Atea’s Bemnifosbuvir/Ruzasvir Combination Shows Modeled 7–8 Week Cure Potential for Hepatitis C

Atea Pharmaceuticals has unveiled new modeling data indicating that its investigational combination of bemnifosbuvir (BEM) and ruzasvir (RZR) may deliver near-complete suppression of hepatitis C virus (HCV) activity, with a predicted time to cure of approximately seven to eight weeks. The findings, were presented at The Liver Meeting 2025, show that the fixed-dose combination (FDC) simultaneously inhibits viral replication as well as the assembly and release of virus particles into the bloodstream—an effect difficult for most regimens to achieve.

These results reinforce phase 2 clinical outcomes in which the BEM/RZR regimen achieved sustained virologic response at 12 weeks post-treatment (SVR12) rates of 98% among fully adherent patients and 95% across all patients, even with an eight-week treatment duration. Additional datasets presented at the conference include a resistance analysis supporting the regimen’s high barrier to resistance and phase 1 data demonstrating strong relative bioavailability of the commercial FDC formulation. The regimen can be taken with or without food or alongside famotidine, providing an important advantage for patients on multiple medications.

Collectively, these findings highlight the combination’s potential best-in-class profile for the diverse and often complex HCV patient population, including those with resistant virus strains or advanced liver disease.

“Our goal has always been to develop a best-in-class regimen for HCV that meaningfully advances the standard of care for as many people as possible by addressing the evolving needs of today’s HCV patients,” Atea Pharmaceuticals CEO and Founder Jean-Pierre Sommadossi, PhD, said in a statement. “These new findings reinforce the differentiated profile of our fixed-dose combination regimen of bemnifosbuvir and ruzasvir as a potent, pan-genotypic and convenient regimen with the potential to transform the treatment landscape and bring us closer to eradication of HCV.”

Watch this previous Contagion interview with Eric Lawitz, MD, clinical professor of medicine at The Texas Liver Institute, University of Texas Health, San Antonio.

Phase 3 Trials

Back in the spring, the company announced it had begun its phase 3 trial program, and this will incorporate its C-BEYOND trial, which will be conducted in the US and Canada, and its C-FORWARD trial, an international study. Each trial will enroll approximately 880 treatment-naïve patients, including those with and without compensated cirrhosis.²

The regimen of bemnifosbuvir and ruzasvir will be administered orally once-daily for 8 weeks (in patients without cirrhosis) or 12 weeks (in patients with compensated cirrhosis) while the regimen of sofosbuvir and velpatasvir will be administered orally once-daily for 12 weeks for all patients with or without compensated cirrhosis. ²

The primary endpoint for each trial is HCV RNA < lower limit of quantitation (LLOQ) at 24 weeks from the start of treatment and encompasses sustained virologic response 12 weeks post-treatment (SVR12) in each arm. Measurement at 24 weeks from the start of treatment is to ensure the primary endpoint occurs at the same relative timepoint from the start of treatment in all patients. While C-BEYOND and C-FORWARD are both open-label trials, Atea has put measures and processes in place that are designed to blind Atea personnel to patient treatment assignments. ²

About the Therapies

Bemnifosbuvir has been shown in in vitro studies to be approximately 10-fold more active than sofosbuvir (SOF), against a panel of laboratory strains and clinical isolates of HCV GT 1–5. In vitro studies have also demonstrated bemnifosbuvir remained fully active against SOF resistance-associated substitutions (S282T), with up to 58-fold more potency than SOF.²

The pharmacokinetic (PK) profile of bemnifosbuvir supports once-daily dosing for the treatment of HCV. Bemnifosbuvir has been shown to have a low risk for drug-drug interactions. Bemnifosbuvir has been administered to over 2,200 subjects and has been well-tolerated at doses up to 550 mg for durations up to 12 weeks in healthy subjects and patients.²

The other half of the combination, ruzasvir, has demonstrated highly potent and pan-genotypic antiviral activity in preclinical (picomolar range) and clinical studies. Ruzasvir has been administered to over 1,500 HCV-infected patients at daily doses of up to 180 mg for 12 weeks and has demonstrated a favorable safety profile. The PK profile of ruzasvir supports once-daily dosing.²

References
1. Atea Pharmaceuticals Presents New Data Supporting the Fixed-Dose Combination of Bemnifosbuvir and Ruzasvir as a Potential Best-in-Class Regimen for Treatment of Hepatitis C Virus Infection at The Liver Meeting® 2025.November 7, 2025. Accessed November 24, 2025.
https://ir.ateapharma.com/news-releases/news-release-details/atea-pharmaceuticals-presents-new-data-supporting-fixed-dose
2. Atea Pharmaceuticals Announces Dosing of First Patient in C-BEYOND, Phase 3 Study Evaluating Regimen of Bemnifosbuvir and Ruzasvir for Treatment of Hepatitis C Virus. Atea Pharmaceuticals press release. April 9, 2025. Accessed November 24, 2025.
https://ir.ateapharma.com/news-releases/news-release-details/atea-pharmaceuticals-announces-dosing-first-patient-c-beyond