P4pal10 is a pepducin with a peptide sequence identical to part of the third intracellular loop of the protease activated receptor 4 (PAR4) which acts as a PAR4 antagonist. P4pal10 has no agonist activity as measured by platelet aggregation, intracellular Ca2+ release or InsP production, but preincubation of human platelets with P4pal10 completely blocks aggregation in response to PAR4 activators. Infusion of P4Pal10 into mice extends bleeding time and protects against systemic platelet activation, and in rat models of myocardial injury, P4pal10 treatment before ischemia significantly decreases infarct size when given before, during, and after ischemia. P4Pal10 also inhibits signaling downstream of the Galphai-coupled FPR2.
