Drug – bio-affecting and body treating compositions – In vivo diagnosis or in vivo testing
Reexamination Certificate
1999-09-08
2001-11-06
Jones, Dameron L. (Department: 1615)
Drug, bio-affecting and body treating compositions
In vivo diagnosis or in vivo testing
C424S600000, C424S001110, C424S009200, C424S001650, C424S601000, C514S007600
Reexamination Certificate
active
06312662
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed towards novel prodrugs of phosphate, phosphonate, and phosphoramidate compounds which in their active form have a phosphate, phosphonate, or phosphoramidate group, to their preparation, to their synthetic intermediates, and to their uses. More specifically, the invention relates to the area of substituted cyclic 1,3-propanyl phosphate, phosphonate and phosphoramidate esters.
BACKGROUND OF THE INVENTION
The following description of the background of the invention is provided to aid in understanding the invention, but is not admitted to be, or to describe, prior art to the invention. All publications are incorporated by reference in their entirety.
Free phosphorus and phosphonic acids and their salts are highly charged at physiological pH and therefore frequently exhibit poor oral bioavailiability, poor cell penetration and limited tissue distribution (e.g. CNS). In addition, these acids are also commonly associated with several other properties that hinder their use as drugs, including short plasma half-life due to rapid renal clearance, as well as toxicities (e.g. renal, gastrointestinal, etc.) (e.g. Antimicrob Agents Chemother 1998 May; 42(5): 1146-50). Phosphates have an additional limitation in that they are not stable in plasma as well as most tissues since they undergo rapid hydrolysis via the action of phosphatases (e.g. alkaline phosphatase, nucleotidases). Accordingly, phosphate esters are frequently used as a prodrug strategy, especially for water insoluble compounds, since the phosphate group enables high water solubility and thereby enables delivery of the drug parenterally.
Prodrugs of phosphorus-containing compounds have been sought primarily to improve the limited oral absorption and poor cell penetration. In contrast to carboxylic acid proesters, many phosphonate and phosphate esters fail to hydrolyze in vivo, including simple alkyl esters. The most commonly used prodrug class is the acyloxyalkyl ester, which was first applied to phosphate and phosphonate compounds in 1983 by Farquhar et al.
J. Pharm. Sci
. 72(3): 324 (1983). The strategy entails cleavage of a carboxylic ester by esterases to generate an unstable hydroxyalkyl intermediate which subsequently breaks down to generate the drug and an aldehyde. In some cases this biproduct (e.g., formaldehyde), can be toxic. This strategy is used to enhance the bioavailability for several drugs. For example, the bis(pivoyloxymethyl) prodrug of the antiviral phosphonate 9-(2-phosphonylmethoxyethyl)adenine (PMEA) has been studied clinically for the treatmentof CMV infection and the bis(pivaloyloxymethyl) prodrug of the squalene synthetase inhibitor BMS187745 is undergoing clinical evaluation for the treatment of hypercholesterolemia and associated cardiovascular diseases. The marketed antihypertensive, fosinopril, is a phosphinic acid angiotensin converting enzyme inhibitor that requires the use of an isobutryloxyethyl group for oral absorption.
Several other esters have been used as prodrugs of phosphorus-containing compounds. For example, aryl esters, especially phenyl esters, are another prodrug class reported to be useful for the delivery of phosphorus-containing compounds. DeLambert et al.,
J. Med. Chem
. 37: 498 (1994). Phenyl esters containing a carboxylic ester ortho to the phosphate have also been described. Khamnei and Torrence,
J. Med. Chem
.; 39:4109-4115 (1996).
Benzyl esters are reported to generate the parent phosphonic acid. In some cases using substituents at the ortho- or para-position can accelerate the hydrolysis. Benzyl analogs with an acylated phenol or an alkylated phenol can generate the phenolic compound through the action of enzymes, e.g. esterases, oxidases, etc., which in turn undergoes cleavage at the benzylic C—O bond to generate the phosphonic acid and the potentially toxic quinone methide intermediate. Examples of this class of prodrugs are described by Mitchell et al.,
J. Chem. Soc. Perkin Trans
. I 2345 (1992); Brook, et al. WO 91/19721. Still other benzylic prodrugs have been described containing a carboxylic ester-containing group attached to the benzylic methylene. Glazier et al. WO 91/19721.
Cyclic phosphonate esters have also been described for phosphorus-containing compounds. In some cases, these compounds have been investigated as potential phosphate or phosphonate prodrugs. Hunston et al.,
J. Med. Chem
. 27: 440-444 (1984). The numbering for these cyclic esters is shown below:
The cyclic 2′,2′-difluoro-1′,3′-propane ester is reported to be hydrolytically unstable with rapid generation of the ring-opened monoester. Starrett et al.
J. Med. Chem
. 37: 1857-1864 (1994).
Cyclic 3′,5′-phosphate esters of araA, araC and thioinosine have been synthesized. Meier et al.
J. Med. Chem
. 22: 811-815 (1979). These compounds are ring-opened through the action of phosphodiesterases which usually require one negative charge.
Cyclic 1′,3′-propanyl phosphonate and phosphate esters are reported containing a fused aryl ring, i.e. the cyclosaligenyl ester, Meier et al.,
Bioorg. Med. Chem. Lett
. 7: 99-104 (1997). These prodrugs are reported to generate the phosphate by a “controlled, non-enzymatic mechanism[s] at physiological pH according to the designed tandem-reaction in two coupled steps”. The strategy was purportedly used to deliver d4-T monophosphate to CEM cells and CEM cells deficient in thymidine kinase infected with HIV-1 and HIV-2.
Unsubstituted cyclic 1′,3′-propanyl esters of the monophosphates of 5-fluoro-2′-deoxy-uridine (Farquhar et al.,
J. Med. Chem
. 26: 1153 (1983)) and ara-A (Farquhar et al.,
J. Med. Chem
. 28: 1358 (1985)) were prepared but showed no in vivo activity. In addition, cyclic 1′,3′-propanyl esters substituted with a pivaloyloxy methyloxy group at C-1′ was prepared for 5-fluoro-2′-deoxy-uridine monophosphate (5-FdUMP; (Freed et al.,
Biochem. Pharmac
. 38: 3193 (1989); and postulated as potentially useful prodrugs by others (Biller et al., U.S. Pat. No. 5,157,027). In cells, the acyl group of these prodrugs underwent cleavage by esterases to generate an unstable hydroxyl intermediate which rapidly broke down to the free phosphate and acrolein following a &bgr;-elimination reaction as well as formaldehyde and pivalic acid.
Cyclic phosphoramidates are known to cleave in vivo by an oxidative mechanism. For example, cyclophosphoramide is thought to undergo oxidation at C-1′ to form the hydroxylated intermediate, which like the 1′-substituted cyclic 1′,3′-propane esters described above, breaks down to acrolein and the corresponding phosphoramidate. Cyclophosphoramidates were also prepared as potential prodrugs of both 5-FdUMP and araAMP and shown to have modest activity in vivo.
A variety of substituted 1′,3′ propanyl cyclic phosphoramidates, wherein 1′ represents the carbon alpha to the nitrogen were prepared as cyclophosphamide analogs (Zon, Progress in Med. Chem. 19, 1205 (1982)). For example, a number of 2′- and 3′-substituted proesters were prepared in order to decrease the propensity of the &agr;,&bgr;-unsubstituted carbonyl bi-product to undergo to a Michael reaction. 2′-Substituents included methyl, dimethyl, bromo, trifluoromethyl, chloro, hydroxy, and methoxy whereas a variety of groups were used at the 3′-position including phenyl, methyl, trifluoromethyl, ethyl, propyl, i-propyl, and cyclohexyl. Analogs with a 3′-aryl group underwent oxidation alpha to the nitrogen and accordingly exhibited anticancer activity in the mouse L1210 assay. A variety of 1′-substituted analogs were also prepared. In general these compounds were designed to be “pre-activated” cyclophosphamide analogs that bypass the oxidation step by already existing as a 1′-substituted analog capable of producing the final compound, e.g. hydroperoxide and thioether. A series of 1′-aryl analogs were also prepared in order to enhance the oxidation p
Erion Mark D.
Reddy K. Raja
Robinson Edward D.
Ugarkar Bheemarao G.
Brobeck Phleger & Harrison LLP
Jones Dameron L.
Metabasis Therapeutics, Inc.
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