This invention provides compounds which are a taxane to which an acyl chain has been attached; the acyl chain has been derivatized by the stereospecific attachment thereto of a hydrolysis-promoting group. Also provided herein are compositions comprising such compounds and racemic mixtures thereof, including lipid carrier-containing pharmaceutical compositions, and methods of administering such compositions to animals, such as humans afflicted with cancers or certain inflammatory conditions.
Taxanes can be isolated from natural sources, and can also be prepared synthetically from naturally occurring precursors. Paclitaxel (TAXOL(copyright), Bristol-Myers Squibb), for example, can be prepared from baccatin by attachment of protecting groups to the hydroxyl groups of baccatin that are to become the hydroxyl groups of paclitaxel, converting the precursor baccatin to paclitaxel, and then removing the protecting groups from the hydroxyl groups to obtain paclitaxel. In addition, paclitaxel has recently been synthesized from simple precursors. (See, e.g., WO93/10076, int. pub. date May 27, 1993; K. V. Rao, U.S. Pat. No. 5,200,534; R. A. Holton, U.S. Pat. No. 5,015,744; PCT/US92/07990; V. J. Stella and A. E. Mathew, U.S. Pat. No. 4,960,790; K. C. Nicolau, Nature 364 (1993), pp. 464-466; Nicolau, K. C. et al. Nature 367 (1994) pp.630-634; Holton, R. A., et al. J. Am. Chem. Soc. 116 (1994) pp. 1597-1600; WO93/16059, int. pub. date Aug. 19, 1993; EP 528,729, published Feb. 24, 1993; EP 522,958, published Jan. 13, 1993; WO91/13053, int. pub. date Sep. 5, 1991; EP 414,610, int. pub. date Feb. 27, 1991; the contents of these documents are incorporated herein by reference).
Taxanes can be used effectively to treat a variety of cancers and recently has been reported to have therapeutic effects in treating certain inflammatory diseases. Paclitaxel, for example, has been found to have activity against ovarian and breast cancers, as well as against malignant melanoma, colon cancer, leukemias and lung cancer (see, e.g., Borman, Chemical and Engineering News, Sep. 2, 1991, pp. 11-18; The Pharmacological Basis of Therapeutics (Goodman Gilman et al., eds.), Pergamon Press, New York (1990), p. 1239: Suffness, Antitumor Alkaloids, in: xe2x80x9cThe Alkaloids, Vol. XXV,xe2x80x9d Academic Press, Inc. (1985), Chapter 1, pp. 6-18: Rizzo et al., J. Pharm. and Biomed. Anal. 8(2):159-164 (1990); and Biotechnology 9:933-938 (October, 1991). Paclitaxel has been hypothesized to act against cancer cells by binding to tubulin in the cells"" nuclei, thereby blocking the disassembly of microtubules and consequently, inhibiting cell division (Schiff et al., Nature 277:665 (1979).
However, formulation of taxanes in therapeutically useful carriers, so as to enable the taxanes to be administered to animals, is made difficult by the nature of the taxane molecules, which can be poorly soluble in both aqueous and lipid carriers. Paclitaxel, for example, is currently supplied as a formulation of polyoxyethylated derivative of castor oil, Cremophor EL(copyright) and ethanol (50:50) because of its lack of significant aqueous or liposome solubility. However, the Cremophor EL(copyright) carrier itself can cause toxic side effects or increase the side effects caused by the taxane when administered to animals. Thus, administration of the Cremophor EL(copyright): ethanol -based paclitaxel formulation generally entails premedication with other drugs, as well as a slow infusion of a large volume of the formulation, thus often necessitating over night hospital stays and their attendant costs. Alternatively, a stable formulation of a taxane with a lower concentration of a polyoxyethylated derivative of castor oil could be important in reducing the toxic side effects of the drug product.
Compositions provided herein provide taxanes in the form of compounds which are taxanes to which an acyl chain has been attached. The acyl chain enhances the taxane""s lipid solubility. Thus, the taxane can be stably associated with a lipid-based carrier such as a liposome, for an extended period of time. However, the compositions provided herein may also be administered in non-liposomal carriers, such as USP/NF Polyoxyl 35 Castor Oil. The acyl chain itself has been derivatized by the attachment thereto of a hydrolysis-promoting group, which is a chemical moiety that promotes hydrolysis of the derivatized acyl chain from the parent taxane, once the taxane has been disassociated from the lipid-based carrier, so as to give the parent taxane in a therapeutically useful form. The hydrolysis-promoting group may take the structure of a single enantiomer or may be administered as a mixture of (S) and (R) enantiomers. There may be a stereospecific difference in the biological and pharmacological activity attributable to the enantiomeric form. While not being limited to this explanation, it is possible that in vivo cleavage may favor one enantiomer. Thus, by providing a method to deliver the preferred enantiomeric form of the hydrolyzable hydrophobic taxane of the present invention, administeration of lower dosage than with mixed racemic forms may provide equivalent therapeutic effect. The present invention, therefore, additionally provides methods for preparing single enantiomeric forms of the hydrolyzable hydrophobic acyl chains and methods for synthesizing the hydrolyzable hydrophobic taxane having a single enantiomeric substituted fatty acid or at least enriched in a single enantiomeric form.
The compounds provided herein can be administered to animals as such, or may be formulated together with a lipid-based carrier prior to administration. Such formulations may enhance delivery of the taxane to its intended site of action in an animal and may alter the pharmacological action by delaying the release of the therapeutic agent in the animal or may delay the clearance of the therapeutic agent from the animal. These formulations may therefore allow increased time of exposure of the animal to the therapeutic agent. However, the drug compound comprising the HPG must be stable in formulations until administration.
This invention provides a taxane having the formula: 
wherein: A1 is H or a group having the formula Zxe2x80x94C(O)NHCH(C6H5)CH(OR)C(O)xe2x80x94; Z is C6H5xe2x80x94, C6H5CH2Oxe2x80x94, (CH3)3Cxe2x80x94Oxe2x80x94 or CH(CH3)=C(CH3)xe2x80x94; A2 is H or CH3C(O)xe2x80x94; and A3 is H or OH. Each of R and R1 is H or a group having the formula Y1Y2, provided that at least one of R and R1 is not H, and provided that when A1 is H, R1 is not H.
Y1 is a group having the formula xe2x80x94C(O)CHX1(CH2)n1(CHxe2x95x90CH)n2(CH2)n3(CHxe2x95x90CH)n4(CH2)n5(CHxe2x95x90CH)n6(CH2)n7(CHxe2x95x90CH)n8(CH2)n9xe2x80x94. The sum of n1+2n2+n3+2n4+n5+2n6+n7+2n8+n9 is an integer of from 1 to 21, with each of n2, n4, n6 and n8 being independently zero or 1. n1 is equal to zero or an integer of from 1 to 21, n3 is equal to zero or an integer of from 1 to 18, n5 is equal to zero or an integer of from 1 to 15, n7 is equal to zero or an integer of from 1 to 12, n9 is equal to zero or an integer of from 1 to 9, and each of n 1 to n9 can be the same or different at each occurrence. Y2 is xe2x80x94CH3, xe2x80x94CO2H or xe2x80x94CH2OH.
X1 is a hydrolysis promoting group (xe2x80x9cHPGxe2x80x9d) including, but not limited to: F, Cl, Br, I, the group xe2x80x94OC6H4X2 or the group xe2x80x94C(O)X2, wherein X2 is F, Cl, Br, I, NH3+, NO2 or CN. Most preferably, X1 is F, Cl, Br or I. The X1 in CHX1 could have (R) or (S) configuration or could be a mixture of (R) and (S) configurations. Preferably, A1 is the group Zxe2x80x94C(O)NHCH(C6H5)CH(OR)C(O)xe2x80x94; Z is preferably C6H5 and A1 is more preferably the group C6H5C(O)NHCH(C6H5)CH(OR)C(O)xe2x80x94. Most preferably, A1 is C6H5C(O)NHCH(C6H5)CH(OR)C(O)xe2x80x94, A2 is CH3C(O)xe2x80x94 and A3 is H, that is, the taxane is a paclitaxel. When R1 is a hydrogen, R is then xe2x80x94Y1Y2, and when R is a hydrogen, R1 is xe2x80x94Y1Y2. The group xe2x80x94Y1Y2 preferably has the formula xe2x80x94Y1CH3, more preferably, the formula xe2x80x94C(O)CHX1(CH2)n1CH3; still more preferably, n1 is then 3, 5, 9, 11, 13 or 15.
Taxanes with xcex1-substituted carbonyl compounds esterified to the 2xe2x80x2 or 7 hydroxy position have therapeutic activity. xe2x80x9cHydrolysis-promoting groupsxe2x80x9d (HPG) that facilitate chemical hydrolysis by means of a redistribution of electronic density may be important in conversion of substituted taxanes to paclitaxel or other therapeutic taxanes. This conversion may also be important to their biological activity. However, the substituted taxane may itself have biological activity without being converted to the parent compound.
The biological activity of paclitaxel is known to be sensitive to the chirality of paclitaxel chemical moieties and therefore, the stereochemistry of xcex1-substituted carbonyl compounds esterified to the 2xe2x80x2 or 7 hydroxy position of taxanes may be important to the biological activity of the compound.
Ester cleavage of xcex1-substituted carbonyl compounds has been shown to be selective for a single enantiomer for many enzymes (xe2x80x9cLipases for Resolution and Asymmetric Synthesisxe2x80x9d Amano Enzymes USA Co. Lombard, Ill., December 1998.). Although chemical hydrolysis of taxanes with xcex1-substituted carbonyl compounds esterified at the 2xe2x80x2 or 7 hydroxy position due to HPG is not stereoselective, biologically mediated cleavage could be stereospecific, as judged by the selectivity of many enzymes. The stereospecific cleavage of xcex1-substituted carbonyl compounds esterified to the 2xe2x80x2 or 7 hydroxy position of taxanes could be a factor affecting conversion of the pro-drug. Thus, the chirality of the linkage at the xcex1-substituted carbonyl group may have pharmacological implications.
Thus, in one embodiment, the invention provides hydrophobic taxane compositions having a preponderance of (S) or (R) xcex1-substituted carbonyl groups, preferably xcex1-substituted fatty acids, for instance, (S) and (R) 2-bromohexadecanoic acids substituted at the 2xe2x80x2 or 7 hydroxy position. Methods for preparing these single enantiomers and for separating them from an enantiomeric mixture is also provided.
Also provided herein are compositions comprising the taxane of this invention. Such compositions can also comprise a pharmaceutically acceptable medium which may be selected from the group consisting of a polyoxyethylated derivative of castor oil, polysorbate (Tween) 80, dimethyl sulfoxide, carboxymethyl cellulose, hydroxypropylcellulose, polyethylene glycols (PEGs) including PEG-400 and PEG-hydroxystearate, triacetin, soybean oil, lecithin and soy lipids or combinations thereof. Preferably, the pharmaceutically acceptable medium is a polyoxyethylated derivative of castor oil. More preferably, the pharmaceutically acceptable medium is USP/NF Polyoxyl 35 Castor Oil. Most preferably, the pharmaceutically acceptable medium is Cremophor-ELP(copyright). The pharmaceutically acceptable medium may also be a lipid carrier and may be any composition which maintains the chemical integrity of the HPG containing taxane throughout an acceptable pharmaceutical shelf life, effectively delivers the derivatized taxane of this invention to an animal in need of such treatment wherein the side effects due to the carrier are within acceptable medical limits. The compositions may comprise a lipid-based carrier, e.g., a fatty acid, phospholipid, lipoprotein, micelle, lipid complex or liposome, with which the taxane is associated so as to deliver the taxane to a site in the body where it can be therapeutically effective.
The lipid carrier may be a liposome or non-liposomal lipid carrier. If the lipid carrier is a liposome, it is most preferably, a multilamellar liposome. The liposome preferably comprises a lipid component which comprises a saturated lipid, more preferably, a saturated phosphatidylcholine such as dimyristoyl phosphatidylcholine, dipalmitoyl phosphatidylcholine or distearoyl phosphatidylcholine. Most preferably, the saturated lipid is dimyristoyl phosphatidylcholine. The liposomal lipid component can consist essentially of a saturated lipid, e.g., dimyristoyl phosphatidylcholine. For taxanes associated with lipid carriers, the sum of n1+2n2+n3+2n4+n5+2n6+n7 +2n8+n9 is preferably an integer of from 3 to 21, more preferably an integer of from 9 to 21, and most preferably, an integer of from 13 to 21. That is, in compositions comprising taxanes associated with liposomal lipid carriers, the carrier has a lipid component comprising or consisting essentially of dimyristoyl phosphatidylcholine and the taxane is derivatized with xcex1-substituted carbonyl compound. If the carrier is not a liposome, then preferably, it is the polyoxyethylated derivative of castor oil (USP/NF Polyoxyl 35 Castor Oil).
Further provided herein is a method of administering a taxane to an animal, which comprises administering a taxane-containing composition of this invention to the animal. Preferably, the taxane thus administered is associated in the composition with a lipid carrier, more preferably, a liposome or the polyoxethylated derivative of caster oil (USP/NF Polyoxyl 35 Castor Oil) and most preferably, if a liposome, a multilamellar liposome and if a non-liposomal carrier, then the polyoxyethylated derivative of castor oil (USP/NF Polyoxyl 35 Caster Oil). The animal can be afflicted with a cancer, e.g., a brain, stomach, lung, colon, prostate, breast or ovarian cancer, cancers of the head and neck, or a leukemia, lymphoma, carcinoma or sarcoma. The compounds of the present invention may also be administered to an animal afflicted with inflammatory diseases such as arthritis. (Arsenalt, A.L., et al. (1998) Clin Immonol Immunopathol, 86(3):280-9.) Cancer treatment by this method involves administering an anticancer effective amount of a taxane to the affected animal. Typically, this anticancer effective amount of the taxane is from about 0.1 mg per kg of body weight of the animal to about 1000 mg per kg. For such anticancer treatment, the composition administered preferably contains a lipid carrier. Preferred anticancer taxanes are paclitaxels, i.e., taxanes wherein A1 is C6H5C(O)NHCH(C6H5)CH(OR)C(O)xe2x80x94, A2 is CH3C(O)xe2x80x94 and A3 is H. More preferably, R or R1 is xe2x80x94C(O)CHX1(CH2)nl CH3, and most preferably, nl is then 3, 5, 9, 11, 13 or 15. Further provided are taxane derivatives wherein the X1 in CHX1 could have either (R) or (S) configuration or could be a mixture of (R) and (S) configurations. Furthermore, an additional bioactive agent can be administered to an animal as part of administration of a taxane to the animal.
Other and further objects, features and advantages will be apparent from the following description of the preferred embodiments of the invention given for the purpose of disclosure when taken in conjunction with the following drawings.