Atreca : Corporate Presentation April 2021

Delivering the Potential of Immunotherapy

Corporate Overview

A p r i l 2 0 2 1

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Legal Disclaimer

This presentation and the accompanying oral commentary contain forward-looking statements about us and our industry that involve substantial risks and uncertainties. All statements other than statements of historical facts contained in this presentation and the accompanying oral commentary, including statements regarding our future results of operations or financial condition, business strategy and plans and objectives of management for future operations, are forward-looking statements. In some cases, you can identify forward-looking statements because they contain words such as ''anticipate,'' ''believe,'' ''continue,'' ''estimate,'' ''expect,'' ''may,'' ''plan,'' ''potential,'' ''predict,'' ''should,'' or ''will'' or the negative of these words or other similar terms or expressions, although not all

forward-looking statements contain these words. These forward-looking statements include, but are not limited to, statements concerning the following: the initiation, timing, progress and results of our research and development programs, preclinical studies, any clinical trials and Investigational New Drug and other regulatory submissions; the initiation, timing, progress and results of our

collaborations and partnerships; our expectations regarding the activity and therapeutic potential of our product candidate ATRC-101 or potential future product candidates; our ability to identify and develop product candidates for treatment of additional disease indications; our or a potential future collaborator's ability to obtain and maintain regulatory approval of any of our current or potential future product candidates; our expectations regarding the achievement and timing of research, development, clinical, regulatory and other corporate milestones; the adequacy of our cash balance to support our anticipated future operations; our anticipated milestones and the implementation of our business model and strategic plans for our business, technologies, and current or potential future product candidates.

You should not rely on forward-looking statements as predictions of future events. We have based the forward-looking statements contained in this presentation and the accompanying oral commentary primarily on our current expectations and projections about future events and trends that we believe may affect our business, financial condition and operating results. The outcome of the events described in these forward-looking statements is subject to risks, uncertainties and other factors described in greater detail in our most recent Quarterly Report on Form 10-Q filed with the U.S. Securities and Exchange Commission, and may cause our actual results, performance or achievement to differ materially and adversely from those anticipated or implied by our forward-looking statements. In addition, statements that "we believe" and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based on information available to us as of the date of this presentation. While we believe that information provides a reasonable basis for these statements, that information may be limited or incomplete. Our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all relevant information. These statements are inherently uncertain, and investors are cautioned not to unduly rely on these statements.

Moreover, we operate in a very competitive and rapidly changing environment. New risks and uncertainties emerge from time to time, and it is not possible for us to predict all risks and uncertainties that could have an impact on the forward-looking statements contained in this presentation and the accompanying oral commentary. The results, events and circumstances reflected in the forward- looking statements may not be achieved or occur, and actual results, events or circumstances could differ materially from those described in the forward-looking statements.

This presentation discusses our current and potential future product candidates that are under clinical investigation and which have not yet been approved for marketing by the U.S. Food and Drug Administration. No representation is made as to the safety or effectiveness of these current or potential future product candidates for the use for which such product candidates are being studied.

The forward-looking statements made in this presentation and the accompanying oral commentary relate only to events as of the date on which the statements are made, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted an exhaustive

inquiry into, or review of, all potentially available relevant information. We undertake no obligation to update any forward-looking statements made in this presentation and the accompanying oral commentary to reflect events or circumstances after the date of this presentation and the accompanying oral commentary or to reflect new information or the occurrence of unanticipated events, except as required by law. We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures or investments. We qualify all of our forward-looking statements by these cautionary statements.

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Company Highlights

Discovering and Developing Novel Antibody-based Cancer Immunotherapeutics

Differentiated

Discovery

Approach

Large

Opportunities

Lead Candidate:

ATRC-101

Pipeline

Expansion

• First-moveradvantages in accessing a potentially large and underexploited target space via interrogation of the human active anti-tumor immune response
• Delivers novel antibodies binding to targets otherwise unlikely discoverable by traditional approaches
• Scalable and industrialized platform
• Approach leads to antibodies that bind to "public" tumor targets
• Potential treatments for large patient populations across multiple tumor types
• Monoclonal antibody with a novel mechanism of action and target
• Demonstrated potent single-agentanti-tumor activity in multiple preclinical solid tumor models
• Dosed First Patient in Phase 1b trial in early 2020, initial summary data expected in 1H2021
• Combination studies with checkpoint inhibitor and chemotherapy planned for 2021
• Growing hit library of >2,000 human antibodies that bind to non-autologous tumor tissue preferentially
• Collaborating with Xencor to develop T cell-engaging antibodies
• Potential for additional product candidates in oncology with distinct mechanisms of action
• Collaborating with IGM Biosciences and BeiGene to develop antibody targeting SARS-CoV-2

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The Atreca Discovery Platform

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Our Novel Approach Inverts the Discovery Paradigm

The HUMAN IMMUNE SYSTEM tells us what is important

Selection &

Screening

"Responder" with anti-	Interrogation of the active B cell	Identification of novel	Currently >2,000 "hit" antibodies against
tumor immune response	response at the single-cell level	antibody-target pairs	non-autologous "public" targets

Leads

Fv Region

Hit Antibodies

Weaponization

Fc Region

Activating Fc	Fc + binding domain	Fc + small molecule
	(e.g., T cell engager)	(e.g., ADC)

ADC, antibody-drug conjugate.

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