Synthesis and biological evaluation of 5-[[3,5-bis(1,1-dimethylethyl)- 4-hydroxyphenyl]methylene]oxazoles, -thiazoles, and -imidazoles: novel dual 5-lipoxygenase and cyclooxygenase inhibitors with antiinflammatory activity.

A variety of benzylideneoxazoles, -thiazoles, and -imidazoles derived from 2,6-di-tert-butylphenol were prepared and evaluated as dual inhibitors of 5-lipoxygenase and cyclooxygenase in rat basophilic leukemia (RBL-1) cells. The target compounds exhibit varying degrees of selectivity toward the two enzymes. Several compounds are orally active in the rat carageenan footpad edema (CFE) and mycobacterium footpad edema (MFE) antiinflammatory models. Structure-activity relationships are discussed. From this work, (Z)-5-[[3,5-bis(1,1-dimethylethyl)-4- hydroxyphenyl]-methylene]-2-imino-4-thiazolidinone methanesulfonate salt (CI-1004) was identified as a potent dual inhibitor of 5-lipoxygenase (IC50 = 0.77 microM) and cyclooxygenase (IC50 = 0.39 microM), with oral activity (ID40 = 0.6 mg/kg) in the rat MFE model of inflammation.

Nonpeptide angiotensin II receptor antagonists. 2. Design, synthesis, and structure-activity relationships of 2-alkyl-4-(1H-pyrrol-1-yl)-1H-imidazole derivatives: profile of 2-propyl-1-[[2'-(1H-tetrazol-5-yl)-[1,1' -biphenyl]-4-yl]-methyl]-4-[2-(trifluoroacetyl)-1H-pyrrol-1-yl]-1H- imidazole-5-carboxylic acid (CI-996).

A novel series of nonpeptide angiotensin II (AII) receptor antagonists containing a 1H-pyrrol-1-yl moiety at the 4-position of the imidazole have been developed. The pyrrole group occupies the same lipophilic pocket at the receptor as the chloro group in DuP 753 (68) and EXP 3174 (69) and the pentafluoro group in DuP 532 (70), respectively. The impetus for its selection came from bioisosteric considerations based on hydrophobic and electronic substituent constants. An extensive study of the structure-activity relationships revealed several highly potent AII receptor antagonists. An acyl substitution at the 2-position of the pyrrole ring improved activity, most notably in the in vivo rat model. In addition, the 2-substituted pyrrole compounds improved chemical stability toward extremely facile decarboxylation reaction associated with unsubstituted pyrrole analogues, thus facilitating development of these agents. The IC50's of 18, 20, and 42 (< 1 nM) were better than the reference compounds 69 and 70, respectively. These compounds were selective AII antagonists that compete at the AT1 receptor and showed no affinity at the AT2 receptor at concentrations up to 10 microM. Upon intravenous administration in a normotensive rat model, compound 18 inhibited the AII-induced responses with ED50 of 6 micrograms/kg per min. In a renal hypertensive rat model, the antihypertensive potency of compound 18, at a dose of 10 mg/kg, was very similar to those 68 and 69, respectively. Compound 18 demonstrated a dose-related (3-30 mg/kg) decrease in blood pressure that was sustained for greater than 24 h. On the basis of its profile, compound 18, designated as CI-996, has been selected for in-depth studies. The design, synthesis, in vitro, and in vivo structure-activity relationships are described.

Design of 5-(3,5-di-tert-butyl-4-hydroxyphenyl)-1,3,4-thiadiazoles, -1,3,4-oxadiazoles, and -1,2,4-triazoles as orally-active, nonulcerogenic antiinflammatory agents.

To discover dual inhibitors of 5-lipoxygenase (LO) and cyclooxygenase (CO) with improved pharmacokinetic properties, we have designed and synthesized series of 1,2,4-triazole, 1,3,4-oxadiazole, and 1,3,4-thiadiazole di-tert-butylphenol derivatives which exhibit a wide range of log P (2.3 to > 4) and pKa (5.5-12) values. From this work 5-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-1,3,4-thiadiazole-2(3H)- thione, choline salt (12a, CI-986) was found to be a potent inhibitor of 5-LO (IC50 = 2.8 microM) and CO (IC50 = 0.8 microM), orally active in rat models of inflammation and nonulcerogenic.

Inhibitors of human purine nucleoside phosphorylase. Synthesis of pyrrolo[3,2-d]pyrimidines, a new class of purine nucleoside phosphorylase inhibitors as potentially T-cell selective immunosuppressive agents. Description of 2,6-diamino-3,5-dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3,2-d] pyrimidin-4-one.

Purine nucleoside phosphorylase (PNP) is a purine-metabolizing enzyme in the purine cascade and has been a target for drug design for sometime. A series of potent human PNP inhibitors, pyrrolo[3,2-d]pyrimidines (9-deazaguanines), has been synthesized and evaluated in the enzyme assay and in the cell line assay using MOLT-4 (T-cell) and MGL-8 (B-cell) lymphoblasts for selectivity. One of the compounds, 2,6-diamino-3,5- dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3,2-d]pyrimidine-4-one (11c; CI-972), was found to be moderately potent, competitive, and reversible inhibitor of PNP with Ki = 0.83 microM. It was also found to be selectively cytotoxic to MOLT-4 lymphoblasts (IC50 = 3.0 microM) but not to MGL-8 lymphoblasts and was evaluated further. Compound 11c (CI-972) is under development in the clinic.

Inhibitors of human purine nucleoside phosphorylase. Synthesis and biological activities of 8-amino-3-benzylhypoxanthine and related analogues.

A series of 3-substituted hypoxanthines (6-10, 14-17) and related analogues (22, 23) have been synthesized as inhibitors of purine nucleoside phosphorylase (PNP), which may conceivably act as T-cell-selective immunosuppressive agents with potential utility in autoimmune disorders such as rheumatoid arthritis, in organ transplantations, and in T-cell leukemias. The compounds were evaluated for their PNP activity by a radiochemical assay and also for their cytotoxic effects on a T-lymphoblastoid cell line (MOLT-4). Appropriate substitutions on 3-benzylhypoxanthine (7a) (IC50 in PNP assay, 112 microM; IC50 in MOLT-4 assay, 204.2 microM) increase potency: 8-amino (17a; 42.6, 65.2), 2-hydroxy (9a; 13.4, 28.6), 2-amino (10a; 11.4, 29.1), and 2,8-diamino (16a; 5.0, 11.9). Variation of the 3-aryl substituents of 16a as in 16b-d has thus far failed to further increase potency. Replacement of the 6-oxygen function in 7a with the analoguous nitrogen or sulfur functions, as in 22a and 23a, resulted in little change in activity. Other variations including the increase of the 3-aliphatic chain length as in 6h and 7h (n = 2), the substitution of the phenyl ring with electron-withdrawing groups as in 7e-g, and replacement of the 2-hydrogen with methylthio as in 8a and 14a resulted in decrease of activity. The values for 16a-d represent moderate but significant activities, as compared to the most active inhibitor presently known, 8-amino-9-thienylguanine (1c; 0.17, 0.82). 2,8-Diamino-3-substituted hypoxanthines (16a-d) represent a novel structural type hitherto unreported in the literature, and efficient methodologies for their synthesis were developed in the present studies. The formation of the aminoimidazole moiety occurred through a base-catalyzed 1,5-(O----N)-carbamimidoyl rearrangement (13 to 14, 20 to 16).

Selective in vitro inhibition of human MOLT-4 T lymphoblasts by the novel purine nucleoside phosphorylase inhibitor, CI-972.

CI-972 (2,6-diamino-3,5-dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3,2- d]pyrimidin-4-one monohydrochloride, monohydrate) is a competitive inhibitor of PNPase (E.C. 2.4.2.1., Ki = 0.83 microM) entering clinical trials as a T cell-selective immunosuppressive agent. Neither CI-972 (less than or equal to 50 microM) nor dGuo (less than or equal to 10 microM) inhibited [3H]Thd uptake by human MOLT-4 (T cell) or MGL-8 (B cell) lymphoblasts, but in the presence of 10 microM dGuo, the IC50 for CI-972 decreased to 3.0 microM for MOLT-4 but remained at greater than 50 microM for MGL-8. Inhibition of MOLT-4 growth was associated with an increase in dGTP that was dependent on CI-972 concentration and inhibited by 2'-deoxycytidine. Growth could not be restored by hypoxanthine or adenine. No alterations in GTP pools were noted in MOLT-4, and neither GTP nor dGTP were altered in MGL-8.

Styrylpyrazoles, styrylisoxazoles, and styrylisothiazoles. Novel 5-lipoxygenase and cyclooxygenase inhibitors.

A series of styrylpyrazoles, styrylisoxazoles, and styrylisothiazoles were prepared and found to be dual inhibitors of 5-lipoxygenase and cyclooxygenase in rat basophilic leukemia cells. Compounds from this series also were found to inhibit the in vivo production of LTB4 when dosed orally in rats. Among these compounds, di-tert-butylphenols 19 and 33 exhibit oral activity in various models of inflammation and, most importantly, are devoid of ulcerogenic potential.

Biochemical and pharmacological properties of CI-972, a novel 9-deazaguanine analog purine nucleoside phosphorylase (PNP) inhibitor.

CI-972 (2,6-diamino-3,5-dihydro-7-(3-thienylmethyl)-4H-pyrrolo[3, 2-d]pyrimidin-4-one monohydrochloride, monohydrate) is a novel inhibitor of PNP (Ki = 0.83 microM) under development as a T cell-selective immunosuppressive agent. CI-972 inhibited proliferation (3H-thymidine uptake) of human MOLT-4 (T cell) but not MGL-8 (B cell) lymphoblasts with respective IC50s of 3.0 and greater than 50 microM when tested with 10 microM 2'-deoxyguanosine. Without addition of exogenous 2'-deoxyguanosine, CI-972 was not inhibitory to any human T or B lymphoblastoid cell line tested. 2'-Deoxycytidine (10 microM), but not hypoxanthine or adenine, restored MOLT-4 cell growth. Inhibition of 3H-thymidine uptake in MOLT-4 cells correlated with accumulation of dGTP, while alterations in guanine nucleotides were not observed. 2'-Deoxycytidine (10 microM) also blocked dGTP accumulation in MOLT-4 cells. CI-972 showed activity in vivo over a broad dose range: At 5-150 mg/kg p.o., CI-972 produced dose-dependent elevation of plasma inosine one hr after administration to rats (mean maximum of 2.62 vs. 0.06 microM in controls). Guanosine was also significantly elevated in a concentration-dependent manner, although the effect was not as impressive. Plasma nucleosides remained statistically-significantly elevated for up to four hr following a single oral dose of CI-972.

Pyrrolo[3,2-d]pyrimidines, a new class of purine nucleoside phosphorylase (PNP) inhibitors as potential T-cell selective immunosuppressive agents.

Previously, we have described the synthesis and biological activity of 2,8-diamino-1,9-dihydro-9-(2-thienylmethyl)-6H-purin-6-one (PD 119229; Cl-950) as a potent and competitive PNP inhibitor. As a part of our continuing efforts to develop a PNP inhibitor for autoimmune diseases, we have synthesized a series of pyrrolo[3,2-d]pyrimidines as PNP inhibitors. In this series, 2,6-diamino-3,5-dihydro-7-(3- thienylmethyl)-4H-pyrrolo-[3,2-d]pyrimidin-4-one (Cl-972) was found to be a potent, competitive inhibitor of PNP with Ki of 0.83 microM. It was also found to be selectively cytotoxic to human MOLT-4 (T cell) (IC50 = 3.0 microM) but non-toxic to MGL-8 (B cell) lymphoblasts. Cl-972 is under development as a potential T-cell selective immunosuppressive agent. Synthesis and biological activities of the series are discussed.