Patent Application
20060128736
The present invention relates to compositions, particularly colloidal nanoaggregates comprising the carboxylate form of a campothecin drug or a derivative thereof associated with at least one organic cationic molecule, which has a positive net charge. The composition or nanoaggregate may be present as an emulsion, droplet, micelle, liposome, nanoparticle or nanocapsule.
Camptothecin (CPT) is a quinoline-based alkaloid, which can be isolated from the Chinese tree Camptotheca acuminata (Wall, Wani et al. 1966). It was first described and tested as an anti-cancer drug in the 60ies and 70ies. Anti-tumor activity was noted in animal models and in clinical studies. However, patients experienced severe side reactions such as neutropenia, thrombocytopenia, haemorrhagic cystitis (Wall and Wani 1996). The therapeutic effect of camptothecin in humans had been questioned (Moertel, Schutt et al. 1972; Muggia, Creaven et al. 1972). It continued to be of high interest as a potential candidate for the development of an anti-cancer drug, and it was found that it has a particular mode of action, wherein binding to the topoisomerase I-DNA complex induces DNA breaks and cell death (topoisomerase I inhibitor) (Hsiang and Liu 1988).
A fundamental molecular property of CPT is its pH dependent equilibrium between the lactone and the carboxylate form (
In subsequent research, the equilibrium between the lactone form and the carboxylate form was found fundamental for the cytostatic activity and the appearance of side effects within anti-cancer treatment: CPT-carboxylate was identified as being responsible for the observed side reactions and it was considered to be significantly less active than CPT-lactone (Hertzberg, et. al. 1989). The lower membrane permeability of the carboxylate form compared to that of the lactone, and the shift of the molecular equilibrium as a function of the pH value at the respective local physiological environment were considered to be involved in these activity differences (see
Due to these detrimental properties of CPT-carboxylate, further efforts for the development of CPT based drugs were concentrated on the manufacture of formulations which contain the lactone form and which are free of the carboxylate form. This is especially important, since under physiological conditions, the carboxylate is the predominant molecular form of CPT, and the lactone form hydrolyses to the carboxylate within a short period of time (typically few hours or less). Therefore, a main objective of the development of CPT drugs was to stabilize the lactone form and to find ways to administer it without difficulties (Zunino et al. 2002).
Various strategies have been followed to stabilize the lactone ring and to concomitantly improve the solubility properties of the molecule in order to provide easier administration. Particularly, functionalisation of the original molecule to different types of derivatives, synthesis of prodrugs, and several methods of administration have been pursued (Kehrer, Soepenberg et al. 2001). However, none of them has brought the desired results of resolving the above described inherent difficulties of camptothecin as an anti-cancer drug.
In another approach, liposomes were used to protect CPT-lactone from hydrolysis. This was realized by encapsulation of CPT in a liposome under acidic conditions, or by embedding CPT into the lipid bilayer of a liposome in order to protect the lactone form from hydrolysis and from blood and serum interactions. In fact, by embedding CPT-lactone in the hydrophobic region of the vesicular lipid bilayer (U.S. Pat. No. 5,552,156) the lactone form was not exposed to the aqueous environment and hydrolysis was significantly slowed down. However, only very low drug/lipid ratios could be achieved and therefore the necessary dosages for clinical use could not be realized.
In a further liposome-based approach, CPT-lactone was embedded into the lipid bilayer of a liposome comprising phospholipids, which contain unsaturated fatty acids (U.S. Pat. No. 5,834,012). Thereby a stabilization effect was reported. It was proposed that the latter was due to the interaction of CPT in the lactone form with the unsaturated fatty acid chains of the lipids.
However, as with other approaches, up to now no substantial breakthrough towards a functional CPT drug formulation could be achieved.
Thus, the problem underlying the present invention was to provide a composition comprising a camptothecin drug and a formulation thereof for most efficient delivery to a subject in need under reduction of side effects.
The solution to the above problem is achieved according to the invention by providing the embodiments characterized in the claims. The invention relates to a composition comprising the carboxylate form of a camptothecin drug or a derivative thereof associated with at least one organic molecule (
In the context of the present invention “camptothecin drug” refers to camptothecin itself or a derivative thereof. A camptothecin derivative is obtained by any chemical derivatization of camptothecin (see structure). A non-limiting list of possible camptothecin drugs is given under: http://dtp.nci.nih.gov as from Aug. 19, 2002. In the sketch of the molecule, the most frequent derivatization sites are outlined as R1—R5.
Structure of camptothecin drugs:
In the following table, typical examples for derivatization at different sites are listed. Camptothecin may be present as a hydrochloride. The lactone ring (E-ring) may be seven-membered instead of six-membered (homocamptothecins).
Derivatization can influence the properties of CPT to make the molecule more hydrophilic or more lipophilic, or that the lactone-carboxylate equilibrium is affected. In the context of the application of CPT as an anti-cancer drug, derivatization is intended to maintain or to increase activity.
For producing the inventive composition, camptothecin or any suitable camptothecin derivative in the carboxylate form is provided. For most efficient preparation, the camptothecin drug is provided as a camptothecin carboxylate salt. The binding efficacy of a given camptothecin derivative to the organic counter molecule can be higher or less high with respect to camptothecin. Suitable residues in the R1—R4 position can be favourable for the binding to an amphiphilic counter molecule.
Subsequently the invention will be explained in detail with camptothecin as working example, however, the illustration also relates to any camptothecin derivative.
The inventive composition is a new entity comprising the carboxylate form of a camptothecin drug associated with at least one organic cationic molecule, preferably an amphiphile or polymer having a positive net charge (cationic molecule), wherein the molar ratio of the charged groups in the entity is up to about 2:1, preferably up to about 1.5:1, more preferably up to about 1.1:1 and most preferably about 1:1 of the organic cationic molecule to the carboxylate form of a camptothecin drug. The composition is substantially free of the lactone form of the camptothecin drug. The inventive composition contains a new entity, constituting a new molecular composition with unique physico-chemical properties.
The organic cationic molecule used in the inventive composition can be an amphiphile with a positive net charge (cationic amphiphile) or a polymer with a positive net charge (cationic polymer). The cationic polymer can be any cationic polyelectrolyte, such as polyallylamine or polyethyleneimine, as well as polyamino acids or polysaccharides. The molecular weight is preferably between about 5 and 500 kDa. The CPT binds to the polymer by simple mixing. The resulting composition can be used as a constituent for the self assembly of different types of nanoaggregates (nanoparticles, nanocapsules).
The cationic amphiphile can be monovalent or polyvalent. It may be selected from lipids, lysolipids or pegylated lipids with a positive net charge. Useful cationic lipids thereby include:
In a preferred embodiment the cationic amphiphile is selected from a quaternary ammonium compound such as N-[1-(2,3-diacyloxy)propyl]-N,N,N-trimethyl ammonium, which may be provided as a salt with a pharmaceutically acceptable counter anion which may be selected from the group consisting of chloride, bromide, fluoride, iodide, nitrate, sulfate, methyl sulfate, phosphate, acetate, benzoate, citrate, glutamate or lactate.
The inventive composition is characterized in that the carboxylate form of a camptothecin drug is associated with an organic cationic molecule. The association is driven by electrostatic forces and optionally amphiphilic interactions. Preferably, the organic counter molecule is a cationic amphiphile or a positively charged polymer. Herein, the term CM-CPT is used to denominate the composition comprising a camptothecin drug and the organic counter molecule. The composition may be obtained by adding CPT-carboxylate to the counter ion, or vice-versa, in any suitable way. Detailed procedures for preparing the inventive composition are given in subsequent sections.
The presence of the CM-CPT can be shown in situ, for example by spectroscopic methods, since the spectra of the CPT-carboxylate, CPT-lactone and CM-CPT are clearly different (
The binding selectivity of CPT to cationic molecules is clearly demonstrated in
These finding are corroborated by fluorescence anisotropy measurements of the CPT. In this experiment, an increase of the fluorescence anisotropy is expected if the fluorophore is inserted into a liposome and thus its mobility is decreased. As can be seen in
For efficient binding, in addition to charge, the phase state of the fatty acid chains is important. This is demonstrated in
Unless defined otherwise, all technical and scientific terms used in this specification shall have the same meaning as commonly understood by persons of ordinary skill in the art to which-the present invention pertains.
“About” in the context of amount values refers to an average deviation of maximum ±20%, preferably ±10% based on the indicated value. For example, an amount of about 30 mol % cationic lipid refers to 30 mol % ±6 mol % and preferably 30 mol % ±3 mol % cationic lipid with respect to the total lipid/amphiphile molarity.
“Amphiphile” refers to a molecule, which consists of a water-soluble (hydrophilic) and an oil-soluble (lipophilic) part. The lipophilic part preferably contains at least one alkyl chain having at least 10, preferably at least 12 carbon atoms.
“Associating” a negatively charged compound to a cationic amphiphile refers to binding said compound to the cationic organic molecule by electrostatic and/or amphipatic (or amphiphilic) forces. The resulting composition is preferably characterized by a charge ratio close to 1:1, but also ratios of 1.5:1 or >2:1 may be used depending on the nature of the molecules.
“Camptothecin” refers to 20(S)-Camptothecine (1H-Pyrano[3′,4′:6,7]indolizino[1,2-b]quinoline-3,14 (4H,12H)-dione, 4-ethyl-4-hydroxy-,(S)—), CAS 7689-03-4.
“Cancer” refers to the more common forms of cancers such as bladder cancer, breast cancer, colorectal cancer, endometrial cancer, head and neck cancer, leukaemia, lung cancer, lymphoma, melanoma, non-small-cell lung cancer, ovarian cancer, prostate cancer and to childhood cancers such as brain stem glioma, cerebellar astrocytoma, cerebral astrocytoma, ependymoma, Ewing's sarcoma/family of tumors, germ cell tumor, extracranial, hodgkin's disease, leukemia, acute lymphoblastic, leukemia, acute myeloid, liver cancer, medulloblastoma, neuroblastoma, non-hodgkin's lymphoma, osteosarcoma/malignant fibrous histiocytoma of bone, retinoblastoma, rhabdomyosarcoma, soft tissue sarcoma, supratentorial primitive neuroectodermal and pineal tumors, unusual childhood cancers, visual pathway and hypothalamic glioma, Wilms' Tumor and other childhood kidney tumors and to less common cancers including acute lymphocytic leukaemia, adult acute myeloid leukaemia, adult non-hodgkin's lymphoma, brain tumor, cervical cancer, childhood cancers, childhood sarcoma, chronic lymphocytic leukaemia, chronic myeloid leukaemia, esophageal cancer, hairy cell leukaemia, kidney cancer, liver cancer, multiple myeloma, neuroblastoma, oral cancer, pancreatic cancer, primary central nervous system lymphoma, skin cancer, small-cell lung cancer.
“Carrier” refers to a diluent, adjuvant, excipient, or vehicle which is suitable for administering a diagnostic or therapeutic agent. The term also refers to a pharmaceutically acceptable component(s) that contains, complexes or is otherwise associated with an agent to facilitate the transport of such an agent to its intended target site. Carriers include those known in the art, such as liposomes, polymers, lipid complexes, serum albumin, antibodies, cyclodextrins and dextrans, chelates, or other supramolecular assemblies.
“Cationic” refers to an agent that has a net positive charge or positive zeta potential under the respective environmental conditions. In the present invention, it is referred to environments where the pH is in the range between 3 and 9, preferably between 5 and 8.
“Cationic amphiphile” or “cationic lipid” refers to encompass any amphiphile or lipid which has a positive charge. In the present invention, it is referred to environments where the pH is in the range between 3 and 9, preferably between 5 and 8.
“Cationic liposome” refers to a liposome which is positively charged. In the present invention, it is referred to environments where the pH is in the range between 3 and 9, preferably between 5 and 8. The cationic liposomes are prepared from the cationic lipids or amphiphiles themselves or in admixture with other amphiphiles, particularly neutral or anionic lipids.
“CM” is used in the text as an abbreviation for cationic molecule.
“Colloids” or colloidal particles refers to particles or molecular aggregates dispersed in a medium in which they are insoluble and have a size between about 5 nm and 5000 nm.
“Colloidal nanoaggregate having an overall positive charge” as used herein refers to a colloidal nanoaggregate comprising optionally the inventive composition and having an excess of positively charged molecules in the outer molecular layer.
“Cryoprotectant” refers to a substance that helps to protect a species from the effect of freezing. “Derivative” refers to a compound derived from some other compound while maintaining its general structural features. Derivatives may be obtained for example by chemical functionalization or derivatization.
“Disease characterized by enhanced angiogenic activity” refers to processes such as tissue inflammation, arthritis, asthma, macular degeneration, tumor growth, and diabetic retinopathy.
“Drug” as used herein refers to a pharmaceutically acceptable pharmacologically active substance, physiologically active substances and/or substances for diagnosis use.
“Homogenization” refers to a physical process that achieves a uniform distribution between several components. One example is high-pressure homogenisation.
“Lipid” refers to its conventional sense as a generic term encompassing fats, lipids, alcohol-ethersoluble constitutents of protoplasm, which are insoluble in water. Lipids compose the fats, fatty oils, essential oils, waxes, steroid, sterols, phospholipids, glycolipids, sulpholipids, aminolipids, chromolipids, and fatty acids. The term encompasses both naturally occurring and synthetic lipids. Preferred lipids in connection with the present invention are: steroids and sterol, particularly cholesterol, phospholipids, including phosphatidyl and phosphatidylcholines and phosphatidylethanolamines, and sphingomyelins. Where there are fatty acids, they could be about 12-24 carbon chains in length, containing up to 6 double bonds, and linked to the backbone, the fatty acids could be different (asymmetric), or there may be only 1 fatty acid chain present, e.g., lysolecithins. Mixed formulations are also possible, particularly when the non-cationic lipids are derived from natural sources, such as lecithins (phosphatidylcholines) purified from egg yolk, bovine heart, brain, or liver, or soybean.
“Liposome” refers to a microscopic spherical membrane-enclosed vesicle (about 50-2000 nm diameter) made artificially in the laboratory. The term “liposome” encompasses any compartment enclosed by a lipid bilayer. Liposomes are also referred to as lipid vesicles. In order to form a liposome the lipid molecules comprise elongated nonpolar (hydrophobic) portions and polar (hydrophilic) portions. The hydrophobic and hydrophilic portions of the molecule are preferably positioned at two ends of an elongated molecular structure. When such lipids are dispersed in water they spontaneously form bilayer membranes referred to as lamellae. The lamellae are composed of two mono layer sheets of lipid molecules with their non-polar (hydrophobic) surfaces facing each other and their polar (hydrophilic) surfaces facing the aqueous medium. The membranes formed by the lipids enclose a portion of the aqueous phase in a manner similar to that of a cell membrane enclosing the contents of a cell. Thus, the bilayer of a liposome has similarities to a cell membrane without the protein components present in a cell membrane. As used in connection with the present invention, the term liposome includes multilamellar liposomes, which generally have a diameter in the range of about 1 to about 10 micrometers and are comprised of anywhere from two to hundreds of concentric lipid bilayers alternating with layers of an aqueous phase, and also includes unilamellar vesicles which are comprised of a single lipid bilayer. The latter can be produced by subjecting multilamellar liposomes to ultrasound, by extrusion under pressure through membranes having pores of defined size, or by high pressure homogenization. A further result of these procedures is, that often well defined size distributions of the liposomes are achieved. By extrusion through membranes of defined pore size (typical values are 100, 200, 400 or 800 nm), liposomes with a size distribution close to the pore size of the membrane can be achieved. By ultrasound and high pressure homogenisation procedures, defined size distributions are obtained by molecular self-organization as a function of the experimental conditions.
“Lysolipid” refers to a lipid where one fatty acid ester has been cleaved resulting in a glycerol backbone bearing one free hydroxyl group.
“Lysophospholipid” refers to a phospholipid where one fatty acid ester has been cleaved resulting in a glycerol backbone bearing one free hydroxyl group.
“Micelle” refers to an aggregate of amphiphilic molecules in a colloidal suspension.
“Nanoaggregate” refers to an assembly on a nanometer to micrometer scale assembled from smaller particles held together by attractive physical forces.
“Nanoparticle” refers to an entity in the dimensions of nanometers to micrometers.
“Negatively Charged Lipids” refer to lipids that have a negative net charge. In the present invention, it is referred to environments where the pH is in the range between 3 and 9, preferably between 5 and 8. Examples are phosphatidic acid, phosphatidylserine, phosphatidylglycerol, phosphatidylinositol (not limited to a specific sugar), fatty acids, sterols.
“Neutral Lipids” refer to lipids that have a neutral net charge such as cholesterol, 1,2-diacyl-sn-glycero-3-phosphoethanolamine, including but not limited to dioleoyl (DOPE), 1,2-diacyl-glycero-3-phosphocholines, Sphingomyelin. In the present invention, it is referred to environments where the pH is in the range between 3 and 9, preferably between 5 and 8.
“Particle diameter” refers to the size of a particle. To experimentally determine particle diameters, dynamic light scattering (DLS) measurements, using Malvern Zetasizer 1000 or 3000 (Malvern, Herrenberg, Germany) were performed. For quantitative data analysis (determination of Z (average and PI), in all cases parameters (refractive index, density, viscosity) of pure water were plugged in, even if the aqueous phase contained cryoprotectants to a certain extend. Therefore, for the absolute numbers, a certain systematic deviation with respect to literature data may have to be taken into account.
“Pegylated lipid” refers to a lipid bearing one ore more polyethylene glycol residues.
“Pharmaceutical composition” refers to a combination of two or more different materials with superior pharmaceutical properties than are possessed by either component.
“Phospholipid” refers to a lipid consisting of a glycerol backbone, a phosphate group and one or more fatty acids wich are bound to the glycerol backbone by ester bonds.
“Positively Charged Lipids” refer to a synonym for cationic lipids (for definition see definition of “cationic lipids”). In the present invention, it is referred to environments where the pH is in the range between 3 and 9, preferably between 5 and 8.
“Sterol” refers to a steroid alcohol. Steroids are derived from the compound called cyclopentanoperhydrophenanthrene. Well-known examples of sterols include cholesterol, lanosterol, and phytosterol.
“Therapeutic agent” refers to a species that reduces the extent of the pathology of a disease such as cancer. Such a compound may, for example, reduce primary tumor growth and, preferably, the metastatic potential of a cancer. Alternatively, such a compound may reduce tumor vascularity, for example either by decreasing microvessel size or number or by decreasing the blood vessel density ratio.
“Virtually free” of a species refers to as not detectable by HPTLC.
“Zeta potential” refers to a surface potential of a particle such as a colloidal particle measured with an instrument such as a Zetasizer 3000 using Laser Doppler micro-electrophoresis under the conditions specified. The zeta potential describes the potential at the boundary between bulk solution and the region of hydrodynamic shear or diffuse layer. For the present patent, zeta potential measurements were performed with a Malvern Zetasizer 3000 (Malvern, Herrenberg, Germany).
The present invention follows a strategy, which is contrary to the development of CPT drugs within the last 30 years, since it bases on using the carboxylate form instead of the lactone from of a CPT drug. The inventive composition is obtained from CPT-carboxylate and a cationic organic counter molecule (
CM-CPT is characterized by its physico-chemical properties, which are clearly different to those of the constituting molecules. It can be identified as an independent molecular form in contrast to the carboxylate and the lactone form for example by spectroscopic measurements (
The advantages of the present invention are as follows:
It is well known, that, in aqueous environment, amphiphiles as well as polymers mentioned herein can form various types of colloidal nanoparticulate systems. These include suspensions of micelles, liposomes, nanocapsules, any other type of nanoparticles or as well emulsions and gels. The physico-chemical properties of the described inventive composition are determined as well by the constituting amphiphile or polymer. Therefore, suspensions of stable nanoaggregates can be made from the inventive composition in an analogous way as with the constituting amphiphiles and/or polymers.
Thus, a further aspect of the present invention relates to a colloidal nanoaggregate comprising the inventive composition and having an overall positive charge. The proportion of a CPT drug in the cationic colloidal nanoaggregates is preferably less than about 50 mol % (in case of liposomes, the aqueous compartment is disregarded in this balance). In some embodiments, the nanoaggregate comprise a camptothecin drug in a proportion from about 0.1 mol % to about 50 mol % and in other embodiments from about 1 mol % to about 30 mol %. In other embodiments, a camptothecin drug is present in about 3 mol % to about 10 mol %.
The colloidal nanoaggregate may comprise cationic lipids in an amount of at least about 30 mol % to at most about less than 100 mol %, preferably 40 mol % to about 98 mol %, more preferably about 50 mol % to about 98 mol % in the surface layer.
The inventive nanoaggregate can further comprise amphiphiles with a negative and/or neutral net charge (anionic and/or neutral amphiphile). These can be selected from sterols or lipids such as cholesterol, phospholipids, lysolipids, lysophospholipids, sphingolipids or pegylated lipids with a negative or neutral net change. Useful anionic and neutral lipids thereby include: Phosphatidic acid, phosphatidylserine, phosphatidylglycerol, phosphatidylinositol (not limited to a specific sugar), fatty acids, sterols containing a carboxylic acid group, cholesterol, 1,2-diacyl-sn-glycero-3-phosphoethanolamine, including but not limited to dioleoyl (DOPE), 1,2-diacyl-glycero-3-phosphocholines, sphingomyelin. The fatty acids linked to the glycerol backbone are not limited to a specific length or number of double bonds. Phospholipids may also have two different fatty acids.
In a preferred embodiment the neutral amphiphile is diacylphosphatidylcholine.
The inventive nanoaggregate may comprise neutral and/or anionic lipids in an amount of about 0 to about 70 mol %, preferably of about 20 mol % to about 50 mol % and most preferably of about 30 mol % to about 40 mol % in the surface layer.
In the context of the present invention overall positive charge means an excess of positively charged molecules in the molecular surface layer of the colloidal nanoaggregate. Thus, in a preferred embodiment, the inventive nanoaggregate comprises an excess of cationic lipids of at least 20 mol %, preferably at least 30 mol % and most preferably at least 40 mol %. As an example, if the surface of the nanoaggregate contains 10 mol % negatively charged lipids or negatively charged CPT drug, the amount of positively charged lipid has to be at least 30%, preferably at least 40 mol % and most preferably at least 50 mol % in order to fulfil these charge requirements. Measurements of the zeta potential can be used to proof the net charge of the colloidal nanoaggregates. Preferably, zeta potentials are in the range between 25 mV and 100 mV, more preferably between 35 mV and 70 mV, depending on the composition (measured in about 0.05 M KCl solution at about pH 7.5 at room temperature are useful in the context of the present patent. However, measured under that conditions, zeta potential values lower than 25 mV can be determined for polymer graft colloidal nanoaggregates, for example when the surface of the nanoaggregates comprises pegylated lipids.
The inventive nanoaggregate can be present as different types of supramolecular assemblies with different size ranges. Thus, in further preferred embodiments, the inventive nanoaggregate is an emulsion droplet, a liposome, a micelle, a nanoparticle or a nanocapsule. The particle diameter may range from about 5 nm to about 2000 nm, preferably between 50 nm and 1000 nm and more preferably between 100 to 500 nm.
Preferred nanoaggregates of the present invention are cationic liposomes comprising DOTAP, DSTAP, DPTAP, DMTAP, DLTAP, DODAP, other analogues of DOTAP or DODAP or any other cationic lipid in an amount, that the net excess of positively charged moieties is at least about 20%, preferably of at least about 30mol %, more preferably of at least about 40%, and most preferably of at least about 50% with respect to the total number of molecules. The liposomes may further contain DOPC, pegylated lipids or any other lipid that has a neutral or negative net charge. The fraction of pegylated lipids is preferably up to about 10%, more preferably up to about 5%. In case the liposomes do not contain pegylated lipids, the zeta potential of this liposomes is preferably above about 30 mV, more preferably above about 40 mV, and most preferably above about 50 mV. If pegylated lipids are present or any other lipid, the zeta potential of the preferred formulation as measured under the conditions given above can be as well be lower, i.e. in the range close to zero.
It is a further object of the present invention to provide a cationic colloidal nanoaggregate such as a liposome, which can be freeze-dried (lyophilized), stored for an extended time period and then reconstituted by adding the removed amount of water to the dry lyophilisates. Reconstitution of the lyophilisates is performed when and where they are to be used without losing a substantial portion of their contents during the freeze-drying process (lyophilization), storage and reconstitution step. To achieve the latter, one or more protective agents such as cryoprotectants can be present. Thus, preferably the inventive nanoaggregate comprises a cryoprotectant wherein the cryoprotectant is selected from a sugar or an alcohol or a combination thereof. Preferably, the cryoprotectant is selected from trehalose, maltose, sucrose, glucose, lactose, dextran, mannitol or sorbitol. The cryoprotectant can be present in an amount of about 1% to about 20%, preferably 5% to 15%, most preferably 6% to 12%, with respect to the aqueous solution (m/v) from which the lyophilisate is formed. The corresponding molar ratio lipid/cryoprotectant depends on the liposome concentration. For a 30 mM formulation, the molar ratio is about 1:1 to 1:20, preferably 1:5 to 1:15, most preferably 1:6 to 1:12. For the molar ratios for other liposome concentrations these numbers have to be multiplied by the factor as given by the relation between the two concentrations.
It is a further object of the present invention to provide a concentrated lipid and CM-CPT drug suspension or gel. The concentration of the suspension or gel is preferably higher than 100 mM, but it can be as well at 200 mM, 500 mM or higher. The concentrate may be stored as it is, or freezing or lyophilization may be applied. One or more protective agents such as cryoprotectants, buffers or other additives can be present. The concentrate can be reconstituted with an aqueous phase, which can contain buffers, and other additives in order to obtain a more diluted liposome suspension.
In accordance with other aspects of the invention, a pharmaceutical preparation comprising a pharmaceutically effective amount of the inventive composition or an inventive colloidal nanoaggregate together with a pharmaceutically acceptable carrier, diluent and/or adjuvant is provided.
A further aspect of the present invention relates to a method of producing the inventive nanoaggreagates. Colloidal nanoaggregates can be formed by various methodologies, well known to ordinarily skilled artisans. Sonication, vortexing, mechanical stirring, static mixing, homogenization, injection, microfluidization, colloid mills and/or pressure emulsifiers can be used to prepare nanoaggregates of various types including various orders of addition of materials. The nanoaggregates of the present invention can be formed by a homogenization, a lipid film, a solvent mixing or by a solvent injection procedure.
The nanoaggregates of the present invention can be produced by a method comprising the following steps:
Preferred procedures for preparing CPT-carboxylate are as follows:
In each case standard inorganic or organic bases can be used, such as NaOH, KOH, NH4OH, TRIS, etc. The solution can comprise H2O and organic solvents (methanol, ethanol, propanol, isopropanol, acetone) in any suitable relation.
The solvent injection procedure is performed wherein
The solvent mixing procedure is performed wherein an aqueous solution and a non-aqueous solution are mixed, where the solutions can contain cationic amphiphiles, anionic amphiphiles neutral amphiphiles, polymers buffers, cryoprotectants and other additives, and at least part of the amphiphiles are dissolved in the non-aqueous phase. Then the non-aqueous solvent and other undesired components are removed by suitable methods, preferably evaporation or dialysis. A colloidal suspension of liposomes or a concentrated gel, comprising lipids and a camptothecin drug is obtained. The gel or suspension can be frozen or lyophilised for storage. It can be reconstituted with suitable aqueous phase to give the desired colloidal nanoaggregates.
Alternatively, in a preferred embodiment a lipid film can be formed by two different methods:
The camptothecin drug can be incorporated either directly by dissolving it in an organic solution comprising at least one cationic amphiphile and optionally at least one anionic and/or neutral amphiphile and the camptothecin drug or by forming a lipid film without the drug first. In the first case, the lipid film is subsequently taken up by an aqueous solution comprising no drug and in the second case with the camptothecin drug.
In a further preferred embodiment, the organic solution comprises an organic solvent selected from methanol, ethanol, propanol, isopropanol, ethylene glycol, tetrahydrofuran, chloroform or diethylether or a mixture of these solvents.
The aqueous solution may further comprise a cryoprotectant, which is selected from a sugar or an alcohol or a combination thereof such as trehalose, maltose, sucrose, glucose, lactose, dextran, mannitol or sorbitol in the range of up to about 20% (m/v). Preferably the stabilizing agent is used in the range of about 1% (m/v) to about 20% (m/v) and most preferably in the range of about 5% (m/v) to about 15% (m/v) with respect of the total volume of the liposomal dispersion. The corresponding molar ratio lipid/cryoprotectant depends on the liposome concentration. For a 30 mM formulation, the molar ratio is preferably about 1:1 to 1:20, most preferably 1:5 to 1:15. The molar ratios for other liposome concentrations are given from these numbers multiplication with the factor as given from the relation of the two concentrations.
In an other preferred embodiment the inventive method can further comprise at least one dialysis and/or at least one homogenization and/or optionally at least one sterile filtration and/or optionally a freeze-drying and/or optionally a reconstitution step. Dialysis might be necessary in order to remove free camptothecin drug, or in order to remove non-aqueous solvent or other components from the solution. Since the nanoaggregates as achieved by the above-described method do not necessarily have the desired size distribution, a homogenization step may be performed subsequently. Homogenization can be performed by extrusion through a membrane with defined pore size, high-pressure homogenization, ultrasound treatment, high speed homogenization, or any other homogenization technique well known in the art.
In another embodiment of the inventive method an aqueous solution of the camptothecin drug is added to a suspension of preformed cationic liposomes without active compound. The liposome suspension can be at a concentration ranging from 5 mM to 100 mM lipid or it can be at concentrations from 100 mM to 500 mM lipid or higher (gel). Angiogenesis associated diseases are dependent on blood supply. The local interruption of the vasculature will produce an avalanche of cell death. The vascular endothelium is in direct contact with the blood. It is contemplated that a variety of diseases can be prevented and treated with the foregoing methods and compositions. In a preferred embodiment, a composition, a colloidal nanoaggregate or a pharmaceutical formulation as provided by the present invention can be used for preventing and/or treating a disease such as cancer, a variety of inflammatory diseases, diabetic retinopathy, rheumatoid arthritis, inflammation, dermatitis, psoriasis, stomach ulcers, macular degeneration, hematogenous and solid tumors. In a further preferred embodiment, the methods and compositions of the present invention can be applied for producing a medicament for preventing and/or treating solid tumors and their metastases such as bladder, brain, breast, cervical, colorectal, endometrial, head and neck or kidney cancer, leukemia, liver or lung cancer, lymphoma, melanoma, non-small-cell lung, ovarian, pancreatic or prostate cancer.
The compositions and nanoaggregates of the invention are particularly suitable for the targeting of endothelial cells. Thus, a further objective of the present invention is producing a medicament for the selective delivery of a camptothecin drug with antimitotic activity to an angiogenic vascular target site, wherein delivery comprises the steps of
In a preferred embodiment, in step a) the inventive composition and/or the inventive colloidal nanoaggregate and/or a pharmaceutical composition thereof is provided.
Preferably, step d) comprises endocytosis and/or fusion with the cell membrane and/or passive or active diffusion across the cell membrane, wherein endocytosis comprises releasing said camptothecin into the lysosomal compartment.
The following examples should be illustrative only but are not meant to be limiting to the scope of the invention. Other generic and specific configurations will be apparent to those skilled in the art.
1. CPT-Carboxylate Salt Preparation
The carboxylate salt of a CPT drug is obtained by exposing the CPT drug to an alkaline environment, preferably with a pH above 9. Explicitly, two procedures comprising the following steps, were applied:
A CM-CPT (composition of cationic molecule and camptothecin) is obtained from CPT-carboxylate salt by adding a solution of a cationic amphiphile to the carboxylate salt. If desired, subsequently the solvent can be evaporated. The solvent can be Ethanol, Chloroform, Chloroform/Methanol, or any other suitable organic solvent or solvent mixture. Alternatively, the solution of the cationic amphiphile can be added to an aqueous solution of the CPT-carboxylate. In case of a positively charged polymer as a countermolecule, the latter can be present as well in the aqueous phase. For further treatment, the CM-CPT solution or suspension can be used as it was prepared, or the solvent can be removed in order to obtain the pure composition. Subsequently it can be brought into a desired medium. For example in order to obtain a 1 mM CPT-DOTAP composition with a molar ratio of about 1:1, 1 mmol of CPT is dissolved in NH4OH and then the solvent is evaporated according to procedure 1 b). To the remaining salt (in that case present as a thin film at the inner wall of a flask), 1000 ml of a 1 mM solution of DOTAP in EtOH are added. In other cases, if this is favourable for further formulation, lower molar ratios CM/CPT may be realized, such as, 10/90, 5/95, 1/99 or 0.5/99.5.
3. Liposome Formulation
The formulation procedure may consist of the following steps:
For the formation of the colloidal liposome suspensions, different methodologies can be applied. Subsequently, the most relevant techniques are briefly outlined.
Film Method
Liposomes can be formed by the well-known film method, such as described in the literature. Briefly, from the organic solution of the lipid, or the lipid plus the drug, the solvent is evaporated, and a thin film of lipid (or lipid plus drug) is formed at the inner wall of a flask. The thin molecular film is resuspended in an aqueous phase, which can contain further components such as buffers, ions, cryoprotectants and the like. With this procedure, liposomal suspensions are formed in a self-assembly process. A standard formulation is obtained by forming a film of 90 μmol DOTAP and 10 μmol camptothecin from a solution in chloroform/methanol, 10/1. The film is then reconstituted with 10 ml of the aqueous phase, in order to achieve a suspension where the total liposomal concentration (lipid+drug) is 10 mM.
The aqueous solution can contain a cryoprotectant, e.g. glucose or trehalose and/or buffers (Tris), to achieve a desired pH after reconstitution. A typical pH is in the range between 7 and 8. However, depending on the lipid, as well higher (up to pH 9) or lower (down to pH 5) values can be selected. For the cryoprotectant, typical conditions correspond to 5-10% of trehalose present in the aqueous solution. The pH of the liposomal formulation can be altered after formulation for further treatment.
Thus, a liposomal formulation with the drug/lipid ratio of 1:9, and with a total (lipid+drug) concentration of 10 mM is obtained. Other typical molarities are 15 mM, 20 mM, 25 mM or 30 mM. If necessary, molarities up to 50 mM or higher can be formulated. In that cases, the same formulation procedure as described for 10 mM is applied, where the total amounts of drug, lipid and solvent are adopted to the desired concentration. The drug:lipid ratio usually is selected to be in the rage from 1:99 to 20:80. Another frequently used molar ratio is 5/95. These formulations can be realized by the above described procedure with the molar amounts of the components adopted to the desired final formulation.
For example, for 10 ml of a 25 mM formulation with a molar composition of 5/95, a film of 23.75 μmol DOTAP and 12.5 μmol camptothecin is reconstituted with 10 ml of buffer. The lipid phase can consist of only cationic lipid, such as DMTAP, DOTAP, DPTAP, DSTAP, DOTMA, or DDAB, or it can comprise up to 60% of charged and non-charged colipids.
Standard formulations which have been used by us most frequently consist of CPT/DOTAP/DPOC=5:47.5:47.5, or 5:55:45 or 10:45:45 or 10:60:30.
In table 1 the results form physico-chemical characterization of such liposomal formulations are given. The listed formulations have been tested as well in an efficacy study (
In an alternative embodiment of procedure 1a) the camptothecin is converted into the carboxylate, or the carboxylate salt for formulation. Such a way the CPT is ‘activated’ for easier association of the drug to the cationic lipid, as, in fact, the carboxylate is the molecular form which associates to the latter. CPT is solubilized in NH3, and the volume which contains the necessary amount of the drug (i.e., 10 μM in the example described in 1a) is added to a flask. After evaporation of the solvent a film of the ammonium salt of the CPT-carboxylate is formed. Then the organic solution of the lipid is added and the solvent is evaporated. Thus a film comprising camptothecin and lipid is obtained, where the camptothecin binds more readily to the cationic lipid. Particularly for low pH values, it is easier to obtain liposomes with high drug/lipid values. The subsequent procedure is analogous to the one described above.
In a further embodiment, the CPT-carboxylate can be part of the aqueous solution for reconstitution of the pure lipid film. In that case, a separation step (such as outlined below), or a concentration step (such as below) can be performed after formulation.
Organic Solution Injection
Liposomal suspensions can be achieved through the injection of a solution of the lipid, or the lipid+drug, into the aqueous solution. A typical solvent for the lipid or the lipid+drug phase is ethanol (‘ethanol injection’). In the present case, a new procedure is employed, in the sense that ethanol injection into the aqueous solution of the camptothecin-carboxylate is performed. As due to the attractive interaction between the drug and the cationic lipid, camptothecin-containing liposomes are formed in a self-assembly process. In order to achieve 10 ml of a 10 mM suspension of CPT/DOTAP 1:9, a 10 μM solution of CPT-carboxylate, optionally containing further additives as outlined in the previous section, is prepared. Other typical molarities are 15 mM, 20 mM, 25 mM or 30 mM of the total lipid+drug concentration. In order to obtain 10 ml of a 25 mM suspension of CPT/DOTAP 5:95, a 12.5 μM solution of CPT-carboxylate, optionally containing further additives as outlined in the previous section, is prepared. The solution of the carboxylate can be prepared directly by dissolving CPT-lactone in a suitable amount of base, or it can be prepared from dry salt. Preferentially, the ammonium salt solution or the Na-salt solution of the CPT-carboxylate is used.
The aqueous phase can have a pH between 5 and 9, according to the necessities of the experiment. In the examples which are presented here (tab. 2) a pH of 7.5 was selected. The ethanolic lipid solution has a concentration between 200-400 mM. The suitable volume of the lipid solution in ethanol is injected under vigorous stirring. All compositions and concentrations as described in the previous section can be achieved by this approach. In case of the 10 mM 1:9 suspension, ca. 0.23 ml of a 400 mM DOTAP solution in Ethanol can be used and in case of the 25 mM 5:95 suspension, ca. 0.59 ml of a 400 mM DOTAP solution in Ethanol can be used. As an alternative to ethanol, as well other suitable solvents or mixtures thereof can be taken. Typically, these are alcohols, ethers, chloroform, hydrocarbons, etc. As well solvents in the supercritical state can be applied, such as hydrocarbons, carbon dioxide, perfluorinated compounds, etc. Subsequently to the described formulation procedure, extrusion (2) dialysis (3), a concentration step (4) or freeze drying can be performed.
Alternatively to the injection of the pure lipid solution, both, the lipid(s) and the CM-CPT drug can be dissolved in the injection solution. All other steps are equivalent. In the described formulation procedures, for better perceivability DOTAP and CPT were taken as representatives, however, the procedures are applicable for the other listed lipids and CPT drugs. Examples for formulations which have been performed with the described procedures with DMTAP, DSTAP, and DDAP as cationic lipids are given in Tab. 4 (Appendix). As well formulations with several colipids and pegylated lipids (DOPC, Cholesterol, PEG-DOPE) are listed. Depending on the used cationic lipid, the fraction of the colipid can be from 1 to 70 mole %. Pegylated lipids are preferentially used in the range from 1 to 15 mole %.
Further, in the table formulation examples with other CPT drug are given. Formulations with other CPT derivates are formed in the analogous way. In order to optimise the results, the explicit formulation procedure is adopted according to the molecular properties of the CPT drug and the cationic lipid. In this context the CPT drugs which are (i) more hydrophilic, which are (ii) more hydrophobic or (iii) which have similar properties as CPT can be distinguished. For CPT drugs which are more hydrophilic, preferentially ethanol injection into the aqueous solution of the drug, as described above, is performed. Examples for such molecules are Topotecan and Irinotecan, and formulation examples with these compounds are listed in Tab. 4. For CPT drugs which are more hydrophobic than CPT, preferentially film method, or ethanol injection where both, drug and lipid, are present in the ethanol solution, is performed. An example for a more hydrophobic derivate is CPT-oleate, which can be obtained from 10-OH-CPT as described in the literature (Lundberg 1998). A formulation example with CPT-oleate using the film method is given in Tab. 4. Examples for compounds which, in the present context, have similar molecular properties as CPT are 10-OH-CPT and SN38. Therefore, as for CPT, either of the described methods can be applied. In Tab. 4 formulation examples with 10-OH-CPT and SN38 using ethanol injection are given.
Extrusion
The liposomal suspensions as achieved by the above-described methods do not have necessarily the desired size distribution. Therefore, an extrusion through a membrane of defined pore size can be performed subsequently.
In our experiments we have usually performed extrusion through membranes of 200 nm pores size (Osmonics Inc., Poretics, polycarbonate 0.2 Microns). Other typical extrusion membranes were with 100 nm or with 400 nm pore size. Size distributions were controlled by quasi-elastic light scattering (Malvern, Herrenberg, Germany). Examples of liposomal sizes after extrusion are given in Tables 1 and 2.
Separation of Low Molecular Compounds
Dialysis techniques were used to separate low molecular components from the liposomal suspensions. This was particularly the case for the experiments with ethanol injection, where in addition to a fraction of non-liposomal camptothecin, a certain amount of ethanol was present in the suspension. Dialysis tubes from regenerated cellulose with a MWCO of 8,000-10,000 (Roth, Karsruhe Germany) were used. Alternatively, the so called “cross-flow” technique (Vivascience, Sartorius Group, Göttingen, Germany) with Polyethersulfone membranes, MWCO 50,000 were used. The release of the free CPT was monitored by UV-vis spectroscopy. The amount of the released CPT-carboxylate depends on the lipid and drug concentration, the drug/lipid ratio, pH and other parameters. An example is given in
Freezing and Freeze-Drying
Freeze drying of the liposomal formulations was performed using standard equipment and adopted protocols (for example: Epsilon 2-12D, Control Unit LMC-2, Christ, Osterode, Germany). The composition and the physical state of the suspensions were characterized after reconstitution such as described below. The suspension as described above could be frozen and brought back to room temperature, without drastically affecting the aggregation state of the liposomes, such as proven by quasi-elastic light scattering measurements.
Results from size measurements before and after lyophilization/freezing are given in Tab. 2.
Freeze drying enables to realize formulations which in liquid formulations are unstable. For example, thermodynamically metastable states can be ‘frozen’ and, after reconstitution, such formulations can be obtained with a reasonable in-use stability. Formulations, which in the liquid state have only a stability of hours or days can be frozen and reconstituted directly before application. Therefore, freeze drying permits to apply compositions, which have a stability of only few days or hours. In the context of the present invention, freeze drying permits to realize formulations in a wider pH range as it is possible in liquid formulations. In liquid formulations with CPT and DOTAP, the preferential pH range is between 6.5 and 8. Below, CPT-lactone formation is favoured and above lipid hydrolysis may occur. For lyophilisates as well formulations with lower (down to 4) and higher (up to 8-9) pH values can be realized.
Further, by using volatile acids or bases, favourable pH conditions during formulation and after lyophilization can be achieved, and these conditions can be selected different for the state during formulation, i.e., before lyophilization, and after lyophilization, i.e., for the reconstituted lyophilisates. By adding HCl during formulation, the pH can be lowered during that production state. As the HCl is lost on lyophilization, the pH of the suspension after reconstitution is again higher. This enables to increase in-use stability of compositions from a CPT drug and a cationic molecule, where the lactone-carboxylate equilibrium of the CPT drug is shifted towards the lactone and the binding constant to the cationic molecule is low. By using NH4OH during formulation, a camptothecin drug can be ‘activated’ for efficient binding to the cationic molecule (higher pH is favourable for carboxylate formation) before lyophilization. After lyophilization the excess NH4OH is lost, and the thus obtained lower pH can be favourable for lipid stability.
4. Concentrated Liposome Suspensions and Gels
Pre-formed liposome suspensions are concentrated by standard techniques such as dialysis against polymer solutions, ‘cross-flow’, or evaporation of solvent. The concentrated suspensions can be brought back to the previous, or any other concentration, without substantial changes of the original size distribution.
To directly prepare concentrated liposome suspensions and gels, an aqueous phase, containing (optionally) one or more of the components, and an organic phase, containing the other components are mixed. For example, an aqueous solution of 2 mM CPT carboxylate, 0.5% trehalose and 1% tris/HCl buffer is mixed with a 6 mM solution of DOTAP in ethanol, that the final CPT-carboxylate/DOTAP ratio is 10/90. A homogeneous mixture is obtained. The solvent is then evaporated under reduced pressure at room temperature, until the desired concentration is obtained. It is possible to evaporate only the ethanol (together with the eutectic fraction of water) or, with higher vacuum, as well the water. It is possible to add ethanol to the semi-concentrated suspension for further evaporation. In this way, for example, suspension with a concentration of 100 mM, 200 mM and 500 mM can be obtained. After reconstitution with water or buffer to a lower concentration, a liposome suspension, where the size distribution is a function of the previous maximum concentration is obtained. Examples are given in Tab. 3.
In a further realization of this concept, concentrated gels of pure lipid are prepared for storage. Before application, the gels are diluted with an aqueous solution of a CPT drug. In this way, liposomal formulations of the CPT-CM compound can be achieved. Storage problems of the formulation are avoided, because each component can be stored individually under optimal conditions.
5. Mixing of Pure Lipid Liposomes and Drug Solution Directly Before Use
CPT containing liposomes can be prepared by mixing of an aqueous solution of CPT carboxylate with a suspension of cationic liposomes from pure lipids. Further, lyophilisates of cationic liposome suspensions from pure lipids can be reconstituted with an aqueous solution of CPT carboxylate to form ready to use liposomal formulations of CM-CT. This has the advantage that liposome suspension and CPT-carboxylate solution can be prepared and stored separately. The liposome suspension can be stored as it is or it can be lyophilised. The CPT-carboxylate can be stored as a solution, as a dry salt or as a lyophilisate. As an example a 30 mM suspension of liposomes from 100% DOTAP in 10% trehalose was lyophilised. Subsequently, the lyophilisate was reconstituted with 2.088 ml of a 1.5 mM solution of CPT carboxylate. Further, 250 μl of a 100 mM tris/HCl buffer solution, pH 7.5, was added. Physico-chemical measurements of the efficacy of insertion yielded a similar fraction of liposomal CPT as for formulations which had been prepared by the procedures as described before. The size distribution of the liposomes was not significantly affected.
6. Cationic Polymer Bound CPT
CPT binding to cationic polymers is achieved by mixing a solution of CPT-carboxylate and of the polymer. The solutions can be in water and/or in organic solvents, depending on the experimental necessities and the type of the polymer.
A typical type of polymers are polyelectrolytes, such as polyallyamine polyethyleneimine or polysaccarides (chitosan). The components are provided in the aqueous phase, containing, optionally buffers, ions and cryoprotectants. The polyelectrolytes are deposited onto oppositely charged surfaces and nanoparticles by physisorption. By repetitive deposition of positively and negatively charged polymer (such as polyallyamine or polyallyamine/CPT and polystyrene sulfonate) organized layered structures are obtained. For the deposition procedure, standard protocols are applied (Radtchenko et al. 2000) With this technique, nanoparticles, comprising CPT/polyelectrolyte, are assembled in a controlled way.
7. Physico-Chemical Characterization
a. Fundamental Aspects of CPT Interaction with Cationic Lipids
For the present invention the interaction between CPT and the cationic organic molecules is fundamental. Therefore, the binding of CPT-carboxylate to lipids was characterized by a variety of methods. Particularly, the binding properties to DOTAP and to DOPC were compared, in order to highlight the advantages of the present invention with respect to other, earlier approaches.
Liposomal suspensions were prepared by ethanol injection of a lipid solutions into aqueous solutions of CPT-carboxylate, and the suspensions were dialized in order to remove free, non-liposomal CPT. The amount of the liposomal and the released CPT were determined by UV-vis spectroscopy. In
In order to get further information on the CPT-lipid interaction form an independent method, fluorescence anisotropy measurements were performed. Colloidal suspensions from DOTAP and from DOPC together with CPT in different molecular forms were made up. The fluorescence anisotropy was taken as a measure for the binding strength of CPT to the liposome. In
This conjecture is clearly supported by the data depicted in
Summarizing, these data indicate consistently, that for highest binding efficiency of CPT to a lipid, it is necessary to provide the CPT in the carboxylate form, and to use a positively charged lipid as a counter molecule. The resulting CM-CPT can be clearly individualized and characterized by its physico-chemical properties. On the contrary, no such CM-CPT aggregate is formed with anionic or neutral lipids. This holds as well if the latter contain unsaturated fatty acids.
b. Characterization of the Liposomal Formulations
All stages of formulation are monitored by HPLC analysis (lipid+drug) and by UV-vis and fluorescence spectroscopy. In HPLC analysis a slight loss of material after extrusion can be observed. UV-vis and fluorescence spectroscopy serves as a qualitative means in order to control formulation efficacy.
It is well known, that the spectrum of CPT depends strongly on the molecular state and on the local environment. Therefore, qualitatively, the spectra of the lactone form, the carboxylate and the liposomal CPT can be distinguished from the shape of the spectra (
Quasi-elastic light scattering (Zetasizer 1000 and Zetasizer 3000, Malvern Instruments, Herrenberg, Germany) was measured in order to determine the size distribution of the liposomes. The zeta potential was determined by a Zetasizer 3000 (Malvern Instruments). In Tab. 1, the results from the characterization of some exemplary formulations are shown.
8. In vitro Determination of the Cytostatic Efficacy of LipoCam
The efficacy of a cytostatic drug is determined in vitro by analysing the decrease of cell viability in correlation to the drug concentration. The drug concentration at which cell viability is inhibited to 50% (“IC50”) is used as index for the inhibitory potential of a respective drug. The higher the cytostatic potential, the lower is the IC50 value. Drugs with high inhibitory potential have IC50 values in the nM range. Here we compared 3 formulations of liposomally encapsulated camptothecin carboxylate (RM544=Lipocam I, RM541=Lipocam II, RM542=Lipocam III) with free carboxylate (RM543).
Principle:
A suitable cell line (i.e. endothelial or tumor cell line) is seeded at a constant densities in four 24-well plates. After one or two days, a series of 11 consecutive drug dilutions is added to cover the range between 0-5000 nM final drug concentration. Each individual concentration is measured in 2 wells independently to increase the accuracy of the assay. Two wells without drug serve as control. The cells are incubated at optimal growth conditions (5-5.5% CO2, 37° C., ˜90% humidity). After 72 h, the cell viability in each well is determined by measuring the activity of mitochondrial dehydrogenases (MTT assay). In viable cells the MTT substrate is converted to a blue, cell impermeable dye (Formazan). After around 1 h, the medium is removed, cells are lysed with isopropanol/0.04% HCl and the amount of the blue Formazan quantitated in an ELISA reader at 550 nm (measured against lysis buffer as blank). The experiment is evaluated using the Sigma Plot analysis software by plotting the mean OD550nm value (of the 2 wells containing the identical drug concentration) against the respective drug concentration. The IC50 concentration is taken at the half-maximal OD550nm value. A high inhibitory potential results in a low IC50 value.
Experiment:
2×104/cm2 Ea.Hy926 cells (transformed human endothelial line) are seeded into four 24-well plates and cultivated over night. At day 1, a series of eleven 5× concentrated master dilutions of each camptothecin formulation in cell culture medium is prepared (25000, 10000, 5000, 2500, 1250, 500, 250, 50, 25, 12.5, 5 nM). Having prepared all dilutions, the culture medium is removed from the cells and 400 μl of fresh culture medium+100 μl of the respective master drug concentration is added (each concentration to 2 wells). This results in a 1:5 dilution of the master series (final drug concentrations between 1 nm and 5000 nM). To two wells no drug is added (controls). The plates are cultivated further 72 h. After this incubation period, the medium is replaced by fresh medium containing the MTT substrat and incubated for 1 h. The medium is removed, the cells are lysed in isopropanol/0.04% HCl and the OD at 550 nm is measured.
Result:
As demonstrated in
9. Therapeutic Efficacy of LipoCam in A-375 Melanoma of Nude Mice
NMRI-nude mice were purchased from Elevage Janvier and housed in isolated ventilated cages under save environmental conditions (SPF facility, 22° C., 30-70% humidity, 12 h light/dark cycle) with food and water ad libitum. Experimental design was reviewed and approved by local government.
Tumor cells (A-375 human melanoma cell line, ATCC Nr.: CRL-1619) were grown as described in the data sheet supplied by ATCC. Tumor cells (5×106 in PBS) were inoculated s.c. in the right dorsal flank of mice in a volume of 50 μl on day 0.
Mice were assigned to the experimental groups (8 animals per cage), housed and handled (including monitoring of the body weight gain) at least five days before tumor inoculation (=day −6 to 0). Treatment begins after tumors reached a volume of approximately 100 mm3. Drugs were given by iv injection, three times a week (Mo, Wed, Fri) for the following three weeks at equitoxic doses. Drugs were prepared as described earlier. Equitoxic doses of the compounds were determined in separate experiments, where toxicity was evaluated based on haematological parameters, body weight and animal clinical observations (see Tab. 3). The solutions were administered slowly in a volume of ˜10 μl/g body weight. Animals were clinically monitored during the whole experiment, monitoring of tumor size was performed three times a week. The tumor dimensions were measured by caliper and the tumor size was calculated according to the following formula: V=πL W2/6 (L=greatest length, W=width of perpendicular axis). The body weight of individual animals was monitored at least twice during handling period, after tumor inoculation and after start of treatment. EDTA blood was collected from the retrobulbar plexus at three different points: during handling, tumor staging and in the middle of treatment from 4 animals of all treatment groups for hematology. The number of red and white blood cells and platelets were determined using an automated cell counter (Abbott Cell Dyn 3500).
Whereas tumors in the control group showed a rapid and progressive tumor growth, all drug formulations—applied at equitoxic doses—showed an anti-tumor effect (
10. Human Therapy Treatment Protocols
This example is concerned with human treatment protocols using the formulations disclosed. Treatment will be of use for diagnosing, preventing and/or treating various human diseases and disorders associated with enhanced angiogenic activity. It is considered to be particularly useful in anti-tumor therapy, for example, in treating patients with solid tumors and hematological malignancies or in therapy against a variety of chronic inflammatory diseases such as psoriasis.
A feature of the invention is that several classes of diseases and/or abnormalities are treated without directly treating the tissue involved in the abnormality e.g., by inhibiting angiogenesis the blood supply to a tumor is cut off and the tumor is killed without directly treating the tumor cells in any manner.
Methods of treating such patients using lipid:drug complexes have already been formulated, for example, see document incorporated herein by reference. It is contemplated that such methods may be straightforwardly adapted for use with the method described herein. As discussed above, other therapeutic agents could be administered either simultaneously or at distinct times. One may therefore employ either a pre-mixed pharmacological composition or “cocktail” of the therapeutic agents, or alternatively, employ distinct aliquots of the agents from separate containers.
The various elements of conducting a clinical trial, including patient treatment and monitoring, will be known to those of skill in the art in light of the present disclosure.
For regulatory approval purposes, it is contemplated that patients chosen for a study would have failed to respond to at least one course of conventional therapy and would have objectively measurable disease as determined by physical examination, laboratory techniques, or radiographic procedures. Such patients would also have no history of cardiac or renal disease and any chemotherapy should be stopped at least 2 weeks before entry into the study.
Prior to application, the formulations can be reconstituted in an aqueous solution in case the formulation was freeze dried. Again, the required application volume is calculated from the patient's body weight and the dose schedule.
The disclosed formulations may be administered over a short infusion time. The infusion given at any dose level should be dependent upon the toxicity achieved after each. Hence, if Grade II toxicity was reached after any single infusion, or at a particular period of time for a steady rate infusion, further doses should be withheld or the steady rate infusion stopped unless toxicity improved. Increasing doses should be administered to groups of patients until approximately 60% of patients showed unacceptable Grade III or IV toxicity in any category. Doses that are ⅔ of this value would be defined as the safe dose.
Physical examination, tumor measurements, and laboratory tests should, of course, be performed before treatment and at intervals of about 3-4 weeks later. Laboratory tests should include complete blood counts, serum creatinine, creatine kinase, electrolytes, urea, nitrogen, SGOT, bilirubin, albumin, and total serum protein.
Clinical responses may be defined by acceptable measure or changes in laboratory values e.g. tumormarkers. For example, a complete response may be defined by the disappearance of all measurable disease for at least a month. Whereas a partial response may be defined by a 50% or greater reduction.
All of the compositions and methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the compositions and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the composition, methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. More specifically, it will be apparent that certain agents which are both chemically and physiologically related may be substituted for the agents described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims.
Some variation in dosage will necessarily occur depending on the condition of the subject being treated. The person responsible for administration will, in any event, determine the appropriate dose for the individual subject. Moreover, for human administration, preparations should meet sterility, pyrogenicity, general safety and purity standards as required by FDA Office of Biologics standards.
Administration and Dosing
The present invention includes a method of delivery of a pharmaceutically effective amount of the inventive formulation of a camptothecin drug to an angiogenic vascular target site of a subject in need thereof. A “subject in need thereof” thereby refers to a mammal, e. g. a human.
The route of administration comprises peritoneal, parenteral or topic administration and the formulations are easily administered in a variety of dosage forms such as injectable solutions, drug release capsules and the like.
For use with the present invention the term “pharmacologically effective amount” of a compound administered to a subject in need thereof (which may be any animal with a circulatory system with endothelial cells which undergo angiogenesis) will vary depending on a wide range of factors. For example, it would be necessary to provide substantially larger doses to humans than to smaller animal. The amount of the compound will depend upon the size, age, sex, weight, and condition of the patient as well as the potency of the substance being administered. Having indicated that there is considerable variability in terms of dosing, it is believed that those skilled in the art can, using the present disclosure, readily determine appropriate dosing by first administering extremely small amounts and incrementally increasing the dose until the desired results are obtained. Although the amount of the dose will vary greatly based on factors as described above, in general, the present invention makes it possible to administer substantially smaller amounts of any substance as compared with delivery systems which target the surrounding tissue e. g., target the tumor cells themselves.
The pharmaceutically effective amount of a therapeutic agent as disclosed herein depends on the kind and the type of action of the agent. For the examples mentioned herein, it is within the range of about about 0.1 to 20 mg/kg in humans. Typically, for camptothecin drugs, doses in the order of about 5 mg/kg are applied.
9. Preparation of LipoCam Formulations
Procedures for the production of LipoCam formulations
The carboxylate salt of a CPT drug is obtained by exposing the CPT drug to an alkaline environment with a pH above 9.2 mg/ml of CPT drug are dissolved in 25% NH4OH. Subsequently the solvent is evaporated. In this way, the pure ammonium salt of the CPT drug-carboxylate is obtained. The salt is dissolved in water (ca. 2-3 mM) and a suitable amount is added to a trehalose Tris/HCl, pH 7.5, stock solution to obtain a final concentration of 10% trehalose (w/v), 10 mM Tris and x mM CPT where x is 1.5 for example a) and c), and 0.75 for example b).
Ethanol Injection
A 400 mM ethanolic solution of the lipid or lipid mixture is injected into the CPT-carboxylate solution under vigorous stirring. The solution contains only DOTAP for example a) and b) and it contains DOTAP/PEG-DOPE in the molar ratio 95/5 for example c). Thus, by a self-assembly process, polydisperse multilamellar vesicles are formed.
Extrusion
In order to obtain unilamellar vesicles of uniform size, the liposome suspensions were extruded five times through membranes of 200 nm pores size (Osmonics Inc., Poretics, polycarbonate 0.2 Microns). An additional optional step in case of animal studies was sterile filtration (Millipak 200, 0.22 μm).
The formulations were checked by HPLC for composition. Size distributions were controlled by quasi-elastic light scattering (Malvern, Herrenberg, Germany).
Results form HPLC and PCS analysis
10. Therapeutic Efficacy of LipoCam IV and VI in A-375 Melanoma of Nude Mice
NMRI-nude mice were purchased from Elevage Janvier and housed in isolated ventilated cages under save environmental conditions (SPF facility, 22° C., 30-70% humidity, 12 h light/dark cycle) with food and water ad libitum. Experimental design was reviewed and approved by local government.
Tumor cells (A-375 human melanoma cell line, ATCC Nr.: CRL-1619) were grown as described in the data sheet supplied by ATCC. Tumor cells (5×106 in PBS) were inoculated s.c. in the right dorsal flank of mice in a volume of 50 μl on day 0.
Mice were assigned to the experimental groups (8 animals per cage), housed and handled (including monitoring of the body weight gain) at least five days before tumor inoculation (=day −6 to 0). Treatment begins after the tumors reached a volume of approximately 80 mm3. Drugs were given by iv injection, three times a week (Mo, Wed, Fri) for the following three weeks. Drugs were prepared as described earlier (see Example 9). Toxicity was evaluated based on hematological parameters, body weight and animal clinical observations. The solutions were administered slowly in a volume of ˜5 μl/g body weight.
Animals were clinically monitored during the whole experiment, monitoring of tumor size was performed three times a week. The tumor dimensions were measured by caliper and the tumor size was calculated according to the following formula: V=πL W2/6 (L=greatest length, W=width of perpendicular axis). The body weight of individual animals was monitored at least twice during handling period, after tumor inoculation and after start of treatment. EDTA blood was collected from the retrobulbar plexus at three different points: during handling, tumor staging and in the middle of treatment from 4 animals of all treatment groups for hematology. The number of red and white blood cells and platelets were determined using an automated cell counter (Abbott Cell Dyn 3500).
As shown in
11. Therapeutic Efficacy of LipoCam IV and PEG-LipoCam IV in A-375 Melanoma of Nude Mice
NMRI-nude mice were purchased from Elevage Janvier and housed in isolated ventilated cages under save environmental conditions (SPF facility, 22° C., 30-70% humidity, 12 h light/dark cycle) with food and water ad libitum. Experimental design was reviewed and approved by local government.
Tumor cells (A-375 human melanoma cell line, ATCC Nr.: CRL-1619) were grown as described in the data sheet supplied by ATCC. Tumor cells (5×106 in PBS) were inoculated s.c. in the right dorsal flank of mice in a volume of 50 μl on day 0.
Mice were assigned to the experimental groups (8 animals per cage), housed and handled (including monitoring of the body weight gain) at least five days before tumor inoculation (=day −6 to 0). Treatment begins after the tumors reached a volume of approximately 300 mm3. Drugs were given by iv injection, three times a week (Mo, Wed, Fri) for the following three weeks. Drugs were prepared as described earlier (see Example 9). Toxicity was evaluated based on hematological parameters, body weight and animal clinical observations. The solutions were administered slowly in a volume of ˜5 μl/g body weight.
Animals were clinically monitored during the whole experiment, monitoring of tumor size was performed three times a week. The tumor dimensions were measured by caliper and the tumor size was calculated according to the following formula: V=πL W2/6 (L=greatest length, W=width of perpendicular axis). The body weight of individual animals was monitored at least twice during handling period, after tumor inoculation and after start of treatment. EDTA blood was collected from the retrobulbar plexus at three different points: during handling, tumor staging and in the middle of treatment from 4 animals of all treatment groups for hematology. The number of red and white blood cells and platelets were determined using an automated cell counter (Abbott Cell Dyn 3500).
In
Zunino F, et al. (2002) Current status and perspectives in the development of camptothecins. Curr Pharm Des. 8(27):2505-20.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP03/06760 | 6/26/2003 | WO | 12/21/2005 |
| Number | Date | Country | |
|---|---|---|---|
| 60391244 | Jun 2002 | US | |
| 60391246 | Jun 2002 | US |
