Assembly Biosciences Inc. (NASDAQ: ASMB) announced plans to expand clinical development of its experimental drug ABI-6250 into cholestatic liver diseases, specifically primary biliary cholangitis and primary sclerosing cholangitis.

The biotechnology company expects to initiate a Phase 2 basket study in cholestatic liver diseases in the first quarter of 2027, subject to regulatory feedback. This expansion builds on a completed Phase 1a study and ongoing development for chronic hepatitis delta virus infection.

ABI-6250 is an oral small-molecule inhibitor of the sodium taurocholate co-transporting polypeptide (NTCP), a membrane protein on liver cells that facilitates bile acid transport and serves as an entry receptor for hepatitis delta virus infection. By inhibiting NTCP, the drug blocks bile acid uptake into liver cells, a mechanism relevant to cholestatic liver diseases where bile acid accumulation drives liver inflammation and injury.

The company plans to begin a Phase 2 clinical study of ABI-6250 in hepatitis delta virus in the fourth quarter of 2026. Assembly Biosciences recently conducted a pre-IND meeting with the U.S. Food and Drug Administration to discuss the planned development in cholestatic liver diseases.

Primary biliary cholangitis and primary sclerosing cholangitis are chronic, autoimmune cholestatic liver diseases characterized by impaired bile flow and progressive liver damage. While multiple therapies exist for primary biliary cholangitis treatment, a significant percentage of patients have inadequate responses. No approved therapies currently exist for primary sclerosing cholangitis.

The Phase 1a study demonstrated target engagement, including dose-dependent elevations in plasma total bile acids consistent with NTCP inhibition. Chronic toxicology studies have been completed to support potential longer-term dosing in planned Phase 2 trials.

ABI-6250 remains an investigational product candidate that has not been approved globally, and its safety and efficacy have not been established.