An interim review of two triple combination studies has torpedoed Assembly Biosciences’ plan to build a functional cure regimen around vebicorvir. Accepting that the core inhibitor will fall short, the biotech is pivoting to earlier-stage candidates—and laying off 30% of staff to eke out its remaining cash.
One year ago, Assembly was racing two hepatitis B prospects, vebicorvir and ABI-H2158, through phase 2 clinical trials. ABI-H2158 hit the buffers in September when increased liver toxicity drove Assembly to stop development of the candidate. Work on vebicorvir, also known as VBR, continued in collaboration with Arbutus Biopharma and Antios Therapeutics in the wake of the setback.
Now, having pulled out of the Antios collaboration in May, Assembly has halted vebicorvir development in response to lackluster data. The Arbutus-partnered trial will continue to the primary endpoint, with data due in the second half of 2022, but Assembly is giving up on the idea of combining vebicorvir with nucleos(t)ide analogue reverse transcriptase inhibitors (NrtIs).
“By combining VBR with NrtI therapy, we achieved a more rapid and a deeper level of viral suppression than with NrtI alone and we have continued to see a favorable safety and tolerability profile for VBR. Unfortunately, we do not believe, based on the interim data from our current studies, that either VBR triple combination is likely to achieve a meaningful rate of functional cure for patients with chronic HBV infection,” Assembly CEO John McHutchison, M.D., said in a statement.
The conclusion led Assembly to immediately stop its own phase 2 trial while agreeing to see the Arbutus study through to the end. Having axed vebicorvir, Assembly is now focused on ABI-H3733 and ABI-4334. ABI-H3733 is in a phase 1b clinical trial. Initial data are due by the end of the year. ABI-4334 is scheduled to move into a phase 1a study this year.
McHutchison said the candidates “are significantly more potent and provide the secondary mechanism against cccDNA,” a form of DNA that is thought to be at the root of chronic hepatitis B. According to McHutchison, the secondary mechanism may be “critical to finite and curative treatments for HBV.”
Assembly is slimming down to extend its cash runway out into the first half of 2024. The biotech plans to part company with 30 employees, almost one-third of its current headcount. Chief Medical Officer Luisa Stamm, M.D., Ph.D., is among the people leaving Assembly. Michele Anderson, senior vice president of development operations, will take up the post of chief development officer at the start of next month.
To read more about layoffs across the biotech industry, check out Fierce Biotech's Layoff Tracker.