Stable sterile filterable liposomal encapsulated taxane and other antineoplastic drugs

This application is a continuation of PCT/US04/03157, filed on Feb. 3, 2004, which claims priority to U.S. Provisional Patent Application 60/444,958, filed on Feb. 3, 2003. The disclosures of these applications are incorporated herein in their entireties by reference thereto.

The present invention relates to liposomal encapsulated taxane and other antineoplastic drugs.

The use of taxanes, such as paclitaxel, as anti-tumor agents for patients suffering from diseases, such as ovarian and breast cancer, is known. In addition, paclitaxel has been shown to be clinically potent as a synergistic agent when used in conjunction with radiation treatment. Paclitaxel has a unique mechanism of action and a broad spectrum of anticancer activity because paclitaxel shows stabilization of microtubules rather than disassembly of microtubules.

However, paclitaxel has extremely low solubility in water, which makes it difficult to provide a suitable dosage form. Currently, paclitaxel is prepared and administered in a vehicle containing 6 mg/mL paclitaxel, 527 mg/mL of purified cremophor EL (a polyethoxylated castor oil), and 49.7% dehydrated alcohol, USP. This solution is diluted 1:10 in saline before being administered to humans. The stability of paclitaxel once diluted in saline solution is quite low. The drug degrades within 24 hours, and it has been shown that taxol is incompatible with common PVC intravenous bag and infusion sets, thus, handling of dosage for the patients becomes very difficult. Since the drug precipitates from dilution, an on-line filter is utilized for the infusion of the drug to the patients. The decreased solubility and presence of Cremophor EL in the formulations presents risks to patients, such as anaphylactoid reactions and cardiotoxicity. The long-term use of taxol also can contribute to the development of multidrug resistence in cancer cells, which only complicates the etiology of the very disease for which taxol treatment is sought.

Attempts have been made to improve upon the currently-available formulations of taxol. To this end, U.S. Pat. No. 5,648,090 (Rahman et al.) and U.S. Pat. No. 5,424,073 (Rahman et al.) provide a liposomal encapsulated paclitaxel for a method for treating cancer in mammals using such a liposomal-encapsulated paclitaxel, or antineoplastic derivative thereof. The '090 and '073 patents disclose a method of modulating multidrug resistance in cancer cells in a mammalian host by administering to the host a pharmaceutical composition of a therapeutically effective number of liposomes, which include a liposome-forming material, cardiolipin, and an agent such as paclitaxel, or an antineoplastic derivative of paclitaxel, or a mixture thereof, and a pharmaceutically acceptable excipient. However, there remains a need for a liposomal formulation of taxanes that remain stable for a prolonged period of time.

The present invention provides a formulation of antineoplastic drugs, such as taxanes, derivatives thereof, and related compounds, at clinically relevant concentrations that exhibit improved stability and reduced toxicity. The inventive formulation preferably contains one or more stabilizing agents, antioxidants, and lyoprotectants. In many preparations, the inventive formulation is stable for many days at room temperature, even after post-reconstitution and dilution in injectable fluids. The inventive formulation can increase therapeutic efficacy and minimize multidrug resistance over that observed with present taxane formulations. These and other advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein and from the accompanying figures.

FIG. 1 graphically presents the results of a study of the effect of liposome entrapped paclitaxel (LEP) and Taxol on growth of ectopic human lung tumor (A549) in SCID mice.

FIG. 2 graphically presents the results of a study of the effect of liposome entrapped paclitaxel (LEP) and Taxol on body weight of human lung tumor bearing SCID mice.

The present invention is predicated, at least in part, on providing a formulation of one or more antineoplastic drugs encapsulated in liposomes including at least a lipid fraction in addition to the antineoplastic drug, wherein the composition is stable in an aqueous solution at room temperature, typically stable for at least 3 days. Preferably, the formulation is free or substantially free of antineoplastic drug crystals or precipitate, and most preferably, there are no antineoplastic drug crystal and precipitate forms in the formulation.

Any suitable antineoplastic drug can be used in the context of the invention. Preferred compounds for use in the inventive formulation include taxanes or derivatives, such as docetaxel, paclitaxel and related compounds (e.g., epothilones A and B, epothilone derivatives, etc.). Preferably, the compound is paclitaxel. A suitable derivative of paclitaxel is taxane. Other suitable compounds are 7-epipaclitaxel, t-acetyl paclitaxel, 10-desacetyl-paclitaxel, 10-desacetyl-7-epipaclitaxel, 7-xylosylpaclitaxel, 10-desacetyl-7-glutarylpaclitaxel, 7-N,N-dimethylglycylpaclitaxel, 7-L-alanylpaclitaxel, taxotere, and mixtures thereof.

As the invention provides a liposomal formulation of antineoplastic drug, the formulation also includes one or more compounds able to form liposomes. Thus, for example, the formulation can include cholesterol or derivatives thereof, lipids or phospholipids, and other similar compounds. Preferably, the lipid fraction of the inventive liposomal formulation includes one or more cardiolipins, such as synthetic or naturally occurring cardiolipins or cardiolipin analogues.

Typically, the lipid fraction comprises at least about 3.5% (w/v) and more preferably at least about 4.0% (w/v) of the inventive composition, such as at least about 5.0% or even at least about 5.5% (w/v) of the composition. Generally, it is not expected that the lipid fraction will exceed about 8.5% (w/v), and more preferably, the maximal lipid fraction will be about 8.0% (w/v) of the composition, such as a top lipid concentration of about 7.0% (w/v) or even a maximal lipid concentration of about 6.0% (w/v). Preferably, the liposomes of the inventive formulation will have between about 4.0% (w/v) and about 8.0% (w/v) lipid, such as between about 5.0% (w/v) and about 6.0% (w/v) lipid.

Moreover, the ratio of lipid to antineoplastic drug used in the inventive formulation typically is at least about 5:1 by molar ratio, and more preferably at least about 10:1 by molar ratio, at least where the antineoplastic drug is a taxane (or related compound or derivative thereof). Typically, the ratio of lipid to antineoplastic drug used in the inventive formulations is at least about 20:1 by molar ratio, such as at least about 30:1 or even 40:1 by ratio. However, generally, the ratio of lipid to antineoplastic drug used in the inventive formulation generally does not exceed about 75:1 by molar ratio, and is more typically at most about 70:1 by molar ratio. Typically, the ratio of lipid to antineoplastic drug, especially a taxane (or related compound or derivative) used in the inventive formulations is at most about 60:1 by molar ratio, such as at most about 50:1 or even at most about 40:1 by molar ratio. Preferably, the ratio of lipid to drug in the inventive formulation is between about 10:1 and about 70:1 by molar ratio, such as between about 25:1 and about 55:1 by molar ratio.

Desirably, a majority of the antineoplastic drug in the formulation is entrapped in the liposomes. More preferably, at least about two-thirds (such as at least about 75%) of the antineoplastic drug in the formulation is entrapped in the liposomes, and it is even more preferable for at least about 85% (or even more than about 90%) of the antineoplastic drug to be entrapped in the liposomes in the inventive formulation.

Preferably the lipid fraction of the formulation includes one or more lipids selected from the group consisting of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), tetramyristoyl cardiolipin (CL), and cholesterol (CH), as these constituents lend stability to the formulation and can function as stabilizing agents. Other saturated phospholipids such as dimyristolphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC) and distearoylphasphatidylcholine (DSPC) and unsaturated phospholipids such as hydrogenated purified soy bean phosphatidylcholine, hydrogenated purified egg yolk phosphatidylcholine, dilinoleoylphosphatidylcholine (DLPC), phasphatidylcholine (DOPC), palmitoyloleoyl dioleoylphosphatidylcholine (POPC) and sphingomyelin may be used. Suitable negatively charged lipids such as dioleoylphsophatidylglycerol (DOPG), dioleoyl phosphatidylserine (DOPS), dimyristolphosphatidylglycerol (DMPG) also can be used.

Most preferred constituents for inclusion in the lipid fraction of the inventive composition include 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), tetramyristoyl cardiolipin (CL), and cholesterol (CH). It is desirable for two or more of these lipid constituents to be present in the lipid fraction, and most preferably all three of these lipid constituents (DOPC, CL, and CH) are present. Indeed, the DOPC preferably comprises between about 85% and about 95% of the lipid components, and even more preferably between about 90% and about 92% of the lipid components. Suitable formulations include ratios of DOPC:CH:CL between about 92:0:8 to about 90:5:5, although the amounts of CH and CL do not have to be equal. In this respect, the concentration of CH typically is between about 0.3 mg/ml and about 3.5 mg/ml, such as between about 0.5 mg/ml and about 3.0 mg/ml, or even between about 1 mg/ml and about 2 mg/ml; whereas the amount of CL typically is between about 1 mg/ml and about 10 mg/ml (more typically between about 2 mg/ml and about 8 mg/ml), such as about 5 mg/ml. However, the amount of DOPC in the lipid fraction of the inventive formulation generally exceeds that of CH or CL, and typically the amount of DOPC in the inventive formulation exceeds the amount of both CH and CL combined. In this respect, the amount of DOPC in the lipid fraction of the inventive formulation typically is about 60 mg/ml, and is generally at least about 40 mg/ml, such as at least about 45 mg/ml or even at least about 50 mg/ml. Typically, the DOPC represents no greater than about 75 mg/ml, such as at most about 65 mg/ml or 70 mg/ml. An ideal range of DOPC is between about 44 mg/ml and about 74 mg/ml.

To further assist in enhancing the stability, the inventive formulation can typically include one or more antioxidants, in addition to the active drug (e.g., taxane or related compounds) and the lipid fraction. While any commonly-used lipid soluble antioxidants can be employed, in some embodiments, antioxidants such as butylated hydroxyanisole, butylated hydroxytoulene and propyl gallate may be used. D-alpha tocopheryl acid succinate is preferred because of its stability-enhancing properties. Where present, the antioxidant typically is included in the formulation in concentrations between about 0.1 and about 0.6 mg/ml, such as between about 0.2 mg/ml and between about 0.5 mg/ml, or even between about 0.3 mg/ml and about 0.4 mg/ml.

The liposomes can be formulated by any suitable method. Preferred methods include thin film hydration, solvent injection, freeze-thawing and dehydration-rehydration, removal of surfactant, reverse phase evaporation and ethanol injection. For example, the antineoplastic drug and lipid fraction can be dissolved in a suitable solvent, such as methylene chloride, ethanol, methyl acetate, ethyl formate and the like. Where antioxidants are employed, they also can be dissolved in the solvent with the lipid fraction. For the purpose of formulating the inventive composition, any suitable amount of solvent can be employed, which typically is between about 1000 and 1100 mg/ml where methylene chloride is used as the solvent. Typically, however, the method will require at least about 500 mg/ml methylene chloride, such as least about 750 mg/ml mg/ml methylene chloride, and as much as about 2000 mg/ml methylene chloride, such as up to about 1500 mg/ml methylene chloride can be used to dissolve the lipid fraction.

After the antineoplastic drug, lipid fraction, and antioxidant are dissolved in the solvent, the solution then is dried. Any suitable drying methodology and apparatus can be employed, a preferred drying step comprising a rotary evaporator under reduced pressure, followed by further drying in a dessicator.

Following drying, the lipid (and antioxidant) residue can be hydrated in an aqueous system, such as water, which can be a solution or suspension. Preferably, the solution contains one or more lyoprotectants to aid in enhancing the stability of the formulation during subsequent lyophilization and while present in lyophilized form. Any suitable lyoprotectant, such as sugars and mannitol can be employed, although such compounds typically are sugars. While sucrose is a most preferred lyoprotetant, other suitable lyoprotectants include, for example, trehalose, maltose, lactose, glucose, dextran, aminoglycosides and streptomycin and combinations of these can suitably be employed, as desired. Typically, the lyoprotectant represents less than about 50% (w/v) of the formulation, if it is employed. More typically, the lyoprotectant represents at most about 40% (w/v) of the formulation, such as at most about 30% (w/v) of the formulation. Where the lyoprotectant represents as little as about 1% (w/v), it can enhance the stability of the inventive formulations; however, more typically, the lyoprotectant represents at least about 5% (w/v) of the formulation, such as at least about 10% (w/v) or at least about 20% (w/v) of the formulation. The hydration solution also can contain a tonicity adjuster, which preferably is sodium chloride (NaCl), but can be another suitable salt or disaccharide. The hydration can be accomplished in any suitable volume of hydration solution.

Re-hydration in the hydration solution results in the formation of multilamellar vesicles (MLV). In certain methods, suitable preparations can be mixtures of multilamellar vesicles and unilamellar vesicles. Once the solution is added, liposomes can be formed by mixing, for example, as by vortexing or by using any suitable mixing devise. Where smaller vesicles are desirable, the solution can be sonicated. If desired, the size of these MLV can be manipulated, for example, by extrusion through a sieve, which is typically formed of polycarbonate fibers or by homogenization using high pressure homogenizer. Thus, the size of the MLV in the composition can be controlled, using a sieve of a pre-selected size (e.g., via extrusion through a sieve of a desired size, such as 0.81 μm, 0.4 μm, 0.2 μm, 0.1 μm, etc.). In the present invention, a sizing treatment is preferably applied to make the particle size of the drug-encapsulating liposomes more uniform. Prior to lyophilization, the formulations of the present invention can be sterile filtered through a 0.22 micron filter. The average particle size of the formulation is about 50 to 200 nm, preferably 100-180 nm, more preferably 120-160 nm.

Following re-hydration and (if desired) extrusion to achieve a defined particle size, the composition preferably is lyophilized using any suitable device or method. A preferred device is a benchtop and any suitable size of lyophilizer (e.g., such as is manufactured by VerTis). The SUV preparation can be maintained in lyophilized form (e.g., in cold storage at about −5-8° C.) for an extended period of time, such as for at least about several months or years. Preferably the lyophilized formulation is stable for at least 9 months.

For use, the lyophilized SUV liposomal formulation can be reconstituted with a suitable volume of reconstitution solution, more preferably is a polar solvent, and most preferably an aqueous system, which can be deionized water or a suitable aqueous saline solution. Any suitable volume of reconstitution solution can be employed, such as between about 1 ml and about 50 ml, more typically between about 3 ml and about 25 ml. For use, the liposomal formulation can be diluted as desired, such as in a suitable physiologically-compatible buffer or saline solution. To assist in reconstitution, the preparation can be mixed gently or vigorously (e.g., vortexed) as desired, or even sonicated.

However produced, the resultant liposomal-encapsulated taxane is stable for at least about one day, and more typically for at least 3 or 4 days following re-constitution. Indeed, formulations of the present invention can remain stable at room temperature for at least about 4 days, such as a week or two weeks, or even longer times. As indicated below in the Example sections, formulations of the present invention can remain stable under such conditions for at least about 17 days. Stability can be monitored, for example, by assessing the particle size of the liposomes over time (stability in this context can be indicated by a change of mean particle size of less than about 20% over one day and more preferably a change of particle size of less than about 5% in one day, or a change of less than about 10% or even 5% over a 3- or 4-day timecourse) using particle size analyzer, such as Nicomp Submicron Particle Sizer. Alternatively, stability can be assessed by assessing (e.g., using a light microscope) for the presence of crystalline taxane. The absence of more than trace amounts of such crystals is indicative of a stable preparation, and desirably, the inventive formulation will remain substantially, or even relatively completely, free of taxane crystals after three or four days of reconstitution or dilution in saline, even at room temperature.

The present liposomal formulations provide a drug-delivery system which allows infusion of high concentrations of taxanes or other antineoplastic drugs in a stable form and which provides sustained therapeutic benefits at target sites, while maintaining low concentrations of insoluble free taxane and minimal adverse toxic effects than were previously known.

The present pharmaceutical composition can be administered in amounts of at least 50 to 400 mg of active compound/m 2 of mammalian host surface area, within a period of less than about three hours, preferably in less than about two hours, and most preferably 90 minutes without causing a substantial toxic reaction. For example, in a 70 kg human, about 0.5 to 7.0 mg active compound per kg of body weight can be safely administered in about 90 minutes. Preferably, about 1.0-5.0 mg of active compound per kg of body weight is administered. Alternatively, preferable amounts include 75, 135, 175, 250, 300, 325, and 375 mg/m 2 .

The present liposome compositions can be administered intravenously or intraperitoneally to an isolated portion of a mammalian body, particularly a human body, such as an arm or leg, or in the case of a human, a hand, or can be injected directly into a tumor. Preferrably the formulations of the present invention can be in injectable form.

Liposomal encapsulated taxane has a substantial beneficial effect in overcoming multidrug resistance in cancer cells, which are subjected to chemotherapy. By using the liposomal composition of the present invention, it is possible to reduce the tendency of cancer cells subjected to chemotherapy to develop resistance to the chemotherapeutic agents used for chemotherapy such as anthracycline glycosides. This method includes administering to a host a pharmaceutical composition of a liposomal encapsulated taxane of the present invention in accordance with the administration protocol.

Taxanes and the anti-neoplastic derivatives thereof may be used to treat any form of mammalian cancer. Such compounds are thought to function by promoting the assembly of microtubules or prohibiting the tubulin disassembly process. Taxane and the anti-neoplastic derivatives thereof are of particular advantageous use in the treatment of mammalian lymphoma, ovarian, breast, lung and colon cancer, and particularly those conditions in humans.

The following examples further illustrate the present invention but, of course, should not be construed as in any way limiting its scope.

CD2F1 mice (4-6 weeks old, Male and Female) used for the study were obtained through Harlan Sprague Dawley Laboratories. The individual animal was identified by ear tag. Upon arrival, the animals were placed in quarantine for 7 days. The animals were kept in an environmentally monitored, well-ventilated room maintained at a temperature of 64-84° F. and a relative humidity of 30%-70%. Fluorescent lighting provided illumination approzimately 12hours per day. Mice were offered ad libitum 8656 HT Rodent Diet (Harlan Teklad, Madison, Wis.) during the quarantine and study periods. The average weight of mice on day 1 of study was 16-22 g (female) and 20-27 (male). The age of mice on day 1 of study was 6-7 weeks.

Test Articles:

1. Lyophilized Liposomal Paclitaxel (LEP-ETU) vials prepared in accordance with the present invention were stored at 2-8 ° C. 2. Taxol vials (30 mg/vial; concentration 6 mg/mL) were received from Mead Johnson, Inc.

Control Article:

1. Placebo liposome was stored at 2-8 ° C.

Dose Formulations Preparation:

Vehicle formulations (LEP and Placebo liposome) were prepared fresh on each day of dosing. The stability of reconstituted and diluted formulations (up to 8 fold with 0.9% saline) is 12 hours at 20-25° C. All the dosing solutions were used within 12 hours after reconstitution and dilution.

Experimental Design

Randomization and Group Assignment

Randomization was done during week 1. Animals were weighed prior to randomization and only the animals whose weight ranged between 16-23 g (Female) and 17-26 g (Male) were used for randomization and were assigned to the following groups (7 animals/sex/group). The randomization is presented in Table 16:

Article (Control and Test) Administration:

Each animal was weighed prior to dosing. Mice received control or test article intravenously via tail vein once a day for 5 consecutive days. The injection volume was based on individual mouse body weight. The control animals in Group 1 received approximately the same amount of lipids as in 50 mg/kg dose of LEP. The control animals in Groups 4 and 5 received the equivalent amount of Cremophor EL/Ethanol as in Group 6 and 7, respectively but without Paclitaxel.

Observations

Animals were weighed daily during the dosing period (Day 1-5) and thereafter three times a week for up to 22 days. Animals were observed once daily during the study period for morbidity/mortality. Animals were observed approximately 1 to 2 hours post dosing for clinical signs and daily thereafter. Detailed physical examination for toxicity was done on Day 1 and thereafter once a week.

Results

Body Weights

There was no body weight loss in animals that received placebo liposome. Female mice given IV doses of LEP (25 mg/kg/dose) lost weight by 5.2% on Day 8 and recovered completely by Day 10. There was a 12.5% body weight loss for male mice that received LEP (25 mg/kg/dose) by Day 8 and the complete recovery was achieved by Day 15. The weight loss for male and female mice in Group 3 (50 mg/kg/dose, LEP) were 20.6 and 28.7% by Day 8. The control animals that were injected with Cremophor EL/Ethanol had no body weight loss. The weight loss for females in Group 5 (12.5 mg/kg/dose, Taxol) was negligible. The male animals in Group 5 had a body weight loss of 4.7% by Day 5 and the recovery was complete by Day 12. Female animals in Group 7 (25 mg/kg/dose, Taxol) had a body weight loss of 6.3% by Day 8 and they recovered completely from body weight loss by Day 12. The weight loss for male animals in Group 7 was 10.4% on Day 8 and the recovery was complete by Day 15. The percentage of survival (Total/Number surviving) is presented in Tables 17 and 18. On Day 4, one male animal in Group 7 (25 mg/kg/dose, Taxol) died 1 hour after administration of article. One animal in Group 4 was sacrificed on Day 17 because of wounded tail.

Clinical Signs of Toxicity

Clinical signs of toxicity of animals in each group on various days is presented in Table 19. Clinical signs of toxicity as manifested by hunched posture and rough coats were observed in animals in Group 7 (25 mg/kg/dose, Taxol) starting from Day 4. Starting from Day 9 till Day 15, the animals in Group 7 showed neurological signs of toxicity manifested by problems in walking and dragging the back legs towards abdomen. On Day 6, four male animals in Group 6 (12.5 mg/kg/dose, Taxol) had rough coats and three were dehydrated but by Day 7, they appeared to be normal. Animals in Group 3 (50 mg/kg/dose LEP), had severe signs of toxicity as manifested by hunched posture, dehydration and rough coats between Day 6-9 and the animals in this group were either dead or moribund sacrificed by Day 9.

Clinical Observations

The detailed physical for toxicity was done on Days 1, 10, 17, and 22 and is presented in Table 20.

Unscheduled Observations

All the animals in Group 5 receiving a dose of Cremophor EL/Ethanol equivalent to that present in 25 mg/kg/dose of Taxol and Group 7 (25 mg/kg/dose, Taxol) had decreased activity after dosing. All the unscheduled observations after dosing are presented in a tabular form (Table 21).

Conclusions

The tolerated dose for LEP was 25 mg/kg/day (once daily×5 days, whereas for Taxol, a dose of 12.5 mg/kg/day (once daily×5 days) could be administered safely to CD2F1 mice.

This example presents the results of a Therapeutic efficacy evaluation of liposome based formulation taxol (LEP) in SCID mice bearing human lung tumor (A549).

Materials and Methods

Cell Line and Culture Condition:

The lung adenocarcinoma cell line A-549 was obtained from the American Type Culture Collection (Rockville, Md.) and maintained in RPMI-1640 medium (Life Technologies Inc., Grand island, N.Y.) supplemented with 10% heat inactivated fetal bovine serum (Life Technologies Inc., Grand island, N.Y.). The cell line was grown at 37° C. in a humidified 5% CO 2 incubator.

Mice:

C.B.-17 SCID female mice (3-4 weeks old) were received from Harlan Sprague Dawley (Indianapolis, Ind.). Mice were handled aseptically and housed in a micro isolator in accordance with standard operating procedures (SOPs) of NeoPharm Research and Development, and received sterile food and water ad libitum. Mice were acclimated for at least five days before initiating the study.

Drug and Formulation:

Taxol was obtained from MeadJohonson (Lot #IL5302). Liposome entrapped taxol and blank liposome were obtained as described above.

Tumor Transplantation:

Logarithmically grown A549 cells suspension 50×106/mL was prepared and mice were transplanted with 5×106 cells (0.1 mL) subcutaneously at the left flank region (6). Tumor growth was measured with digital caliper (Mitutoyo Corporation, Japan) and tumor volume was determined by using formula: [length×(width/2) 2×p].

Experimental Design:

After appropriate growth of tumors (23 days) animals were randomly divided into different treatment groups (5-7 animals/group) and treated with LEP (12.5 or 25 50 mg/kg×3) or taxol (12.5 or 25.0 mg/kg×3) or blank liposome or cremophor-EL on day 1, 4, and 8. Tumor growth inhibition was monitored till day 28 of post treatment.

Results and Discussion:

Antitumor efficacy was evaluated in established human lung tumor xenograft model implanted subcutaneously in SCID mice. The efficacy of LEP and taxol was determined in multiple dose intravenous injection on day 1,4 and 8. Animal groups treated with taxol at 12.5 and 25.0 mg/kg resulted in a 37% and 57% inhibition of tumor growth, respectively, compared to blank liposome treated groups.( FIG. 1 ). However, inhibition of tumor growth was much more pronounced in animal groups treated with LEP. LEP treatment at 12.5, 25.0 and 50 mg/kg resulted in 44%, 85% and 95% tumor growth inhibition, respectively, compared to the control group.

Both LEP and taxol were well tolerated at all the doses tested as judged by body weight loss ( FIG. 2 ). Only less than 5% body weight loss was noticed in case of LEP 50 mg/kg treated animal group.

Higher tumor growth inhibition of LEP treated animals could be due to the optimal availability of taxol at target site for longer period of time. Liposome based formulation of taxol has two advantages. Firstly, it helps to deliver the drug without using any surfactants. In addition, it provides sustained levels of drug for longer periods of time, which thus provides for greater antitumor effects.

All of the references cited herein, including patents, patent applications, and publications, are hereby incorporated in their entireties (SP) by reference.

While this invention has been described with an emphasis upon preferred embodiments, it will be obvious to those of ordinary skill in the art that variations of the preferred embodiments may be used and that it is intended that the invention may be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications encompassed within the spirit and scope of the invention as defined by the following claims.