Bemnifosbuvir (AT-527) Program Update for COVID-19
Bemnifosbuvir to Advance to Late-Stage Development for COVID-19: In July, Atea had an End-of-Phase 2 meeting with the FDA and met with the EMA Emergency Task Force to discuss bemnifosbuvir’s program to-date and the design of a global late-stage clinical trial for the treatment of mild-to-moderate COVID-19. The trial will focus on high-risk patients, including those who are immunocompromised, and patients will be enrolled regardless of vaccination status. The primary endpoint of the study will be hospitalization and death. The study will evaluate bemnifosbuvir 550 mg twice-daily (BID) for five days. Operational planning for this trial is currently underway with the goal of initiation during the fourth quarter of 2022.
Topline Efficacy Results from Phase 3 MORNINGSKY Trial: In May, Atea reported a topline analysis of data from the MORNINGSKY trial in which the primary endpoint, time to symptom alleviation, was not achieved. However, a 71% reduction in hospitalization (2.9% versus 10%) was observed (p=0.047, unadjusted, exploratory) in the bemnifosbuvir arm (n=137) versus placebo (n=70). There were no deaths in the trial. Hospitalization and death are study endpoints that are currently preferred by the FDA and other regulatory authorities.
MORNINGSKY was a randomized, double-blind, multi-center, placebo-controlled Phase 3 trial evaluating the efficacy, safety, antiviral activity, and pharmacokinetics of bemnifosbuvir, which intended to enroll up to 1,400 patients randomized 2:1 to receive bemnifosbuvir 550 mg BID or placebo in an outpatient setting. Consistent with previous studies, bemnifosbuvir 550 mg BID was generally safe and well tolerated with no drug-related serious adverse events. The study was closed out early in December 2021, having enrolled 216 patients of which 207 were evaluable for efficacy.
Data from Final Analysis of Phase 2 Hospitalized Study in High-Risk Patients: In May, Atea reported final clinical results from the Phase 2 hospitalized study in high-risk patients (n=83) and results suggest potential clinical benefits. The global Phase 2 trial was a randomized, double-blind, placebo-controlled, multi-center study to evaluate bemnifosbuvir in patients with moderate COVID-19 in the hospital setting. There were 3 deaths in the study, no deaths were reported in patients treated with bemnifosbuvir versus 3 deaths reported with placebo. Final virology results (secondary endpoint) were consistent with previously reported interim data from this study. Bemnifosbuvir was generally safe and well tolerated with no drug-related serious adverse events.
New: Bemnifosbuvir Retains Antiviral Activity Against Omicron Subvariant In Vitro: AT-511, the free base of bemnifosbuvir, has been shown to be a potent inhibitor of SARS-CoV-2 in vitro. New results demonstrated that AT-511 retained potent antiviral activity against the SARS-CoV-2 variant Omicron BA.2. AT-511 has previously demonstrated in vitro potent antiviral activity against variants of concern and/or of interest, including Alpha, Beta, Gamma, Epsilon, Delta and Omicron BA.1.
Advancing a Multipronged Approach for COVID-19 Future Preparedness
COVID-19 Program for Second-Generation Protease Inhibitors: As part of a multipronged approach against COVID-19, Atea is advancing an internal program focused on the discovery of second-generation protease inhibitors that have clinical profiles well suited for combination therapy with bemnifosbuvir. As part of this effort, Atea’s target profile is a protease inhibitor that is highly potent, has a good safety profile with limited drug-drug interactions and does not require a booster (e.g., ritonavir). The optimization of lead compounds is ongoing with a target of late 2022 for selection of a clinical candidate.
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