Atea Pharmaceuticals Provides Clinical and Corporate Update and Reports Second Quarter 2021 Financial Results New Data in Healthy Volunteers Confirmed that AT-527 s Active Metabolite Achieved Target Antiviral Levels in L

Atea Pharmaceuticals Provides Clinical and Corporate Update and Reports Second Quarter 2021 Financial

BOSTON, Mass., August 12, 2021 Atea Pharmaceuticals, Inc. (Nasdaq: AVIR) ( Atea ), a clinical-stage

biopharmaceutical company, today reported financial results for the second quarter ended June 30, 2021 and provided a clinical and corporate update.

We are very encouraged by new data, reported for the first time, that an investigational, direct-acting antiviral for

COVID-19 achieved target drug levels in the lungs. In healthy volunteers, AT-527 s active metabolite achieved target antiviral levels in lining fluid of the lungs,

where SARS-CoV-2 virus replicates. These data not only provide further confidence for treatment but also support development of

AT-527 for prophylaxis of COVID-19 and build upon our recent Phase 2 interim results showing treatment with AT-527 resulted in a

rapid decline in viral load, which led to viral clearance. Impacting key sites of infection will be important in helping patients recover faster while minimizing virus transmission, said Jean-Pierre Sommadossi, PhD, Chief Executive Officer and

Founder of Atea Pharmaceuticals.

As COVID-19 becomes endemic and continues to evolve with the highly

transmissible Delta variant and other variants, we need a multi-pronged treatment approach including safe and effective oral antiviral options that may play an important role in helping to reduce the global burden of disease, said Janet

Hammond, MD, PhD, Chief Development Officer of Atea Pharmaceuticals. We are very pleased with our results showing AT-527 s strong antiviral potential and we continue to advance multiple global

clinical studies in parallel with our collaborator Roche, to provide further clinical evidence in support of AT-527 as an oral, potent, direct-acting antiviral treatment for

Recent AT-527 Clinical Development Highlights

Drug Levels in Lung Lining Fluid in Healthy Volunteers: First investigational direct-acting antiviral (DAA) being developed for COVID-19 to report target antiviral levels in lungs, primary site of infection for the virus

New Preclinical and Clinical Results: Expanding AT-527 s favorable profile

Global Phase 2 Trial of AT-527 in Hospitalized Setting: Positive

interim virology results demonstrated rapid and sustained viral load decrease and viral clearance

Protocol Amendment for Global Phase 2 Study in Hospitalized Setting: Reflecting evolving COVID-19

Global Phase 2 MOONSONG Trial of AT-527 in Outpatient Setting:

Study ongoing with interim virology data expected in 2H 2021

Global Phase 3 MORNINGSKY Registrational Trial of AT-527 in Outpatient Setting: Recruitment ongoing with

results anticipated in 2H 2021

Global Phase 3 Follow-on MEADOWSPRING Initiated: Long-term

study to understand the impact of AT-527 treatment on long COVID

Recent AT-752 Clinical Development Highlights

Phase 1a Trial of AT-752 for Dengue Fever: Completed single ascending dose portion and initiated multiple

ascending dose portion

Corporate Highlights

$50 Million Development Milestone Achieved Under License Agreement with Roche

Appointment of Jerome Adams, M.D., M.P.H., to Board of

Senior Management Appointment

Second Quarter 2021 Financial Results

and Cash Equivalents: $816.5 million at June 30, 2021 compared to $850.1 million at December 31, 2020. The cash balance at June 30, 2021 does not include the $50 million

milestone payment realized under the license agreement Atea entered into with F. Hoffmann-La Roche Ltd. and Genentech, Inc. in October 2020 ( Roche License Agreement ), which was received in July 2021.

Revenue: Collaboration revenue for the quarter ended June 30, 2021 in the amount of $60.4 million increased by $60.4 million

from $0 million for the quarter ended June 30, 2020. All collaboration revenue was derived from the Roche License Agreement which was entered into in October 2020.

Research and Development Expenses: Research and development expenses for the quarter ended June 30, 2021 in the amount of

$39.8 million increased by $32.0 million from $7.8 million for the quarter ended June 30, 2020. The increase in research and development expenses was primarily due to an increase in external expenses incurred

related to the CRO and CMO services in conjunction with the advancement of product candidates for the treatment of COVID-19 and dengue fever, including our share of costs incurred by Roche, and increases in

internal spend primarily due to an increase in personnel-related expenses, including salaries, benefits and stock-based compensation expense for our research and product development employees and consulting fees and other research and development

General and Administrative Expenses: General and administrative expenses for the quarter ended June 30, 2021

in the amount of $11.9 million increased by $9.7 million from $2.2 million for the quarter ended June 30, 2020. The increase in general and administrative expenses was primarily due to the expansion of

our organization and reflected an increase in payroll and personnel-related expenses, including salaries, benefits and stock-based compensation expense and other general and administrative expenses.

Income Tax Expense: Income tax expense for the quarter ended June 30, 2021 in the amount of $7.2 million increased by

$7.2 million from $0 million for the three months ended June 30, 2020. The increase in income tax expense was primarily due to realization of income as a result of the recognition of revenue in 2021 associated with the Roche License

Agreement. The tax provision was calculated based on the year-to-date effective rate.

Net Income (loss): Net income for the quarter ended June 30, 2021 in the amount of

$1.5 million increased by $11.5 million from a net loss of $10.0 million for the quarter ended June 30, 2020.

Condensed Consolidated Balance Sheets

(in thousands, except share and per share amounts)

Condensed Consolidated Statement of Operations and Comprehensive Income

(in thousands, except share and per share data)

Conference Call and Webcast

Atea will host a conference call and live audio webcast to discuss the second quarter 2021 financial results and provide a corporate update today at 4:30 p.m.

ET. To access the live conference call, please dial (833) 301-1150 (domestic) or (914) 987-7391 (international) at least five minutes prior to the start time and refer

to conference ID 5795073.

A live audio webcast of the call and accompanying slide presentation will also be available in the Investors

Events & Presentations section of the Company s website, www.ateapharma.com. An archived webcast will be available on the Atea website approximately two hours after the event.

About the AT-527 COVID-19 Clinical Development Program

AT-527 is an oral direct-acting antiviral agent derived from Atea s nucleotide prodrug platform. AT-527 is currently under evaluation as a treatment for patients with COVID-19. In collaboration with Roche, AT-527 is being evaluated

in the global Phase 3 MORNINGSKY trial, a global Phase 2 study for hospitalized patients with moderate COVID-19 and a Phase 2 MOONSONG virology study in patients with mild or moderate COVID-19 in an outpatient setting. In addition, MEADOWSPRING, a Phase 3 long-term follow-on study, will evaluate the impact of prior administration of AT-527 in long COVID.

A direct-acting antiviral aims to prevent disease progression by minimizing or eliminating viral

replication and thereby reducing the severity of the disease, preventing or shortening hospitalization, and also potentially preventing transmission of the virus to others. This makes it well suited for potential use in both pre- and post-exposure prophylactic settings and complementary to vaccines.

About Atea Pharmaceuticals

Atea Pharmaceuticals is a clinical stage biopharmaceutical company focused on discovering, developing and commercializing oral therapies to address the unmet

medical needs of patients with life-threatening viral diseases. Leveraging the Company s deep understanding of antiviral drug development, nucleos(t)ide chemistry, biology, biochemistry and virology, Atea has built a proprietary nucleotide

prodrug platform to develop novel product candidates to treat single stranded ribonucleic acid, or ssRNA, viruses, which are a prevalent cause of severe viral diseases. Currently, Atea is focused on the development of orally-available, potent, and

selective nucleotide prodrugs for difficult-to-treat, life-threatening viral infections, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19, dengue virus, hepatitis C virus (HCV) and respiratory syncytial virus (RSV). For more

information, please visit www.ateapharma.com.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements contained in

this press release that do not relate to matters of historical fact should be considered forward-looking statements, including without limitation statements regarding our expectations surrounding the potential of

our product candidates, AT-527, and expectations regarding our pipeline, including trial design and development timelines. These statements are neither

promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements

expressed or implied by the forward-looking statements, including, but not limited to, the following: uncertainty around and costs associated with the development of AT-527 as a potential treatment for COVID-19 and our other product candidates; dependence on management, directors and other key personnel; the impact of the COVID-19 pandemic on our business; our limited

operating history and significant losses since inception; our need for substantial additional funding; our ability to use our net operating loss carryforwards; our dependence on the success of our most advanced product candidates; risks related to

the regulatory approval process; risks associated with the clinical development process and reliance on interim or topline clinical trial results; risks related to healthcare laws and other legal compliance matters; risks related to potential

commercialization; risks related to manufacturing and our dependence on third parties; risks relating to intellectual property; our ability to maintain effective internal control over financial reporting and the significant costs as a result of

operating as a public company. These and other important factors discussed under the caption Risk Factors in our most recent Quarterly Report on Form 10-Q, and our other filings with the SEC 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 we may

elect to update such forward-looking statements at some point in the future, we disclaim any obligation to do so, even if subsequent events cause our views to change.

SVP, Investor Relations and Corporate Communications

Stern Investor Relations