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Updated: Oct 15, 2025

A High-Throughput Luciferase Assay to Evaluate Proteolysis of the Single-Turnover Protease PCSK9
Published on: August 28, 2018
A Series of Novel, Highly Potent, and Orally Bioavailable Next-Generation Tricyclic Peptide PCSK9 Inhibitors
Thomas J Tucker1, Mark W Embrey1, Candice Alleyne2
1Department of Medicinal Chemistry, Merck & Co., Inc., 770 Sumneytown Pike, P.O. Box 4, West Point, Pennsylvania 19486 United States.
Abstract:
Proprotein convertase subtilisin-like/kexin type 9 (PCSK9) is a key regulator of plasma LDL-cholesterol (LDL-C) and a clinically validated target for the treatment of hypercholesterolemia and coronary artery disease. Starting from second-generation lead structures such as 2, we were able to refine these structures to obtain extremely potent bi- and tricyclic PCSK9 inhibitor peptides. Optimized molecules such as 44 demonstrated sufficient oral bioavailability to maintain therapeutic levels in rats and cynomolgus monkeys after dosing with an enabled formulation. We demonstrated target engagement and LDL lowering in cynomolgus monkeys essentially identical to those observed with the clinically approved, parenterally dosed antibodies. These molecules represent the first report of highly potent and orally bioavailable macrocyclic peptide PCSK9 inhibitors with overall profiles favorable for potential development as once-daily oral lipid-lowering agents. In this manuscript, we detail the design criteria and multiparameter optimization of this novel series of PCSK9 inhibitors.
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