LIPID PRODRUGS FOR ORAL ADMINISTRATION

Abstract: The oral delivery of many classes of drugs is facilitated by converting drugs having suitable functional groups to 1-0-alkyl-, 1-0-acyl-, 1-S-acyl, and 1-S-alkyl-sn-glycero-3-phosphate derivatives. The method confers the ability to be absorbed through the digestive tract to drugs that are not orally bioavailable in the non-derivatized state, and enhances the effectiveness of drugs that are poorly absorbed or rapidly eliminated. The method provides orally bioavailable lipid prodrugs of pharmaceutical compounds having diverse physiological activities, including anticancer and antiviral agents, anti-inflammatory agents, antihypertensives and antibiotics. Potency of the lipid prodrugs is comparable to that of the corresponding non-derivatized drugs.

Description: LIPID PRODRUGS FOR ORAL ADMINISTRATION This application relates to methods of drug delivery. relates particularly to methods for facilitating the or bioavailability of drugs. The oral route is the most ancient method of dr .administration; it is also the safest, most convenient, a most economical. Drugs administered orally can be absorb through the oral mucosa or through the lining of the " stoma and intestines; however, the rate of absorption depends on t ability of the drug to pass through the lipoid barrier epithelial membranes. For example, alcohol, a lipid soluble non-ionic compound, is rapidly absorbed into the bloodstrea by diffusion across the gastric mucosa. Weak acids are als well absorbed through the lining of the stomach, while wea bases are absorbed mainly in the intestine. Drugs that ar ionized, or lipid insoluble, for example, quaternary ammoniu compounds and streptomycin, are poorly absorbed in th digestive tract, and must be administered by injection. There are several disadvantages to the injection of drugs Strict asepsis must be maintained in order to avoid infection an unintentional intravascular injection may occur, injectio may be painful, and it is difficult for the patient Parenteral administration is also more expensive. Under normal circumstances, intact dietary lipids, mostl triglycerides and diglyceride phospholipids, are not readil absorbed through the intestinal mucosa. Phospholipids ar present physiologically in the gut as phosphatidylcholine phosphatidylethanolamine , phosphatidy1-inositol phosphatidylserine, phosphatidylglycerol, and phosphatidi acid. The normal physiological mechanism for lipid absorptio requires conversion of " the phosphatidyl forms of phospholipi to lysophospholipids, by removal of the sn-2 acyl group by th hydrolytic action of the pancreatic enzyme phospholipase A 2 o the sn-2 acyl ester bond. Conversion of lipids t phospholipids and then to lysophospholipids thus provides th normal mechanism for absorption and transport of lipids fro the gut, and accounts for the uptake of several grams o phospholipid per day. It would be therapeutically useful to convert drugs tha are not absorbed through the intestine because of thei chemical structure to orally bioavauable prodrug forms, thu eliminating the inconvenience and expense of parentera administration of these drugs. According to the invention there is provided a method o converting a drug, or other pharmaceutical compound, " that i unavailable or poorly available through the oral route to a orally available form, comprising preparing a lipid derivativ of the pharmaceutical compound, the lipid derivativ comprising a l-O-alkyl-sn-glycerol-3-phosphate group, a 1-0 acyl-sn-glycerol-3-phosphategroup, al-S-alkyl-sn-glycerol-3 phosphate group, or a 1-S-acyl-sn-glycerol-3-phosphate grou covalently linked to a functional group of the drug eithe directly through a phosphate ester or through a linke molecule; whereby the oral bioavailability and/or tissu levels of the administered pharmaceutical compound ar enhanced. A preferred lipid prodrug, comprising a 1-O-alkyl sn-glycerol-3-phosphate derivative of a drug, has th structure of formula [I] . In particularly preferre embodiments of the method of the invention, the pharmaceutica compound is an anticancer nucleoside having a carboxyl, hydroxyl, or amino group available for covalent binding; fo example, 9-?-D-arabinofuranosylcytosine (ara-C) , 5- fluorouridine, 6-mercaptopurine riboside, 9 - β -O- arabinofuranosyladenine (ara-A) , 2' -arafluoro-2-chloro- deoxyadenosine or 5-amino-4-imidazole carboxamid ribonucleoside (AICA-riboside) . In alternative preferre embodiments, the pharmaceutical compound is a therapeutic peptide, or a peptidomimetic of from 3 to 35 amino ac residues or analogues thereof. In particular embodiments this aspect of the invention, the pharmaceutical compound n-muramyl tripeptide or enalkiren. In yet other embodiment D is selected from the group consisting of antibiotics of t penicillin and cephalosporin class; for example, D is select from the group consisting of penicillin G, cefazoli ceftazidime, ceftriaxone, and piperacillin. According to another aspect of the invention there provided a method of enhancing the pharmacokinetic properti of an orally administered pharmaceutical compound, comprisi preparing a lipid derivative of the pharmaceutical compoun the lipid derivative comprising a l-0-alkyl-sn-glycerol- phosphate, a l-O-acyl-sn-glycerol-3-phosphate, a 1-S-alkyl-s glycerol-3-phosphate, or a 1-S-acyl-sn-glycerol-3-phospha group covalently linked to a functional group of the compou either directly through a phosphate ester or through a link molecule, whereby the metabolic clearance of the compound decreased, and the physiological half-life of the compound extended. In embodiments of this aspect of the invention, t pharmaceutical compound is 3 ' -azido-3' -deoxythymidine (AZT) 3' -azido-3 ' -acycloguanosine (ACG) . According to yet another aspect of the invention the are provided antineoplastic prodrugs, comprising taxol or substituted taxol compound, covalently bound to a phospholip compound. In preferred embodiments, the taxol prodr comprises a phospholipid compound selected from the gro consisting of phosphatidylglycerols, l-0-alkyl-sn-glycero- phosphatidic acids, l-0-acyl-sn-glycero-3-phosphatidic acid l-S-alkyl-sn-glycero-3-phosphatidic acids, and 1-S-acyl-s glycero-3-phosphatidic acids. In preferred embodiments this aspect of the invention, the taxol compound is a tax analogue having lipophilic substituents at the S-amino gro of the taxol side chain. These lipophilic substituents can be selected from t group consisting of benzoyl, pivaloyl, acetate, peptides, amino acids. The taxol analogue side chain can furth comprise an aliphatic C__ 1C hydrocarbon group to furth increase lipophilicity. According to another aspect of the invention there a provided taxol side chains bound to a phospholipid and havi the structure of formula II, disclosed herein. According to yet another aspect of the invention the are provided methods of synthesizing a lipid derivative taxol or a substituted taxol compound, comprising the steps (a) covalently attaching a phospholipid through a phospha group to the amino alcohol or hydroxy carboxylic acid grou of the taxol side chain, the propanoic acid group of said si chain being protected by esterification, thus forming a lip derivative of said side chain; (b) removing the protecti group from said propionic acid group; and (c) coupling t lipid derivative of the taxol side chain through the propion acid group to the allylic alcohol group of baccatin III or 1 deacetyl baccatin. In another embodiment of this aspect of the inventi there is provided a method of synthesizing phospholip derivatives of taxol or taxol-related compounds, comprisi the steps of (a) providing a acyl or alkyl substituted-s glycero-3-phosphate and a <3-amino-α;-hydroxy-benzene propana ester; (b) linking the glycero-3-phosphate and the benze propanate ester through a covalent bond between the phospha group of the phosphatidic acid and the α-hydroxyl group of t benzene propanate ester; (c) de-esterifying the benze propanate ester group of the lipid derivative of (b) hydrolysis; (d) linking the lipid derivative of (c) to a tax related group by condensation of the propanoic acid group the derivative and the 13-OH group of a taxol ring skeleto In preferred embodiments of either of the metho disclosed the acyl or alkyl-substituted glycero-3-phosphate a 1-O-alkyl-sn-glycero-3-phosphate. In particularlypreferr embodiments, the l-O-alkyl-≤Η-glycero-3-phosphate is 1- octadecyl-sn-glycero-3-phosphate. Figures 1 through ' 6 demonstrate the pharmacokinetics o orally administered l-0-alkyl-sn-glycero-3-phosphat derivatives of drugs by graphical comparisons of th concentration of 3' -azido-3' -deoxythymidine (AZT) in specifi tissues of animals treated by oral administration of 1-0- octadecyl-sn-glycero-3-P-AZT[ 3 H] (batyl-P-AZT- [ 3 H] ) , and those treated by intraperitoneal administration of free AZT. Figure 1 is a graph showing the comparative levels of AZ in plasma. Figures 2, 3, and 4 are graphs showing the comparative levels of AZT in the stomach, duodenum and jejunum respectively. Figures 5, 6, and 7 are graphs showing the comparative levels of AZT in the liver, spleen and lymph nodes respectively. Figures 8, 9, 10, and 11 are graphs showing the comparative levels of AZT in the kidney, skin, skeletal, and heart muscle tissues respectively. Figures 12 and 13 are graphs showing the comparative levels of AZT in the lung and adrenals respectively. Figure 14 is a graph showing the comparative levels of AZT in brain. Figure 15 is a graph showing the effect of batyl-P-AZT on spleen weight in Rauscher leukemia virus-infected mice after a single daily oral administration. Figures 16-20 show the chemical structures of several classes of drugs from which orally bioavauable prodrugs can be prepared by attaching a lipid moiety to an available functional group according to the methods of the invention. Available groups are boxed; dashed boxes = weak acids: Figure 16: representative antineoplastic agents (a) actinomycin D; (b) daunomycin; (c) etoposide; (d) taxol. Figure 17: representative anti-infective agents (a) kanamycin A; (b) neomycin B; (c) amphotericin B. Figure 18: representative antiviral agents (a) 5-F-3 ' -thia-2' ,3' -dideoxycytidine; (b) foscarnet; (c) ganciclovir. Figure 19: representative therapeutic peptides (a) desmopressin; (b) goserelin; (c) muramyl dipeptide; and (d) enalkiren. Figure 20: representative drugs having other therapeuti applications (a) morphine; (b) cyclosporine. The invention provides a method for facilitating th transport and absorption by the oral route of several classe of drugs by converting these drugs to lipid prodrugs . number of drugs that have poor oral bioavailablity can be mad suitable for oral administration by conversion to phospholipi derivatives, particularly to monoglyceride phospholipi derivatives, wherein an alkyl group is attached to the 1 position of the glycerol moiety by an ether linkage. Th strategy is generally applicable to any drug which has chemical group capable of covalently binding to a phosphat group or capable of covalently binding to a linking group tha can covalently bind to a phosphate group. As disclose herein, drugs having an available hydroxyl, sulfhydryl carboxyl or amine group can be covalently linked, by eithe strategy, to a phosphate group of a l-0-alkyl-sn-glycero-3 phosphate, or to 1-O-acyl, 1-thioether, and 1-thioeste analogs to promote oral absorption of the drug. The linkin group is a multifunctional molecule having the require covalent binding properties; for example, a hydroxylate carboxylic acid, or a polypeptide. The alkyl group of the monoglyceride of the phospholipi derivatives of the invention can be a straight, branched, o cyclic hydrocarbon chain, having from 2 to 24 carbons, and ca be saturated or unsaturated with up to six double bonds. Preferably the alkyl group has 8 to 20 carbon atoms. Alky groups having from 14 to 18 carbon atoms are most preferred. The alkyl group is attached to the glycerol moiety by an ethe or vinyl ether bond. The preferred lipid derivatives used in the method of th invention are of the formula HC-O-R I HC-OH 0 O I I! I! HC — O-P — O ( P-0) n - (L ) -D [ I ] I I 0 o wherein R is a substituted or unsubstituted, saturated o unsaturated, straight or branched chain, or cyclic C x . 2li alky group, covalently linked to the glycerol moiety in an ethe linkage; n = 0 to 2; L is a linking molecule, of the formula X-(CH 2 ) n -Y wherein X and Y are functional groups independentl selected from hydroxyl, sulfhydryl, carboxyl and amine groups, and n = 1 to 24; or L is absent; and D is a therapeutic compound having a functional group selecte from the group consisting of hydroxyl, sulfhydryl, carboxyl, or amino groups. U.S. Patent Numbers 5,223,263 and 5,194,654 disclose lipid prodrugs having l-O-alkyl-sn-glycero-3-phosphate moieties. Linking groups can be any of several molecules having multifunctional groups comprising hydroxyl, sulfhydryl, carboxyl, and amino groups. Particularly suitable for use as linkers are: (1) the amino alcohols, having the general structure HO- (CH 2 ) n -NH 2 , where n = 1 to 24, " preferably where n = 2 or 3 , and suitable for insertion at the carboxyl group of a candidate drug which is an active drug moiety or a chemically modified drug. A monoglyceride phosphorylethanolamine is a naturally occurring phospholipid that incorporates a linker of the amino alcohol type, and a 1-O-alkyl-sn-glycero- phosphorylethanolamine can be conveniently coupled to drugs having an available carboxyl group to prepare a lipid prodrug of the invention. (2) the hydroxyalkyl carboxylic acids, having the general structure HO- (CH 2 ) n -COOH, where n = 1 to 12, and suitable for insertion at the amino group of an activ candidate drug. Naturally occurring molecules such as hydrox fatty acids, beta-hydroxybutyric acid, and hydroxyaminoacid such as serine and hydroxyproline may also be convenientl used. The present invention provides a means for improving th usefulness, efficacy, biological half life, transport acros cellular membrane and oral bioavailabilities of any dru having a chemical structure suitable for binding as describe herein. The method of the invention is advantageousl applicable to drugs that are poorly bioavauable, and tha must otherwise be administered parenterally. Examples of th variety of therapeutic classes of drugs that can b effectively administered by the oral route comprise 1-O-alkyl-, 1-O-acyl-, 1-S-alkyl- (thioether) , or 1-S-acyl (thioester) phospholipid derivatives of: (a) anticancer agents, comprising nucleoside analogues, fo example, 9-5-D-arabinofuranosylcytosine (hereinafter, cytosin arabinoside or ara-C) , 9-3-D-arabinofuranosyladenin (hereinafter, adenine arabinoside or ara-A) , 5-fluorouridine, 6-mercaptopurine riboside, or 2 ' -ara-fluoro-2 chlorodeoxyadenosine; (b) antiviral nucleosides, particularly the 1-O-alky phospholipid derivatives of those antiviral nucleoside disclosed in U.S. Patent No. 5,223,263; (c) therapeutic peptides or peptidomimetics, or peptides tha are enzyme inhibitors, comprising D-amino acids, L-amin acids, or amino acid analogues, and having up to about 35 amino acids, preferably less than 6 amino acids, or analogue thereof, particularly the lipid derivatives. In a preferre embodiment of this species, a l-0-alkyl-sn-glycero-3-phosphate derivative of desmopressin, n-muramyl tripeptide, or enalkire is synthesized and administered orally. (d) antibiotics, particularly those of the penicillin an cephalosporin class, including penicillin G, cefazolin, ceftazidime, ceftriaxone, or piperacillin. (e) phosphonoacid compounds, particularly the 1-0-alk phospholipid derivatives of phosphonoformic acid a phosphonoacetic acid, and nucleoside phosphonates disclosed i U.S. Patent No. 5,194,654; (f) AICA-riboside (5-amino-4-imidazole carboxamid ribonucleoside) , a drug used parenterally for the treatment o ischemic heart disease, and in the treatment of arthritis autoimmune disease, psoriasis, and other inflammator conditions, and which is poorly available (<5%) whe administered orally in solution (Dixon, R. et al. , 1991) Other drugs of this type are 5-amino- (1-beta-D-ribofuranosyl imidazole carboxamide or 1-beta-D-ribofuranosyl 1,2,4-triazol carboxamide, which are used for the treatment of allergy including asthma and urticaria eczema; autoimmune disease including Lesch-Nyhan disease; and cardiac disorders"relate to restricted blood flow. (g) non-steroidal anti-inflammatory compounds, particularl the 1-O-alkylphospholipid derivatives of these compounds. Table 1 lists preferred drug candidates for the method o the invention according to therapeutic class. TABLE 1 Candidate Drugs for Preparation of Orally Bioavauable Lipid Prodrugs THERAPEUTIC CLASS MERCK INDEX I - Antineoplastic agents actinomycin D bleomycin 132 cisplatin and Pt analogues: carboplatin, iproplatin 2319,182 cytosine arabinoside 279 daunorubicin 282 doxofluoridine 342 doxorubicin 342 etoposide 384 floxuridine 404 mithramycin mitomycin C 613 mitoxanthrone 613 pentostatin (deoxycoformycin) 709 phosphonoacids streptozotocin 879 taxol and taxotere 904 vinca alkaloids: vincristine, - 989 vinblastine 988 vindesine 989 II . Anti-Infectives aminoglycosides : netilmycin, 638 amikacin, 41 gentamycin, 428 streptomycin, 878 ' kanamycin A, 516 tobramycin. 941 neomycin B 636 plicamycin 751 amphotericin B 62 vancomycin 983 III . Antivirals 3'-deoxy, 3' -azidothymidine (AZT; anti-HIV) acyclovir (herpes simplex, anti-HSV) foscarnet ganciclovir (anti-CMV) __ idoxuridine (anti-HSV keratitis) ribavarin 5-fluoro-3' -thia-2' ,3' -dideoxycytidine (anti-HBV, trifluridine (herpes group, eye) vidarabine (HSV encephalitis) IV. Short Peptides corticotropin (ACTH) calcitonin desmopressin (DDAVP) gonadotropin RH (LH-RH) goserelin (LHRF) insulin lypressin beta-melanotropin ( / S-MSH) alpha-melanotropin (α-MSH) muramyl dipeptide oxytocin vasopressin FK-506 octreotide 6682 enalkiren (renin inhibitor) protease inhibitors V. Miscellaneous Agents morphine (narcotic analgesic) 6186 prostaglandins 7891 leukotrienes 5339 cyclosporine (immunosuppressive) 2759 A significant aspect of the compounds of the invention and related methods for oral administration of drugs is that 1-O-alkyl-, 1-O-acyl-, 1-S-alkyl-, and 1-S-acyl-glycero- phosphate derivatives -require no metabolic conversions fo oral absorption. These lipid prodrugs are in this wa distinct from phosphatidyl derivatives, for which metaboli processing requires preliminary conversion to a lyso phospholipid. Furthermore, the alkyl group at the 1-positio of the glycerol moiety of the 1-O-alkyl derivative cannot b degraded by intestinal lysophospholipases because of the ethe bond linking the alkyl group to the glycerol structure. Thi metabolic feature prevents digestive degradation an facilitates the intestinal uptake of the intact 1-O-alkyl-sn glycero-3-phosphate drug conjugate together with othe lysophospholipids that are undergoing membrane transport i the small intestine. The 1-O-acyl and the correspondin thioether and thioester analogs may also be absorbe substantially but are less preferred in applications " wherei this property is required. Coupling of Lipid Moiety to a Candidate Drug The compounds of the invention are formed according t synthetic procedures which couple a l-O-alkyl-sn-glycero-3- phosphate, or 1-O-acyl, 1-thioether, or 1-thioester analog thereof to a drug or which couple a 1-O-alkyl monoglyceride o 1-O-acyl, 1-thioether, or 1-thioester analogs thereof, to a phosphorylated functional group of a drug. The 1-O-alkyl glycerol moiety, or any other analo described above, and the drug can be covalently linked throug mono-, di-, or triphosphate groups at the sn-3-position of the glycerol structure. When the 1-O-alkyl glycerol and the drug are joined through a linking group, the linker molecule is conveniently attached to the terminal phosphate of, for example, l-O-alkyl-sn-glycero-3-phosphate. In either case the candidate drug has an available functional group. A reaction is typically carried out at a temperature of 25° to 60°C, preferably 30° to 50°C, for a period of from 2 to 25h, preferably 8 to lOh. N,N' -dicyclohexylcarbodiimide (DCC) is added in measured portions generally over a period of 0.5 to 3h, preferably 0.75 to 1.5h. The reaction mixture is worked up by addition of wate and azeotroped by successive additions of toulene and ethanol . The resulting crude product is purified by ion-exchange an silica chromatography to afford the desired compound with the desired purity. The process of the invention is preferably conducted i the liquid phase. Upon addition of either tri- isopropylbenzenesulfonyl chloride (TIPS) or N,N'- dicyclohexylcarbodiimide (DCC) , the reaction mixture is heated to a temperature of 30° to 60°C. It is noted that the presence of equivalent, (or more than stoichiometric) , amounts of either TIPS or DCC does not impede the course of the reaction. The temperature of the reaction mixture can rise up to its boiling point. The heat of the reaction can be removed by external cooling of the reaction vessel or by means of a cooled reflux condenser. Suitable solvents for the reaction are amines or derivatives thereof. Preferred solvents include tertiary amines such as diisopropylethylamine, triethylamine, tributylamine, or heterocyclic amines such as pyridine or picolines. 1-O-alkyl analogs of the invention, for example 1-0- octadecyl-sn-glycero-3-phosphate derivatives, or any of the other 1-O-acyl or 1-S-acyl or 1-S-alkyl analogs, can be produced by any of the synthetic organic procedures known to those in the art, for example, condensation of batyl alcohol and the monophosphate of the drug candidate such as ara-C monophosphate as described in Example 2 (compound Ila) . An alternative approach links the monophosphate of batyl alcohol to a candidate drug in the presence of a condensing agent such as DCC or TPS (Example 5) . In another variation of the method, l-0-octadecyl-2- benzyl-sn-glycero-3-phosphate was condensed with ara-C while the hydroxy group in 2-position of the batyl alcohol was protected as the benzyl ether. Subsequent Lewis acid catalyzed debenzylation, afforded the orally bioavauabl batyl-P-ara-C (Example 5) . Lipid prodrug derivatives of taxol-related compounds Lipid derivatives of taxol are prepared according to procedure wherein the amino alcohol and hydroxy carboxyli acid units of the taxol side chain are covalently attached t a phosphatidic acid, preferably a 1-0-alkyl glycerophosphat as set forth in Examples 13 through 16. The lipid- derivativized side chain is then attached to the rin structure of taxol, at the allylic alcohol, as baccatin III, or 10-deacetyl baccatin III. The side chain can b derivatized by the insertion of an aliphatic group (CH 2 ) n t increase lipophilicity. According to the general procedure, a substituted / 5-amino-α-hydroxy-benzene propanoate is covalently linked to a phosphatidylglycerol or a 1-O-alkyl- or l-0-acyl-2-benzyl- sn-glycero-3-phosphatidic acid in the presence of a condensing agent, such as DCC, to provide compounds of the formula: HzC-OR 1 HC-OR 2 O H 2 C-0 P—O—C- (CH 2 ) n -C0 2 R 3 [II] O I CH 3 -CI--phenyl R 4 NH wherein R 1 and R 2 are the same or different and are straight or branched, saturated or unsaturated C 8 -C 18 acyl or alkyl groups; or R 2 can be benzyl or H; R 3 is any hydrolyzable ester group, for example, methyl, ethyl, or pivaloyl; R 4 is benzoyl, pivaloyl, acetate, peptides, or amino acids; and n is 0-10. In alternative embodiments, R x and R 2 are attached to the glycerol group by thioester or thioether bonds . In a preferred embodiment, R 1 is an ether-linked baty group, and R 2 and R 4 are benzyl, and an 1-0-alkyl-2-benzyl - sn glycero-3-phosphate is condensed with a β- (benzoylamino) -a hydroxybenzene propanoate ester to form a lipid derivative o the taxol side chain. The propanoate ester is then hydrolyze to yield the propanoic acid which is ready for coupling wit baccatin III, or 10-deacetyl baccatin, having the formula: baccatin III OR 10-deacetyl baccatin to form an orally bioavauable taxol compound. Lipids comprising fatty acids, fatty alcohols, glycerides, and phospholipids for use in preparing the lipi prodrugs of the invention may be purchased from commercial suppliers (Avanti Polar Lipids, Inc., Pelham, Alabama; o Genzyme Corp., Cambridge, Massachusetts) or may be synthesize according to known methods. 1-0-octadecyl-sn-glycerol (batyl alcohol) is available from Sigma, St. Louis, and a 2-benzyl derivative of batyl alcohol is available from Bachem, Inc., Basel, Switzerland. Other lysophosphatidic acids useful i preparing the prodrugs of the invention are available fro Genzyme, Cambridge, Massachusetts. The drugs to which these lipids are covalently linked can be purchased from the pharmaceutical manufacturers. It is important that all traces of water be removed fro the reactants in order for the coupling reactions to proceed. Therefore, the lipids are first either freeze-dried by solven evaporation under vacuum, or in a vacuum oven over P 2 0 5 . Th reactions are also carried out under an inert gas, such as, for example, argon. The synthetic reactions are followed using thin laye chromatography (TLC) with appropriate solvents. When the reaction is complete as determined by TLC, the product is extracted with an organic solvent and purified by chromatog¬ raphy on a support suitable for lipid separation, for example, silicic acid. Efficacy and potency of 1-O-alkyl glycerol phosphate prodrugs The lipid derivative prodrugs of the invention, preferably l-0-alkyl-sn-glycero-3-phosphate prodrugs, have advantageous pharmacological properties in comparison to the non-derivatized drugs. The efficacy of the lipid prodrugs of the invention was demonstrated in tests carried out both in vitro and in vivo. l-0-octadecyl-sn-glycero-3-phospho-3' -deoxy, 3' -azidothymidine (AZT) was used in oral absorption studies. This compound has an 18-carbon alkyl ether at position 1 of glycerol; the hydroxyl at position 2 of glycerol is open, and position 3 is linked by a phosphodiester bond to 3 '-deoxy, 3'- azidothymidine (AZT) -5' -monophosphate. 1-0-octadecyl-sn- glycero-3-phospho-AZT does not require any metabolic conversions for absorption and appears to be absorbed directly from the gastrointestinal tract. It is not subject to deacylation by lysophospholipases in the gut because of the ether bond at position 1 of glycerol. Its metabolism is not known but it is hypothesized that the compound is metabolized by cellular enzymes and phosphodiesterases releasing 3'-deoxy, 3 ' -azido-thymidine (AZT) or AZT-MP inside the cell. The batyl alcohol derivative of AZT-monophosphate was evaluated in vivo for oral bioavailability in pharmacokinetic tests as described in Example 12 for which the results are shown in Figures 1-14. To interpret the results, it should be understood that free " AZT is available orally but has a exceedingly short physiological half-life of about 30-60 min In this study, the tissue level of the batyl-derivative AZ prodrug after oral administration was compared to the level o free AZT after intraperitoneal administration by noting th area under the curve (AUC) as the dose level in the tissu integrated over time. Notably, the AUC of AZT in plasma afte oral administration of the lipid prodrug was 1.38 time greater than that of free AZT administered intraperitoneally, demonstrating clearly the anticipated advantage of this nove method of administration in maintaining the drug level in th plasma for a longer period of time. 1-0-octadecyl-sn-glycero- 3-phospho- [ 3 H]AZT was demonstrated in the plasma by lipi extraction and thin layer radiochromatography. Significant amounts of free [ 3 H]AZT were not found until 12 hours following oral administration. The in vivo study as described in Example 15 demonstrates that a l-0-alkyl-sn-glycero-3-phosphate drug derivative has the same pharmacological efficacy as that of the non- derivatized agent. It further demonstrates that oral dosing with the batyl-P derivative can allow more convenient and effective administration of AZT. l-O-batyl-sn-glycero-3- phospho-AZT was compared to free AZT in treating mice infected with Rauscher murine leukemia virus (RLV) . RLV is a murine retrovirus, and RLV-infected mice are useful as a model system for evaluating therapeutic effectiveness of candidate anti- AIDS drugs against retrovirus induced disease in vivo. RLV infects splenocytes and the infected animals exhibit massive splenomegaly. Effective antiviral agents inhibit the splenomegaly, and a reduction in organ weight correlates with the elimination of virus (Ruprecht, R. , et al. , Nature 323:467-469 (1986)) . Because AZT has a short physiological half-life, the most effective mode of AZT therapy should be continuous oral administration. The closest practical approach to optimum administration is the intake of AZT in drinking water. Oral administration of batyl-P-AZT on a once a day regimen of gavage proved to be as effective, in comparable doses, as virtually continuous free AZT administration, as determined by inhibition of splenomegaly in the infected mice (Figure 15) . In in vitro studies, l-0-octadecyl-sn-glycero-3-phospho- AZT had an IC 50 ranging from 0.4 to 1.1 μM in HIV-infected HT4- 6C cells. The anti-HIV activity of the sn-3 isomer and the racemic compound was identical. Therapeutic use of the lipid derivatives The dosage of 1-O-alkyl glycerol phosphate prodrugs for a mammal, including a human, may vary depending upon the extent and severity of the condition that is treated and the activity of the administered compound. The dosage of the lipid prodrug is determined by reference to the recommended dosages of the active agent, bearing in mind that, in selecting the appropriate dosage in any specific- case, consideration must be given to the patient's weight, general health, metabolism, age and other factors which influence response to the drug. Dosage levels for most commercially available therapeutic agents, as well as many agents that are being clinically investigated, are well established. For example, the dosage of 5-amino-4-imidazole carboxamide ribonucleoside (AICA-riboside) is reported to be from 0.1 to 500 mg/kg/day, preferably from about 15 to 200 mg/kg/day. The dosage of l-O-octadecyl-sn-glycero-3-P-AZT, for example, can be from about 1 to 100 mg/kg/day, preferably 10 mg/kg/day. Formulations for oral ingestion are in the form of tablets, capsules, pills, ampoules of powdered active agent, or oily or aqueous suspensions or solutions. Tablets or other non-liquid oral compositions may contain acceptable excipients, vehicles, diluents, fragrances, or flavors known to the art for the manufacture of pharmaceutical compositions, to make the medication palatable or pleasing to use. The formulation can therefore include diluents, such as lactose or calcium carbonate; binding agents such as gelatin or starch; and one or more agents selected from the group consisting of sweetening agents, flavoring agents, coloring or preserving agents to provide a palatable preparation. Moreover, such oral preparations may be coated by known techniques to furthe delay disintegration and absorption in the intestinal tract. Aqueous suspensions may contain the active ingredient i admixture with pharmacologically acceptable excipients, comprising suspending agents, such as methyl cellulose; an wetting agents, such as lecithin or long-chain fatty alcohols. The aqueous suspensions may also contain preservatives, coloring agents, flavoring agents and sweetening agents in accordance with industry standards. The preparations may further comprise antioxidants, such as ascorbic acid or tocopherol, and preservatives, such as p- hydroxybenzoic acid esters. The present invention is described below in detail using the following examples, but the chemical reactions described are disclosed in terms of their general application-to the preparation of the lipid prodrugs of the invention. Occasionally, the reaction may not be applicable as described to each compound included within the disclosed scope of the invention. The compounds for which this occurs will be readily recognized by those skilled in the art. In all such cases, either the reactions can be successfully performed by conventional modifications known to those skilled in the art, e.g., by appropriate protection of interfering groups, by changing to alternative conventional reagents, or by routine modification of reaction conditions. Alternatively, other reactions disclosed herein or otherwise conventional will be applicable to the preparation of the corresponding compounds of the invention. In all preparative methods, all starting materials are known or readily preparable from known starting materials; all temperatures are set forth uncorrected in degrees Celsius; and, unless otherwise indicated, all parts and percentages are by weight. EXAMPLE 1 Preparation of Lipid Moieties Used in the Coupling Procedures Synthesisof l-0-alkyl-2-benzyl-sn-glycero-3-phosphatidicac (1) To a vigorously stirred solution of 1-octadecyl-2-benz glycerol (Bachem, Inc., Basel, Switzerland), hereinaft referred to as OBG, a mixture of pyridine, triethylamine a tetrahydrofuran (THF) was added. Neat phosphoro oxychloride, POCl 3 , was added dropwise while maintaining t temperature between -5° to 5°C. The reaction mixture w stirred for 90 minutes at a temperature of 4°-C. T precipitated triethylamine hydrochloride was filtered and t residue treated with toluene at least twice (2xl0mi) and t solvent removed under reduced pressure. The resulting oil w converted to the ammonium salt upon careful addition methanolic ammonium hydroxide. The yield was 55%, and t target compound was a white to pale yellow solid. N-tritylethanolamine (2) A mixture of ethanolamine, trityl chloride and pyridi was refluxed for 15h. Water was added slowly to the cool reaction and the precipitate collected by filtration. T crude product recrystallized from a 1:1 mixture of ethanol a water. N-trityl-0- (l-0-octadecyl-2-benzyl-sn-glycero-3-phosphoryl) ethanolamine A mixture of 1, 2, and trisopropylbenzenesulfon chloride in pyridine was stirred at a temperature of 25°C f a period of 24h. The desired compound was extracted from t reaction mixture and detritylation was carried out by metho familiar to those skilled in the art. EXAMPLE 2 Coupling of 1-O-alkyl glycerol to a Phosphorylated Drug Derivative I. Synthesis of Batyl-P-Acyclovir (Batyl-P-ACV) : la Preparation from ACV monophosphate and batyl alcohol Acyclovir was phosphorylated by addition of phosphorou oxychloride, P0C1 3 . After l-2h at 0°C, acyclovir wa extracted with ether as the phosphoryl dichloride. A 2N NaO solution was added to an aqueous solution of the dichloride t bring the pH to about 9 to 10, converting the compound to th disodium form. Chromatography on Dowex 50 converted th disodium salt to acyclovir monophosphate. A solution o acyclovir monophosphate as its salt, such as tributylamine o trioctylamine, in pyridine was treated with batyl alcoho followed by triisopropylbenzenesulfonyl chloride (TIPS) at temperature of 45°C for a period of 28h. The dark-colore solution was treated with water, followed by toluene, and th resulting solution was concentrated under reduced pressure. The crude product was purified by ion exchange chromatograph followed by silica column chromatography to obtain the desire compound as a white chloroform-soluble powder in a yield of 50% with a purity >95%. II. Synthesis of Batyl-p-ara-C: Ila: Preparation from ara-C monophosphate and batyl alcohol A solution of cytosine arabinoside (ara-C) -5' - monophosphate (Sigma, St. Louis, Missouri), batyl alcohol, and triisopropylbenzenesulfonyl chloride (TIPS) in pyridine was allowed to stir at a temperature of 45°C over a period of 25h. Water was added to the reaction mixture followed by toluene and the solvents removed under reduced pressure. The crude product was chromatographed on silica gel to afford the desired compound. lib: Preparation from l-O-alkyl-2-benzyl-glvcerol (OBG) Alternatively, batyl-P-ara-C can be prepared starting from OBG as delineated in the preparation of 1 in Example 1 in which OBG can be used to couple with ara-C-monophosphate. IIc: Preparation from I-O-stearoyl glycerol A solution of ara-C-monophosphate, 1-0-stearoylglycer and triisopropylbenzenesulfonyl chloride (TIPS) in pyridi was allowed to stir at a temperature of 45°C over a period 25h. Water was added to the reaction mixture followed toulene and the solvents removed under reduced pressure. T crude product was purified by silica chromatography to affo the desired compound with the desired purity. EXAMPLE 3 Coupling of Drugs Having a Free Carboxyl Group to the Amino Group of a Monoglyceride Phosphorylethanolamine Preparation of the batyl derivative of cefazolin l-O-octadecyl-sn-glycero-3-phosphoethanolamine (1 mmol and cefazolin (1.2 mmol, 3 [ [ (5-methyl-1.3.4-thiadiazol-2-yl) thio] -δ-oxo-7 [ [ (lH-tetrazol-1-yl) acetyl] amino] 5-thia-l azabicyclo [4.2.0]oct-2-ene-2-carboxylic acid) were dissolve in pyridine followed by N,N-dicyclohexylcarbodiimide (3 mmol DCC) . The reaction mixture was stirred for 24h at 10°C. Th reaction was stopped by the addition of cold water and th solvents were evaporated and the product was purified b preparative thin layer chromatography. The following compounds were similarly coupled to 1-0 octadecyl-sn-glycero-phosphoethanolamine by using the abov procedure. 3a: ceftazidime {l- [ [7- [ [ (2-amino-4-thiazolyl) [1-carboxy-l methylethyoxy) imino] acetyl] amino] -2-carboxy-8-oxo-5-thia-l azabicyclo[4.2.0]] oct-2-en-3-yl]methyl]pyridiniumhydroxide} 3 b : c e f t i a x o n e { 7 - [ [ 2 - a m i n o - 4 thiazolyl) (methoxyimino) acetyl] amino] 8-oxo-3- [[1,2,5,6 tetrahydro-2-methyl-5, 6-dioxo-1,2,4-triazin-3-yl)thio]methyl] 5-thia-l-azabicyclo [4.2.0] oct-2-ene-2-carboxylic acid}; and 3c : piperacillin { [ [ [ [ (4-ethyl-2 , 3-dioxo-l piperazinyl)carbonyl] amino]phenylacetyl] amino] -3,3-dimethyl-7 oxo-4-thia-l-azabicyclo [3.2.0] heptane-2-carboxylic acid} EXAMPLE 4 Coupling Drugs Containing a Free Amino Group to a Monoglyceride Phosphate through an Aliphatic Chain Linke Preparation of 1-0-alkyl-sn-glycero phosphate derivatives ceftazolin 4a: Hydroxycarboxylic acid linker Hydroxybutyric acid sodium salt (0.5 mol, Aldrich) w dissolved in methanol and dry HC1 was passed to convert t acid to its methyl ester. Methanol was evaporated and the d methyl ester linking compound was coupled to 1-O-alkyl-s glycero-3-phosphate by using N,N' -dicyclohexyl carbodiimi (DCC) as a coupling agent. The resulting compound w subjected to a base-catalyzed methanolysis, by us-ing 0. methanolic sodium hydroxide and the free acid derivative w again coupled to various drugs containing free amino_ group such as, for example, the methyl ester of ceftazidime, sulfmethazine as described above. The protective ester gro was removed frm the drug by treatment with base. 4b: Dihydroxyl linker In another embodiment, the carboxylic acid group of t linker was reduced to an alcohol group (after coupling to 1- alkyl-sn-glycero-3-phosphate) to couple to free drugs havin a free acid moiety. EXAMPLE 5 1-O-Octadecyl-2-benzyl-sn-glycero-3-phosphoryl Ara-C(3) and l-O-Octadecyl-sn-glycero-3-phosphoryl Ara-C(4) (Batyl-P-Ara-C) 5a: A solution of l-0-alkyl-2-benzyl-sn-glycero-3 phosphatidic acid (1) and ara-C in pyridine was treated wit TIPS at a temperature of 40°C over a period of 24h. Th reaction was stopped by addition of water and the solven evaporated under reduced pressure. The crude product purifie by chromatography to afford (3) . Debenzylation of 3 usin standard procedures afforded the desired compound 4. 5b: Alternative preparation of compound 3 and 4 involved th coupling of OBG and ara-C monophosphate using pyridine as th solvent and TIPS as the coupling agent. Purification of 3 a debenzylation was effected using the standard procedures afford 4. 5c: 2' -ara-fluoro-2-chlorodeoxyadenosine 5d: 5-fluorouridine 5e: 6-mercaptopurine riboside 5f: 3 ' -thia-dideoxycytidine 5g: 3' -thia-5-fluoro-dideoxycytidine EXAMPLE 6 Synthesis of Batyl-P-5-aιnino-4-iπιidazole Carboximi Ribonucleoside (Batyl-P-AICA Riboside) A solution of l-0-alkyl-2-benzyl-sn-glycero-3 phosphatidic acid (1) and AICA riboside in pyridine containin TIPS was reacted at a temperature of 40°C over a period o 24h. The reaction was stopped by addition of water .and th solvents evaporated under reduced pressure. The crude produc purified by chromatography and debenzylated using standar procedures to afford the batyl-P-AICA-riboside Alternatively, batyl alcohol and AICA-riboside monophosphat in pyridine, in the presence of TIPS, was stirred at temperature of 50°C over a period of 25h. The reaction wa worked up as before to afford batyl-P-AICA riboside. EXAMPLE 7 Synthesis of l-0-octadecyl-glycero-rac-3-phospho-5' - (3' -deoxy, 3' -azido)thymidine: Dry l-0-octadecyl-rac-3-glycerol (batyl alcohol, 250 mg) 3' -azido-3' -deoxythymidine monophosphate sodium salt (0.72 gm) and 2,4, 6, -triisopropylbenzenesulfonyl chloride (TPS 1.219 gm) were mixed in dry pyridine and stirred overnigh under nitrogen. Chloroform (50 ml) was added and the reactio mixture was washed twice with cold 0.2N HCl and 0.2N sodiu bicarbonate. The organic phase was removed in vacuo with rotary evaporator and the product was crystallized at -20° from 20 ml of chloroform/acetone (12:8 by volume) . The fina purification of the compound was done by preparative thi layer chromatography using 500 micron layers of silica gel developed with chloroform/methanol/concentrated ammonia/wat (70/30/1/1 by volume) . EXAMPLE 8 Synthesis of Batyl-Phosphonoformate A quantity of 0.9 grams of racemic batyl alcohol (1-0 octadecyl-2, 3-glycerol, Sigma Chemical, St. Louis, MO) , 2. grams of triisopropylbenzenesulfonyl chloride (TPS, Aldric Milwaukee, WI) and 0.16 grams of phosphonoformate, acid for were reacted in 15 ml of dry pyridine at room temperatur under nitrogen. The reaction was monitored at half hou intervals by thin layer chromatography and was judged to b complete at about 24 hours. The reaction was stopped by th addition of 10 ml of chloroform/methanol/water (1/2/0.8 b volume) . The organic (lower) phase was separated by-furthe addition of 2 ml of chloroform and 2 ml of water. The organi phase was removed and evaporated in vacuo and the product wa obtained as a white powder. The crude product was dissolve in a small volume of chloroform/methanol (1/1 by volume) an subjected to preparative thin layer chromatography using 0. mm layer of chloroform/methanol/concentrated ammonia/wate (70/30/1/1) . Two phosphonoformate (PFA) -containing spots wer visualized, scraped and extracted with chloroform methanol/water. The two compounds are referred to as batyl PFA, top and bottom, respectively. EXAMPLE 9 Coupling 1-O-alkyl-sn-glycerophosphatidic acid to the Amino Group of a Peptide 1-0-alkyl-2-benzyl-sn-glycero-3-phosphatidic acid prepared as in Example 1 above, was partitioned betwee chloroform:methanol (2:1 (v/v) ; 200 ml) and cold 1 N HCl (5 ml) . The aqueous layer was re-extracted with chlorofor methanol (2:1 (v/v) ; 100 ml) . The combined organic phase wa evaporated and dried under vacuum over P 2 0 5 . The resultin free phosphatidic acid was dissolved in a mixture of DMF ( ml) and pyridine (2 ml) and to the solution was added th appropriate peptide having a free amino group (1 mmol) followed by N,N' -dicyclohexylcarbodiimide (DCC; Aldric Chemical Co. Milwaukee WI, MW: 206, 620 mg, 3 mmol) . Th reaction mixture was stirred for 24 hours at room temperature. The solvents were evaporated and the product was purified b flash chromatography over silica gel column (2.5 x 50 cm) using a linear gradient of 0 to 50% methanol in chloroform. Fractions containing the desired product as indicated by TL and HPLC were pooled and evaporated. The product was furthe purified, if necessary, by preparative HPLC or b crystallization. Debenzylation of the compound offered 1-0- alkyl-sn-glycero-3-phosphoramidate. EXAMPLE 10 Coupling 1-O-alkyl-2-benzyl-3-phosphoethanolamine to the amino group of a therapeutic peptide using succinate as a linking group A solution of l-0-alkyl-2-benzyl-3-phosphatidic acid and ethanolamine in pyridine was treated with N,N' -dicyclohexyl¬ carbodiimide and the mixture was to stir at room temperature for a period of 24h. The solvents were evaporated and the product purified by chromatogrphy. Fractions containing the desired product was pooled and evaporated. The l-0-alkyl-2- benzyl-3-phosphoethanolamine was next treated with succinic anhydride to afford the hemisuccinate of l-0-alkyl-2-benzyl-3- phosphoethanolamine. The free carboxyl group of the hemisuccinate was coupled to the N-terminal amino group of a HIV protease inhibitor [D-Phe] - [D-α-napthylalanine] -pipecolic acid - [α-OH-Leu] -Val amide (VST 7140) or a peptide such as VST 7194 or a renin inhibitor, enalkiren (A64662) . Preparation of DPPE-succinic acid The lipid-linker material 1, 2-dipalmitoyl-sn-glycero-3- phospho-O- (N-succinyl) -ethanolamine (DPPE-Suc) was prepared by reacting one equivalent of 1, 2-dipalmitoyl-sn-glycero-3- phosphatidylethanolamine (DPPE; Avanti Polar Lipids, Birmingham, Alabama) and one equivalent of triethylamine with three equivalents of succinic anhydride (Sigma Chemical Co., St . Louis, Missouri) in chloroform. The reaction was stirre at room temperature under dry nitrogen atmosphere for 1 hours. Upon completion of the reaction, the product materia was purified by silica gel chromatography using a solven gradient of 100% chloroform to 15% methanol in chloroform. Lipid-peptide derivatives The lipid-derivatized polypeptide HIV protease inhibito designated VST-7172 was prepared by reacting one equivalent o DPPE-Suc in dimethylformamide DMF) with one equivalent of VST 7140 peptide containing a free amine function at the N terminal and 3 equivalents of N,N' -dicyclohexylcarbodiimid (DCC) in dichloromethane. The reaction was stirred for 2 hours at room temperature under dry conditions, after whic time, the product was purified by silica gel chromatograph using a solvent gradient of increasing methanol in chloroform The C-terminally derivatized HIV protease inhibitor VST 7196 from iBOC- [L-Phe] - [O-jS-Nal] - [ce-OH-Leu] -Val-COOH (VS 7194) was prepared by reacting one equivalent of DPPE and th 7194 peptide in DMF with two equivalents each of DCC and 1 hydroxybenzotriazole. The reaction was stirred for 16 hour at room temperature under dry conditions, and the targe compound was then purified by preparative thin laye chromatography using a solvent system of 85:10: chloroform:methanol:acetic acid on 1000 μm 20x20 cm silica ge GF plates from Analtech Inc. (Newark, DE) . The purified lipid derivatives were subsequentl characterized by HPLC, amino acid analysis, fast ato bombardment mass spectrometry and gas chromatography fatt acid ratio analysis. EXAMPLE 11 Coupling 1-O-alkyl-sn-glycero-phosphatidic acid to the Hydroxy Group of a Peptide l-0-alkyl-2-benzyl-sn-glycero-3-phosphatidic aci (1 mmol) prepared as above was dissolved in a mixture of DM (2 ml) and pyridine (2 ml) and to the solution were added th appropriate peptide having a free hydroxyl group (1 mmol) followed by DCC (620 mg, 3 mmol) . The reaction was carrie out and the product was isolated as described in Example 1. The condensation of the phosphatidic acid and th hydroxyl group of a peptide was also conveniently carried ou by using 2,4, 6-triisopropylbenzenesulfonyl chloride (TPS-C1 Aldrich Chemical Co., Milwaukee, Wisconsin; MW: 302.86; 75 mg, 2.5 mmol) as a coupling agent in place of DCC Debenzylation was effected as in Example 9. EXAMPLE 12 Coupling a Peptide Containing a Free Carboxyl Group to the Amino Group of a Monoalkyl Phosphorylethanolamine A mixture of the appropriate peptide (1 mmol),"and 1-0 octadecyl-sn-glycero-3-phosphoethanolamine (1 mmol) wa dissolved in pyridine (5 ml) and DCC (3 mmol) followed b 1-hydroxybenzotriazole (HOBt; Aldrich Chemical Co., HOBt, MW 153; 450 mg, 3 mmol) was added. The reaction mixture wa stirred for 24 hours at room temperature and the product wa purified by silica gel chromatography as described in Exampl 1 followed by debenzylation as in Example 1. EXAMPLE 13 Synthesis of Lipid Derivative of a Taxol Side Chain Synthesis of β- (Benzoylamino) -a-((l,2-diacyl-sn-glycero-3 phospho) -benzenepropanoate, ester (1) . A solution of 1,2-diacyl-sn-glycero phosphate such a 1,2-dipalmitoyl-sn-glycero phosphatidic acid (0.5 mol, Genzyme) and / 3- (benzoylamino) -αe-hydroxybenzenepropanoateeste either in an ethereal solvent like diethyl ether, tetrahydrofuran or a halogenated solvent like dichloromethan or chloroform was added DCC either neat or as a solution an allowed to stir for 2-25h at a temperature of 4°C. Water wa added to the reaction mixture and the solvents removed unde reduced pressure. The crude product was chromatographed o silica gel to afford the desired compound. Synthesis of β- (Benzoylamino) -a- ( (l-0-octadecyl-2-benzyl-sn- glycero-3-phospho) -benzenepropanoate, ester (2) . A solution of l-0-octadecyl-2-benzyl-sn-glycero-3- phosphatidic acid (0.1 mol) , β- (benzoylamino) -ct- hydroxybenzenepropanoate ester in pyridine or chloroform was stirred in the presence of DCC (0.4 mol) at a temperature of 4°C for a period of 6h. Water was added to the reaction mixture and the contents extracted with chloroform. The solvent was removed under reduced pressure and the crude product purified by chromatography to afford the benzenepropanoate ester. EXAMPLE 14 Synthesis of β-amino Substituted Taxol Side Chain Synthesis of β-Amino-α- (l-0-octadecyl-2-benzyl-sn-glycero-3- phospho) -benzenepropanoate ester. A solution of l-0-octadecyl-2-benzyl-sn-glycero-3- phosphatidic acid (0.1 mol) , β-amino- -hydroxy¬ benzenepropanoate ester (0.1 mol) in chloroform or pyridine was added DCC (0.4 mol) and allowed to stir at a temperature of 4°C for a period of 5h. Water was added to the reaction mixture and the contents extracted with chloroform or other halogenated solvent. The solvent was removed under reduced pressure and the crude product purified by chromatography to afford the substituted ethanolamine of batylbenzyl phosphatidic acid. EXAMPLE 15 Hydrolysis of Propanoate Esters of Lipid Derivatized Taxol Side Chain Synthesis of β- (Benzoylamino) -a- ( (1,2-diacyl-sn-glycero-3- phospho) -benzenepropanoic acid (3) . The propanoate ester (0.1 mol) from (1) was hydrolyzed using sodium methoxide in methanol or sodium carbonate in methanol at a temperature of 5°C for a period of 4h to afford the desired compound which is ready for coupling with baccati III or 10-deacetyl baccatin III. Synthesis of β- (Benzoylamino) -a- (l-0-octadecyl-2-benzyl-sn glycero-3-phospho) -benzenepropanoic acid. To a solution of 2(0.1 mol) in methanol was added solution of sodium methoxide in methanol and the resultin solution was stirred at a temperature of 5°C for a period o 4h. The reaction mixture was neutralized and the resultin solution concentrated under reduced pressure to afford th crude product . Purification by column chromatography gave th desired compound which is suitable for coupling with baccati III or 10-deacetylbacatin. EXAMPLE 16 Coupling of Lipid Derivative of Taxol Side Chain to Baccatin A. Coupling of lipid derivative of phosophoethanolamine side chain to 10-deacetyl baccatin III. To a solution of β- (benzoylamino) -a- (1,2-diacyl-sn- glycero-3-phospho) -benzenepropanoic acid (example 15) (O.lmol) and 10-deacetylbaccatin III (O.lmol) in chloroform was added DCC (0.4mol) and allowed to stir at a temperature of 25°C for a period of 7h. Water was added to the reaction mixture and the contents extracted with chloroform. The organic layer was separated and the aqueous phase was extracted with chloroform. The combined organic layer was concentrated under reduced pressure and the crude product purified by chromatography to afford the 1,2-diacyl-sn-glycero-3-phosphoethanolamine derivative of taxol. B. Coupling of batylbenzylphosphoethanolamine side chain to 10-deacetyl baccatin III. To a solution of β- (benzoylamino) -a- (l-0-octadecyl-2- benzyl-sn-glycero-3-phospho) -benzenepropanoic acid (O.lmol) , 10-deacetyl baccatin III (O.lmol) in chloroform was added DCC (0.4mol) and allowed to stir at room temperature for a period of lOh. Water was added to the reaction mixture and the contents extracted with chloroform. The organic layer was separated and the aqueous layer was extracted with chloroform. The combined organic layer was concentrated under reduced pressure and the crude product purified by chromatography to afford the batylbenzylphosphoethanolamine derivative of taxol. In the preceding syntheses, proton NMR spectra were obtained with a General Electric QE-300 spectrometer, using tetramethylsilane as internal standard (key: s=singlet, d=doublet, t=triplet, q=quartet, dd=doublet of doublets, b=broad) , UV spectra were recorded on Shimadzu UV-160, spectrophoto eter. Fast atom bombardment mass spectra were determined by Mass Spectrometry Service Laboratory, University of Minnesota. Elemental analyses were determined by Galbraith Laboratories, Knoxville, TN. and Schwarzkopf Microanalytical Laboratory, N.Y. Melting points were obtained with a Fisher- Johns melting apparatus. Column chromatography was carried out on Merck silica gel 60 (70-230 mesh) . Rf values were obtained with HPTLC Merck, Kieselgel 60 pre-coated plates, lOxlOcm. Anhydrous pyridine, 2,4, 6-Triisopropylbenzenesulfonyl chloride (TPS) , and 3' -azido-3' -deoxythymidine (AZT) were purchased from Aldrich Chemical Co., Milwaukee, WI . Dimyristoylphosphatidic acid, disodium salt, was purchased from Avanti; batyl alcohol was obtained from Sigma Chemical, St. Louis, Missouri and 1-O-octadecyl, 2-benzylglycerol from Bachem Bioscience Inc., Philadelphia, Pennsylvania. EXAMPLE 17 ORAL ADMINISTRATION OF l-O-OCTADECYL-sn-GLYCERO-3- PHOSPHO-AZT- 3 H A quantity of 8 μmol of l-0-octadecyl-sn-glycero-3- phospho-AZT- 3 H (spec. act. 5890 DPM/nmole) and 96.7 μmol of egg phosphatidyl choline (PC) was suspended in 1.0 ml of 250 mM acetate buffer, pH 5.5. The sample was sonicated at 55°C for one hour. Drug concentration was determined by counting the final sonicate. 0.1 ml doses equivalent to lOmg AZT/kg body weight were given orally to mice using a feeding tube. After the indicated time, the mice were sacrificed and blood and tissues were-collected. Plasma was collected fro two mice, using an orbital bleed, and a third mouse wa sacrificed for blood and organs . Plasma was processed a described below. Tissues were removed, rinsed in saline, blotted dry, and placed into scintillation vials for furthe processing. To liver samples, 3 ml of distilled H 2 0 was adde before homogenization with a Polytron. A quantity of 0.5 ml was removed for solubilization and counting. All othe samples received 0.5 ml of distilled H 2 0. A quantity of 3 ml of TS-2 tissue solubilizer (RPI International) was added t all samples followed by incubation for 48 hours at 50°C. The solution was then neutralized with 120 μl of acetic acid, 17.5 ml of Liquiflor ® counting cocktail (NEN/DuPont) was added, and the samples were counted. The tissue content of 1-0- octadecyl-sn-glycero-P-AZT and metabolites was determined based on the specific activity. The results are expressed as nmol AZT/gm tissue or per ml of plasma. Drug retention over time measured was determined by integrating the area under the curve (AUC) for each tissue. Results are as follows and are illustrated graphically in Figures 1 to 14. : a. Plasma levels Plasma samples were extracted by the method of Folch, J., et al. (JBC, 1957) and the lipids chromatographed on thin layers of silica which were scanned with a radioscanner. Spots corresponding to l-0-octadecyl-sn-glycero-3-P-AZT- 3 H and the 3 H-AZT reference standards were identified and the radioactivity measured. Orally administered 1-0-octadecyl-sn- glycero-3-P-AZT- 3 H gave initial plasma levels of 7 nmol/ml at 1 hr as shown in Figure 1 and Table 1. Plasma levels >1 nmol/ml were observed throughout the 24 hr. period and seemed to rise slightly between 12 and 24 hours to a final level of 3.0 nmol/ml (3μM) . The IC 50 of l-O-octadecyl-sn-glycero-3-P- AZT ranged from 0.4 to 1.1 μM in LAV-infected HT4-6C cells as measured by the method of Larder et al . , Science 243; 1731-34 (1989) . Drug availability was also determined by calculating the integrated dose during the measurement period (area under the curve, or AUC) . AUC was determined and compared to that of free AZT. The AUC ratio of 1-0-octadecyl-sn-glycero-3-P- AZT/AZT was 1.38, indicating excellent gastrointestinal absorption of the liponucleotide . b. Stomach, duodenum and jejunum Levels of batyl-P-AZT (bPAZT) in stomach peaked at 75 nmol/ml at 6 hr. and declined to 26 nmol/gm at 24 hr. (Figure 2) . Drug levels in the duodenum also peaked at 28 nmol/gm at 6 hr. and were variable thereafter (Figure 3) . bPAZT levels in jejunum were highest at 1 hr., declined to 5 nmol/gm, rising gradually thereafter to 12 nmol/gm at 24 hr. (Figure 4) . c. Liver, spleen and lymph nodes In these tissues, bPAZT levels were maximal at 1 hr. , ranging from 5.5 to 10 nmol/gm. Tissue levels declined gradually thereafter to 2.5 (spleen, Figure 5), and 4.3 nmol/gm (liver, Figure 6 and lymph nodes, Figure 7) at 24 hr. d. Kidney, skin, skeletal and heart muscle bPAZT levels in kidney (Figure 8) were highest at 1 hr. (15 nmol/gm) declining to 3.6 nmol/gm at 24 hrs (Figure 9) . Similar bPAZT profiles were also seen in skeletal muscle (Figure 10) and heart (Figure 11) . e. Lung and adrenal bPAZT levels in lung were highest at 1 and 3 hrs. at 1.4 nmol/gm as shown in Figure 12. From 6 to 24 hr. drug levels ranged from 1.4 to 2.4 nmol/gm. Adrenal levels were variable (Figure 13) . f. Brain Brain levels of bPAZT- 3 H were maximal at 6 hours at 1.4 nmol/gm as shown in Figure 14. Plasma levels at 6 hrs . were 3.14 nmol/ml, making it unlikely that the material measured in brain plasma background. At 24 hours brain bPAZT levels continued to be significant at 1.1 nmol/gm (versus 3.0 nmol/ml in plasma) . g. Urine and feces At 6 hrs., 40 ± 16 % of the total administered dose of bPAZT- 3 H was recovered in the urine and 0.41 ± 0.11 percent of the administered dose was recovered in the feces . TABLE 2 Pharmacokinetics of lipid derivatives of AZT in vivo Free AZT in plasma:nmol/ml Conclusions: Oral l-O-octadecyl-sn-glycero-3-phospho AZT- 3 H Plasma and tissue levels of AZT were much higher following the oral administration of l-O-octadecyl-sn-glycero-3-phospho- AZT(bPAZT) than those observed above with free AZT. With bPAZT tissue levels of 1.5 to 5 nmol/gm were detected at 24 hrs. This compares very favorably to tissue levels obtained with intraperitoneal administration of free AZT. EXAMPLE 18 Single-Dose l-O-octadecyl-sn-glycero-3-phospho-AZT Oral Administration Compared to Continuous Oral AZT Administration Treatment of Rauscher Leukemia Virus-Infected Mice: Female BALB/C mice were infected with 1 x 10 4 plaque- forming units (PFU) of Rauscher leukemia virus complex (RLV) on day 0. Control animals were injected with saline. Beginning on day 2, groups of the infected mice as indicated in Figure 15 were treated with AZT at doses from about 1.0 mg/kg/day to 15.0 mg/kg/day for 21 days either by offering AZT in drinking water or by gavaging with batyl-PAZT once a day. On day 23 post-inoculation, the mice in both treatment protocols were sacrif-iced, and the spleen weights of th animals were determined. The mean spleen weights, indicatin relative level of virus infection, for each dose level in th two protocols, are represented in the bar graphs of Figure 15 The effective doses (ED50) of daily batyl-P-AZT given by single oral administration and AZT given by ora administration in the drinking water were comparable. It is apparent from the foregoing that other 1-0-alky glycerol phosphate derivatives of therapeutic drugs can b substituted in the Examples 2-11 to obtain similar results o delivering a drug, otherwise orally non-bioavailable, mor effectively through the oral route. It should be furthe emphasized that the present invention is not limited to th use of any particular drug or therapeutic agent in th compounds of the invention; rather the beneficial results o the invention flow from the synthesis of 1-0-acyl-, 1-0-alkyl-, 1-S-acyl-, or 1-S-alkyl-sn-glycerophosphat prodrugs of these drugs and agents. Thus, regardless o whether a specific drug or agent is presently known, o whether it becomes known in the future, the methods of formin the presently contemplated lipid prodrugs therefrom are base on established chemical techniques, as will be apparent t those of skill in the art, and therefore these compounds ar broadly enabled by the preceding disclosure. It should b emphasized again that the present syntheses are broadl applicable to formation of compounds from essentially all drugs having an appropriate structure, and the effectiveness of which can be improved by preparing a lipid prodrug form fo use in the practice of the invention.

Claims: WHAT IS CLAIMED IS: 1. A method of converting a drug that is unavailable o poorly available through the oral route of administration to an orally available form, comprising: preparing a lipid derivative of said drug, said lipid derivative comprising a l-0-alkyl-sn-glycerol-3- phosphate, a l-0-acyl-sn-glycerol-3-phosphate, a 1-S- alkyl-sn-glycerol-3-phosphate, ora 1-S-acyl-sn-glycerol- 3-phosphate group covalently linked to a functional group of said drug either directly through a phosphate ester or through a linker molecule; whereby the oral bioavailability and/or tissue levels of said pharmaceutical drug are enhanced. 2. A method of enhancing the pharmacokinetic properties of an orally administered drug, comprising: preparing a lipid derivative of said pharmaceutical drug, said lipid derivative comprising a 1-O-alkyl-sn- glycerol-3-phosphate, a l-0-acyl-sn-glycerol-3-phosphate, a 1-S-alkyl-sn-glycerol-3-phosphate, or a 1-S-acyl-sn- glycerol-3-phosphate group covalently linked to a functional group of said drug either directly through a phosphate ester or through a linker molecule, whereby the metabolic clearance of said agent is decreased, and the physiological half-life of said agent is extended. 3. The method of Claim 1 or Claim 2 wherein said lipid derivative is a l-0-alkyl-sn-glycerol-3-phosphate derivative of a drug, of the formula H— I O PI!-O (PII-0) n -(L)-D [I] 0 0 wherein R is a substituted or unsubstituted, saturated or unsaturated, straight or branched chain, or cyclic C x _ 24 alkyl group, covalently linked to the glycerol moiety in an ether linkage; n = 0 to 2 ; L is a linking molecule, of the formula X-(CH 2 ) n -Y wherein X and Y are functional groups independentl selected from hydroxyl, sulfhydryl, carboxyl and amine groups and n = 1 to 24; or L is absent; and D is a drug having a functional group selected from the grou consisting of hydroxyl, sulfhydryl, carboxyl, or amino groups 4. The method of Claim 3, wherein D is an anticance nucleoside having a carboxyl, hydroxyl, or amino grou available for covalent binding. 5. The method of Claim 3, wherein D is 9- / S-D arabinofuranosylcytosine (ara-C) , 5-fluorouridine, 6 mercaptopurine riboside, 9-<5-D-arabinofuranosyladenine (ara A) , or 2' -arafluoro-2-chloro-deoxyadenosine. 6. The method of Claim 3, wherein D is 5-amino-4 imidazole carboxamide ribonucleoside (AICA-riboside) . 7. The method of Claim 3, wherein D is a therapeuti peptide, or a peptidomimetic of from 3 to 35 amino aci residues or analogues thereof. 8. The method of Claim 7, wherein D is n-muramy tripeptide. 9. The method of Claim 7, wherein D is enalkiren. 10. The method of Claim 3 , wherein D is selected fro the group consisting of antibiotics of the penicillin an cephalosporin class. 11. The method of Claim 10, wherein D is selected fro the group consisting of penicillin G, cefazolin, ceftazidime, ceftriaxone, piperacillin. 12. The method of Claim 2, wherein said pharmaceutica agent is 3' -azido-3 ' -deoxythymidine (AZT) . 13. The method of Claim 2, wherein said drug is 3' azido-3' -acycloguanosine (ACG) . 14. An antineoplastic prodrug, comprising taxol, or substituted taxol drug covalently bound to a phospholipi compound. 15. The taxol prodrug of Claim 14, wherein sai phospholipid compound is selected from the group consisting of phosphatidylglycerols, 1-0-alkyl-sn-glycero-3-phosphatidic acids, l-0-acyl-sn-glycero-3-phosphatidic acids, 1-S-alkyl-sn- glycero-3-phosphatidic acids, and l-S-acyl-sn-glycero-3- phosphatidic acids. 16. The taxol prodrug of Claim 14 or 15, wherein said substituted taxol compound is selected from the group consisting of taxol compounds having lipophilic substituents at the / S-amino group of the taxol side chain. 17. The taxol prodrugs of Claim 16, wherein said lipophilic substituents are selected from the group consisting of benzoyl, pivaloyl, acetate, peptides, or amino acids. 18. Phospholipid derivatives of taxol-related compounds, comprising (a) a taxol side chain of the formula H 2 C-0 P — 0 C- ( CH 2 ) n - C0 2 R 3 I I O CH 3 -C- -phenyl R 4 NH OR H 2 C i-0 " PI — 0 C- ( CH 2 ) n - C0 2 R 3 I I O CH 3 -C- -phenyl I R 4 NH covalently attached at the allylic alcohol group of baccatin III OR 10-deacetyl baccatin wherein R 1 and R 2 are the same or different and are straight o branched, saturated or unsaturated C 8 -C 18 acy or alkyl groups; or R 2 is benzyl or OH; R 3 is taxol, taxotene, baccatin III, or 10-deacety baccatin III; R 4 is benzoyl, pivaloyl, acetate, peptides, or amin acids; and n is 0-10. 19. The compound of Claim 18, wherein R 1 is an ethe linked alkyl group; R 2 is OH, and R 4 is benzoyl. 20. The compound of Claim 18, wherein R 1 is 1-0 octadecyl . 21. A taxol side chain bound to a phospholipid an having the structure [II] R 1 and R 2 are the -same or different and are straight o branched, saturated or unsaturated C 8 -C 1S acy or alkyl groups; or R 2 can be benzyl or H; R 3 is any hydrolyzable ester group, for example, methyl, ethyl, or pivaloyl; R 4 is benzoyl, pivaloyl, acetate, peptides, or amin acids; and n is 0-10. 22. A method of synthesizing a lipid derivative of taxo or a substituted taxol compound, comprising the steps of: (a) covalently attaching a phospholipid through phosphate group to the amino alcohol or hydroxy carboxyli acid groups of the taxol side chain, the propanoic acid grou of said side chain being protected by esterification, thu forming a lipid derivative of said side chain; (b) removing the protective group from sai propionic acid group; and (c) coupling said lipid derivative of said taxol side chain through said propionic acid group to the allylic alcohol group of baccatin III, or 10-deacetyl baccatin. 23. A method of synthesizing phospholipid derivatives of taxol or taxol-related compounds, comprising the steps of: (a) providing a acyl or alkyl substituted-sn-glycero-3- phosphate and a β-amino-α-hydroxy-benzene propanate ester; (b) linking said glycero-3-phosphate and said benzene propanate ester through a covalent bond between the phosphate group of said phosphatidic acid and the - hydroxyl group of said benzene propanate ester; (c) de-esterifying the benzene propanate ester group of the lipid derivative of (b) by hydrolysis; (d) linking the lipid derivative of (c) to a taxol related group by condensation of the propanoic acid group of said derivative and the 13-OH group of a taxol ring skeleton. 24. The method of Claim 22 or 23 wherein said acyl o alkyl-substituted glycero-3-phosphate is a 1-O-alkyl-sn glycero-3-phosphate. 25. The method of Claim 22 or 23 wherein said 1-O-alkyl sn-glycero-3-phosphate is l-0-octadecyl-sn-glycero-3 phosphate.

Inventors: HOSTETLER KARL Y, KUMAR RAJ, SRIDHAR NAGARAJAN C, HOSTETLER, KARL, Y., KUMAR, RAJ, SRIDHAR, NAGARAJAN, C.
Applicants: VESTAR INC, VESTAR, INC.
Application year: 1993
Main classification: A61K47
IPC codes: A61K31, A61K47, A61P35, C07F9, C07H15, C07H19