Atea Pharmaceuticals Reports First Quarter 2025 Financial Results and Provides Business Update Enrollment Ongoing in Phase 3 C-BEYOND Trial for Treatment of HCV Full Phase 2 Results for Regimen of Bemnifosbuvir and Ruzas

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

Enrollment Ongoing in Phase 3 C-BEYOND Trial for Treatment of HCV

Full Phase 2 Results for Regimen of Bemnifosbuvir and Ruzasvir for HCV and Results from Three Additional Phase 1 Studies Supporting

Potential Best-in-Class Profile Presented at European Association for the Study of the Liver (EASL) Congress 2025

Virtual Investor Event with Key Opinion Leader Insights on HCV to be Held May 14, 2025, at 10:00 AM ET

BOSTON, May 12, 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 first quarter ended March 31, 2025 and provided a business update.

The Company s combination regimen of bemnifosbuvir (BEM), a nucleotide analog polymerase inhibitor, and ruzasvir (RZR), an NS5A inhibitor, is in Phase 3

development for the treatment of hepatitis C virus (HCV).

Atea has made very significant progress thus far in 2025, initiating and continuing to

enroll patients in C-BEYOND, our Phase 3 clinical trial evaluating the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV in the US and Canada, said Jean-Pierre Sommadossi, PhD, Chief

Executive Officer and Founder of Atea. We are also focused on initiating our second Phase 3 trial, C-FORWARD, which will be conducted at clinical sites outside of North America. We expect enrollment of

patients in C-FORWARD to begin mid-year.

encouraged by the positive results of the Phase 2 clinical study and additional data presented at EASL 2025 supporting the efficacy, safety and potential best-in-class

profile of our regimen of bemnifosbuvir and ruzasvir, including short treatment duration, low risk for drug-drug interactions, and convenience with no food effect, continued Dr. Sommadossi. We believe our regimen, if approved, has

the potential to increase the number of treated and cured HCV patients and to disrupt the global HCV market of approximately $3 billion in net sales.

HCV KOL Investor Event to be Held May 14, 2025 at 10:00 AM ET

Atea will host a virtual key opinion leader (KOL) investor event with a panel of HCV experts and prescribers on Wednesday, May 14, 2025, at 10:00 AM ET.

To register, click here.

This KOL event will replace Atea s first quarter 2025 earnings conference call, and Quarterly calls will resume

with the second quarter 2025 financial results.

This investor event will include an expert panel of several leaders in hepatology, gastroenterology,

infectious diseases, and HCV treatments in the US, Canada and Europe. These experts and prescribers will discuss the current challenges experienced by people living

with HCV, the full results of Atea s global Phase 2 study evaluating the regimen of BEM/RZR for the treatment of HCV, and what a new optimized HCV therapy could provide for prescribers and

patients. Company management will discuss the HCV commercial market opportunity and the ongoing global Phase 3 clinical development.

Results Presented at EASL

Poster Title: Efficacy and Safety of Bemnifosbuvir and Ruzasvir after 8 Weeks of Treatment in Patients with

Chronic Hepatitis C Virus (HCV) Infection (TOP-251)

Conclusion: The Phase 2 study results

demonstrated that an 8-week combination regimen of BEM (550 mg) and RZR (180 mg) achieved SVR12 in 98% of treatment-adherent patients and 95% of patients regardless of treatment adherence. The regimen was safe

and well-tolerated with low rates of virologic failure and no study-drug-related serious adverse events or treatment discontinuations. Treatment emergent adverse events (TEAEs) were reported in 43% (118/275) of patients. Most TEAEs were mild to

moderate in intensity, with headache (9%) and nausea (8%) being the most reported. These results reinforce the potential of the combination regimen of BEM and RZR as a

best-in-class treatment for HCV.

Poster Title: Pharmacokinetics of

Bemnifosbuvir in Participants with Hepatic Impairment (WED-278)

Conclusion: A Phase 1 pharmacokinetic

study evaluating a single 550 mg dose of BEM in participants with varying degrees of hepatic impairment showed increased drug exposure in individuals with moderate to severe liver dysfunction. However, these changes did not meaningfully affect

levels of AT-273, the plasma marker for the active intracellular antiviral metabolite of BEM. No safety concerns were identified. These results support the use of BEM without dose adjustment in patients with

Poster Title: No DDI Between Bemnifosbuvir/Ruzasvir and Bictegravir/Emtricitabine/Tenofovir Alafenamide (WED-279)

Conclusion: Findings from a Phase 1 drug-drug interaction study in healthy participants demonstrated

that co-administration of BEM/RZR with the standard human immunodeficiency virus (HIV) regimen bictegravir/emtricitabine/tenofovir alafenamide (B/FTC/TAF) resulted in no clinically significant pharmacokinetic

changes. The co-administered HCV/HIV combinations were generally safe and well tolerated. These results support the future inclusion of HCV/HIV co-infected patients

receiving these HIV therapies in the Phase 3 clinical development program for BEM/RZR.

It is estimated that in the US as many as 6 to 30% of HCV patients

are co-infected with HIV.1

Pharmacokinetics of Bemnifosbuvir in Participants with Renal Impairment (WED-280)

1 renal impairment study showed that a single 550 mg dose of BEM was safe and well-tolerated across participants with normal kidney function, moderate-to-severe

renal impairment, and those with end-stage renal disease on hemodialysis. While the circulating inactive nucleoside metabolites of BEM increased as

expected in renally impaired individuals, exposure of BEM remained consistent. These findings suggest that BEM may be used without dose adjustment in patients with renal dysfunction, including those undergoing dialysis.

About the Bemnifosbuvir / Ruzasvir HCV Phase 3 Program

Atea s HCV Phase 3 program includes two open-label Phase 3 trials, C-BEYOND in the US and Canada, and C-FORWARD, a global trial outside of North America. Each Phase 3 trial will enroll approximately 880 treatment-na ve patients, including those with and without

compensated cirrhosis. The trials will compare the fixed-dose combination (FDC) regimen of BEM/RZR to the FDC regimen of sofosbuvir and velpatasvir. The regimen of BEM/RZR will be administered orally once-daily for eight 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 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. Patient

enrollment in the C-BEYOND trial is ongoing and enrollment in the C-FORWARD trial is expected to begin in mid-2025.

The initiation of the Phase 3 program follows a successful engagement with the US Food and Drug Administration (FDA) at an End-of-Phase 2 meeting in January 2025, shortly after the Company announced the topline results from the Phase 2 study evaluating the potential

best-in-class regimen of BEM/RZR, including data demonstrating that the regimen met its primary endpoints of efficacy (SVR12) and safety.

Business and Organizational Updates

First Quarter 2025 Financial Results

Cash, Cash Equivalents and Marketable Securities: $425.4 million at March 31, 2025, compared to $454.7 million at December 31, 2024.

Research and Development Expenses: Research and development expenses decreased by $28.0 million from $57.6 million for the three months

ended March 31, 2024, to $29.6 million for the three months ended March 31, 2025. The net decrease was primarily driven by lower external spend as Atea s COVID-19 Phase 3 SUNRISE-3 clinical trial was completed in 2024. The decrease was offset by an increase in external spend principally related to startup activities for the Company s HCV Phase 3 clinical

development. Additionally, a decrease in internal research and development expenses was primarily related to lower stock-based compensation expense in the three-month period ended March 31, 2025.

General and Administrative Expenses: General and administrative expenses decreased by $2.8 million from $12.2 million for the three months

ended March 31, 2024, to $9.5 million for the three months ended March 31, 2025. The net decrease was primarily related to lower stock-based compensation expense, partially offset by increased professional fees.

Interest Income and Other, Net: Interest income and other, net, decreased by $1.9 million for the three months ended March 31, 2025, compared

to the three months ended March 31, 2024, primarily due to lower investment balances.

Income Taxes: Income tax expense was $0.2 million

for the three months ended March 31, 2025, and March 31, 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 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 regimen of BEM and RZR for the treatment

of HCV, the potential opportunity created by the regimen to increase the number of patients treated and cured, the opportunity to disrupt the global HCV market, the expected time of commencement of enrollment in the

C-FORWARD Phase 3 clinical trial, 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, the timing and outcome of the Company s strategic alternatives review, the timing and agenda of the Company s KOL event and the Company s plans to resume Quarterly

earnings calls in the second quarter of 2025. 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