Patent Application
20090209494
The 90 kDa heat shock protein (Hsp90) is an abundant molecular chaperone involved in the folding and assembly of proteins, many of which are involved in signal transduction pathways (for reviews see Neckers, 2002; Sreedhar et al., 2004a; Wegele et al., 2004 and references therein). So far nearly 50 of these so-called client proteins have been identified and include steroid receptors, non-receptor tyrosine kinases e.g. src family, cyclin-dependent kinases e.g. cdk4 and cdk6, the cystic transmembrane regulator, nitric oxide synthase and others (Donze and Picard, 1999; McLaughlin et al., 2002; Chiosis et al., 2004; Wegele et al., 2004; http://www.picard.ch/downloads/Hsp90 interactors.pdf). Furthermore, Hsp90 plays a key role in stress response and protection of the cell against the effects of mutation (Bagatell and Whitesell, 2004; Chiosis et al., 2004). The function of Hsp90 is complicated and it involves the formation of dynamic multi-enzyme complexes (Bohen, 1998; Liu et al., 1999; Young et al., 2001; Takahashi et al., 2003; Sreedhar et al., 2004; Wegele et al., 2004). Hsp90 is a target for inhibitors (Fang et al., 1998; Liu et al., 1999; Blagosklonny, 2002; Neckers, 2003; Takahashi et al., 2003; Beliakoff and Whitesell, 2004; Wegele et al., 2004) resulting in degradation of client proteins, cell cycle dysregulation/or normalisation and apoptosis. More recently, Hsp90 has been identified as an important extracellular mediator for tumour invasion (Eustace et al., 2004). Hsp90 was identified as a new major therapeutic target for cancer therapy which is mirrored in the intense and detailed research about Hsp90 function (Blagosklonny et al., 1996; Neckers, 2002; Workman and Kaye, 2002; Beliakoff and Whitesell, 2004; Harris et al., 2004; Jez et al., 2003; Lee et al., 2004) and the development of high-throughput screening assays (Carreras et al., 2003; Rowlands et al., 2004). Hsp90 inhibitors include compound classes such as ansamycins, macrolides, purines, pyrazoles, coumarin antibiotics and others (for review see Bagatell and Whitesell, 2004; Chiosis et al., 2004 and references therein).
The benzenoid ansamycins are a broad class of chemical structures characterised by an aliphatic ring of varying length joined either side of an aromatic ring structure. Naturally occurring ansamycins include: macbecin and 18,21-dihydromacbecin (also known as macbecin 1 and macbecin 11 respectively) (1 & 2; Tanida et al., 1980), geldanamycin (3; DeBoer et al., 1970; DeBoer and Dietz, 1976; WO 03/106653 and references therein), and the herbimycin family (4; 5, 6, Omura et al., 1979, Iwai et al., 1980 and Shibata et al, 1986a, WO 03/106653 and references therein).
Ansamycins were originally identified for their antibacterial and antiviral activity, however, recently their potential utility as anticancer agents has become of greater interest (Beliakoff and Whitesell, 2004). Many Hsp90 inhibitors are currently being assessed in clinical trials (Csermely and Soti, 2003; Workman, 2003). In particular, geldanamycin has nanomolar potency and apparent specificity for aberrant protein kinase dependent tumour cells (Chiosis et al., 2003; Workman, 2003).
It has been shown that treatment with Hsp90 inhibitors enhances the induction of tumour cell death by radiation and increased cell killing abilities (e.g. breast cancer, chronic myeloid leukaemia and non-small cell lung cancer) by combination of Hsp90 inhibitors with cytotoxic agents has also been demonstrated (Neckers, 2002; Beliakoff and Whitesell, 2004). The potential for anti-angiogenic activity is also of interest: the Hsp90 client protein HIF-1α plays a key role in the progression of solid tumours (Hur et al., 2002; Workman and Kaye, 2002; Kaur et al., 2004).
Hsp90 inhibitors also function as immunosuppressants and are involved in the complement-induced lysis of several types of tumour cells after Hsp90 inhibition (Sreedhar et al., 2004).
The use of Hsp90 inhibitors as potential anti-malaria drugs has also been discussed (Kumar et al., 2003). Furthermore, it has been shown that geldanamycin interferes with the formation of complex glycosylated mammalian prion protein PrPc (Winklhofer et al., 2003).
As described above, ansamycins are of interest as potential anticancer and anti-B-cell malignancy compounds, however the currently available ansamycins exhibit poor pharmacological or pharmaceutical properties, for example they show poor water solubility, poor metabolic stability, poor bioavailability or poor formulation ability (Goetz et al., 2003; Workman 2003; Chiosis 2004). Both herbimycin A and geldanamycin were identified as poor candidates for clinical trials due to their strong hepatotoxicity (review Workman, 2003) and geldanamycin was withdrawn from Phase I clinical trials due to hepatotoxicity (Supko et al., 1995, WO 03/106653).
Geldanamycin was isolated from culture filtrates of Streptomyces hygroscopicus and shows strong activity in vitro against protozoa and weak activity against bacteria and fungi. In 1994 the association of geldanamycin with Hsp90 was shown (Whitesell et al., 1994). The biosynthetic gene cluster for geldanamycin was cloned and sequenced (Allen and Ritchie, 1994; Rascher et al., 2003; WO 03/106653). The DNA sequence is available under the NCBI accession number AY179507. The isolation of genetically engineered geldanamycin producer strains derived from S. hygroscopicus subsp. duamyceticus JCM4427 and the isolation of 4,5-dihydro-7-O-descarbamoyl-7-hydroxygeldanamycin and 4,5-dihydro-7-O-descarbamoyl-7-hydroxy-17-O-demethylgeldanamycin were described recently (Hong et al., 2004). By feeding geldanamycin to the herbimycin producing strain Streptomyces hygroscopicus AM-3672 the compounds 15-hydroxygeldanamycin, the tricyclic geldanamycin analogue KOSN-1633 and methyl-geldanamycinate were isolated (Hu et al., 2004). The two compounds 17-formyl-17-demethoxy-18-O-21-O-dihydrogeldanamycin and 17-hydroxymethyl-17-demethoxygeldanamycin were isolated from S. hygroscopicus K279-78. S. hygroscopicus K279-78 is S. hygroscopicus NRRL 3602 containing cosmid pKOS279-78 which has a 44 kbp insert which contains various genes from the herbimycin producing strain Streptomyces hygroscopicus AM-3672 (Hu et al., 2004). Substitutions of acyltransferase (AT) domains have been made in four of the modules of the polyketide synthase of the geldanamycin biosynthetic cluster (Patel et al., 2004). AT substitutions were carried out in modules 1, 4 and 5 leading to the fully processed analogues 14-desmethyl-geldanamycin, 8-desmethyl-geldanamycin and 6-desmethoxy-geldanamycin and the not fully processed 4,5-dihydro-6-desmethoxy-geldanamycin. Substitution of the module 7 AT led to production of three 2-desmethyl compounds, KOSN1619, KOSN1558 and KOSN1559, one of which (KOSN1559), a 2-demethyl-4,5-dihydro-17-demethoxy-21-deoxy derivative of geldanamycin, binds to Hsp90 with a 4-fold greater binding affinity than geldanamycin and an 8-fold greater binding affinity than 17-AAG. However this is not reflected in an improvement in the IC50 measurement using SKBr3. Another analogue, a novel nonbenzoquinoid geldanamycin, designated KOS-1806 has a monophenolic structure (Rascher et al., 2005). No activity data was given for KOS-1806.
In 1979 the ansamycin antibiotic herbimycin A was isolated from the fermentation broth of Streptomyces hygroscopicus strain No. AM-3672 and named according to its potent herbicidal activity. The antitumour activity was established by using cells of a rat kidney line infected with a temperature sensitive mutant of Rous sarcoma virus (RSV) for screening for drugs that reverted the transformed morphology of the these cells (for review see Uehara, 2003). Herbimycin A was postulated as acting primarily through the binding to Hsp90 chaperone proteins but the direct binding to the conserved cysteine residues and subsequent inactivation of kinases was also discussed (Uehara, 2003).
Chemical derivatives have been isolated and compounds with altered substituents at C19 of the benzoquinone nucleus and halogenated compounds in the ansa chain showed less toxicity and higher antitumour activities than herbimycin A (Omura et al., 1984; Shibata et al., 1986b). The sequence of the herbimycin biosynthetic gene cluster was identified in WO 03/106653 and in a recent paper (Rascher et al., 2005).
The ansamycin compounds macbecin (1) and 18,21-dihydromacbecin (2) (C-14919E-1 and C-14919E-1), identified by their antifungal and antiprotozoal activity, were isolated from the culture supernatants of Nocardia sp No. C-14919 (Actinosynnema pretiosum subsp pretiosum ATCC 31280) (Tanida et al., 1980; Muroi et al., 1980; Muroi et al., 1981; U.S. Pat. No. 4,315,989 and U.S. Pat. No. 4,187,292). 18,21-Dihydromacbecin is characterized by containing the dihydroquinone form of the aromatic nucleus. Both macbecin and 18,21-dihydromacbecin were shown to possess similar antibacterial and antitumour activities against cancer cell lines such as the murine leukaemia P388 cell line (Ono et al., 1982). Reverse transcriptase and terminal deoxynucleotidyl transferase activities were not inhibited by macbecin (Ono et al., 1982). The Hsp90 inhibitory function of macbecin has been reported in the literature (Bohen, 1998; Liu et al., 1999). The conversion of macbecin and 18,21-dihydromacbecin after adding to a microbial culture broth into a compound with a hydroxy group instead of a methoxy group at a certain position or positions is described in U.S. Pat. No. 4,421,687 and U.S. Pat. No. 4,512,975.
During a screen of a large variety of soil microorganisms, the compounds TAN-420A to E were identified from producer strains belonging to the genus Streptomyces (7-11, EP 0 110 710).
In 2000, the isolation of the geldanamycin related, non-benzoquinone ansamycin metabolite reblastin from cell cultures of Streptomyces sp. S6699 and its potential therapeutic value in the treatment of rheumatoid arthritis was described (Stead et al., 2000).
A further Hsp90 inhibitor, distinct from the chemically unrelated benzoquinone ansamycins is Radicicol (monorden) which was originally discovered for its antifungal activity from the fungus Monosporium bonorden (for review see Uehara, 2003) and the structure was found to be identical to the 14-membered macrolide isolated from Nectria radicicola. In addition to its antifungal, antibacterial, anti-protozoan and cytotoxic activity it was subsequently identified as an inhibitor of Hsp90 chaperone proteins (for review see Uehara, 2003; Schulte et al., 1999). The anti-angiogenic activity of radicicol (Hur et al., 2002) and semi-synthetic derivates thereof (Kurebayashi et al., 2001) has also been described.
Recent interest has focussed on 17-amino derivatives of geldanamycin as a new generation of ansamycin anticancer compounds (Bagatell and Whitesell, 2004), for example 17-(allylamino)-17-desmethoxy geldanamycin (17-AAG, 12) (Hostein et al., 2001; Neckers, 2002; Nimmanapalli et al., 2003; Vasilevskaya et al., 2003; Smith-Jones et al., 2004) and 17-desmethoxy-17-N,N-dimethylaminoethylamino-geldanamycin (17-DMAG, 13) (Egorin et al., 2002; Jez et al., 2003). More recently geldanamycin was derivatised on the 17-position to create 17-geldanmycin amides, carbamates, ureas and 17-arylgeldanamycin (Le Brazidec et al., 2003). A library of over sixty 17-alkylamino-17-demethoxygeldanamycin analogues has been reported and tested for their affinity for Hsp90 and water solubility (Tian et al., 2004). A further approach to reduce the toxicity of geldanamycin is the selective targeting and delivering of an active geldanamycin compound into malignant cells by conjugation to a tumour-targeting monoclonal antibody (Mandler et al., 2000).
Whilst many of these derivatives exhibit reduced hepatotoxicity they still have only limited water solubility. For example 17-AAG requires the use of a solubilising carrier (e.g. Cremophore®, DMSO-egg lecithin), which itself may result in side-effects in some patients (Hu et al., 2004).
Most of ansamycin class of Hsp90 inhibitors bear the common structural moiety: the benzoquinone which is a Michael acceptor that can readily form covalent bonds with nucleophiles such as proteins, glutathione, etc. The benzoquinone moiety also undergoes redox equilibrium with dihydroquinone, during which oxygen radicals are formed, which give rise to further unspecific toxicity (Dikalov et al., 2002). For example treatment with geldanamycin can result in induced superoxide production (Sreedhar et al., 2004a).
Therefore, there remains a need to identify novel ansamycin derivatives devoid of the benzoquinone moiety, which may have utility in the treatment of cancer and/or B-cell malignancies, preferably such ansamycins have improved water solubility, an improved pharmacological profile and reduced side-effect profile for administration. The present invention discloses novel ansamycin analogues generated by genetic engineering of the parent producer strain. In particular the present invention discloses 21-deoxymacbecin analogues, which generally have improved pharmaceutical properties compared with the presently available ansamycins; in particular they show improvements in respect of one or more of the following properties: toxicity, conjugation with nucleophiles such as glutathione, water solubility, metabolic stability, bioavailability and formulation ability. Preferably the 21-deoxymacbecin analogues show improved toxicity and/or water solubility.
The inventors of the present invention have made significant effort to clone and elucidate the gene cluster that is responsible for the biosynthesis of macbecin. With this insight, the gene that is responsible for the production of the benzoquinone moiety has been specifically targetted, e.g. by integration into mbcM, targeted deletion of a region of the macbecin cluster including all or part of the mbcM gene optionally followed by insertion of gene(s), or other methods of rendering MbcM non-functional e.g. chemical inhibition, site-directed mutagenesis or mutagenesis of the cell for example by UV, in order to produce novel derivatives devoid of a benzoquinone moiety. Optionally targeted inactivation or deletion of further genes responsible for the post-PKS modifications of macbecin may be carried out. Additionally, some of these genes, but not mbcM may be re-introduced into the cell. The optional targeting of the post-PKS genes may occur via a variety of mechanisms, e.g. by integration, targeted deletion of a region of the macbecin cluster including all or some of the post-PKS genes optionally followed by insertion of gene(s) or other methods of rendering the post-PKS genes or their encoded enzymes non-functional e.g. chemical inhibition, site-directed mutagenesis or mutagenesis of the cell for example by the use of UV radiation. As a result, the present invention provides 21-deoxymacbecin analogues, methods for the preparation of these compounds, and methods for the use of these compounds in medicine or as intermediates in the production of further compounds.
Therefore, in a first aspect the present invention provides analogues of macbecin which are lacking the oxygen atom usually present at the C21 position, in macbecin this oxygen atom is present as a keto group, in 18,21-dihydromacbecin this oxygen atom is present as a hydroxyl group.
In a more specific aspect the present invention provides 21-deoxymacbecin analogues according to the formula (I) below, or a pharmaceutically acceptable salt thereof:
wherein:
R1 represents H, OH or OCH3
R2 represents H or CH3
R3 and R4 either both represent H or together they represent a bond (i.e. C4 to C5 is a double bond)
R5 represents H or —C(O)—NH2
21-deoxymacbecin analogues are also referred to herein as “compounds of the invention” such terms are used interchangeably herein.
The above structure shows a representative tautomer and the invention embraces all tautomers of the compounds of formula (I) for example keto compounds where enol compounds are illustrated and vice versa.
The invention embraces all stereoisomers of the compounds defined by structure (I) as shown above.
In a further aspect, the present invention provides 21-deoxymacbecin analogues such as compounds of formula (I) or a pharmaceutically acceptable salt thereof, for use as a pharmaceutical.
The articles “a” and “an” are used herein to refer to one or to more than one (i.e. at least one) of the grammatical objects of the article. By way of example “an analogue” means one analogue or more than one analogue.
As used herein the term “analogue(s)” refers to chemical compounds that are structurally similar to another but which differ slightly in composition (as in the replacement of one atom by another or in the presence or absence of a particular functional group).
As used herein, the term “homologue(s)” refers to a homologue of a gene or of a protein encoded by a gene disclosed herein from either an alternative macbecin biosynthetic cluster from a different macbecin producing strain or a homologue from an alternative ansamycin biosynthetic gene cluster e.g. from geldanamycin, herbimycin or reblastatin. Such homologue(s) encode a protein that performs the same function or can itself perform the same function as said gene or protein in the synthesis of macbecin or a related ansamycin polyketide. Preferably, such homologue(s) have at least 40% sequence identity, preferably at least 60%, at least 70%, at least 80%, at least 90% or at least 95% sequence identity to the sequence of the particular gene disclosed herein (Table 3, SEQ ID NO: 17 which is a sequence of all the genes in the cluster, from which the sequences of particular genes may be deduced). Percentage identity may be calculated using any program known to a person of skill in the art such as BLASTn or BLASTp, available on the NCBI website.
As used herein, the term “cancer” refers to a benign or malignant new growth of cells in skin or in body organs, for example but without limitation, breast, prostate, lung, kidney, pancreas, brain, stomach or bowel. A cancer tends to infiltrate into adjacent tissue and spread (metastasise) to distant organs, for example to bone, liver, lung or the brain. As used herein the term cancer includes both metastatic tumour cell types, such as but not limited to, melanoma, lymphoma, leukaemia, fibrosarcoma, rhabdomyosarcoma, and mastocytoma and types of tissue carcinoma, such as but not limited to, colorectal cancer, prostate cancer, small cell lung cancer and non-small cell lung cancer, breast cancer, pancreatic cancer, bladder cancer, renal cancer, gastric cancer, gliobastoma, primary liver cancer and ovarian cancer.
As used herein the term “B-cell malignancies” includes a group of disorders that include chronic lymphocytic leukaemia (CLL), multiple myeloma, and non-Hodgkin's lymphoma (NHL). They are neoplastic diseases of the blood and blood forming organs. They cause bone marrow and immune system dysfunction, which renders the host highly susceptible to infection and bleeding.
As used herein, the term “bioavailability” refers to the degree to which or rate at which a drug or other substance is absorbed or becomes available at the site of biological activity after administration. This property is dependent upon a number of factors including the solubility of the compound, rate of absorption in the gut, the extent of protein binding and metabolism etc. Various tests for bioavailability that would be familiar to a person of skill in the art are described herein (see also Egorin et al. (2002)).
The term “water solubility” as used in this application refers to solubility in aqueous media, e.g. phosphate buffered saline (PBS) at pH 7.3. A test for water solubility is given below in the Examples as “water solubility assay”.
As used herein the term “post-PKS genes(s)” refers to the genes required for post-polyketide synthase modifications of the polyketide, for example but without limitation monooxygenases, O-methyltransferases and carbamoyltransferases. Specifically, in the macbecin system these modifying genes include mbcM, mbcN, mbcP, mbcMT1, mbcMT2 and mbcP450.
The pharmaceutically acceptable salts of compounds of the invention such as the compounds of formula (I) include conventional salts formed from pharmaceutically acceptable inorganic or organic acids or bases as well as quaternary ammonium acid addition salts. More specific examples of suitable acid salts include hydrochloric, hydrobromic, sulfuric, phosphoric, nitric, perchloric, fumaric, acetic, propionic, succinic, glycolic, formic, lactic, maleic, tartaric, citric, palmoic, malonic, hydroxymaleic, phenylacetic, glutamic, benzoic, salicylic, fumaric, toluenesulfonic, methanesulfonic, naphthalene-2-sulfonic, benzenesulfonic hydroxynaphthoic, hydroiodic, malic, steroic, tannic and the like. Other acids such as oxalic, while not in themselves pharmaceutically acceptable, may be useful in the preparation of salts useful as intermediates in obtaining the compounds of the invention and their pharmaceutically acceptable salts. More specific examples of suitable basic salts include sodium, lithium, potassium, magnesium, aluminium, calcium, zinc, N,N′-dibenzylethylenediamine, chloroprocaine, choline, diethanolamine, ethylenediamine, N-methylglucamine and procaine salts. References hereinafter to a compound according to the invention include both compounds of formula (I) and their pharmaceutically acceptable salts.
As used herein the terms “18,21-dihydromacbecin” and “macbecin II” (the dihydroquinone form of macbecin) are used interchangeably.
The present invention provides 21-deoxymacbecin analogues, as set out above, methods for the preparation of these compounds, methods for the use of these compounds in medicine and the use of these compounds as intermediates or templates for further semi-synthetic derivatisation or derivatisation by biotransformation methods.
Preferably R1 represents H or OH. In one embodiment of the invention R1 represents H.
In another embodiment of the invention R1 represents OH.
Preferably R2 represents H
Preferably R3 and R4 both represent H
Preferably R5 represents —C(O)—NH2
In one preferred embodiment of the invention R1 represents H, R2 represents H, R3 and
R4 both represent H and R5 represents —C(O)—NH2
In another preferred embodiment of the invention R1 represents OH, R2 represents H, R3 and R4 both represent H and R5 represents —C(O)—NH2.
The preferred stereochemistry of the non-hydrogen sidechains to the ansa ring is as shown in structure (15) below and in
The present invention also provides a pharmaceutical composition comprising a 21-deoxymacbecin analogue, or a pharmaceutically acceptable salt thereof, together with a pharmaceutically acceptable carrier.
The present invention also provides for the use of a 21-deoxymacbecin analogue as a substrate for further modification either by biotransformation or by synthetic chemistry.
Some existing ansamycin Hsp90 inhibitors that are in or have been in clinical trials, such as geldanamycin and 17-AAG, have poor pharmacological profiles, poor water solubility and poor bioavailability. The present invention provides novel 21-deoxymacbecin analogues which have improved properties such as water solubility. A person of skill in the art will be able to readily determine the water solubility of a given compound of the invention using standard methods. A representative method is shown in the examples herein.
In one aspect the present invention provides for the use of a 21-deoxymacbecin analogue in the manufacture of a medicament. In a further embodiment the present invention provides for the use of a 21-deoxymacbecin analogue in the manufacture of a medicament for the treatment of cancer and/or B-cell malignancies. In a further embodiment the present invention provides for the use of a 21-deoxymacbecin analogue in the manufacture of a medicament for the treatment of malaria, fungal infection, diseases of the central nervous system, diseases dependent on angiogenesis, autoimmune diseases and/or as a prophylactic pretreatment for cancer.
In another aspect the present invention provides for the use of a 21-deoxymacbecin analogue in medicine. In a further embodiment the present invention provides for the use of a 21-deoxymacbecin analogue in the treatment of cancer and/or B-cell malignancies. In a further embodiment the present invention provides for the use of a 21-deoxymacbecin analogue in the manufacture of a medicament for the treatment of malaria, fungal infection, diseases of the central nervous system and neurodegenerative diseases, diseases dependent on angiogenesis, autoimmune diseases and/or as a prophylactic pretreatment for cancer.
In a further embodiment the present invention provides a method of treatment of cancer and/or B-cell malignancies, said method comprising administering to a patient in need thereof a therapeutically effective amount of a 21-deoxymacbecin analogue. In a further embodiment the present invention provides a method of treatment of malaria, fungal infection, diseases of the central nervous system and neurodegenerative diseases, diseases dependent on angiogenesis, autoimmune diseases and/or a prophylactic pretreatment for cancer, said method comprising administering to a patient in need thereof a therapeutically effective amount of a 21-deoxymacbecin analogue.
As noted above, compounds of the invention may be expected to be useful in the treatment of cancer and/or B-cell malignancies. Compounds of the invention and especially those which may have good selectivity for Hsp90 and/or a good toxicology profile and/or good pharmacokinetics may also be effective in the treatment of other indications for example, but not limited to malaria, fungal infection, diseases of the central nervous system and neurodegenerative diseases, diseases dependent on angiogenesis, autoimmune diseases such as rheumatoid arthritis or as a prophylactic pretreatment for cancer.
Diseases of the central nervous system and neurodegenerative diseases include, but are not limited to, Alzheimer's disease, Parkinson's disease, Huntington's disease, prion diseases, spinal and bulbar muscular atrophy (SBMA) and amyotrophic lateral sclerosis (ALS).
Diseases dependent on angiogenesis include, but are not limited to, age-related macular degeneration, diabetic retinopathy and various other ophthalmic disorders, atherosclerosis and rheumatoid arthritis.
Autoimmune diseases include, but are not limited to, rheumatoid arthritis, multiple sclerosis, type I diabetes, systemic lupus erythematosus and psoriasis.
“Patient” embraces human and other animal (especially mammalian) subjects, preferably human subjects. Accordingly the methods and uses of the 21-deoxymacbecin analogues of the invention are of use in human and veterinary medicine, preferably human medicine.
The aforementioned compounds of the invention or a formulation thereof may be administered by any conventional method for example but without limitation they may be administered parenterally (including intravenous administration), orally, topically (including buccal, sublingual or transdermal), via a medical device (e.g. a stent), by inhalation, or via injection (subcutaneous or intramuscular). The treatment may consist of a single dose or a plurality of doses over a period of time.
Whilst it is possible for a compound of the invention to be administered alone, it is preferable to present it as a pharmaceutical formulation, together with one or more acceptable carriers. Thus there is provided a pharmaceutical composition comprising a compound of the invention together with one or more pharmaceutically acceptable diluents or carriers. The diluents(s) or carrier(s) must be “acceptable” in the sense of being compatible with the compound of the invention and not deleterious to the recipients thereof. Examples of suitable carriers are described in more detail below.
The compounds of the invention may be administered alone or in combination with other therapeutic agents. Co-administration of two (or more) agents may allow for significantly lower doses of each to be used, thereby reducing the side effects seen. It might also allow resensitisation of a disease, such as cancer, to the effects of a prior therapy to which the disease has become resistant. There is also provided a pharmaceutical composition comprising a compound of the invention and a further therapeutic agent together with one or more pharmaceutically acceptable diluents or carriers.
In a further aspect, the present invention provides for the use of a compound of the invention in combination therapy with a second agent eg a second agent for the treatment of cancer or B-cell malignancies such as a cytotoxic or cytostatic agent.
In one embodiment, a compound of the invention is co-administered with another therapeutic agent eg a therapeutic agent such as a cytotoxic or cytostatic agent for the treatment of cancer or B-cell malignancies. Exemplary further agents include cytotoxic agents such as alkylating agents and mitotic inhibitors (including topoisomerase II inhibitors and tubulin inhibitors). Other exemplary further agents include DNA binders, antimetabolites and cytostatic agents such as protein kinase inhibitors and tyrosine kinase receptor blockers. Suitable agents include, but are not limited to, methotrexate, leukovorin, prednisone, bleomycin, cyclophosphamide, 5-fluorouracil, paclitaxel, docetaxel, vincristine, vinblastine, vinorelbine, doxorubicin (adriamycin), tamoxifen, toremifene, megestrol acetate, anastrozole, goserelin, anti-HER2 monoclonal antibody (e.g. trastuzumab, trade name Herceptin™), capecitabine, raloxifene hydrochloride, EGFR inhibitors (e.g. gefitinib, trade name Iressa®, erlotinib, trade name Tarceva™, cetuximab, trade name Erbitux™), VEGF inhibitors (e.g. bevacizumab, trade name Avastin™), proteasome inhibitors (e.g. bortezomib, trade name Velcade™) or imatinib, trade name Glivec®. Further suitable agents include, but are not limited to, conventional chemotherapeutics such as cisplatin, cytarabine, cyclohexylchloroethylnitrosurea, gemcitabine, Ifosfamid, leucovorin, mitomycin, mitoxantone, oxaliplatin, taxanes including taxol and vindesine; hormonal therapies; monoclonal antibody therapies; protein kinase inhibitors such as dasatinib, lapatinib; histone deacetylase (HDAC) inhibitors such as vorinostat; angiogenesis inhibitors such as sunitinib, sorafenib, lenalidomide; and mTOR inhibitors such as temsirolimus. Additionally, a compound of the invention may be administered in combination with other therapies including, but not limited to, radiotherapy or surgery.
The formulations may conveniently be presented in unit dosage form and may be prepared by any of the methods well known in the art of pharmacy. Such methods include the step of bringing into association the active ingredient (compound of the invention) with the carrier which constitutes one or more accessory ingredients. In general the formulations are prepared by uniformly and intimately bringing into association the active ingredient with liquid carriers or finely divided solid carriers or both, and then, if necessary, shaping the product.
The compounds of the invention will normally be administered orally or by any parenteral route, in the form of a pharmaceutical formulation comprising the active ingredient, optionally in the form of a non-toxic organic, or inorganic, acid, or base, addition salt, in a pharmaceutically acceptable dosage form. Depending upon the disorder and patient to be treated, as well as the route of administration, the compositions may be administered at varying doses.
For example, the compounds of the invention can be administered orally, buccally or sublingually in the form of tablets, capsules, ovules, elixirs, solutions or suspensions, which may contain flavouring or colouring agents, for immediate-, delayed- or controlled-release applications.
Such tablets may contain excipients such as microcrystalline cellulose, lactose, sodium citrate, calcium carbonate, dibasic calcium phosphate and glycine, disintegrants such as starch (preferably corn, potato or tapioca starch), sodium starch glycollate, croscarmellose sodium and certain complex silicates, and granulation binders such as polyvinylpyrrolidone, hydroxypropylmethylcellulose (HPMC), hydroxy-propylcellulose (HPC), sucrose, gelatin and acacia. Additionally, lubricating agents such as magnesium stearate, stearic acid, glyceryl behenate and talc may be included.
Solid compositions of a similar type may also be employed as fillers in gelatin capsules. Preferred excipients in this regard include lactose, starch, a cellulose, milk sugar or high molecular weight polyethylene glycols. For aqueous suspensions and/or elixirs, the compounds of the invention may be combined with various sweetening or flavouring agents, colouring matter or dyes, with emulsifying and/or suspending agents and with diluents such as water, ethanol, propylene glycol and glycerin, and combinations thereof.
A tablet may be made by compression or moulding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine the active ingredient in a free-flowing form such as a powder or granules, optionally mixed with a binder (e.g. povidone, gelatin, hydroxypropylmethyl cellulose), lubricant, inert diluent, preservative, disintegrant (e.g. sodium starch glycolate, cross-linked povidone, cross-linked sodium carboxymethyl cellulose), surface-active or dispersing agent. Moulded tablets may be made by moulding in a suitable machine a mixture of the powdered compound moistened with an inert liquid diluent. The tablets may optionally be coated or scored and may be formulated so as to provide slow or controlled release of the active ingredient therein using, for example, hydroxypropylmethylcellulose in varying proportions to provide desired release profile.
Formulations in accordance with the present invention suitable for oral administration may be presented as discrete units such as capsules, cachets or tablets, each containing a predetermined amount of the active ingredient; as a powder or granules; as a solution or a suspension in an aqueous liquid or a non-aqueous liquid; or as an oil-in-water liquid emulsion or a water-in-oil liquid emulsion. The active ingredient may also be presented as a bolus, electuary or paste.
Formulations suitable for topical administration in the mouth include lozenges comprising the active ingredient in a flavoured basis, usually sucrose and acacia or tragacanth; pastilles comprising the active ingredient in an inert basis such as gelatin and glycerin, or sucrose and acacia; and mouth-washes comprising the active ingredient in a suitable liquid carrier.
It should be understood that in addition to the ingredients particularly mentioned above the formulations of this invention may include other agents conventional in the art having regard to the type of formulation in question, for example those suitable for oral administration may include flavouring agents.
Pharmaceutical compositions adapted for topical administration may be formulated as ointments, creams, suspensions, lotions, powders, solutions, pastes, gels, impregnated dressings, sprays, aerosols or oils, transdermal devices, dusting powders, and the like. These compositions may be prepared via conventional methods containing the active agent. Thus, they may also comprise compatible conventional carriers and additives, such as preservatives, solvents to assist drug penetration, emollient in creams or ointments and ethanol or oleyl alcohol for lotions. Such carriers may be present as from about 1% up to about 98% of the composition. More usually they will form up to about 80% of the composition. As an illustration only, a cream or ointment is prepared by mixing sufficient quantities of hydrophilic material and water, containing from about 5-10% by weight of the compound, in sufficient quantities to produce a cream or ointment having the desired consistency.
Pharmaceutical compositions adapted for transdermal administration may be presented as discrete patches intended to remain in intimate contact with the epidermis of the recipient for a prolonged period of time. For example, the active agent may be delivered from the patch by iontophoresis.
For applications to external tissues, for example the mouth and skin, the compositions are preferably applied as a topical ointment or cream. When formulated in an ointment, the active agent may be employed with either a paraffinic or a water-miscible ointment base.
Alternatively, the active agent may be formulated in a cream with an oil-in-water cream base or a water-in-oil base.
For parenteral administration, fluid unit dosage forms are prepared utilizing the active ingredient and a sterile vehicle, for example but without limitation water, alcohols, polyols, glycerine and vegetable oils, water being preferred. The active ingredient, depending on the vehicle and concentration used, can be either suspended or dissolved in the vehicle. In preparing solutions the active ingredient can be dissolved in water for injection and filter sterilised before filling into a suitable vial or ampoule and sealing.
Advantageously, agents such as local anaesthetics, preservatives and buffering agents can be dissolved in the vehicle. To enhance the stability, the composition can be frozen after filling into the vial and the water removed under vacuum. The dry lyophilized powder is then sealed in the vial and an accompanying vial of water for injection may be supplied to reconstitute the liquid prior to use.
Parenteral suspensions are prepared in substantially the same manner as solutions, except that the active ingredient is suspended in the vehicle instead of being dissolved and sterilization cannot be accomplished by filtration. The active ingredient can be sterilised by exposure to ethylene oxide before suspending in the sterile vehicle. Advantageously, a surfactant or wetting agent is included in the composition to facilitate uniform distribution of the active ingredient.
The compounds of the invention may also be administered using medical devices known in the art. For example, in one embodiment, a pharmaceutical composition of the invention can be administered with a needleless hypodermic injection device, such as the devices disclosed in U.S. Pat. No. 5,399,163; U.S. Pat. No. 5,383,851; U.S. Pat. No. 5,312,335; U.S. Pat. No. 5,064,413; U.S. Pat. No. 4,941,880; U.S. Pat. No. 4,790,824; or U.S. Pat. No. 4,596,556. Examples of well-known implants and modules useful in the present invention include: U.S. Pat. No. 4,487,603, which discloses an implantable micro-infusion pump for dispensing medication at a controlled rate; U.S. Pat. No. 4,486,194, which discloses a therapeutic device for administering medicaments through the skin; U.S. Pat. No. 4,447,233, which discloses a medication infusion pump for delivering medication at a precise infusion rate; U.S. Pat. No. 4,447,224, which discloses a variable flow implantable infusion apparatus for continuous drug delivery; U.S. Pat. No. 4,439,196, which discloses an osmotic drug delivery system having multi-chamber compartments; and U.S. Pat. No. 4,475,196, which discloses an osmotic drug delivery system. Many other such implants, delivery systems, and modules are known to those skilled in the art.
The dosage to be administered of a compound of the invention will vary according to the particular compound, the disease involved, the subject, and the nature and severity of the disease and the physical condition of the subject, and the selected route of administration. The appropriate dosage can be readily determined by a person skilled in the art.
The compositions may contain from 0.1% by weight, preferably from 5-60%, more preferably from 10-30% by weight, of a compound of invention, depending on the method of administration.
It will be recognized by one of skill in the art that the optimal quantity and spacing of individual dosages of a compound of the invention will be determined by the nature and extent of the condition being treated, the form, route and site of administration, and the age and condition of the particular subject being treated, and that a physician will ultimately determine appropriate dosages to be used. This dosage may be repeated as often as appropriate. If side effects develop the amount and/or frequency of the dosage can be altered or reduced, in accordance with normal clinical practice.
In a further aspect the present invention provides methods for the production of 21-deoxymacbecin analogues.
Macbecin can be considered to be biosynthesised in two stages. In the first stage the core-PKS genes assemble the macrolide core by the repeated assembly of 2-carbon units which are then cyclised to form the first enzyme-free intermediate “pre-macbecin”, see
This biosynthetic production may be exploited by genetic engineering of suitable producer strains to result in the production of novel compounds. In particular, the present invention provides a method of producing 21-deoxymacbecin analogues said method comprising:
a) providing a first host strain that produces macbecin or an analogue thereof when cultured under appropriate conditions
b) deleting or inactivating one or more post-PKS genes, wherein at least one of those post-PKS genes is mbcM, or a homologue thereof
c) culturing said modified host strain under suitable conditions for the production of 21-deoxymacbecin analogues; and
d) optionally isolating the compounds produced.
In step (a) by “macbecin or an analogue thereof” is meant macbecin or those analogues of macbecin that are embraced by the definitions of R1-R5.
In step (b), deleting or inactivating one or more post-PKS genes, wherein at least one of those post-PKS genes is mbcM, or a homologue thereof will suitably be done selectively.
In a further embodiment, step b) comprises inactivating mbcM (or a homologue thereof) by integration of DNA into the mbcM gene (or a homologue thereof) such that functional mbcM protein is not produced. In an alternative embodiment, step b) comprises making a targeted deletion of the mbcM gene, or a homologue thereof. In a further embodiment mbcM, or a homologue thereof, is inactivated by site-directed mutagenesis. In a further embodiment the host strain of step a) is subjected to mutagenesis and a modified strain is selected in which one or more of the post-PKS enzymes is not functional, wherein at least one of these is MbcM. The present invention also encompasses mutations of the regulators controlling the expression of mbcM, or a homologue thereof, a person of skill in the art will appreciate that deletion or inactivation of a regulator may have the same outcome as deletion or inactivation of the gene.
In a particular embodiment of the present invention, a method of selectively deleting or inactivating a post PKS gene comprises:
(i) designing degenerate oligos based on homologue(s) of the gene of interest (e.g. from the geldanamycin PKS biosynthetic cluster and/or from the rifamycin biosynthetic cluster) and isolating the internal fragment of the gene of interest (e.g. mbcM) from a suitable macbecin producing strain, by using these primers in a PCR reaction;
(ii) integrating a plasmid containing this fragment into either the same, or a different macbecin producing strain followed by homologous recombination, which results in the disruption of the targeted gene (e.g. mbcM or a homologue thereof),
(iii) culturing the strain thus produced under conditions suitable for the production of the macbecin analogues, i.e. 21-deoxymacbecin analogues.
In a specific embodiment, the macbecin-producing strain in step (i) is Actinosynnema mirum (A. mirum). In a further specific embodiment the macbecin-producing strain in step (ii) is A. pretiosum
A person of skill in the art will appreciate that an equivalent strain may be achieved using alternative methods to that described above, e.g.:
In further aspects of the invention, additional post-PKS genes may also be deleted or inactivated in addition to mbcM.
In further aspects of the invention, an engineered strain in which one or more post-PKS genes including mbcM have been deleted or inactivated as above, has re-introduced into it one or more of the same post PKS genes not including mbcM, or homologues thereof, e.g. from an alternative macbecin producing strain, or even from the same strain.
Thus according to a further aspect of the invention there is provided a method for the production of a 21-deoxymacbecin analogue, said method comprising:
a) providing a first host strain that produces macbecin when cultured under appropriate conditions
b) deleting or inactivating one or more post-PKS genes, wherein at least one of the post-PKS genes is mbcM, or a homologue thereof,
c) re-introducing some or all of the post-PKS genes not including mbcM.
d) culturing said modified host strain under suitable conditions for the production of 21-deoxymacbecin analogues; and
e) optionally isolating the compounds produced.
In a further embodiment an engineered strain in which one or more post-PKS genes including mbcM have been deleted or inactivated is complemented by one or more of the post PKS genes from a heterologous PKS cluster including, but not limited to the clusters directing the biosynthesis of rifamycin, ansamitocin, geldanamycin or herbimycin.
Specifically, the host strain may be an engineered strain based on a macbecin producing strain in which mbcM has been deleted or inactivated. Alternatively the host strain may be an engineered strain based on a macbecin producing strain in which mbcM, mbcMT1, mbcMT2, mbcP and mbcP450 have been deleted or inactivated.
It may be observed in these systems that when a strain is generated in which mbcM, or a homologue thereof, does not function as a result of one of the methods described including inactivation or deletion, that more than one macbecin analogue may be produced. There are a number of possible reasons for this which will be appreciated by those skilled in the art. For example there may be a preferred order of post-PKS steps and removing a single activity leads to all subsequent steps being carried out on substrates that are not natural to the enzymes involved. This can lead to intermediates building up in the culture broth due to a lowered efficiency towards the novel substrates presented to the post-PKS enzymes, or to shunt products which are no longer substrates for the remaining enzymes possibly because the order of steps has been altered.
The ratio of compounds observed in a mixture can be manipulated by using variations in the growth conditions such as the setting of revolutions per minute (rpm) in the shaking incubator, and the throw of the shaking incubator. As described in the examples, incubation of production cultures of BIOT-3806 in an incubator with a smaller throw (2.5 cm) but higher rpm (300) lead to a bias towards less processed analogues whilst a parallel experiment in an incubator with a wider throw (5 cm) and lower rpm (200 or 250) lead to a bias towards more processed intermediates.
One skilled in the art will appreciate that in a biosynthetic cluster some genes are organised in operons and disruption of one gene will often have an effect on expression of subsequent genes in the same operon.
When a mixture of compounds is observed these can be readily separated using standard techniques some of which are described in the following examples.
21-Deoxymacbecin analogues may be screened by a number of methods, as described herein, and in the circumstance where a single compound shows a favourable profile a strain can be engineered to make this compound preferably. In the unusual circumstance when this is not possible, an intermediate can be generated which is then biotransformed to produce the desired compound.
The present invention provides novel macbecin analogues generated by the selected deletion or inactivation of one or more post-PKS genes from the macbecin PKS gene cluster. In particular, the present invention relates to novel 21-deoxymacbecin analogues produced by the selected deletion or inactivation of at least mbcM, or a homologue thereof, from the macbecin biosynthetic gene cluster. In one embodiment, mbcM, or a homologue thereof, alone is deleted or inactivated. In an alternative embodiment, other post-PKS genes in addition to mbcM are additionally deleted or inactivated. In a specific embodiment, additional genes selected from the group consisting of: mbcN, mbcP, mbcMT1, mbcMT2 and mbcP450 are deleted or inactivated in the host strain. In a further embodiment, additionally 1 or more of the post-PKS genes selected from the group consisting of mbcN, mbcP, mbcMT1, mbcMT2 and mbcP450 are deleted or inactivated. In a further embodiment, additionally 2 or more of the post-PKS genes selected from the group consisting of mbcN, mbcP, mbcMT1, mbcMT2 and mbcP450 are deleted or inactivated. In a further embodiment, additionally 3 or more of the post-PKS genes selected from the group consisting of mbcN, mbcP, mbcMT1, mbcMT2 and mbcP450 are deleted or inactivated. In a further embodiment, additionally 4 or more of the post-PKS genes selected from the group consisting of mbcN, mbcP, mbcMT1, mbcMT2 and mbcP450 are deleted or inactivated.
A person of skill in the art will appreciate that a gene does not need to be completely deleted for it to be rendered non-functional, consequentially the term “deleted or inactivated” as used herein encompasses any method by which a gene is rendered non-functional including but not limited to: deletion of the gene in its entirety, inactivation by insertion into the target gene, site-directed mutagenesis which results in the gene either not being expressed or being expressed in an inactive form, mutagenesis of the host strain which results in the gene either not being expressed or being expressed in an inactive form (e.g. by radiation or exposure to mutagenic chemicals, protoplast fusion or transposon mutagenesis). Further it includes deletion of an internal fragment of the gene. Alternatively the function of an active gene can be impaired chemically with inhibitors, for example metapyrone (alternative name 2-methyl-1,2-di(3-pyridyl-1-propanone), EP 0 627 009) and ancymidol are inhibitors of oxygenases and these compounds can be added to the production medium to generate analogues. Additionally, sinefungin is a methyl transferase inhibitor that can be used similarly but for the inhibition of methyl transferase activity in vivo (McCammon and Parks 1981).
In an alternative embodiment, all of the post-PKS genes may be deleted or inactivated and then one or more of the genes, but not including mbcM, or a homologue thereof, may then be reintroduced by complementation (e.g. at an att site, on a self-replicating plasmid or by insertion into a homologous region of the chromosome). Therefore, in a particular embodiment the present invention relates to methods for the generation of 21-deoxymacbecin analogues, said method comprising:
a) providing a first host strain that produces macbecin when cultured under appropriate conditions
b) selectively deleting or inactivating all the post-PKS genes,
c) culturing said modified host strain under suitable conditions for the production of 21-deoxymacbecin analogues; and
d) optionally isolating the compounds produced.
In an alternative embodiment, one or more of the deleted post-PKS genes are reintroduced, provided that mbcM is not one of the genes reintroduced. In a further embodiment, 1 or more of the post-PKS genes selected from the group consisting of mbcN, mbcP, mbcMT1, mbcMT2 and mbcP450 are reintroduced. In a further embodiment, 2 or more of the post-PKS genes selected from the group consisting of mbcN, mbcP, mbcMT1, mbcMT2 and mbcP450 are reintroduced. In a further embodiment, 3 or more of the post-PKS genes selected from the group consisting of mbcN, mbcP, mbcMT1, mbcMT2 and mbcP450 are reintroduced. In a further embodiment, 4 or more of the post-PKS genes selected from the group consisting of mbcN, mbcP, mbcMT1, mbcMT2 and mbcP450 are reintroduced. In a further alternative embodiment, mbcN, mbcP, mbcMT1, mbcMT2 and mbcP450 are reintroduced.
Additionally, it will be apparent to a person of skill in the art that a subset of the post-PKS genes, including mbcM, or a homologue thereof, could be deleted or inactivated and a smaller subset of said post-PKS genes not including mbcM could be reintroduced to arrive at a strain producing 21-deoxymacbecin analogues.
A person of skill in the art will appreciate that there are a number of ways to generate a strain that contains the biosynthetic gene cluster for macbecin but that is lacking at least mbcM, or a homologue thereof.
It is well known to those skilled in the art that polyketide gene clusters may be expressed in heterologous hosts (Pfeifer and Khosla, 2001). Accordingly, the present invention includes the transfer of the macbecin biosynthetic gene cluster without mbcM or with a non-functional mutant of mbcM, with or without resistance and regulatory genes, either otherwise complete or containing additional deletions, into a heterologous host. Alternatively, the complete macbecin biosynthetic cluster can be transferred into a heterologous host, with or without resistance and regulatory genes, and it can then be manipulated by the methods described herein to delete or inactivate mbcM. Methods and vectors for the transfer as defined above of such large pieces of DNA are well known in the art (Rawlings, 2001; Staunton and Weissman, 2001) or are provided herein in the methods disclosed. In this context a preferred host cell strain is a prokaryote, more preferably an actinomycete or Escherichia coli, still more preferably preferred host cell strains include, but are not limited to Actinosynnema mirum (A. mirum), Actinosynnema pretiosum subsp. pretiosum (A. pretiosum), S. hygroscopicus, S. hygroscopicus sp., S. hygroscopicus var. ascomyceticus, Streptomyces tsukubaensis, Streptomyces coelicolor, Streptomyces lividans, Saccharopolyspora erythraea, Streptomyces fradiae, Streptomyces avermitilis, Streptomyces cinnamonensis, Streptomyces rimosus, Streptomyces albus, Streptomyces griseofuscus, Streptomyces longisporoflavus, Streptomyces venezuelae, Streptomyces albus, Micromonospora sp., Micromonospora griseorubida, Amycolatopsis mediteffanei or Actinoplanes sp. N902-109. Further examples include Streptomyces hygroscopicus subsp. geldanus and Streptomyces violaceusniger.
In one embodiment the entire biosynthetic cluster is transferred. In an alternative embodiment the entire PKS without mbcM is transferred. In an alternative embodiment the entire PKS is transferred without any of the associated post-PKS genes, including mbcM.
In a further embodiment the entire macbecin biosynthetic cluster is transferred and then manipulated according to the description herein.
In an alternative aspect of the invention, the 21-deoxymacbecin analogue of the present invention may be further processed by biotransformation with an appropriate strain. The appropriate strain either being an available wild type strain for example, but without limitation Actinosynnema mirum, Actinosynnema pretiosum subsp. pretiosum, S. hygroscopicus, S. hygroscopicus sp. Alternatively, an appropriate strain may be a engineered to allow biotransformation with particular post-PKS enzymes for example, but without limitation, those encoded by mbcN, mbcP, mbcMT1, mbcMT2, mbcP450 (as defined herein), gdmN, gdmM, gdmL, gdmP, (Rascher et al., 2003) the geldanamycin 17-O-methyl transferase, asm7, asm10, asm11, asm12, asm19 and asm21 (Cassady et al., 2004, Spiteller et al., 2003). Where genes have yet to be identified or the sequences are not in the public domain it is routine to those skilled in the art to acquire such sequences by standard methods. For example the sequence of the gene encoding the geldanamycin 17-O-methyl transferase is not in the public domain, but one skilled in the art could generate a probe, either a heterologous probe using a similar O-methyl transferase, or a homologous probe by designing degenerate primers from available homologous genes to carry out Southern blots on a geldanamycin producing strain and thus acquire this gene to generate biotransformation systems.
In a particular embodiment the strain may have had one or more of its native polyketide clusters deleted, either entirely or in part, or otherwise inactivated, so as to prevent the production of the polyketide produced by said native polyketide cluster. Said engineered strain may be selected from the group including, for example but without limitation, Actinosynnema mirum, Actinosynnema pretiosum subsp. pretiosum, S. hygroscopicus, S. hygroscopicus sp., S. hygroscopicus var. ascomyceticus, Streptomyces tsukubaensis, Streptomyces coelicolor, Streptomyces lividans, Saccharopolyspora erythraea, Streptomyces fradiae, Streptomyces avermitilis, Streptomyces cinnamonensis, Streptomyces rimosus, Streptomyces albus, Streptomyces griseofuscus, Streptomyces longisporoflavus, Streptomyces venezuelae, Micromonospora sp., Micromonospora griseorubida, Amycolatopsis mediteffanei or Actinoplanes sp. N902-109. Further possible strains include Streptomyces hygroscopicus subsp. geldanus and Streptomyces violaceusniger.
In a further aspect the present invention provides host strains which naturally produce macbecin or analogue thereof, in which the mbcM gene, or a homologue thereof, has been deleted or inactivated such that it thereby produces 21-deoxymacbecin or an analogue thereof (e.g. a 21-deoxymacbecin analogue as defined by compounds of formula (I)) and their use in the production of 21-deoxymacbecin or analogues thereof.
Therefore, in one embodiment the present invention provides a genetically engineered strain which naturally produces macbecin in its unaltered state, said strain having one or more post-PKS genes from the macbecin PKS gene cluster deleted wherein one of said deleted or inactivated post-PKS genes is mbcM, or a homologue thereof.
The invention embraces all products of the inventive processes described herein.
Although the process for preparation of the 21-deoxymacbecin analogues of the invention as described above is substantially or entirely biosynthetic, it is not ruled out to produce or interconvert 21-deoxymacbecin analogues of the invention by a process which comprises standard synthetic chemical methods.
In order to allow for the genetic manipulation of the macbecin biosynthetic gene cluster, first the gene cluster was sequenced from Actinosynnema pretiosum subsp. pretiosum however, a person of skill in the art will appreciate that there are alternative strains which produce macbecin, for example but without limitation Actinosynnema mirum. The macbecin biosynthetic gene cluster from these strains may be sequenced as described herein for Actinosynnema pretiosum subsp. pretiosum, and the information used to generate equivalent strains.
Further aspects of the invention include:
Compounds of the invention are advantageous in that they may be expected to have one or more of the following properties: tight binding to Hsp90, fast on-rate of binding to Hsp90, good solubility, good stability, good formulation ability, good oral bioavailability, good pharmacokinetic properties including but not limited to low glucuronidation, good cell up-take, good brain pharmacokinetics, low binding to erythrocytes, good toxicology profile, good hepatotoxicity profile, good nephrotoxicity, low side effects and low cardiac side effects.
Conditions used for growing the bacterial strains Actinosynnema pretiosum subsp. pretiosum ATCC 31280 (U.S. Pat. No. 4,315,989) and Actinosynnema mirum DSM 43827 (KCC A-0225, Watanabe et al., 1982) were described in the U.S. Pat. No. 4,315,989 and U.S. Pat. No. 4,187,292. Methods used herein were adapted from these patents and are as follows for culturing of broths in tubes or flasks in shaking incubators, variations to the published protocols are indicated in the examples. Both strains were grown on ISP2 agar (Medium 3, Shirling, E. B. and Gottlieb, D., 1966) at 28° C. for 2-3 days and used to inoculate seed medium (Medium 1, see below adapted from U.S. Pat. No. 4,315,989 and U.S. Pat. No. 4,187,292). The inoculated seed medium was then incubated with shaking between 200 and 300 rpm with a 5 or 2.5 cm throw at 28° C. for 48 h. For production of macbecin, 18,21-dihydromacbecin and macbecin analogues such as 21-deoxymacbecins the fermentation medium (Medium 2, see below and U.S. Pat. No. 4,315,989 and U.S. Pat. No. 4,187,292) was inoculated with 2.5%-10% of the seed culture and incubated with shaking between 200 and 300 rpm with a 5 or 2.5 cm throw initially at 28° C. for 24 h followed by 26° C. for four to six days. The culture was then harvested for extraction.
In 1 L of distilled water
Sterilisation by autoclaving at 121° C. for 20 minutes.
Apramycin was added when appropriate after autoclaving to give a final concentration of 50 mg/L.
In 1 L of distilled water
Sterilisation by autoclaving at 121° C. for 20 minutes.
In 1 L of distilled water
Sterilisation by autoclaving at 121° C. for 20 minutes.
In 1 L of distilled water
Sterilisation by autoclaving at 121° C. for 20 minutes.
Culture broth (1 mL) and ethyl acetate (1 mL) was added and mixed for 15-30 min followed by centrifugation for 10 min. 0.5 mL of the organic layer was collected, evaporated to dryness and then re-dissolved in 0.25 mL of methanol.
LCMS analysis procedure for fermentation broth analysis and in vivo transformation studies LCMS was performed using an integrated Agilent HP1100 HPLC system in combination with a Bruker Daltonics Esquire 3000+ electrospray mass spectrometer operating in positive and/or negative ion mode. Chromatography was achieved over a Phenomenex Hyperclone column (C18 BDS, 3u, 150×4.6 mm) eluting over 11 min at a flow rate of 1 mL/min with a linear gradient from acetonitrile+0.1% formic acid/water+0.1% formic acid (40/60) to acetonitrile+0.1% formic acid/water+0.1% formic acid (80/20). UV spectra were recorded between 190 and 400 nm, with extracted chromatograms taken at 210, 254 and 276 nm. Mass spectra were recorded between 100 and 1500 amu.
In vitro evaluation of compounds for anticancer activity in a panel of 38 human tumour cell lines in a monolayer proliferation assay was carried out at the Oncotest Testing Facility, Institute for Experimental Oncology, Oncotest GmbH, Freiburg. The characteristics of 9 of the selected cell lines are summarised in Table 1.
The Oncotest cell lines are established from human tumor xenografts as described by Roth et al., (1999). The origin of the donor xenografts was described by Fiebig et al., (1999). Other cell lines are either obtained from the NCl (H460, SF-268, OVCAR-3, DU145, MDA-MB-231, MDA-MB-468) or purchased from DSMZ, Braunschweig, Germany (LNCAP).
All cell lines, unless otherwise specified, were grown at 37° C. in a humidified atmosphere (95% air, 5% CO2) in a ‘ready-mix’ medium containing RPMI 1640 medium, 10% fetal calf serum, and 0.1 mg/mL gentamicin (PAA, Cölbe, Germany).
A modified propidium iodide assay was used to assess the effects of the test compound(s) on the growth of human tumour cell lines (Dengler et al., (1995)).
Briefly, cells were harvested from exponential phase cultures by trypsinization, counted and plated in 96 well flat-bottomed microtitre plates at a cell density dependent on the cell line (5-10.000 viable cells/well). After 24 h recovery to allow the cells to resume exponential growth, 0.010 mL of culture medium (6 control wells per plate) or culture medium containing a 21-deoxymacbecin analogue was added to the wells. Each concentration was plated in triplicate. Compounds were applied in five concentrations (100; 10; 1; 0.1 and 0.01 μM). Following 4 days of continuous exposure, cell culture medium with or without test compound was replaced by 0.2 mL of an aqueous propidium iodide (PI) solution (7 mg/L). To measure the proportion of living cells, cells were permeabilized by freezing the plates. After thawing the plates, fluorescence was measured using the Cytofluor 4000 microplate reader (excitation 530 nm, emission 620 nm), giving a direct relationship to the total number of viable cells.
Growth inhibition was expressed as treated/control×100 (% T/C). For active compounds, IC70 values were estimated by plotting compound concentration versus cell viability.
A modified propidium iodide assay was also used to assess the effects of combined applications of the compounds on the growth of the DU145 cells as described above, except that for each standard agent 4 plates were prepared: one for the standard agent alone and three plates for the combinations of the standard agent with 3 different fixed concentrations of compound 14, respectively. Standard agents were applied at 10 concentrations in sextuplicates in half-log increments. Untreated cells, as well as cells incubated with the compound 14 alone were covered with 6 wells/plate, respectively. Growth inhibition is expressed as treated/control×100 (% T/C), and IC70 values for each combination were determined by plotting compound concentration versus cell viability.
Genomic DNA was isolated from Actinosynnema pretiosum (ATCC 31280) and Actinosynnema mirum (DSM 43827, ATCC 29888) using standard protocols described in Kieser et al., (2000) DNA sequencing was carried out by the sequencing facility of the Biochemistry Department, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW using standard procedures.
Primers BIOSG104 5′-GGTCTAGAGGTCAGTGCCCCCGCGTACCGTCGT-3′ (SEQ ID NO: 7) AND BIOSG105 5′-GGCATATGCTTGTGCTCGGGCTCAAC-3′ (SEQ ID NO: 8) were employed to amplify the carbamoyltransferase-encoding gene gdmN from the geldanamycin biosynthetic gene cluster of Streptomyces hygroscopicus NRRL 3602 (Accession number of sequence: AY179507) using standard techniques. Southern blot experiments were carried out using the DIG Reagents and Kits for Non-Radioactive Nucleic Acid Labelling and Detection according to the manufacturers' instructions (Roche). The DIG-labeled gdmN DNA fragment was used as a heterologous probe. Using the gdmN generated probe and genomic DNA isolated from A. pretiosum 2112 an approximately 8 kb EcoRI fragment was identified in Southern Blot analysis. The fragment was cloned into Litmus 28 applying standard procedures and transformants were identified by colony hybridization. The clone p3 was isolated and the approximately 7.7 kb insert was sequenced. DNA isolated from clone p3 was digested with EcoRI and EcoRI/SacI and the bands at around 7.7 kb and at about 1.2 kb were isolated, respectively. Labelling reactions were carried out according to the manufacturers' protocols. Cosmid libraries of the two strains named above were created using the vector SuperCos 1 and the Gigapack III XL packaging kit (Stratagene) according to the manufacturers' instructions. These two libraries were screened using standard protocols and as a probe, the DIG-labelled fragments of the 7.7 kb EcoRI fragment derived from clone p3 were used. Cosmid 52 was identified from the cosmid library of A. pretiosum and submitted for sequencing to the sequencing facility of the Biochemistry Department of the University of Cambridge. Similarly, cosmid 43 and cosmid 46 were identified from the cosmid library of A. mirum. All three cosmids contain the 7.7 kb EcoRI fragment as shown by Southern Blot analysis.
An around 0.7 kbp fragment of the PKS region of cosmid 43 was amplified using primers BIOSG124 5′-CCCGCCCGCGCGAGCGGCGCGTGGCCGCCCGAGGGC-3′ (SEQ ID NO: 9) and BIOSG125 5′-GCGTCCTCGCGCAGCCACGCCACCAGCAGCTCCAGC-3′ (SEQ ID NO:10) applying standard protocols, cloned and used as a probe for screening the A. pretiosum cosmid library for overlapping clones. The sequence information of cosmid 52 was also used to create probes derived from DNA fragments amplified by primers BIOSG130 5′-CCAACCCCGCCGCGTCCCCGGCCGCGCCGAACACG-3′ (SEQ ID NO: 11) and BIOSG131 5′-GTCGTCGGCTACGGGCCGGTGGGGCAGCTGCTGT-5′ (SEQ ID NO: 12) as well as BIOSG132 5′-GTCGGTGGACTGCCCTGCGCCTGATCGCCCTGCGC-3′ (SEQ ID NO: 13) and BIOSG133 5′-GGCCGGTGGTGCTGCCCGAGGACGGGGAGCTGCGG-3′ (SEQ ID NO: 14) which were used for screening the cosmid library of A. pretiosum. Cosmids 311 and 352 were isolated and cosmid 352 was sent for sequencing. Cosmid 352 contains an overlap of approximately 2.7 kb with cosmid 52. To screen for further cosmids, an approximately 0.6 kb PCR fragment was amplified using primers BIOSG136 5′-CACCGCTCGCGGGGGTGGCGCGGCGCACGACGTGGCTGC-3′ (SEQ ID NO: 15) and BIOSG 137 5′-CCTCCTCGGACAGCGCGATCAGCGCCGCGCACAGCGAG-3′ (SEQ ID NO: 16) and cosmid 311 as template applying standard protocols. The cosmid library of A. pretiosum was screened and cosmid 410 was isolated. It overlaps approximately 17 kb with cosmid 352 and was sent for sequencing. The sequence of the three overlapping cosmids (cosmid 52, cosmid 352 and cosmid 410) was assembled. The sequenced region spans about 100 kbp and 23 open reading frames were identified potentially constituting the macbecin biosynthetic gene cluster, (SEQ ID NO: 17). The location of each of the open reading frames within SEQ ID NO: 17 is shown in Table 3
Actinosynnema mirum ATCC 29888
Actinosynnema mirum ATCC 29888
Actinosynnema pretiosum ATCC 31280
Actinosynnema pretiosum ATCC 31280
Actinosynnema pretiosum ATCC 31280
Actinosynnema pretiosum ATCC 31280
A summary of the construction of pLSS308 is shown in
2.1. Construction of Plasmid pLSS308
The DNA sequences of the gdmM gene from the geldanamycin biosynthetic gene cluster of Streptomyces hygroscopicus strain NRRL 3602 (AY179507) and orf19 from the rifamycin biosynthetic gene cluster of Amycolatopsis mediteffanei (AF040570 AF040571) were aligned using VectorNTI sequence alignment program (
where n=G, A, T or C; y=C or T; s=G or C
The template for PCR amplification was Actinosynnema mirum cosmid 43. The generation of cosmid 43 is described in Example 1 above.
Oligos FPLS1 and FPLS3 were used to amplify the internal fragment of a gdmM homologue from Actinosynnema mirum in a standard PCR reaction using cosmid 43 as the template and Taq DNA polymerase. The resultant 793 bp PCR product was cloned into pUC19 that had been linearised with SmaI, resulting in plasmid pLSS301. The cloned region was sequenced and was shown to have significant homology to gdmM, (
2.2 Transformation of Actinosynnema pretiosum subsp. pretiosum
Escherichia coli ET12567, harbouring the plasmid pUZ8002 was transformed with pLSS308 by electroporation to generate the E. coli donor strain for conjugation. This strain was used to transform Actinosynnema pretiosum subsp. pretiosum by vegetative conjugation (Matsushima et al., 1994). Exconjugants were plated on Medium 4 and incubated at 28° C. Plates were overlayed after 24 h with 50 mg/L apramycin and 25 mg/L nalidixic acid. As pLSS308 is unable to replicate in Actinosynnema pretiosum subsp. pretiosum, any apramycin resistant colonies were anticipated to be transformants that contained plasmid integrated into the mbcM gene of the chromosome by homologous recombination via the plasmid borne mcbM internal fragment (
Colonies were patched onto Medium 4 (with 50 mg/L apramycin and 25 mg/L nalidixic acid). A 6 mm circular plug from each patch was used to inoculate individual 50 mL falcon tubes containing 10 mL seed medium (variant of Medium 1-2% glucose, 3% soluble starch, 0.5% corn steep solids, 1% soybean flour, 0.5% peptone, 0.3% sodium chloride, 0.5% calcium carbonate) plus 50 mg/L apramycin. These seed cultures were incubated for 2 days at 28° C., 200 rpm with a 5 cm throw. These were then used to inoculate (5% v/v) fermentation medium (Medium 2) and were grown at 28° C. for 24 hours and then at 26° C. for a further 5 days. Metabolites were extracted from these according to the standard protocol described above. Samples were assessed for production of macbecin analogues by HPLC using the standard protocol described above.
The productive isolate selected was designated BIOT-3806.
2.3 Identification of Compounds from BIOT-3806
LCMS was performed using an Agilent HP1100 HPLC system in combination with a Bruker Daltonics Esquire 3000+ electrospray mass spectrometer operating in positive and/or negative ion mode. Chromatography was achieved over a Phenomenex Hyperclone column (C18 BDS, 3u, 150×4.6 mm) eluting at a flow rate of 1 mL/min using the following gradient elution process; T=0, 10% B; T=2, 10% B; T=20, 100% B; T=22, 100% B; T=22.05, 10% B; T=25, 10% B. Mobile phase A=water+0.1% formic acid; mobile phase B=acetonitrile+0.1% formic acid. UV spectra were recorded between 190 and 400 nm, with extracted chromatograms taken at 210, 254 and 276 nm. Mass spectra were recorded between 100 and 1500 amu.
Vegetative stocks of BIOT-3806 were prepared after growth in Medium 1 with 50 mg/L apramycin, and preserved in 20% w/v glycerol:10% w/v lactose in distilled water and stored at −80° C. Vegetative stocks were recovered onto plates of ISP2 medium (Medium 3) supplemented with 50 mg/L apramycin and incubated for 48 hours at 28° C. Vegetative cultures were prepared by removing two agar plugs, 5 mm in diameter from the ISP2 plate and inoculating them into 30 mL Medium 1 in 250 mL shake flasks containing 50 mg/L apramycin. The flasks were incubated at 28° C., 200 rpm (5 cm throw) for 48 h.
Vegetative cultures were inoculated at 5% v/v into 200 ml production medium (Medium 2) in 2 L shake flasks. Cultivation was carried out for 1 day at 28° C. followed by 5 days at 26° C., 300 rpm (2.5 cm throw).
The fermentation broth of BIOT-3806 (1 L, pink colour) was extracted three times with an equal volume of ethyl acetate (EtOAc). The solvent was removed from the combined EtOAc extract in vacuo to yield 2.34 g of brown oil. The extract was then chromatographed over Silica Gel 60 eluting initially with a CHCl3 and MeOH mixture (95:5) followed by an increase in MeOH concentration up to 10% and collection of several fractions (approx. 250 mL per fraction). The fractions were assayed for the presence of metabolites using HPLC. A particular fraction containing a new compound (fraction 5; 334 mg crude mass after removal of solvent) was further purified by chromatography over a Phenomenex Luna C18-BDS column (21.2×250 mm; 5 um particle size) eluting with a gradient of water:acetonitrile (80:20) to (50:50) over a period of 25 min, with a flow rate of 21 mL/min. Fractions were assayed by analytical HPLC and those containing the new compound were combined and the solvents removed to yield an off white solid (86 mg). Analysis by LCMS/MS, and by 1D and 2D NMR experiments carried out in acetone-d6 identified the compound as 7-O-carbamoylpre-macbecin (14)
3.2 Fermentation and Isolation of 7-O-carbamoyl-15-hydroxypre-macbecin
Vegetative stocks of BIOT-3806 were prepared after growth in medium 1 containing 50 mg/L apramycin and preserved in 20% w/v glycerol:10% w/v lactose in distilled water and stored at −80° C. Vegetative stocks were recovered onto plates of ISP2 medium (Medium 3) supplemented with 50 mg/L apramycin and incubated for 48 hours at 28° C. Vegetative cultures were prepared by removing two agar plugs, 5 mm in diameter, from the ISP2 plate and inoculating them into 30 mL Medium 1 in 250 mL shake flasks containing 50 mg/L apramycin. The flasks were incubated at 28° C., 200 rpm (5 cm throw) for 48 h.
Vegetative cultures were inoculated at 5% v/v into 200 mL production medium (medium 2) in 2 L shake flasks. Cultivation was carried out for 1 day at 28° C. followed by 5 days at 26° C., 200 rpm (5 cm throw).
The fermentation broth of BIOT-3806 (1.3 L, cream colour) was extracted three times with an equal volume of ethyl acetate (EtOAc). The solvent was removed from the combined extract in vacuo to yield 2.87 g of a brown oil. The extract was then chromatographed over Silica Gel 60 eluting initially with a CHCl3 and MeOH mixture (95:5) followed by an increase in MeOH concentration up to 10% and collection of several fractions (about 250 mL per fraction). The fractions were assayed for the presence of metabolites using HPLC. A particular fraction containing a new compound (fraction 7; 752 mg crude mass after removal of solvent) was further purified by chromatography over a Phenomenex Luna C18-BDS column (21.2×250 mm; 5 um particle size) eluting with a gradient of water; acetonitrile (85:15) to (55:45) over 25 min, with a flow rate of 21 mL/min. Fractions were assayed by analytical HPLC and those containing the new compound were combined and the solvents removed to yield an off white solid (245.5 mg). For identification and characterisation MS, and 1 and 2D NMR experiments were carried out in Acetone-d6. Analysis by LCMS/MS, and by 1D and 2D NMR carried out in acetone-d6 identified the compound as 7-O-carbamoyl-15-hydroxypre-macbecin (15).
A range of MS and NMR experiments were performed, viz LCMS, MSMS, 1H, 13C, APT, COSY-45, HMQC, HMBC. A thorough and exhaustive review of these data enabled the assignment of the majority of the protons and carbons of two analogues of pre-macbecin. The NMR assignments are described in Table 5.
1H-NMR
13C-NMR
4.1 Cloning of DNA Homologous to the Downstream Flanking Region of mbcM.
Oligos BV145 (SEQ ID NO: 22) and BV146 (SEQ ID NO: 23) were used to amplify a 1421 bp region of DNA from Actinosynnema pretiosum (ATCC 31280) in a standard PCR reaction using cosmid 52 (from example 1) as the template and Pfu DNA polymerase. A 5′ extension was designed in each oligo to introduce restriction sites to aid cloning of the amplified fragment (
4.2 Cloning of DNA Homologous to the Upstream Flanking Region of mbcM.
Oligos BV147 (SEQ ID NO: 24) and BV148 (SEQ ID NO: 25) were used to amplify a 1423 bp region of DNA from Actinosynnema pretiosum (ATCC 31280) in a standard PCR reaction using cosmid 52 (from example 1) as the template and Pfu DNA polymerase. A 5′ extension was designed in each oligo to introduce restriction sites to aid cloning of the amplified fragment (
The products PCRwv308 and PCRwv309 were cloned into pUC19 in the same orientation to utilise the PstI site in the pUC19 polylinker for the next cloning step.
The 1443 bp AvrII/PstI fragment from pWV309 was cloned into the 4073 bp AvrII/PstI fragment of pWV308 to make pWV310. pWV310 therefore contained a SpeII/XbaI fragment encoding DNA homologous to the flanking regions of mbcM fused at an AvrII site. This 2816 bp SpeII/XbaI fragment was cloned into pKC1132 (Bierman et al., 1992) that had been linearised with SpeI to create pWV320.
4.3 Transformation of Actinosynnema pretiosum subsp. pretiosum
Escherichia coli ET12567, harbouring the plasmid pUZ8002 was transformed with pWV320 by electroporation to generate the E. coli donor strain for conjugation. This strain was used to transform Actinosynnema pretiosum subsp. pretiosum by vegetative conjugation (Matsushima et al, 1994). Exconjugants were plated on Medium 4 and incubated at 28° C. Plates were overlayed after 24 h with 50 mg/L apramycin and 25 mg/L nalidixic acid. As pWV320 is unable to replicate in Actinosynnema pretiosum subsp. pretiosum, apramycin resistant colonies were anticipated to be transformants that contained plasmid pWV320 integrated into the chromosome by homologous recombination via one of the plasmid borne mbcM flanking regions of homology.
Genomic DNA was isolated from six exconjugants and was digested and analysed by Southern blot. The blot showed that in four out of the six isolates integration had occurred in the upstream region of homology and in two of the six isolates homologous integration had occurred in the downstream region. One strain resulting from homologous integration in the upstream region (designated BIOT-3831) was chosen for screening for secondary crosses. One strain resulting from homologous integration in the downstream region (BIOT-3832) was also chosen for screening for secondary crosses.
Strains were patched onto medium 4 (supplemented with 50 mg/L apramycin) and grown at 28° C. for four days. A 1 cm2 section of each patch was used to inoculate 7 mL modified ISP2 (0.4% yeast extract, 1% malt extract, 0.4% dextrose in 1 L distilled water) without antibiotic in a 50 mL falcon tube. Cultures were grown for 2-3 days then subcultured on (5% inoculum) into another 7 mL modified ISP2 (see above) in a 50 mL falcon tube. After 4-5 generations of subculturing the cultures were sonicated, serially diluted, plated on Medium 4 and incubated at 28° C. for four days. Single colonies were then patched in duplicate onto Medium 4 containing apramycin and onto Medium 4 containing no antibiotic and the plates were incubated at 28° C. for four days. Patches that grew on the no antibiotic plate but did not grow on the apramycin plate were re-patched onto +/−apramycin plates to confirm that they had lost the antibiotic marker. Genomic DNA was isolated from all apramycin sensitive strains and analysed by Southern blot. At this stage, half the secondary crossover strains had reverted to wild-type but half had produced the desired mbcM deletion mutants. The mutant strain encodes an mbcM protein with an in-frame deletion of 502 amino acids (
mbcM deletion mutants were patched onto Medium 4 and grown at 28° C. for four days. A 6 mm circular plug from each patch was used to inoculate individual 50 mL falcon tubes containing 10 mL seed medium (adapted from medium 1-2% glucose, 3% soluble starch, 0.5% corn steep solids, 1% soybean flour, 0.5% peptone, 0.3% sodium chloride, 0.5% calcium carbonate). These seed cultures were incubated for 2 days at 28° C., 200 rpm with a 2 inch throw. These were then used to inoculate (0.5 mL into 10 mL) production medium (medium 2-5% glycerol, 1% corn steep solids, 2% yeast extract, 2% potassium dihydrogen phosphate, 0.5% magnesium chloride, 0.1% calcium carbonate) and were grown at 28° C. for 24 hours and then at 26° C. for a further 5 days. Secondary metabolites were extracted from these cultures by the addition of an equal volume of ethyl acetate. Cell debris was removed by centrifugation. The supernatant was transferred to a clean tube and solvent was removed in vacuo. Samples were reconstituted in 0.23 mL methanol followed by the addition of 0.02 mL of 1% (w/v) FeCl3 solution. Samples were assessed for production of macbecin analogues
Chemical analysis by LCMS using the methods described in example 2.3 above unambiguously identified the presence of compounds 14 and 15 based on them having identical retention times and mass spectra.
Protoplasts were generated from BIOT-3872 using a method adapted from Weber and Losick 1988 with the following media alterations; Actinosynnema pretiosum cultures were grown on ISP2 plates (medium 3) for 3 days at 28° C. and a 5 mm2 scraping used to inoculate 40 mL of ISP2 broth supplemented with 2 mL of sterile 10% (w/v) glycine in water. Protoplasts were generated as described in Weber and Losick 1988 and then regenerated on R2 plates (R2 recipe—Sucrose 103 g, K2SO4 0.25 g, MgCl2.6H2O 10.12 g, Glucose 10 g, Difco Casaminoacids 0.1 g, Difco Bacto agar 22 g, distilled water to 800 mL, the mixture was sterilised by autoclaving at 121° C. for 20 minutes. After autoclaving the following autoclaved solutions were added; 0.5% KH2PO4 10 mL, 3.68% CaCl2.2H2O 80 mL, 20% L-proline 15 mL, 5.73% TES buffer (pH7.2) 100 mL, Trace element solution (ZnCl2 40 mg, FeCl3.6H2O 200 mg, CuCl2.2H2O 10 mg, MnCl2.4H2O 10 mg, Na2B4O7.10H2O 10 mg, (NH4)6Mo7O24.4H2O 10 mg, distilled water to 1 litre) 2 mL, NaOH (1N) (unsterilised) 5 mL).
80 individual colonies were patched onto MAM plates (Medium 4) and analysed for production of macbecin analogues as described above in example 2.3. The majority of protoplast generated patches produced at similar levels to the parental strain. 15 out of the 80 samples tested produced significantly more 14 and 15 than the parental strain. The best producing strain, WV4a-33 (BIOT-3870) was observed to produce 14 and 15 at significantly higher levels than the parent strain.
In vitro evaluation of the test compounds for anticancer activity in a panel of human tumour cell lines in a monolayer proliferation assay was carried out as described in the general methods using a modified propidium iodide assay.
The results for 9 cell lines are displayed in Table 6 below; each result represents the median of duplicate experiments. Table 7 shows the mean IC70 for the compounds across the 38 cell line panel tested, with macbecin shown as a reference.
Solutions (25 mM) of the test compounds were prepared by dissolving 3-5 mg aliquots in the appropriate amount of DMSO.
Aliquots (0.01 mL) were added to 0.490 mL of pH 7.3 PBS in glass vials. For each time point, 3 PBS vials were prepared in amber glass vials. For the six hour time point triplicate aliquots in DMSO were also prepared.
The resulting 0.5 mM solutions were shaken for up to six hours, with vials removed for analysis at 1, 3 and 6 hours. Samples were analysed by HPLC (0.025 mL injections). Compounds were quantified by peak area measurement at 274 nm.
Solubility in 2% DMSO in PBS at each time point was determined by comparing total peak areas for each chromatogram with mean total peak area for chromatograms produced from the corresponding 6 hour DMSO solutions. (Mean total peak area in DMSO solutions was assumed to be equivalent to a 0.5 mM solution). The results are shown below in Table 8.
Yeast Hsp90 was dialysed against 20 mM Tris pH 7.5 containing 1 mM EDTA and 5 mM NaCl and then diluted to 0.008 mM in the same buffer, but containing 2% DMSO. The test compounds were dissolved in 100% DMSO at a concentration of 50 mM and subsequently diluted to 0.1 mM in the same buffer as for Hsp90 with 2% DMSO. Heats of interaction were measured at 30° C. on a MSC system (Microcal), with a cell volume of 1.458 mL. 10 aliquots of 0.027 mL of 0.100 mM of each test compound were injected into 0.008 mM yeast Hsp90. Heats of dilution were determined in a separate experiment by injecting the test compound into buffer containing 2% DMSO, and the corrected data fitted using a nonlinear least square curve-fitting algorithm (Microcal Origin) with three floating variables: stoichiometry, binding constant and change in enthalpy of interaction. The results are shown below in Table 9.
8.1 Cloning of DNA Homologous to the Downstream Flanking Region of mbcMT2
Oligos Is4del1 (SEQ ID NO: 29) and Is4del2a (SEQ ID NO: 30) were used to amplify a 1595 bp region of DNA from Actinosynnema pretiosum (ATCC 31280) in a standard PCR reaction using cosmid 52 (from example 1) as the template and Pfu DNA polymerase. A 5′ extension was designed in oligo Is4del2a to introduce an AvrII site to aid cloning of the amplified fragment (
8.2 Cloning of DNA Homologous to the Upstream Flanking Region of mbcM.
Oligos Is4del3b (SEQ ID NO: 32) and Is4del4 (SEQ ID NO: 33) were used to amplify a 1541 bp region of DNA from Actinosynnema pretiosum (ATCC 31280) in a standard PCR reaction using cosmid 52 (from example 1) as the template and Pfu DNA polymerase. A 5′ extension was designed in oligo Is4del3b to introduce an AvrII site to aid cloning of the amplified fragment (
The products 1+2a and 3b+4 were cloned into pUC19 to utilise the HindIII and BamHI sites in the pUC19 polylinker for the next cloning step.
The 1621 bp AvrII/HindIII fragment from pLSS1+2a and the 1543 bp AvrII/BamHI fragment from pLSS3b+4 were cloned into the 3556 bp HindIII/BamHI fragment of pKCl 132 to make pLSS315. pLSS315 therefore contained a HindIII/BamHI fragment encoding DNA homologous to the flanking regions of the desired four ORF deletion region fused at an AvrII site (
8.3 Transformation of BIOT-3870 with pLSS315
Escherichia coli ET12567, harbouring the plasmid pUZ8002 was transformed with pLSS315 by electroporation to generate the E. coli donor strain for conjugation. This strain was used to transform BIOT-3870 by vegetative conjugation (Matsushima et al, 1994). Exconjugants were plated on MAM medium (1% wheat starch, 0.25% corn steep solids, 0.3% yeast extract, 0.3% calcium carbonate, 0.03% iron sulphate, 2% agar) and incubated at 28° C. Plates were overlayed after 24 h with 50 mg/L apramycin and 25 mg/L nalidixic acid. As pLSS315 is unable to replicate in BIOT-3870, apramycin resistant colonies were anticipated to be transformants that contained plasmid integrated into the chromosome by homologous recombination via the plasmid borne regions of homology.
Three primary transformants of BIOT-3870:pLSS315 were selected for subculturing to screen for secondary crosses.
Strains were patched onto MAM media (supplemented with 50 mg/L apramycin) and grown at 28° C. for four days. Two 6 mm circular plugs were used to inoculate 30 mL of ISP2 (0.4% yeast extract, 1% malt extract, 0.4% dextrose, not supplemented with antibiotic) in a 250 ml conical flask. Cultures were grown for 2-3 days then subcultured (5% inoculum) into 30 mL of ISP2 in a 250 ml conical flask. After 4-5 rounds of subculturing the cultures were protoplasted as described in Example 3.6, the protoplasts were serially diluted, plated on regeneration media (see Example 3.6) and incubated at 28° C. for four days. Single colonies were then patched in duplicate onto MAM media containing apramycin and onto MAM media containing no antibiotic and the plates were incubated at 28° C. for four days. Seven patches derived from clone no 1 (no 32-37) and four patches derived from clone no 3 (no 38-41) that grew on the no antibiotic plate but did not grow on the apramycin plate were re-patched onto +/−apramycin plates to confirm that they had lost the antibiotic marker.
Production of macbecin analogues was carried out as described in the General Methods. Analysis was performed as described in General Methods and example 2. Compound 14 was produced in yields comparable to the parent strain BIOT-3870 and no production of compound 15 was observed for patches 33, 34, 35, 37, 39 and 41. This result shows that the desired mutant strains have a deletion of 3892 bp of the macbecin cluster containing the genes mbcP, mbcP450, mbcMT1 and mbcMT2 in addition to the original deletion of mbcM.
In vitro evaluation of 14 for anticancer activity when combined with standard cytotoxic agents against the tumour cell line DU145 in a monolayer proliferation assay was carried out as described in the general methods using a modified propidium iodide assay. Four separate concentrations of 14 were used from 0-80 nM for mitomycin C, and O-160 nM for ifosfamid, CCNU, mitoxantrone and vindesine along with 10 concentrations of the standard agent. The relative cell growth percentage treated/control (% T/C) values were plotted and used to draw the graphs shown in
The data shows that the effect of standard cytotoxic agents, such as the alkylating agents mitomycin C, ifosfamid and CCNU, the topoisomerase II inhibitor mitoxantrone and the mitotic inhibitor vindesine may be improved by the addition of Compound 14. The usefulness of cytotoxic agents such as mitomycin C, ifosfamid, CCNU, mitoxantrone and vindesine is known to be limited by their toxicity and they are conventionally employed in therapy at high levels close to their maximum tolerated dose. It may therefore be deduced that Compound 14 and other compounds of the invention should have useful effect in sparing the amount of cytotoxic agent (such as mitomycin C, ifosfamid, CCNU, mitoxantrone, vindesine) to be used in therapy. Thus it may be possible to achieve greater therapeutic efficacy or efficacy with fewer side effects than can be achieved with the cytotoxic agent alone or combinations of a cytotoxic agent with another cytotoxic agent.
All references including patent and patent applications referred to in this application are incorporated herein by reference to the fullest extent possible.
Throughout the specification and the claims which follow, unless the context requires otherwise, the word ‘comprise’, and variations such as ‘comprises’ and ‘comprising’, will be understood to imply the inclusion of a stated integer or step or group of integers but not to the exclusion of any other integer or step or group of integers or steps.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0526473.4 | Dec 2005 | GB | national |
| 0606549.4 | Mar 2006 | GB | national |
| 0614374.7 | Jul 2006 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/GB2006/050476 | 12/22/2006 | WO | 00 | 9/12/2008 |
