Atreca : Corporate Presentation January 2023

Delivering the Potential of Immunotherapy

Corporate Overview

J a n u a r y 2 0 2 3

NON-CONFIDENTIAL

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 within the meaning of the Private Securities Litigation Reform Act of 1995. In some cases, you can identify forward-looking statements because they contain words such as "potential," "believe," "target," will," "demonstrate," "expect," ''anticipate,'' ''continue,'' "may," "plan," or "present," 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: our ability to identify and develop potentially valuable therapeutic antibodies and product candidates through our discovery platform and collaborations with third-parties, including potential treatments for large

patient populations across multiple tumor types; the implementation of our business model and our strategy and future plans for our business, technologies, and current or potential future product candidates; the initiation, timing, progress and results of our research and development programs, preclinical studies, and clinical trials, including our Phase 1b trial of ATRC-101 and plans for our Phase 2/pivotal trial(s) of ATRC-101 in 2024; statements regarding the development of ATRC-101,ATRC-501, and our preclinical, clinical, and regulatory plans, and the timing thereof; the availability and timing of data from the monotherapy cohorts in our Phase 1b trial of ATRC-101, including our plans to report data in the first quarter of 2023, and from combination cohorts evaluating ATRC-101 with pembrolizumab, including our plans to report data in the first quarter of 2023, and from combination cohorts with chemotherapy and other data readouts; our ability to obtain sufficient clinical enrollment; our plans to continue enrolling participants based on target expression in archival or newly obtained biopsies; our ability to weaponize or otherwise optimize our lead antibodies; our plans for utilizing weaponization technology from Xencor and Zymeworks; our plans to utilize the ZymeLink™ platform; the safety and potential efficacy of our current or potential future product candidates, including ATRC-101 and ATRC-501; our ongoing evaluation, optimization and expansion of our pipeline of oncology programs, including APN497444, APN-346958,APN-122597, and our other lead-stage oncology programs advancing in various formats; our plans regarding the evaluation of clinical data and timing thereof; our ability to commence commercialization of ATRC-501 and any other product candidate; the potential market for malaria prophylactic therapeutics and any other of our therapeutic antibodies and product candidates; our ability to continue to develop new clinical candidates for IND applications, including our ability to submit an IND filing for

ATRC-501 in 2023 and our ability to submit subsequent IND filings for our product candidates in oncology in 2024 and 2025; our ability to fund current operations, including our ability to fund our operations through 2023, and develop and commercialize our current or potential future product candidates; our ability to obtain intellectual property rights for our current and potential future product candidates; and our expectations regarding the achievement and timing of our anticipated milestones, including our research, development, clinical, regulatory and other corporate milestones. 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 filings with the Securities and Exchange Commission (SEC) and available on the SEC's website

at www.sec.gov, including in the "Risk Factors" and "Management's Discussion and Analysis of Financial Condition and Results of Operations" sections of our most recently filed Annual Report on Form 10- K and Quarterly Report on Form 10-Q, and may cause our actual results, performance or achievement to differ materially and adversely from those anticipated or implied by our forward-looking statements.

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. 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 plans, expectations, 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. 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. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures or investments. We qualify all our forward-looking statements by these cautionary 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.

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Company Highlights

Discovering and Developing Novel Antibody-based Cancer Immunotherapeutics

Differentiated

Discovery

Approach

Large

Opportunities

Lead Candidate:

ATRC-101

Pipeline Assets

• Scalable and industrialized platform 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
• 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
• Anti-tumoractivity associated with target expression in Phase 1b monotherapy/combo trial
• Enrolling patients based on target expression in monotherapy and pembrolizumab combination arms
• Multiple additional lead-stage oncology programs against novel targets and target epitopes
• Tumor-targetingantibodies active in various weaponization formats (ADC, T-cell engager, 4-1BB, etc.)
• ATRC-501:monoclonal antibody licensed to Gates Medical Research Institute for malaria prophylaxis

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Our Novel Approach Inverts the Discovery Paradigm

The HUMAN IMMUNE SYSTEM tells us what is important

Immune Repertoire	Selection in silico	Screening in vitro
Capture®

Patient with immune	The active B cell response at the	Synthesized novel antibodies	Hit Antibodies binding to
response	single-celllevel		relevant targets

Clinical Candidates

Hit Antibodies

Optimization via

Engineering

Naked optimized	Bi-specific	Antibody drug
antibodies	antibodies	conjugates
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Atreca's Pipeline

Candidate / LeadTarget

ONCOLOGY

ATRC-101	Novel RNP Complex
APN-497444	Glycan
(tumor-specific)
APN-346958	RNA-binding
protein
APN-122597	EphA2
(novel epitope)

Format / MOA	Lead	Candidate /	Phase 1	Phase 2
Preclinical

IgG Antibody w/ Driver

Antigen Engagement

ADC (Cytotoxic)

T Cell Engagement

(via CD3)

T Cell Engagement

(via CD3)

Weaponization Tech

INFECTIOUS DISEASE

P. falciparum

ATRC-501 /MAM01 Circumsporozoite IgG antibody

(Malaria)Protein

Partner

ADC, antibody-drug conjugate; EphA2, erythropoietin-producing hepatocellular receptor A2; IgG, immunoglobulin G; MOA, mechanism of action; RNA, ribonucleic acid; RNP, ribonucleoprotein.

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