Development of orally active nonpeptidic inhibitors of human neutrophil elastase.

5-Amino-2-phenylpyrimidin-6-ones, some of their desamino derivatives, and miscellaneous derivatives were synthesized and biologically evaluated on both in vitro activity and oral activity in an acute hemorrhagic assay. These compounds contained an alpha-keto-1,3,4-oxadiazole moiety to bind covalently to the Ser-195 hydroxy group of human neutrophil elastase (HNE). Among those tested, compounds 11a-c,e,i-l(F), 11d,e,k(H), 21d,e,k(F), and 21d,e(H) showed a good oral profile. RS-Mixture 3(H) was selected for clinical evaluation based on its oral potency, duration of action, enzyme selectivity, safety profile, and ease of synthesis. Structure-activity relationships (SARs) are discussed.

Biochemical characterization of alpha-ketooxadiazole inhibitors of elastases.

A series of alpha-ketooxadiazole compounds was prepared and evaluated in vitro as potential inhibitors of human neutrophil elastase (HNE), proteinase-3 (PR-3), and porcine pancreatic elastase (PPE). Several compounds have been found to be very potent, fast, reversible, and selective inhibitors of HNE with Ki values below 100 pM. The highest kon value exceeded 10(7) M(-1) s(-1). Some alpha-ketooxadiazoles were also very effective against PR-3 and PPE with Ki values in the range of 5(-10) nM and 0.1(-2) nM, respectively. The two rings, 1,2,4- and 1,3,4-oxadiazole, are amenable to substitutions, extending the P' side of the inhibitor and allowing additional binding interactions at S' subsites of the enzyme. Nonpeptidic HNE inhibitors containing the oxadiazole heterocycle displayed promising oral bioavailability.

Biologically active heteroarotinoids exhibiting anticancer activity and decreased toxicity.

A series of retinoids, containing heteroatoms in a cyclic ring and called heteroarotinoids, were synthesized, and their biological activity was evaluated using tissue culture lines that have measurable responses to trans-retinoic acid (t-RA). Transglutaminase (TGase) was assessed in the human erythroleukemia cell line (GMO6141A) as an indicator of differentiation and apoptosis. Proliferation was evaluated in a human cervical cell line, CC-1, which exhibits dose-dependent alterations in growth rate in response to treatment with trans-retinoic acid. Activation of nuclear retinoic acid receptors was determined in a reporter cell line established from CC-1. The reporter line, called CC-B, contains a reporter gene controlled by a retinoic acid responsive element (RARE) and a thymidine kinase (tk) promoter. Treatment of the CC-B line with the heteroarotinoids resulted in a dose-responsive and retinoid-dependent regulation of reporter gene expression. The heteroarotinoids exhibited activity in all assays and correlated in a statistically significant manner between assays. RARE transactivation activity in CC-B cells correlated with induction of TGase in GMO6141A (R = 0.96) and with a decrease in the growth rate of CC-1 cells (R = -0.90). The ability of the selected heteroarotinoids to induce differentiation, inhibit proliferation, and activate nuclear receptors demonstrates the chemotherapeutic potential of these agents. In view of the biological activity cited, an in vivo toxicity study was conducted on male B6D2F1 mice with three heteroarotinoids, namely 8 [(2E,4E,6E)-3,7-dimethyl-7-(1,2,3,4-tetrahydro-4,4-dimeth ylthiochroman-6-yl)-2,4,6-heptatrienoic acid], 10 [(2E,4E,6E)-3,7-dimethyl-7-(1,2,3,4-tetrahydro-4,4-dimeth ylchroman-6-yl)-2, 4,6-heptatrienoic acid], and 13 [(E)-p-[2-(4,4-dimethylchroman-6-yl)propenyl]benzoic acid]. The mice were used with gavage of heteroarotinoids in corn oil [0.1, 0.2, 0.4, or 0.8 mg/kg] and with 0.01 or 0.05 mg/kg of TTNPB (5) [(E)-4-[2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)-1- propenyl]benzoic acid] as reference controls. The target organs affected in the mice by the three heteroarotinoids were those typically associated with t-RA (1) toxicity. The maximum tolerated dose (MTD) of 13 was 9.4 mg/kg/day, which was equal in toxicity to that of t-RA (1) and 1000-fold less toxic than TTNPB (5). The MTDs of 8 and 10 were 34 and 32 mg/kg/day, respectively, which is 3-fold less toxic than t-RA (1) and 3000-fold less toxic than TTNPB (5). The 3000-fold reduced toxicity, compared with only a 27% reduction biological activity of 8 and 10 with respect to that of TTNPB, observed in our assays indicates a good therapeutic ratio of these heteroarotinoids over the parent compound. The biological activity and reduced toxicity of these heteroartinoids demonstrate the potential efficacy as anticancer agents.

Bradykinin antagonists in human systems: correlation between receptor binding, calcium signalling in isolated cells, and functional activity in isolated ileum.

The determination of the relationship between ligand affinity and bioactivity is important for the understanding of receptor function in biological systems and for drug development. Several physiological and pathophysiological functions of bradykinin (BK) are mediated via the B2 receptor. In this study, we have examined the relationship between B2 receptor (soluble and membrane-bound) binding of BK peptidic antagonists, inhibition of calcium signalling at a cellular level, and in vitro inhibition of ileum contraction. Only human systems were employed in the experiments. Good correlations between the studied activities of BK antagonists were observed for a variety of different peptidic structures. The correlation coefficients (r) were in the range of 0.905 to 0.955. In addition, we analyzed the effect of the C-terminal Arg9 removal from BK and its analogs on B2 receptor binding. The ratios of binding constants (Ki(+Arg)/Ki(-Arg)) for the Arg9 containing compounds and the corresponding des-Arg9 analogs varied from about 10 to 250,000. These ratios strongly depend on the chemical structures of the compounds. The highest ratios were observed for two natural agonist pairs, BK/des-Arg9-BK and Lys0-BK/des-Arg9-Lys0-BK.

Novel heteroarotinoids: synthesis and biological activity.

In this study, 13 heteroarotinoids were synthesized. The key step in each preparation was the condensation of the appropriate chroman-, thiochroman-, or benzothienyl-substituted phosphorus ylide, obtained from the independent synthesis of the corresponding phosphonium salts, with selected polyene-substituted aldehyde esters. Nine of these heterocycles contained a thiochroman group, two had a chroman group, and two others had a benzothienyl system. Screening of the compounds was with one of two assays. One assay measured the ability of a retinoid to inhibit the phorbol ester induced increase of mouse epidermal ornithine decarboxylase (ODC) activity. The other assay measured retinoid-induced differentiation of the human myoloid leukemia cell line HL-60. In the ODC assay, all thirteen compounds were screened. The most active heteroarotinoids were ester 10 [methyl (E)-4-[2-(2,2,4,4-tetramethylthiochroman-6-yl)-1- propenyl]benzoate] and acid 11 [(E)-4-[2-(2,2,4,4-tetramethyl-3,4- dihydro-2H-1- benzothiopyran-6-yl)-1-propenyl]benzoic acid]. Both of these retinoids had ID50 values (dose required for half-maximal inhibition of phorbol ester induced ODC activity) of about 0.3 nmol. In comparison, the ID50 value for trans-retinoic acid (1) was 0.12 nmol while the ID50 values for acids 7 and 9, namely (2Z,4E,6E)-3,7-dimethyl-7-(4,4-dimethyl-thiochroman -6-yl)-2,4,6-heptatrienoic acid and (2E,4E,6E)-3,7-dimethyl-7-(2,2,4,4-tetramethylthiochroman -6-yl)-2,4,6- heptatrienoic acid, respectively, were about 3.5 nmol. Heteroarotinoids 8 and 12-17 had ID50 values of 35 nmol or greater. With a thiochroman unit, the most active acids in decreasing order of activity in the ODC assay were 7 greater than 9 greater than 8. Thus, simple replacement of the terminal propenyl system [C(16,17,18)] in 7 with a cyclopropyl group produced acid 8 [(2E,4E,6E)-7-methyl-7-(4,4-dimethylthiochroman-6-yl)- 2,3-methylene-4,6-heptadienoic acid with markedly reduced activity. With a benzoic acid group as part of the structure attached to the thiochroman unit, the ODC activity was enhanced as shown in 10 and 11. The combination of the 2,2,4,4-tetramethylthiochroman group and the benzoic acid (or ester) terminal group seemed to enhance the biological action which resembles that found with (E)-4-[2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)- 1-propenyl]benzoic acid (TTNPB, 6b), a well-known model system.(ABSTRACT TRUNCATED AT 400 WORDS)

Heteroarotinoids. Synthesis, characterization, and biological activity in terms of an assessment of these systems to inhibit the induction of ornithine decarboxylase activity and to induce terminal differentiation of HL-60 cells.

The synthesis of certain heteroarotinoids has been achieved, namely the systems (2E,4E,6E)-3,7-dimethyl-7-(1,2,3,4-tetrahydro-4,4-dimethyl-6 -thiochromanyl)-2,4,6-heptatrienoic acid (1a), ethyl (2E,4E,6E)-3,7-dimethyl-7- (1,2,3,4-teterahydro-4,4-dimethyl-6-thiochromanyl)-2,4,6- heptatrienoate (1b), (2E,4E,6E)-3,7-dimethyl-7-(1,2,3,4-tetrahydro-4,4-dimethyl-6 -chromanyl)-2,4,6-heptatrienoic acid (1c), 2-phthalimidoethyl 3,7-dimethyl-7-(1,2,3,4-tetrahydro-4 4-dimethyl-6-thiochromanyl)-2,4,6-heptatrienoate (1d), methyl (E)-p-[2-(4,4- dimethyl-6-chromanyl)-1-propenyl]benzoate (2a), (E)-p-[2-(4,4-dimethyl-6-chromanyl)-1-propenyl]benzyl alcohol (2b), (E)-p-[2-(4,4-dimethyl-6-chromanyl)-1-propenyl]benzonitrile (2c), (E)-p-[2-(4,4-dimethyl-6-chromanyl)-1-propenyl]benzaldehyde (2d), methyl 4-[2-(2,3-dihydro-3,3-dimethyl-5-benzofuranyl)-1-propenyl] benzoate (3a), and (E)-p-[2-(2,3-dihydro-3,3-dimethyl-5-benzofuranyl)-1- propenyl]benzoic acid (3b). Characterization via elemental, IR, 1H NMR, and 13C NMR analyses was completed for these heterocycles. The biological activity of these heteroarotinoids was assayed by either the suppression of the 12-O-tetradecanoylphorbol 13-acetate (TPA) induced synthesis of ornithine decarboxylase (ODC) in mouse skin or the induction of differentiation of human (HL-60) promyelocytic cells. In the ODC assay, systems 1a-c exhibited strong activity (within 10% of or less than the control) whereas alcohols 2b and 3a showed good activity (within 50% of the control) as compared to either 13-cis-retinoic acid or trans-retinoic acid. Moderate activity was observed with 2a and 2b while 1d and 2c were essentially inactive. With the HL-60 assay, 1a and 1c were approximately 2- and 5-fold less active, respectively, than trans-retinoic acid. In contrast, 2a, 3a, and 3b induced differentiation of only a very small percentage of the cells. Acids 1a and 1c were the most active heteroarotinoids in the two biological assays. Consequently, the presence of the heteroatom does not eradicate the activity of the heteroarotinoids and thus they may have potential as chemotherapeutic agents.