Antios therapy could be a 'bridge' in hep B treatment, but first: an FDA hold to resolve

Antios Therapeutics’ hepatitis B therapy slowed the virus’s rebound, and patients did not have to start back on Gilead Sciences' Viread medicine during a phase 2a clinical trial. But casting a shadow over the results is a clinical hold placed by the FDA on a separate hepatitis B study.

First, the data: Antios reported on the midstage trial of ATI-2173 over the weekend at the European Association for the Study of the Liver's International Liver Congress 2022. The 90-day study combined ATI-2173 with tenofovir disoproxil fumarate, which is marketed by Gilead as Viread.

Antios found that patients who received ATI-2173 and Viread had a slower virological rebound after they stopped treatment compared to those who received Viread and placebo. At 24 weeks off treatment, 75% of patients who had received the study drug did not have to restart Viread, compared with 0% in the placebo group.

The therapy also spurred the normalization of alanine aminotransferase, or ALT, a biomarker used to determine whether treatment needs to be initiated or resumed. Patients receiving ATI-2173 did not experience any ALT flares when off treatment. The therapy was well-tolerated, and all patients completed the full 90-day dosing period without experiencing serious adverse events or dose-limiting toxicities.

“ATI-2173 can act as a bridge on the path to an HBV cure,” according to Antios Chief Medical Officer Douglas Mayers, M.D. The data show that the therapy can have a meaningful clinical benefit to patients with hepatitis B, he added.

However, in the U.S., ATI-2173 has been placed on clinical hold by the FDA on reports of “a serious, unexpected, suspected adverse reaction of bradycardia and hypotension,” a spokesperson told Fierce Biotech. The safety event occurred in a separate trial being conducted in Moldova testing the therapy in combination with Assembly Biosciences' vebicorvir and a nucleotide reverse transcriptase inhibitor.

“While we do not believe this was a treatment-related adverse event, we are working diligently to address the deficiencies identified by the FDA in order to resume clinical trials under the [investigational new drug application],” the spokesperson said.

The hold prompted trial partner Assembly to walk away from the clinical trial collaboration agreement. Antios snagged $171 million in financing last year to move the hepatitis B prospect into the clinic. The med was previously advanced into phase 3 study a decade ago, only to be sidelined due to cases of muscle weakness in long-term users.