Atea Pharmaceuticals : Bemnifosbuvir Program Update Call Presentation

Bemnifosbuvir Phase 3 Program Update

September 13, 2022

June 2020

DISCLAIMERS

Forward-Looking Statements

This presentation contains "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements are neither historical facts nor assurances of future performance. Instead, they are based on our current beliefs, expectations and assumptions regarding the future of our business, future plans and strategies, our clinical results and other future conditions. All statements other than statements of historical facts contained in this presentation are forward-looking statements, including statements by Atea Pharmaceuticals, Inc. (the "Company") regarding future results of operations and financial position, including our anticipated cash runway; business strategy; current and prospective product candidates; anticipated milestone events; potential benefits of our product candidates and market opportunity; planned clinical trials, including, without limitation, anticipated initiation, enrollment, regulatory submission and data readout timelines; preclinical activities; product approvals; manufacturing availability; degree of market acceptance of any products that may be approved; research and development costs; current and prospective collaborations; and prospects and opportunities for investors. In some cases, you can identify forward-looking statements by terms such as "may," "will," "should," "expects," "plans," "anticipates," "could," "intends," "targets," "projects," "contemplates," "believes," "estimates," "predicts," "potential" or "continue" or the negative of these terms or other similar expressions.

The information in this presentation, including without limitation the forward-looking statements contained herein, represent our views as of the date of this presentation. 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 anticipated results, performance or achievements expressed or implied by the forward-looking statements. Risks and uncertainties that may cause actual results to differ materially include uncertainties inherent in the drug development process and the regulatory approval process, in particular for bemnifosbuvir and AT-752, our reliance on third parties over which we may not always have full control, competition from treatments for COVID-19 and hepatitis C and vaccines for COVID-19 and dengue, risks related to the COVID-19 pandemic on our business, and other important risks and uncertainties that are described in our Annual Report on Form 10-K filed for the year ended December 31, 2021 and our most recent quarterly report on Form 10Q filed with the Securities and Exchange Commission ("SEC") and our other filings with the SEC. New risk factors and uncertainties may emerge from time to time, and it is not possible to predict all risk factors and uncertainties. Accordingly, you are cautioned not to place undue reliance on these forward-looking statements.

Except as required by applicable law, we do not plan to publicly update or revise any forward-looking statements contained herein, whether as a result of any new information, future events, changed circumstances or otherwise. No representations or warranties (expressed or implied) are made about the accuracy of any such forward-looking statements.

Industry Information

Market data and industry information used throughout this presentation are based on management's knowledge of the industry and the good faith estimates of management. We also relied, to the extent available, upon management's review of independent industry surveys and publications and other publicly available information prepared by a number of third-party sources. All of the market data and industry information used in this presentation involves a number of assumptions and limitations, and you are cautioned not to give undue weight to such estimates. Although we believe that these sources are reliable, we cannot guarantee the accuracy or completeness of this information, and we have not independently verified this information. While we believe the estimated market position, market opportunity and market size information included in this presentation are generally reliable, such information, which is derived in part from management's estimates and beliefs, is inherently uncertain and imprecise. No representations or warranties are made by the Company or any of its affiliates as to the accuracy of any such statements or projections. Projections, assumptions and estimates of our future performance and the future performance of the industry in which we operate are necessarily subject to a high degree of uncertainty and risk due to a variety of factors, including those described above.

2 These and other factors could cause results to differ materially from those expressed in our estimates and beliefs and in the estimates prepared by independent parties.

Bemnifosbuvir

Phase 3 Program Update for COVID-19

• Bemnifosbuvir Global Phase 3 Clinical Trial Design and Update
• Strategy for Bemnifosbuvir Mono- and Combination Therapy

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COVID-19

Novel Phase 3 Design to Evaluate Mono- and Combination Therapy

• Trial enriched by enrolling high-risk patients who are at the greatest risk of disease progression with COVID-19
• Phase 3 trial protocol reviewed with FDA
• • Study drug (bemnifosbuvir or placebo) to be initiated at the same time as locally available standard of care (SOC)
  • Two study populations derived from the type of SOC received:

 Supportive⎼ care population - monotherapy (primary analysis)

Defined as the patient does not qualify for an approved antiviral treatment or where antivirals are not locally available

• Combination⎻antiviral population - combination therapy (secondary analysis)
• • SOC includes treatment with other compatible antiviral drugs against COVID-19Atea is on the forefront of clinical combination development

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COVID-19

Global Phase 3 Registrational Trial in High-Risk Outpatients with COVID-19

Differentiated Phase 3 Trial Design Assessing Mono- and Combination Therapy

Inclusion Criteria: High-risk outpatients with mild or moderate COVID-19, regardless of vaccination status; symptom onset ≤ 5 days before randomization

Geography: US, Europe, Japan and ROW

	Bemnifosbuvir 550 mg BID + SOC (n=~750)
Randomization	Placebo BID + SOC (n~=750)	4Q / 22
Initiation
1:1	5 days of dosing with BEM or placebo

Phase 3 Study Design:

• Randomized, double-blind,placebo-controlled
• Study drug (bemnifosbuvir or placebo) to be initiated at the same time as locally available standard of care (SOC)
• Two study populations derived from the type of SOC received:
• • "Supportive care population" - monotherapy (primary analysis)
  • "Combination antiviral population" - combination therapy (secondary analysis, local SOC includes treatment with other compatible antiviral drugs against COVID-19)
• Interim analysis to be conducted

Primary Endpoint:

• All-causehospitalization or death through Day 29 in supportive care population (n ≥1,300 patients)

Secondary Endpoints (assessed in each population):

• COVID-19complications
• Medically attended visits
• Symptom rebound / relapse
• Viral load rebound

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