Assembly Biosciences (NSDQ:ASMB) is halting the development of the hepatitis drug ABI-H2158 (2158) after observing elevated alanine aminotransferase (ALT) in participants in a Phase 2 trial.

High ALT levels can indicate liver damage.

“Patient safety is always our priority, which is why we have elected to discontinue the development of 2158,” said Dr. John McHutchison, chief executive officer and president of Assembly Bio, in a statement.

The company intends to focus on another investigational drug for hepatitis B from its portfolio and “ultimately choose the best and safest candidate to take forward into later-stage clinical trials,” McHutchison explained.

The company notes that its capsid inhibitor vebicorvir (VBR/ABI-H0731), has demonstrated safety and efficacy in patients for up to 1.5 years in a Phase 2 clinical trial.

Last month, Assembly Biosciences announced that it chose the core inhibitor candidate, ABI-4334 (4334), to proceed into clinical development.

In February, the company announced that it would launch a Phase 2 clinical trial of vebicorvir (VBR) in combination with the GalNAc delivered RNAi therapeutic candidate, AB-729 from Arbutus Biopharma (Vancouver). That trial will provide the combination treatment in conjunction with standard-of-care nucleos(t)ide reverse transcriptase inhibitor (NrtI) therapy.