and tested for their abilities to inhibit mCOX-2-dependent oxygenation of 2-AG and AA in vitro.
IC50 values were determined by incubating five concentrations of each inhibitor and a solvent control in DMSO with purified murine COX-2 (50 nM) for three minutes, followed by addition of 2-AG or AA (5 mM) at 37° C. for 30 seconds. The structures of the derivatives and the IC50 values determined are summarized in Table 9.
yMean ± standard deviation (n = 6); dash (-) indicates <50% inhibition of 2-AG oxygenation at 10 mM inhibitor. Numbers in parentheses indicate maximum inhibition (when not equal to 100%) at 10 mM inhibitor.
zInhibitor incubated with enzyme for 15 min before addition of 2-AG or AA.
The data presented in Table 9 demonstrated that in some embodiments, substrate-selective inhibition in the diclofenac/lumiracoxib series required at least one halogen in the anilino ring. For those compounds with only a single halogen in the anilino ring in the diclofenac series that were weak substrate-selective inhibitors, potency could be increased by adding a methyl group in the meta position of the phenylacetic acid ring, thereby making them members of the lumiracoxib series.
All references listed in the instant disclosure, including but not limited to all patents, patent applications and publications thereof, scientific journal articles, and database entries (including but not limited to GENBANK® database entries and including all annotations available therein) are incorporated herein by reference in their entireties to the extent that they supplement, explain, provide a background for, and/or teach methodology, techniques, and/or compositions employed herein.
It will be understood that various details of the presently disclosed subject matter may be changed without departing from the scope of the presently disclosed subject matter. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation.
The presently disclosed subject matter claims the benefit of U.S. Provisional Patent Application Ser. No. 61/673,807, filed Jul. 20, 2012; the disclosure of which is incorporated herein by reference in its entirety.
This invention was made with government support under Grant Nos. CA89450, DA02014, DA022873, DA022873, DA031572, ES07028, GM15431, HL109199, HL96967, MH063232, MH090412, MH100096, NS064278, NS078291, R13DA016280, T32-MH065215, 5P41RR015301-10, and 8P41GM103403-10 awarded by the National Institutes of Health of the United States. The Government has certain rights in the invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2013/051523 | 7/22/2013 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61673807 | Jul 2012 | US |
