PKSI-527 is an inhibitor of plasma kallikrein (Ki = 0.81 μM). It is selective for plasma kallikrein over glandular kallikrein, plasmin, thrombin, urokinase, and Factor Xa (Kis = >500, 390, >500, 200, and >500 μM, respectively). PKSI-527 reduces bradykinin generation induced by kaolin and λ-carrageenan ex vivo in human plasma. It also prolongs partial thromboplastin and euglobulin clot lysis times. In vivo, PKSI-527 (300 mg/kg per day) reduces hyperplasia, pannus formation, and infiltration of inflammatory cells in the tarsal joint of mice with collagen-induced arthritis.

In vivo, PKSI-527 (300 mg/kg per day) reduces hyperplasia, pannus formation, and infiltration of inflammatory cells in the tarsal joint of mice with collagen-induced arthritis.