Atea Pharmaceuticals Presents New Drug-Drug Interaction Results Supporting Potential Best-in-Class Profile of the Regimen of Bemnifosbuvir and Ruzasvir for the Treatment of Hepatitis C Virus at EASL Congress 2026

BOSTON, May 27, 2026 (GLOBE NEWSWIRE) -- Atea Pharmaceuticals, Inc. (NASDAQ:AVIR) (Atea or Company), a late-stage clinical biopharmaceutical company engaged in the discovery and development of oral antiviral therapeutics for serious viral diseases, today announced Phase 1 results which further demonstrate that the fixed-dose combination regimen of bemnifosbuvir and ruzasvir (BEM/RZR) for the treatment of hepatitis C virus (HCV) has a low risk of drug-drug interaction. These results support the use of BEM/RZR with commonly used medications, including the proton pump inhibitor (PPI) omeprazole and the cholesterol-lowering drug rosuvastatin. The Company is also presenting data demonstrating high in vitro antiviral potency and in vivo efficacy for AT-587, its potential first-in-class direct-acting antiviral (DAA) for the treatment of hepatitis E virus (HEV). These data are being presented at the European Association for the Study of the Liver (EASL) Congress 2026, taking place May 27-30^th in Barcelona, Spain.

"These Phase 1 results reinforce the potential of the regimen of BEM/RZR to simplify treatment for patients and healthcare providers and address the evolving needs of today's patients living with HCV," said Jean-Pierre Sommadossi, PhD, Chief Executive Officer and Founder of Atea Pharmaceuticals. "Our market research has shown that most HCV patients in the US manage multiple medications concurrently, which can complicate care. The results being presented demonstrate that the regimen of BEM/RZR can be co-administered with PPIs and other commonly used medications without requiring dose adjustments. As we move toward topline Phase 3 results from C-BEYOND and C-FORWARD, these data give us continued confidence in the regimen's potential to deliver a best-in-class profile for today's patients living with HCV."

HCV continues to be a significant global health burden despite the availability of DAAs. According to US healthcare providers who treat patients with HCV, approximately 80 percent of patients take multiple medications to manage comorbidities and drug-drug interactions are a significant concern in HCV treatment. As a result, a new treatment option offering a low risk of drug-drug interactions together with high efficacy and short treatment duration could meaningfully address patient needs and further the goal of HCV eradication.  

"The data being presented for AT-587 demonstrate high in vitro antiviral potency and in vivo efficacy against HEV, underscoring its potential," Dr. Sommadossi added. "There is a critical gap in the care of patients with chronic HEV with no approved therapies, leaving vulnerable populations including transplant recipients and other immunocompromised patients at risk for rapid disease progression to cirrhosis. Following the encouraging preclinical data, we look forward to advancing our potential first-in-class product candidate, AT-587, into a first-in-human study mid-year."

In recent years, chronic HEV genotype 3 and 4 infections have been increasingly recognized as a potentially life-threatening viral infection in immunocompromised individuals — a population that includes solid organ and hematopoietic stem-cell transplant recipients, and patients with hematologic malignancies. In these vulnerable populations, chronic HEV can result in rapid progression to cirrhosis within three to five years. There is no approved antiviral therapy for HEV, and current off-label treatments have limited efficacy and tolerability, underscoring a clear and urgent unmet medical need.  

Phase 1 Results for the Regimen of BEM/RZR Highlight Favorable Drug-Drug Interaction Profile for Treatment of HCV  

Poster ID: FRI-635

Title: Proton-pump inhibitor omeprazole did not affect the plasma pharmacokinetics of bemnifosbuvir and ruzasvir fixed-dose combination in healthy participants

Presenting Author: Xiao-Jian Zhou

Date and Time: Friday, May 29, 8:30 a.m.–5:00 p.m. CEST

A Phase 1 study in healthy adults (n=20) showed the regimen of BEM/RZR was generally safe and well-tolerated when administered alone or concomitantly with omeprazole, a commonly used medication among HCV-infected patients to treat stomach acid conditions. These results support co-administration of BEM/RZR with PPIs, which often reduce the solubility of DAAs, decreasing their absorption/bioavailability and negatively impacting DAA efficacy. Omeprazole dosed at 20 mg, a common dose for gastroesophageal reflux disease, did not affect plasma exposure to BEM/RZR. Omeprazole dosed at 40 mg administered two hours before BEM/RZR to allow maximal acid-suppressive effect only slightly reduced plasma exposure to BEM/RZR. Co-administered BEM/RZR did not meaningfully affect the pharmacokinetic (PK) profile of omeprazole.

Poster ID: FRI-636

Title: Bemnifosbuvir and ruzasvir administered as a fixed-dose combination have low potential to inhibit P-gp, BCRP or OATP1B1/3 mediated transport

Presenting Author: Xiao-Jian Zhou

Date and Time: Friday, May 29, 8:30 a.m.–5:00 p.m. CEST

A Phase 1 study in healthy adults evaluated interactions between the regimen of BEM/RZR and digoxin (n=18) or rosuvastatin (n=18), sensitive substrates of the drug transporters P-gp and BCRP/OATP1B1/1B3, respectively. These transporters are important for how drugs are absorbed, enter the liver and are cleared from the body. Results demonstrated that BEM/RZR administered with digoxin and rosuvastatin was well tolerated with all treatment-emergent adverse events mild in severity. A single dose of BEM/RZR slightly increased the plasma exposure of digoxin and rosuvastatin. With a geometric mean ratio of less than 2, BEM/RZR has low potential to exhibit clinically meaningful inhibition of these transporters. These results demonstrate that no dose adjustments are needed for drugs that are substrates of these transporters when co-administered with BEM/RZR.

AT-587 Results Demonstrate High In Vitro Antiviral Potency and In Vivo Efficacy Against HEV

Poster ID: TOP-631

Title: Discovery and preclinical profile of a first-in-class potent hepatitis E virus inhibitor AT-587

Presenting Author: Qi Huang

Date and Time: Thursday, May 28, 8:30 a.m.–5:00 p.m. CEST

Results presented support AT-587 as an oral nucleotide analog exhibiting promising preclinical antiviral potency against HEV. In vitro studies demonstrated that AT-587 is a potent inhibitor of HEV replication. Specifically, AT-587 was 30 to 150-fold more potent in vitro against HEV than sofosbuvir (SOF) and ribavirin, which is currently used off-label. AT-587 showed no toxicity in in vitro studies. AT-587 also demonstrated activity against flaviviruses, rubella and chikungunya.

In addition, new results showed that AT-587 inhibited HEV-3 activity in vivo. Using HEV-3-infected gerbil models, fecal samples from the treated groups had significantly lower HEV RNA levels than the control group. In addition, the viral loads in the liver and intestinal samples were significantly lower in the treated groups compared to control. Notably, AT-587 also retained high potency against ribavirin (G1634R) and SOF (A1343V) clinical resistance strains in vitro, further differentiating its profile from existing off-label treatment options. 

About Bemnifosbuvir and Ruzasvir for HCV

Bemnifosbuvir has been shown in in vitro studies to be approximately 10-fold more active than 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. The 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 3,000 subjects and has been well-tolerated at doses up to 550 mg for durations up to 12 weeks in healthy subjects and patients.

Ruzasvir has demonstrated highly potent and pan-genotypic antiviral activity in preclinical (picomolar range) and clinical studies. Ruzasvir has been administered to over 2,800 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.

About HCV

HCV is a blood-borne, single-stranded (ss) RNA virus that primarily infects liver cells. HCV is a leading cause of chronic liver disease and liver transplants, spreading via blood transfusion, hemodialysis and needle sticks, with approximately 240,000 deaths occurring each year. Despite the availability of DAAs, HCV continues to be a significant global healthcare issue. An estimated 50 million people worldwide are chronically infected with HCV and there are approximately one million new infections each year. In the US, approximately four million people are estimated to have HCV with annual new infections outpacing treatment rates. HCV infections in the US predominate in patients in the age group between 20 and 49 years old, and it is estimated that less than 10% of HCV-infected patients in the US have cirrhosis. Chronic HCV infection is a leading cause of liver cancer in the US, Europe and Japan.

About HEV

HEV is a ssRNA virus which infects the liver and remains an under-recognized global health challenge with an estimated 20 million acute infections annually. Waterborne transmission of HEV genotypes 1 and 2 causes mostly acute self-limiting hepatitis in developing regions, whereas foodborne transmission of HEV genotype 3 predominates in the US and Europe and may cause chronic hepatitis in immunocompromised patients, which can lead to cirrhosis in three to five years. There is a growing number of immunocompromised patients, a population that includes solid organ transplant and hematopoietic stem cell transplant recipients and patients with hematologic malignancies such as multiple myeloma. Each year, in the US and Europe, 3% of the approximately 450,000 patients who have these underlying medical conditions are at risk of developing chronic HEV. There is currently no approved antiviral therapy for HEV, and current off-label treatments have limited efficacy and tolerability, underscoring a clear and urgent unmet medical need. Atea's initial HEV clinical efforts will focus on developing AT-587 for the treatment of immunocompromised patients with chronic HEV.

About Atea Pharmaceuticals

Atea is a late-stage clinical biopharmaceutical company focused on discovering, developing and commercializing oral antiviral therapies to address the unmet medical needs of patients with serious viral infections. Leveraging Atea's deep understanding of antiviral drug development, nucleos(t)ide chemistry, biology, biochemistry and virology, Atea has built a proprietary nucleos(t)ide prodrug platform to develop novel product candidates to treat single-stranded ribonucleic acid, or ssRNA, viruses, which are a prevalent cause of serious viral diseases. Atea plans to continue to build its pipeline of antiviral product candidates by augmenting its nucleos(t)ide platform with other classes of antivirals that may be used in combination with its nucleos(t)ide product candidates. Atea's Phase 3 program is evaluating the FDC regimen of bemnifosbuvir, a nucleotide analog polymerase inhibitor, and ruzasvir, an NS5A inhibitor, to treat HCV. Atea anticipates initiating clinical development of AT-587, a nucleotide analog, for the treatment of HEV in mid-2026. For more information, please visit www.ateapharma.com

Forward-Looking Statements

This press release includes "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements in this press release include but are not limited to statements regarding the potential best-in-class profile of the BEM/RZR regimen for the treatment of HCV, the potential to develop a product for the treatment of HEV, anticipated milestone events and timelines for clinical trials including the timeline for readout of the HCV Phase 3 clinical trials results and initiation of the HEV clinical development, future results of operations and business strategy. When used herein, words including "expected," "should," "anticipated," "believe," "will," "plans", and similar expressions are intended to identify forward-looking statements. In addition, any statements or information that refer to expectations, beliefs, plans, projections, objectives, performance or other characterizations of future events or circumstances, including any underlying assumptions, are forward-looking. All forward-looking statements are based upon Atea's current expectations and various assumptions. Atea believes there is a reasonable basis for its expectations and beliefs, but they are inherently uncertain. Atea may not realize its expectations, and its beliefs may not prove correct. Actual results could differ materially from those described or implied by such forward-looking statements as a result of various important factors, including, without limitation, uncertainties inherent in the drug discovery and development process and the regulatory submission or approval process, unexpected or unfavorable safety or efficacy data or results observed during clinical trials or in data readouts; delays in or disruptions to clinical trials or our business; our reliance on third parties over which we may not always have full control; our ability to manufacture sufficient commercial product; competition from approved treatments for HCV; dependence on the success of Atea's most advanced product candidates, in particular the BEM/RZR regimen for the treatment of HCV; as well as the other important factors discussed under the caption "Risk Factors" in Atea's Quarterly Report on Form 10-Q for the quarter ended March 31, 2026 as such factors may be updated from time to time in its other filings with the SEC, which are accessible on the SEC's website at www.sec.gov. These and other important factors could cause actual results to differ materially from those indicated by the forward-looking statements made in this press release. Any such forward-looking statements represent management's estimates as of the date of this press release. While Atea may elect to update such forward-looking statements at some point in the future, except as required by law, it disclaims any obligation to do so, even if subsequent events cause our views to change. These forward-looking statements should not be relied upon as representing Atea's views as of any date subsequent to the date of this press release.

Contacts

Jonae Barnes

SVP, Investor Relations and Corporate Communications

617-818-2985

barnes.jonae@ateapharma.com

Joyce Allaire

LifeSci Advisors

jallaire@lifesciadvisors.com