Search

Structures and PC3 viability IC50 data for compounds in Figure 2.

Supplementary methods, tables S1-S3, and supplementary figures 1-7

[Image: see text] BCL-X(L), an antiapoptotic member of the BCL-2 family of proteins, drives tumor survival and maintenance and thus represents a key target for cancer treatment. Herein we report the rational design of a novel series of selective BCL-X(L) inhibitors exemplified by A-1293102. This molecule contains structural elements of selective BCL-X(L) inhibitor A-1155463 and the dual BCL-X(L)/BCL-2 inhibitors ABT-737 and navitoclax, while representing a distinct pharmacophore as assessed by an objective cheminformatic evaluation. A-1293102 exhibited picomolar binding affinity to BCL-X(L) and both efficiently and selectively killed BCL-X(L)-dependent tumor cells. X-ray crystallographic analysis demonstrated a key hydrogen bonding network in the P2 binding pocket of BCL-X(L), while the bent-back moiety achieved efficient occupancy of the P4 pocket in a manner similar to that of navitoclax. A-1293102 represents one of the few distinct structural series of selective BCL-X(L) inhibitors, and thus serves as a useful tool for biological studies as well as a lead compound for further optimization.

The BET family of proteins consists of BRD2, BRD3, BRD4, and BRDt. Each protein contains two distinct bromodomains (BD1 and BD2). BET family bromodomain inhibitors under clinical development for oncology bind to each of the eight bromodomains with similar affinities. We hypothesized that it may be possible to achieve an improved therapeutic index by selectively targeting subsets of the BET bromodomains. Both BD1 and BD2 are highly conserved across family members (70% identity), whereas BD1 and BD2 from the same protein exhibit a larger degree of divergence (∼40% identity), suggesting selectivity between BD1 and BD2 of all family members would be more straightforward to achieve. Exploiting the Asp144/His437 and Ile146/Val439 sequence differences (BRD4 BD1/BD2 numbering) allowed the identification of compound

Employing a set of empirical guidelines for the design of well-absorbed renin inhibitors, we have followed two strategies to improve potency while maintaining bioavailability. One process involved incorporation of an extended N-terminal residue bearing a weakly basic substituent and is exemplified by compound 25. The other approach centered on the inclusion of an N-terminal sulfonamide and culminated in the discovery of inhibitor 32 (A-72517). Both 25 and 32 showed excellent bioavailability in the rat and ferret (> 25%) and, while subject to hepatic elimination in the monkey, were efficacious in this species.

The development of orally active renin inhibitors has been plagued by limited bioavailability in animals and humans. A-74273 is a novel, potent nonpeptide inhibitor of human renin (IC50 = 3.1 nM). This compound was absorbed into the portal and systemic circulations of anesthetized rats, ferrets, monkeys, and dogs after intraduodenal dosing. This favorable pattern also was observed after oral dosing in conscious animals, except in monkeys. Hepatic extraction of A-74273 was more efficient in rats and monkeys than in dogs or ferrets. A-74273 modestly inhibits dog renin, and when given orally as the base (0, 0.3, 1, 3, 10, and 30 mg/kg; n = 8 per dose) to conscious, salt-depleted dogs it induced dose-related reductions in mean arterial pressure and plasma renin activity. Peak falls in mean arterial pressure from normotensive baselines were -14 +/- 1, -26 +/- 3, and -44 +/- 3 mm Hg for the 3, 10, and 30 mg/kg groups, respectively (p < 0.05). Baseline plasma renin activity values (10.9 +/- 1.1-12.7 +/- 1.1 ng angiotensin I/ml/hr) were maximally inhibited, ranging from 43 +/- 8% at 0.3 mg/kg to 98 +/- 1% at 30 mg/kg. Bioavailability in this model was estimated to be 54 +/- 13% when plasma drug levels were determined by a renin inhibitory activity assay, but bioavailability was lower when compared with high-performance liquid chromatographic analysis of A-74273. This discrepancy was accounted for by the identification of structurally similar metabolites that are as active as the parent drug against human renin but much less potent against dog renin.(ABSTRACT TRUNCATED AT 250 WORDS)

A-74273 is a nonpeptidic, potent inhibitor of human and canine renin (IC50 = 3.1 and 43 nM, respectively, in plasma at pH 7.4) and has been shown to be orally active in dogs. To determine the hemodynamic mechanism underlying this renin inhibitor's hypotensive activity, the cardiac and hemodynamic effects of A-74273 were studied in sodium-depleted and sodium-replete pentobarbital-anesthetized dogs. Vehicle [5% dextrose in water (V, D5W), n = 8] or a single dose of A-74273 was administered intravenously (i.v.) as a bolus followed by a 30-min infusion (one tenth the bolus dose per minute). Baseline mean arterial pressure (MAP) was similar among all treatment groups, but baseline plasma renin activity (PRA) was increased in the sodium-depleted dogs as compared with the sodium-replete dogs. In sodium-depleted dogs (n = 7-8/dose), MAP decreased maximally as compared with baseline by 4 +/- 1, 19 +/- 3, and 23 +/- 3% during infusion of A-74273 at doses of 0.001, 0.01, and 0.1 mg/kg/min, respectively (p < 0.05 vs. baseline or V). The two highest infusion doses also produced significant reductions (p < 0.05 vs. baseline and V) in systemic vascular resistance (SVR, 21 +/- 2 and 25 +/- 2%) and left ventricular end-diastolic pressure (LVEDP, 40 +/- 8 and 47 +/- 12%). In sodium-replete dogs (n = 4/dose), an infusion dose of 0.01 mg/kg/min elicited no hemodynamic response, whereas 0.1 mg/kg/min reduced MAP by 13 +/- 2% (p < 0.05 vs. baseline) and SVR by 7 +/- 6%.(ABSTRACT TRUNCATED AT 250 WORDS)

Previous studies with peptidic renin inhibitors have shown that high intravenous (i.v.) doses can induce unexpectedly large decreases in blood pressure (BP) that appear to be independent of plasma renin inhibition. A-74273 represents a new class of potent and orally bioavailable nonpeptidic renin inhibitors. We evaluated the BP effects of this renin inhibitor administered orally (p.o.) or i.v. at high doses to conscious salt-depleted dogs. Administration of A-74273 at 30 and 60 mg/kg p.o. (n = 6 per dose) produced similar maximum reductions in BP (-40 +/- 4 vs. -46 +/- 5 mm Hg) despite the occurrence of greater plasma drug concentrations at the higher dose. Duration of hypotension, however, was increased (p < 0.05) from 9 h at 30 mg/kg to 18 h at 60 mg/kg. The initial depressor response to 10 and 30 mg/kg i.v. doses of A-74273 (n = 6 per dose) was comparable, although duration and overall BP response was greater at 30 mg/kg i.v. No BP responses to A-74273 were noted in salt-replete dogs (n = 5). The hypotension produced by 30 mg/kg p.o. A-74273 was completely reversed by norepinephrine (NE 5 micrograms/kg/min; n = 5) or isotonic saline (4 ml/min/kg, n = 5) infusion. These studies demonstrate that high doses of A-74273 result in predictable BP responses that are renin-dependent and reversible. Therefore, large decreases in BP with high doses is not an attribute common to all renin inhibitors but appears to be a function of the structural characteristics specific to a particular compound.

Peptidic renin inhibitors have been poorly absorbed across the intestine or rapidly eliminated by the liver and have been reported to have oral bioavailabilities of less than 2%. A peptide-based renin inhibitor, A-72517 (molecular mass of 706 daltons), was devised that has oral bioavailabilities of 8, 24, 32, and 53% in the monkey, rat, ferret, and dog, respectively. Dose-related reductions in blood pressure, plasma renin activity, and plasma angiotensin II in parallel with increased plasma drug concentrations were observed after oral administration of A-72517 to conscious, salt-depleted dogs. Thus, peptide-based molecules of sizable molecular mass can be absorbed intact into the systemic circulation of animals. These findings support the potential of peptide-based drugs for oral administration.