Atea Pharmaceuticals Reports Second Quarter 2025 Financial Results and Provides Business Update Patient Enrollment Advances in Global Phase 3 Program for Treatment of HCV Four Scientific Posters Presented at EASL, Includ

Atea Pharmaceuticals Reports Second Quarter 2025 Financial Results and Provides Business Update

Patient Enrollment Advances in Global Phase 3 Program for Treatment of HCV

Four Scientific Posters Presented at EASL, Including Final Results from Phase 2 Study of

Bemnifosbuvir/Ruzasvir Regimen Confirming 98% Sustained Virologic Response at 12 Weeks

Post-Treatment (SVR12) After Short 8-Week Treatment Duration

Regimen of Bemnifosbuvir/Ruzasvir has Potential Best-in-Class

Profile with Short Treatment

Duration, Low Risk for Drug-Drug Interactions and Convenience with No Food Effect

BOSTON, August 7, 2025 (GLOBE NEWSWIRE) Atea Pharmaceuticals, Inc. (Nasdaq: AVIR) (Atea or Company), a clinical-stage biopharmaceutical company

engaged in the discovery and development of oral antiviral therapeutics for serious viral diseases, today reported financial results for the second quarter ended June 30, 2025, and provided a business update.

The Company s combination regimen of bemnifosbuvir, a nucleotide analog polymerase inhibitor, and ruzasvir, an NS5A inhibitor, is being evaluated in a

global Phase 3 development program for the treatment of hepatitis C virus (HCV). This program is comprised of two Phase 3 clinical trials with C-BEYOND being conducted in the US and Canada and C-FORWARD being conducted outside North America.

Atea has made significant progress this year advancing our

global Phase 3 program evaluating the regimen of bemnifosbuvir/ruzasvir for the treatment of HCV. Global patient enrollment is on track in both C-BEYOND and C-FORWARD

trials, said Jean-Pierre Sommadossi, PhD, Chief Executive Officer and Founder of Atea. We are focused on the successful development of a potential

best-in-class HCV regimen to treat and cure today s patients infected with HCV.

Healthcare providers have stated that test-and-treat models of care,

with seamless diagnosis and treatment for patients infected with HCV, are necessary to make a substantial impact on the eradication of HCV. Based on results to-date, we believe that the profile of our regimen,

which includes a short treatment duration, low risk for drug-drug interactions and convenience with no food effect, is particularly well suited for the test-and-treat

model and has the potential to help advance HCV elimination in the US and globally, continued Dr. Sommadossi.

HCV continues to be a

significant global health burden despite the availability of direct-acting antivirals (DAAs). Between 2.4 to 4.0 million people in the US are living with chronic HCV and an estimated 50 million people are infected worldwide with

approximately one million new infections occurring each year. In the US, HCV diagnoses continually outpace annual cure rates. According to healthcare providers who treat patients with HCV, a new treatment option offering high efficacy, a short

treatment duration, and a low risk of drug-drug interactions is sought to address the needs of a changing patient population and make a meaningful impact on HCV eradication, as up to 80 percent of patients take multiple medications to manage

comorbidities and coinfections.

About the Phase 3 C-BEYOND and

C-FORWARD Trials in Adults with Chronic HCV

Atea s HCV Phase 3 development program includes two

open-label Phase 3 trials, C-BEYOND being conducted in the US and Canada, and C-FORWARD being conducted outside of North America. Patient enrollment in the C-BEYOND trial was initiated in April of 2025 and enrollment in the C-FORWARD trial was initiated in June of 2025.

Each Phase 3 trial is enrolling approximately 880 treatment-na ve patients, including those with and without

compensated cirrhosis. The trials compare the fixed-dose combination (FDC) regimen of bemnifosbuvir/ruzasvir to the FDC regimen of sofosbuvir/velpatasvir. The regimen of bemnifosbuvir/ruzasvir is administered orally once-daily for eight weeks (in

patients without cirrhosis) or 12 weeks (in patients with compensated cirrhosis) while the regimen of sofosbuvir/velpatasvir is administered orally once-daily for 12 weeks to all patients, with or without compensated cirrhosis.

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.

Summary of Presentations at European Association for the Study of the Liver (EASL) Congress 2025

Four scientific posters were presented at the EASL Congress 2025 in early May, and the posters can be accessed here. Highlights from the presentations

HCV Key Opinion Leader (KOL) Discussion Panel Event

Atea hosted a virtual KOL investor event featuring a panel of six HCV experts and prescribers on May 14, 2025. These leaders in hepatology,

gastroenterology, infectious diseases, and HCV research in the US, Canada and Europe discussed the current challenges experienced by people living with HCV, the full results of Atea s global Phase 2 study evaluating the regimen of

bemnifosbuvir/ruzasvir for the treatment of HCV, and what a new optimized HCV therapy could provide for prescribers and patients. Additionally, Company management discussed the commercial market opportunity for a potential best in class HCV DAA and

the ongoing global Phase 3 clinical development of the regimen of bemnifosbuvir/ruzasvir. The replay of the KOL event can be accessed here.

Business and Organizational Updates

Second Quarter 2025 Financial Results

Cash Equivalents and Marketable Securities: $379.7 million at June 30, 2025 compared to $454.7 million at December 31, 2024.

Research and Development Expenses: Research and development expenses decreased by $2.4 million from $34.7 million for the three months ended

June 30, 2024 to $32.3 million for the three months ended June 30, 2025. The net decrease was primarily driven by substantially lower COVID-19 external spend as a result of our COVID-19 Phase 3 SUNRISE-3 clinical trial being completed in 2024 together with a decrease in internal research and development expenses primarily related to lower stock-based

compensation and payroll related expenses in the three months ended June 30, 2025, offset by increased external spend related principally to our HCV Phase 3 clinical development program including the recognition of expense related to the

milestone paid to Merck.

General and Administrative Expenses: General and administrative expenses decreased by $3.2 million from

$12.2 million for the three months ended June 30, 2024 to $9.1 million for the three months ended June 30, 2025. The net decrease was primarily related to lower stock-based compensation expense partially offset by increased

Interest Income and Other, Net: Interest income and other, net, decreased by $2.2 million for

the three months ended June 30, 2025 compared to the three months ended June 30, 2024, primarily due to lower investment balances.

Taxes: Income tax expense was $0.2 million for the three months ended June 30, 2025 and 2024.

Condensed Consolidated

Statement of Operations and Comprehensive Loss

(in thousands, except share and per share amounts)

Selected Condensed Consolidated Balance Sheet Data

HCV is a blood-borne, positive-sense, 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, 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 in the age group between 20-49 years old, and it is estimated that less than 10% of

HCV-infected patients in the US have cirrhosis. Chronic HCV infection is the leading cause of liver cancer in the US, Europe and Japan.

About Atea Pharmaceuticals

Atea is a clinical-stage

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 lead program and current focus is on the development of the combination of bemnifosbuvir, a nucleotide analog polymerase inhibitor, and ruzasvir, an NS5A inhibitor, to treat HCV. For more information, please visit

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 bemnifosbuvir/ruzasvir regimen for the

treatment of HCV, the potential opportunity to advance efforts to eradicate HCV, future results of operations and financial position, business strategy, anticipated milestone events and timelines for clinical trials, benefits of cost savings

initiatives, repurchases under the Company s share repurchase program, and the timing and outcome of the Company s strategic alternatives review. 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; the timeline for the completion of the strategic alternatives review process is unknown and there can be no assurance that the process will result in any particular outcome; dependence on

the success of Atea s most advanced product candidates, in particular the bemnifosbuvir/ruzasvir 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, 2025 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.

SVP, Investor Relations and Corporate