A biocompatible stable composition containing a hydrophobic drug, such as paclitaxel. The composition, which forms a syringeable polymeric micellar solution in aqueous or body fluids, is a freeze-dried product comprising a hydrophobic drug, i.e. paclitaxel, and an amphiphilic block copolymer wherein a hydrophobic group having affinity or attraction with the hydrophobic drug, such as paclitaxel, is incorporated on its end.

SUMMARY OF THE INVENTION

The present invention provides an improved, stable, hydrophobic drug containing polymeric micelle in an aqueous media. The composition of the present invention can be stored for longer than three years in a sterilized container, without any denaturation of the compounds and the polymeric micelles formed in the aqueous infusion fluid of the present invention are stable for longer than 72 hours (3 days). In addition, the formulation of the present invention causes no side effects to a patient and intravascular administration of the formulation provides improved bioavailability with high plasma concentration of the drug, e.g. paclitaxel, being achieved.

The present invention provides a stable biodegradable polymeric micelle-type drug composition which comprises: a modified biodegradable polymeric drug carrier micelle having a hydrophobic drug physically trapped within, but not covalently bonded to the drug carrier micelle. The micelle is capable of dissolving in water to form a stable, injectable solution thereof. The drug carrier micelle comprises an amphiphilic block copolymer having a hydrophilic poly(alkylene glycol) A block component, and a biodegradable hydrophobic polymer B block component selected from the group consisting of poly(lactic acid), poly(glycolic acid), poly(lactic-co-glycolic acid), poly(.epsilon.-caprolactone), and wherein the amphiphilic block copolymer has terminal ends modified by end groups that have an attraction or affinity for the hydrophobic drug contained in the micelle core.

The present invention also provides a method for preparing a pharmaceutical composition, which comprises the following steps: 1) preparing an amphiphilic block copolymer modified to have end groupings which have an affinity or attraction to a hydrophobic drug; 2) preparing a drug-polymer matrix by dissolving a hydrophobic drug and the modified block copolymer in an organic solvent followed by evaporation of the solvent; 3) preparing an aqueous micellar solution by dissolving the drug/modified polymer matrix in water; and 4) preparing a final formulation by freeze-drying the micellar solution followed by appropriate sterilization.

Therefore, the present invention provides for biocompatible, stable, drug containing compositions capable of forming syringeable polymeric micellar solutions in aqueous or body fluids. The composition of the present invention is a freeze-dried product comprising a hydrophobic drug (e.g. paclitaxel) and an amphiphilic block copolymer wherein hydrophobic drug attracting groups are incorporated on its ends. The composition of the present invention also provides i) a shelf life of longer than three years in a sterilized container, ii) stability of longer than three days in an infusion fluid, iii) minimal side effects due to no use of any toxic excipients or organic solvents, and iv) improved bioavailability indicated by the high concentration of the hydrophobic drug such as paclitaxel achieved in plasma.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made to the exemplary embodiments and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Alterations and further modifications of the inventive features illustrated herein, and additional applications of the principles of the invention as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the invention.

The amphiphilic block copolymer micelle composition of the present invention is very effective in solubilizing hydrophobic drugs by way of physically incorporating them within the micelle and improving the stability of the drug by means of the affinity or attraction provided by the end group modifications to the copolymer. The resulting biodegradable polymeric micelle composition containing the hydrophobic drug is soluble in water forming a solution that is suitable for sustained-release of the drug in vivo, thereby enhancing the therapeutic effect of the drug. Such therapeutic effect may be maximized by controlling the molecular weights and the relative ratios of the hydrophilic and hydrophobic blocks. Moreover, the composition of the present invention can be stored for longer than three years in a sterilized container without any denaturation of the components and the polymeric micelles formed in the aqueous infusion fluid of the present invention are stable for longer than 72 hours (3 days). In addition, the formulation of the present invention causes minimal or no side effects to a patient and intravascular administration of the formulation provides for improved bioavailability with high plasma concentrations of the drug being achieved.

The biodegradable polymeric micelle-type drug composition of the present invention, which is capable of forming stable polymeric micelles in aqueous or body fluids, is comprised of a biodegradable modified amphiphilic block copolymer having physically entrapped therein one or more hydrophobic drugs, and when administered, the hydrophobic biodegradable polymer decomposes in vivo by simple hydrolysis into non-toxic small molecules.

The modified amphiphilic block copolymer comprises a hydrophilic poly(alkylene glycol) component and a hydrophobic biodegradable polymer component. The polyalkylene glycol suitable for the hydrophilic component in the block copolymer of the present invention is a member selected from the group consisting of polyethylene glycol, monoalkoxy polyethylene glycol and monoacyloxy polyethylene glycol, wherein the molecular weight of the polyalkylene glycol is preferably within the range of 200.about.20,000 Daltons and more preferably, within the range of 1,000.about.15,000 Daltons.

The hydrophobic biodegradable polymer component of the copolymer of the present invention is a member selected from the group consisting of polylactides, polycarprolactone, copolymers of lactide and glycolide, copolymers of lactide and carprolactone, copolymers of lactide and 1,4-dioxan-2-one, polyorthoesters, polyanhydrides, polyphosphazines, poly(amino acid)s and polycarbonates. Preferably, the hydrophobic biodegradable polymer component of the copolymer of the present invention is a member selected from the group consisting of polylactides, polycaprolactone, a copolymer of lactide and glycolide, a copolymer of lactide and caprolactone, and a copolymer of lactide and 1,4-dioxan-2-one. The molecular weight of the hydrophobic biodegradable polymer component is preferably within the range of 500.about.20,000 Daltons and more preferably within the range of 1,000.about.10,000 Daltons.

As will be more fully described in connection with Formula I that follows, the hydroxy group conventionally found at the end of a hydrophilic polyalkylene glycol can be blocked or capped by a C.sub.1-C.sub.4 alkyl group thereby forming an ether capping, such as is found in monomethoxy polyalkylene glycols (mPEG) or by a C.sub.1-C.sub.4 acyl thereby forming an ester capping, such as is found in monoacyloxy polyalkylene glycols. The hydroxyl group at the end of a hydrophobic polymer block, such as a polylactide, is capped by acylation thereby forming an ester capping wherein the acyl group contains from 2 to 10 carbon atoms such as an alkyl, aryl, alkaryl or aralkyl group as will be more fully explained. Preferably, the end capping of the hydrophilic block will be by a methoxy group and the end capping of the hydrophobic block will be by an acetyloxy or benzoyloxy group.

The amphiphilic block copolymers can be prepared according to methods described in U.S. Pat. Nos. 5,683,723 and 5,702,717, hereby fully incorporated by reference. For example they may be prepared via ring opening bulk polymerization of one of the monomers, such as a lactide, caprolactone, 1,4-dioxan-2-one, or a glycolide, with a polyethylene glycol derivative in the presence of stannous octoate as a catalyst. Block copolymers having a poly(amino acid) block are prepared by the reaction of an amino acid N-carboxy anhydride with a polyethylene glycol derivative. The hydrophilic polyethylene glycol block is preferably in the range of 30.about.70% by weight of the block copolymer, and most preferably 40.about.60% by weight.

The improved stability attributable to the present invention is by means of modifying the block copolymer such that at least one end of the end terminal groups has an affinity or attraction with a hydrophobic drug, which significantly improves the stability of the micelles and the drugs entrapped therein.

Any drug having a water solubility of less than 10 mg/ml can be used as the "hydrophobic drug" or "poorly water soluble drug" to be incorporated in the polymeric micelles of the present invention. Examples of hydrophobic drugs that can be used include anticancer agents, antiinflammatory agents, antifungal agents, antiemetics, antihypertensive agents, sex hormones, and steroids. Typical examples of the hydrophobic drugs are anticancer agents such as paclitaxel, taxotane, camptothecin, doxorubicin, daunomycin, cisplatin, 5-fluorouracil, mitomycin, methotrexate, and etoposide; antiinflammatory agents such as indomethacin, ibuprofen, ketoprofen, flubiprofen, dichlofenac, piroxicam, tenoxicam, naproxen, aspirin, and acetaminophen; antifungal agents such as itraconazole, ketoconazole, amphotericin; sex hormones such as testosterone, estrogen, progestone, and estradiol; steroids such as dexamethasone, prednisodone, and triameinolene; antihypertensive agents such as captopril, ramipril, terazosin, minoxidil, and parazosin; antiemetics such as ondanseiron, and granisetron; antibiotics such as metronidazole, and fusidic acid; cyclosporine; prostagladins; and biphenyl dimethyl dicarboxylic acid. The present invention is particularly useful for administering anti-cancer drugs such as paclitaxel, taxotane, doxorubicin, cisplatin, carboplatin, 5-FU, etoposide, and camptothecin; sex hormones such as testosterone, estrogen, and estradiol; antifungal agents such as itraconazole, ketoconazole, and amphotericin; steroids such as triamoinolone acetonide, hydrocortisone, dexamethasone, prednisolone, and betamethasone; cyclosporine; and prostagladins. The hydrophobic drug may be incorporated in the polymeric micelle composition up to 50 wt % based on the total weight of the block copolymer and the drug.

One embodiment of the present invention provides a pharmaceutical composition, which is capable of forming a stable polymeric micelle in aqueous or body fluids. comprising: a) a taxane analog; and b) b) a block copolymer which is represented by formula (I) -- see Original Patent.

The block copolymer of the present invention can be prepared via ring opening bulk polymerization of heterocyclic ester compounds (lactones), such as DL-lactide, glycolide, .epsilon.-caprolactone, or p-dioxanone, with polyethylene glycol or monomethoxy polyethylene glycol in the presence of stannous octoate. At least one terminal ends of the copolymer is capped in the manner described with a group such as benzoyl or acetyl group having affinity or attraction for a hydrophobic drug such as paclitaxel. One example of the resultant block polymer of this invention is represented by formula (I). Methods of adding an end group to the end of block copolymer were described in the "Preparation Examples 1a, 1b, and 2" -- see Original Patent.

[For a benzoyl group]

mPEG+DL-lactide.fwdarw.mPEG--PLA--OH (block copolymer having hydroxyl group) mPEG--PLA--OH+Cl--(C.dbd.O)--C.sub.6H.sub.5 (benzoyl chloride).fwdarw. mPEG--PLA--O--(C.dbd.O)--C.sub.6H.sub.5 (block copolymer having a benzoyloxy group) [For an acetyl group] mPEG--PLA--OH+Cl--(C.dbd.O)--CH.sub.3 (acetyl chloride).fwdarw. mPEG--PLA--O--(C.dbd.O)--CH.sub.3 (block copolymer having an acetyloxy group)

In this case, the block copolymer and the end group are linked by an ester bond [--O--(C.dbd.O)--], and can be expressed as mPEG--PLA--O--(C.dbd.O)--R, where R could be CH.sub.3, C.sub.6H.sub.5, ethyl, propyl, or others.

An alternative method to modify the block copolymer of the present invention is by using isocyanate; mPEG--PLA--OH+O--C.dbd.N--CH.sub.2CH.sub.3 (ethyl isocyanate).fwdarw. mPEG--PLA--O--(C.dbd.O)--NH--CH.sub.2CH.sub.3 (block copolymer having an ethyl carbamoyloxy group), or mPEG--PLA--OH+O--C.dbd.N--C.sub.6H.sub.5C(.dbd.O)--O--CH.sub.3 (methyl isocyantobenzoate).fwdarw. mPEG--PLA--O--(C.dbd.O)--NH--C.sub.6H.sub.5C(.dbd.O)--O--CH.sub.3 (block copolymer having a methoxycarbonyl phenyl carbamoyloxy group)

In this case, the block copolymer and the end group are linked by a carbamate(urethane) bond [--O--(C.dbd.O)--N--], and can be expressed as mPEG--PLA--O--(C.dbd.O)--NH--R, wherein R is a C.sub.1 to C.sub.9 member selected from the group consisting of alkyl, aryl, alkaryl and aralkyl groups. Representatives of alkyl groups are methyl, ethyl, propyl, and butyl groups. Representative of an aryl group is phenyl as well as functionally equivalent heterocyclic groups such as thienyl, furyl, pyridinyl, and the like. Representative of an aralkyl group is benzyl and representative of an alkaryl group is tolyl. Preferably R.sub.1 is a methyl group and R.sub.2 is a methyl or phenyl group.

Illustratively, the copolymer (10.about.200 mg) prepared as described is then dissolved in an organic solvent (1.about.5 mL) such as acetonitrile, dichloromethane, or tetrahydrofuran (THF). A poorly water soluble drug (2.about.50 mg) such as paclitaxel, is dissolved in the same organic solvent, and then mixed with the polymer solution. A homogeneous drug-polymer matrix is obtained by evaporating the organic solvent at an elevated temperature. The drug-polymer matrix is dissolved in water to produce an aqueous micellar solution at a polymer concentration higher than the critical micelle concentration (CMC). The polymeric micelle having a spherical shape in aqueous media consists of two different regions, a hydrophobic inner core and a hydrophilic outer shell. This particular structure is due to the amphiphilic properties of the polymer which consists of a hydrophobic polylactone block and a hydrophilic polyethylene glycol block. The hydrophobic drug, such as paclitaxel, is trapped in the inner core of the spherical micelle. The stable micellar composition containing paclitaxel, in the hydrophobic core formed by the hydrophobic segments of the copolymer, is prepared by freeze-drying the aqueous micellar solution.

The freeze-dried composition pared by the above-mentioned method can be diluted in an aqueous media, such as 0.9% sodium chloride (normal saline), 5% dextrose, 5% dextrose and 0.9% sodium chloride, or 5% dextrose in Ringer's solution, to achieve a final paclitaxel concentration of 0.1.about.3.0 mg/mL, more preferably 0.2.about.1.5 mg/mL. The diluted solution is placed in a thermostat at 25.degree. C. At predetermined time intervals, 0.5 mL of the solution is taken out with a syringe and filtered through a 0.45 .mu.m PVDF syringe filter (Milipore, Cat No. SLHV004NL). The drug concentration in the filtered solution is then determined by high performance liquid chromatography (HPLC) assay.

Paclitaxel is traditionally administered at a dose of about 175 mg/m.sup.2. For a human adult with 70 Kg body weight, the surface area and the total blood volume are about 1.8 m.sup.2 and 5 L, respectively. When paclitaxel is administered by one bolus intravenous injection at the indicated dose, initial plasma concentrations of paclitaxel are in the range of 0.04.about.0.08 mg/mL. Therefore, the stability test for a diluted concentration of 0.04.about.0.08 g/mL is also carried out at body temperature (37.degree. C.).

The HP1100 series HPLC system (Hewlett-Packard) is used for determination of the drug concentration. Peak detection and integration is performed with HP Chemstation for LC Rev.A.06.01. Chromatographic separation is achieved with 00G-4012-E0 (Phenomenex) column (250.times.4.6 mm, 5 .mu.m). Paclitaxel and the internal standard were eluted with the mobile phase of actonitrile-water (45:55, v/v) using a flow rate of 1.5 mL/min. Ultraviolet (UV) analysis was performed at a wavelength of 227 nm. Propyl-p-hydroxybenzoate was used for the internal standard.

The terminal end capping groups in the block copolymer play an important role in the stability of the hydrophobic drug trapped in the core region of the micelle formed in aqueous media. The formulations employing the diblock copolymers of polyethylene glycol and polylactone which do not have the ends capped with groups having an attraction or affinity for the hydrophobic drug have a drawback in that the drug is precipitated from the micelle into the aqueous infusion fluid within 48 hours due to unstable micellar formation. In order to overcome the precipitation of a drug in the infusion fluid, the block copolymer of the present invention was modified terminal hydroxyl groups that are capped with a group which has affinity or attraction for the hydrophobic drug. Thus, the hydrophobic drug remains in the hydrophobic core of the micelle for a longer period of time due to the affinity or attraction between the drug and the terminal end capping group of the polymer. As a result, the composition provides long-term stability for infusion therapy. Furthermore, the pharmaceutical composition of the present invention incorporates paclitaxel up to 40% by weight.

Traditionally, prior art formulations are supplied as a concentrated solution composition in organic solvents, and they are diluted in aqueous media before use. On the contrary, the final formulation of the present invention is a freeze-dried composition in a sterilized container. It is easily dissolved to a concentration of 0.1.about.3.0 mg/mL, more preferably 0.2.about.1.5 mg/mL, in an appropriate conventional injection fluid prior to infusion. As the composition contains no solvents and is stored in a very stable freeze-dried solid state, the composition of the present invention eliminates any possible denaturation or precipitation of the drug by temperature changes during storage, that is, the composition provides a longer shelf life than those in the prior art.

The polymeric micellar solution of the present invention is stable with no precipitation in the infusion fluid for longer than 72 hours (3 days) at room temperature (25.degree. C.). When the composition is diluted to a concentration of paclitaxel of 0.04.about.0.08 mg/mL, i.e. initial plasma concentration after one bolus iv injection of the recommended dose of Taxol.RTM. inj., the composition is more stable than the compositions formulated with the polymers not having the above-described terminal end capping groups. Furthermore, the composition of the present invention improves the paclitaxel plasma concentration in pharmacokinetic experiments with rats, as described below.

The formulation of the present invention does not contain any potentially harmful material for use in the human body, such as an organic solvent or Cremophor EL which induce various side effects. The polymers incorporated in the composition are biocompatible, they are already approved for use in the human body from the FDA, and their hydrolysis products are easily eliminated from the body.

A pharmacokinetic experiment was performed with Sprague-Dawley rats having a body weight of 200.about.250 g. The freeze-dried composition formulated by the above-mentioned method was dissolved in normal saline to give a paclitaxel concentration of 1.0 mg/mL and the formulation was injected into the tail vein with the does of paclitaxel given being 20 mg/kg. At specified time intervals, blood samples were drawn in heparinized tubes from the tail vein. They were centrifuged at 2000 rpm for 5 minutes for separation. The internal standard, biphenyl dimethyl dicarboxylate, was added to the separated plasma for HPLC assay. The drug was extracted from the plasma using ethyl acetate, and dried by evaporation of the solvent. The dried product was dissolved in actonitrile-water and the paclitaxel plasma concentration was determined by HPLC as described above. A standard solution was prepared by dissolving a known amount of paclitaxel in the plasma, acetonitrile, and the internal standard. The HPLC assay for the stability test was performed with the above-described HPLC system. Chromatographic separation was achieved with a VYDAC (Hesperia) 218MR54 C18 column (250.times.4.6 mm, 5 .mu.m). Paclitaxel and the internal standard were eluted with the mobile phase of actonitrile-water, with a linear gradient from 30:70 (v/v) to 60:40 (v/v) for 40 minutes, using a flow rate of 1.0 mL/min. Ultraviolet (UV) analysis was performed at a wavelength of 227 nm. Biphenyl dimethyl dicarboxylate was used for the internal standard.

 

Claim 1 of 42 Claims

1. A composition capable of forming a polymeric micelle in a body fluid or an aqueous medium, said composition comprising an amphiphilic block copolymer having a hydrophilic A block component and a hydrophobic biodegradable B block component, wherein the hydrophobic biodegradable B block component of the copolymer is capped with an acyl group or carbamyl group of C.sub.1 to C.sub.9 alkyl, aryl, alkaryl or aralkyl group.

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