Atea Pharmaceuticals Advances HCV Phase 3 Program with New Dual Mechanism Data and Expands Pipeline to Hepatitis E
Key Insights
Atea Pharmaceuticals reports that patient enrollment remains on track in its global Phase 3 HCV program, with topline results from the North America C-BEYOND trial expected mid-2026.
New research reveals bemnifosbuvir has a unique dual mechanism of action against HCV, inhibiting both viral replication and assembly/secretion of new virions into the bloodstream.
The company announced expansion of its antiviral pipeline with a new hepatitis E virus (search) program featuring two proprietary candidates with potent nanomolar activity against HEV genotypes.
Atea Pharmaceuticals reported significant progress in its hepatitis C virus (search) (HCV) development program and announced pipeline expansion into hepatitis E virus (search) (HEV) treatment during its third quarter 2025 financial results call. The clinical-stage biopharmaceutical company disclosed that patient enrollment remains on track in both Phase 3 trials evaluating its bemnifosbuvir and ruzasvir combination regimen for HCV treatment.
The company's global Phase 3 program comprises two open-label trials: C-BEYOND conducted in the US and Canada, and C-FORWARD conducted outside North America. Each trial is enrolling approximately 880 treatment-naïve patients, including those with or without compensated cirrhosis (search). Atea currently anticipates that C-BEYOND will be fully enrolled by the end of 2025 with topline results available mid-2026, while C-FORWARD patient enrollment is expected to complete mid-2026 with topline results around the end of 2026.
Novel Dual Mechanism Discovery
New research findings presented at The Liver Meeting 2025 revealed that bemnifosbuvir, a nucleotide analog HCV NS5B polymerase (search) inhibitor, possesses a unique dual mechanism of action against HCV. While bemnifosbuvir has an established mechanism of inhibiting HCV RNA (search) leading to chain termination and blocking viral production inside host cells, new modeling of HCV viral kinetics from a Phase 1 monotherapy trial suggests the drug may also inhibit assembly and secretion of new HCV virions into the bloodstream.
This additional mechanism was previously only associated with NS5A (search) inhibitors such as ruzasvir and velpatasvir. In vitro results confirmed this dual mechanism of action, which helps explain the potency of the bemnifosbuvir and ruzasvir combination regimen. Multiscale modeling predicted that the combination regimen inhibits both intracellular replication of HCV and viral assembly/secretion, with a modeled time to cure of approximately 7 to 8 weeks.
Phase 3 Trial Design and Endpoints
The Phase 3 trials compare the bemnifosbuvir and ruzasvir fixed dose combination (FDC) commercial formulation to the FDC regimen of sofosbuvir and velpatasvir. The bemnifosbuvir and ruzasvir regimen is administered orally once-daily for eight weeks in patients without cirrhosis (search) or 12 weeks in patients with compensated cirrhosis, while sofosbuvir and velpatasvir is administered once-daily for 12 weeks to all patients regardless of cirrhosis status.
The primary endpoint for each trial is HCV RNA (search) below the lower limit of quantitation at 24 weeks from treatment start, encompassing sustained virologic response 12 weeks post-treatment (SVR12) in each arm. This measurement timing ensures the primary endpoint occurs at the same relative time point from treatment start in all patients.
Supporting Clinical Data
Data presented at The Liver Meeting 2025 demonstrated several key advantages of the bemnifosbuvir and ruzasvir regimen. A resistance analysis from a Phase 2 study showed that SVR12 rates were not impacted by resistance associated substitutions, supporting the regimen's high barrier to resistance in HCV-infected patients. Viral kinetics and pharmacokinetic analyses indicated that most viral failures were due to treatment non-adherence rather than resistance.
Results from a Phase 1 study in healthy participants demonstrated high relative bioavailability of the commercial FDC formulation and supported dosing with or without food or with famotidine, an H2 blocker that can substantially diminish the effectiveness of HCV oral antivirals.
Hepatitis E Virus Program Launch
Atea announced expansion of its antiviral pipeline with a new HEV development program featuring two proprietary lead candidates, AT-587 (search) and AT-2490 (search), which have exhibited potent nanomolar antiviral activity in vitro against HEV genotypes GT-1 and GT-3. Investigational new drug enabling studies are ongoing to select the clinical candidate for a Phase 1 program anticipated to begin mid-2026.
Chronic HEV GT-3 and GT-4 infections occur most frequently in immunocompromised individuals with potential for rapid progression to cirrhosis (search), particularly in solid organ transplant recipients and patients with hematological malignancies, history of hematopoietic stem cell transplant, and pre-existing liver disease. There are currently no approved antiviral therapies for this unmet medical need, with current interventions limited to reducing immunosuppressives and treatment with ribavirin, which poses safety concerns and has limited efficacy for HEV.
Market Research Insights
A survey of 153 top prescribers of direct acting antivirals in the US revealed healthcare providers are seeking new treatment options offering high efficacy, short treatment duration, and low risk of drug-drug interactions. Up to 80 percent of HCV patients take multiple medications to manage comorbidities and coinfections, highlighting the need for treatments with minimal interaction potential.
Financial Performance
For the third quarter 2025, Atea reported cash, cash equivalents and marketable securities of $329.3 million compared to $454.7 million at December 31, 2024. Research and development expenses increased to $38.3 million from $26.2 million in the prior year quarter, primarily driven by increased external spend related to the HCV Phase 3 clinical development program.
The company completed a $25 million share repurchase program authorized in April 2025, repurchasing 7,673,793 shares at an average price of $3.26 per share. All repurchased shares were retired, leaving 78,126,796 shares outstanding.
Disease Burden Context
HCV remains a significant global healthcare issue with an estimated 50 million people worldwide chronically infected and approximately one million new infections annually. In the US, between 2.4 and 4.0 million people are estimated to have HCV, with annual new infections outpacing treatment rates. HCV infections in the US predominate in patients aged 20-49 years, with less than 10% of HCV-infected patients estimated to have cirrhosis (search).
For HEV, there are an estimated 20 million infections annually worldwide, resulting in approximately 3 million symptomatic cases and 70,000 HEV-related deaths. While self-limiting in certain populations, immunocompromised patients face risk of rapid progression to cirrhosis (search).