Chugai’s PCO371 is an oral, biased agonist and "molecular wedge" of the class B GPCR, PTHR1, that first entered development for hypoparathyroidism in 2015 (NCT02475616). While Class A GPCRs, which typically have compact ligandable pockets are the most common targets for approved drugs, Class B GPCRs like PTHR1, GLP-1R, and CGRP are notoriously difficult to drug since they normally bind large peptides with long transmembrane tunnels that are not easily bound by small molecules.

This article explains what makes PCO371 a big deal for GPCR drug discovery.