Atea Pharmaceuticals to Present Three Abstracts at EASL 2026 Congress Highlighting Progress Across Viral Hepatitis Pipeline

BOSTON, May 13, 2026 — 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 that three abstracts have been accepted for presentation at the European Association for the Study of the Liver (EASL) Congress 2026, taking place May 27-30th in Barcelona, Spain.

The presentations include two posters supporting Atea’s fixed-dose combination regimen of bemnifosbuvir, a nucleotide analog polymerase inhibitor, and ruzasvir, an NS5A inhibitor, for the treatment of hepatitis C virus (HCV). Also being presented and designated as a top poster presentation is preclinical data for AT-587, a proprietary oral nucleotide analog recently selected as the Company’s lead clinical candidate for the treatment of hepatitis E virus (HEV).

Collectively, these presentations underscore Atea’s continued progress across its antiviral pipeline and highlight Atea’s focus on advancing potential new treatment options for patients with viral hepatitis.

“We look forward to sharing new clinical study results at EASL that further support the differentiated target profile of the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV,” said Jean-Pierre Sommadossi, PhD, Chief Executive Officer and Founder of Atea. “As we approach topline results from our Phase 3 C-BEYOND and C-FORWARD trials, these data reinforce the regimen’s potential to deliver a best-in-class profile for patients living with HCV.”

“We’re also excited to highlight new preclinical data for AT-587, our lead clinical candidate for the treatment of HEV, which has earned designation as a top poster presentation,” added Dr. Sommadossi. “With no approved treatment options, HEV remains a significant, under-recognized disease, particularly among immunocompromised patients. We believe AT-587 has the potential to become a first-in-class therapy and look forward to advancing this program into the clinic mid-year as we expand our efforts to address serious viral infections.”

The accepted abstracts will be available on the EASL Congress 2026 website following the embargo lift on Wednesday, May 13th at 8:00 a.m. Central European Time (CET).

Poster Presentations at EASL 2026 Congress:

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

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

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

About Bemnifosbuvir and Ruzasvir for Hepatitis C Virus (HCV)

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. 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 direct acting antivirals, 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 is a cause of 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 BEM, a nucleotide analog polymerase inhibitor, and RZR, 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.

Contacts

Jonae Barnes SVP, Investor Relations and Corporate Communications 617-818-2985 [email protected]

Joyce Allaire LifeSci Advisors [email protected]