Abstract P233: Inhibition Of Aldosterone Synthesis In Non-human Primates By PB6440, The Novel Highly Selective And Potent CYP11B2 Inhibitor

Abstract

Aldosterone is an important mineralocorticoid responsible for fluid and electrolyte homeostasis produced by aldosterone synthase (CYP11B2). An aldosterone synthase inhibitor (ASI) may be a therapeutic option for primary aldosteronism-related conditions such as resistant hypertension. An ASI with sufficient selectivity for CYP11B2 versus the similar cortisol-producing enzyme CYP11B1 has remained elusive. PB6440 is a novel ASI that is potent and highly selective for CYP11B2. In vitro studies demonstrated 200-300-fold selectivity of PB6440 for human CYP11B2 compared to human CYP11B1. In single and multiple dose cynomolgus monkey studies of orally administered PB6440, dose-and concentration-dependent reduction of plasma aldosterone after ACTH challenge was observed with >90% reduction at higher doses. Consistent with its high selectivity, PB6440 had little effect on the CYP11B1 cortisol pathway. Plasma levels of cortisol, 11-deoxycortisol, and deoxycorticosterone, remained unchanged even at high doses of PB6440. Systolic and diastolic blood pressure was reduced in a dose-dependent manner. Circulating half-life of PB6440 was approximately 17 hours with high oral bioavailability. In summary, PB6440 is a highly selective ASI that demonstrated sustained aldosterone suppression for 14 days with no effect on the CYP11B1 pathway in non-human primates. In single and multiple dose studies, PB6440 appeared well tolerated, demonstrating good oral bioavailability, and a PK profile supportive of once daily dosing. These results suggest that PB6440 may be useful in humans as a novel therapeutic for treating hypertension or other conditions caused by excess aldosterone.