The design and synthesis of a series of novel inhibitors of protein kinase C (PKC) is described. These 2,3-bisarylmaleimides were derived from the structural lead provided by the indolocarbazoles, staurosporine and K252a. Optimum activity required the imide NH, both carbonyl groups, and the olefinic bond of the maleimide ring. 2,3-Bisindolylmaleimides were the most active, and the potency of these was improved by a chloro substituent at the 5-position of one indole ring (compound 28, IC50 0.11 microM). In a series of (phenylindolyl)maleimides, nitro compound 74 was most active (IC50 0.67 microM). Naphthalene 19 and benzothiophene 21 showed greater than 100-fold selectivity for inhibition of PKC over the closely related cAMP-dependent protein kinase (PKA).

Objective Pepducins are membrane-tethered, cell-penetrating lipopeptides that target the cytoplasmic surface of their cognate receptor. Here, we report the first human use of a protease-activated receptor-1–based pepducin, which is intended as an antiplatelet agent to prevent ischemic complications of percutaneous coronary interventions. Approach and Results PZ-128 was administered by 1 to 2 hours continuous intravenous infusion (0.01–2 mg/kg) to 31 subjects with coronary artery disease or multiple coronary artery disease risk factors. Safety, antiplatelet efficacy, and pharmacokinetics were assessed at baseline and 0.5, 1, 2, 6, 24 hours, and 7 to 10 days postdosing. The inhibitory effects of PZ-128 on platelet aggregation stimulated by the protease-activated receptor-1 agonist SFLLRN (8 μmol/L) at 30 minutes to 6 hours were dose dependent with 20% to 40% inhibition at 0.3 mg/kg, 40% to 60% at 0.5 mg/kg, and ≥80% to 100% at 1 to 2 mg/kg. The subgroup receiving aspirin in the 0.5 and 1-mg/kg dose cohorts had 65% to 100% inhibition of final aggregation to SFLLRN at 30 minutes to 2 hours and 95% to 100% inhibition by 6 hours. The inhibitory effects of 0.5 mg/kg PZ-128 were reversible with 50% recovery of aggregation to SFLLRN by 24 hours. There were no significant effects of PZ-128 on aggregation induced by AYPGKF, ADP, or collagen, indicating that the observed effects were specific to protease-activated receptor-1. The plasma half-life was 1.3 to 1.8 hours, and PZ-128 was nondetectable in urine. There were no effects on bleeding, coagulation, clinical chemistry, or ECG parameters. Conclusions PZ-128 is a promising antiplatelet agent that provides rapid, specific, dose dependent, and reversible inhibition of platelet protease-activated receptor-1 through a novel intracellular mechanism. Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT01806077.

These data suggest that targeting the MMP1-PAR1 system may be effective in tamping down chronic inflammatory signaling in plaques and halting the progression of atherosclerosis.