Atea announces results of Phase 2 study of bemnifosbuvir, ruzasvir

Atea Pharmaceuticals (AVIR) presented results from the full cohort of patients enrolled in its Phase 2 study evaluating the once-daily combination of bemnifosbuvir, an oral nucleotide NS5B polymerase inhibitor, and ruzasvir, an oral NS5A inhibitor, for the treatment of hepatitis C virus. The Phase 2 study met its primary endpoints of efficacy and safety. With a short 8-week treatment duration, the Phase 2 results showed a robust 98% sustained virologic response rate at 12 weeks post-treatment with the regimen in the “Per-Protocol Treatment-Adherent Population.” The SVR12 rate was 95% in the “Per-Protocol Regardless of Adherence Population”, which included patients who were not treatment adherent. Results from three additional Phase 1 studies demonstrated that the combination of BEM/RZR had a low risk of drug-drug interactions and supported the safety of the regimen of BEM/RZR in patients co-infected with HCV and human immunodeficiency virus taking a standard HIV treatment, and the safety of BEM in participants with hepatic or renal impairment with no need for dose adjustments. These results were presented at the European Association for the Study of the Liver Congress 2025 from May 7-10 in Amsterdam, Netherlands. The Phase 2 study was conducted in treatment-naive, chronic HCV-infected patients across genotypes either without cirrhosis or with compensated cirrhosis. Results demonstrated 99% of treatment-adherent patients who were non-cirrhotic and infected with genotypes 1-4 achieved SVR12, demonstrating robust pan-genotypic potency and supporting an 8-week treatment duration in non-cirrhotic patients in the Phase 3 program. A 100% SVR12 rate was observed in non-cirrhotic, treatment-adherent patients infected with genotype 3, a historically difficult genotype to treat and cure. Compensated cirrhosis was present in 13.5% of the study participants and the SVR12 rate was 88% in those who were treatment-adherent. Although viral kinetics were slower among patients with cirrhosis, all achieved HCV RNA less thanLLOQ by the end of treatment, suggesting that a 12-week treatment duration will maximize efficacy in this population. Furthermore, exploratory viral kinetic modeling supported time-to-cure estimates of 12 weeks in those with compensated cirrhosis. Poster Title: Efficacy and Safety of Bemnifosbuvir and Ruzasvir after 8 Weeks of Treatment in Patients with Chronic Hepatitis C Virus Infection. Conclusion: The Phase 2 study results demonstrated that an 8-week combination regimen BEM and RZR achieved SVR12 in 98% of treatment-adherent patients and 95% of patients regardless of treatment adherence. Among patients with compensated cirrhosis, SVR12 was 88%, with all individuals reaching undetectable viral levels at the end of the 8-week treatment regimen. The regimen was safe and well-tolerated with low rates of virologic failure and no study-drug-related serious adverse events or treatment discontinuations. Treatment emergent adverse events were reported in 43% of patients. Most TEAEs were mild to moderate in intensity, with headache and nausea being the most reported. These results reinforce the potential of the combination regimen of bemnifosbuvir and ruzasvir as a best-in-class treatment for HCV. Poster Title: Pharmacokinetics of Bemnifosbuvir in Participants with Hepatic Impairment: Conclusion: A Phase 1 pharmacokinetic study evaluating a single 550 mg dose of BEM in participants with varying degrees of hepatic impairment showed increased drug exposure in individuals with moderate to severe liver dysfunction. However, these changes did not meaningfully affect levels of AT-273, the plasma marker for the active intracellular antiviral metabolite of BEM. No safety concerns were identified. These results support the use of BEM without dose adjustment in patients with hepatic impairment. Poster Title: No DDI Between Bemnifosbuvir/Ruzasvir and Bictegravir/Emtricitabine/Tenofovir Alafenamide: Conclusion: Findings from a Phase 1 drug-drug interaction study in healthy participants demonstrated that co-administration of BEM/RZR with the standard human immunodeficiency virus regimen bictegravir/emtricitabine/tenofovir alafenamide resulted in no clinically significant pharmacokinetic changes. The co-administered HCV/HIV combinations were generally safe and well tolerated. These results support the future inclusion of HCV/HIV co-infected patients receiving these HIV therapies in the Phase 3 clinical development program for BEM/RZR.Poster Title: Pharmacokinetics of Bemnifosbuvir in Participants with Renal Impairment: Conclusion: A Phase 1 renal impairment study showed that a single 550 mg dose of BEM was safe and well-tolerated across participants with normal kidney function, moderate-to-severe renal impairment, and those with end-stage renal disease on hemodialysis. While the circulating inactive nucleoside metabolites of BEM increased as expected in renally impaired individuals, exposure of BEM remained consistent. These findings suggest that BEM may be used without dose adjustment in patients with renal dysfunction, including those undergoing dialysis.