Atreca : Corporate Presentation

Atreca, Inc. Corporate Overview

April 2023

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," "predict," "present," "aim," "goal" or the negative of these words or other similar terms or expressions, although not all forward-looking statements contain these words.

This presentation contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. 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 additional data from ATRC- 101, a decision regarding our Phase 2 trial of ATRC-101 in late 2023, plans to nominate multiple oncology clinical candidates in 2023, and planned IND filings for additional oncology programs in late 2024 and early 2025; statements regarding the potential of and continued enrollment in ATRC-101; plans for indication selection and Phase 2 development decisions for ATRC-101 by late 2023; our plans to nominate a candidate for APN-497444 and APN-346958 in 2023; our plans to target IND forAPN- 497444 in late 2024; our plans to target IND for APN-346958 in early 2025; our plans for collaborating with Xencor, including our plans for up to two joint programs with Xencor; our ongoing evaluation, optimization, and expansion of our pipeline of oncology programs and infectious disease programs, and the productivity of such programs, including ATRC-101,APN-497444,APN-346958,APN-122597,ATRC-501/MAM01 and our other programs advancing in various formats; statements regarding Gates MRI's preparation for an IND filing for ATRC-501/MAM01 in 2023; 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 deliver more leads against novel targets more efficiently; greater productivity due to continuing investments; our ability to enable partnership and an internal pipeline due to the scalable nature of our platform; 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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Investment Highlights

Proprietary Platform

• Accesses novel targets via interrogation of active human immune responses
• Delivers novel antibodies binding targets unlikely to be discoverable by traditional approaches
• Uniquely positioned to generate ADC candidates against novel tumor-selective targets
• Investments driving greater productivity

Robust Pipeline

ATRC-101 - Durable anti-tumor activity demonstrated in Phase 1b mono/combo trial

APN-497444 - Targets a novel and tumor-specific glycan - Advancing as an ADC

APN-346958 - Recognizes a cell surface RNA-binding protein target

• Advancing as T cell engager in partnership with Xencor ATRC-501 - Anti-malaria antibody licensed to Gates MRI for prophylaxis

Upcoming Milestones

• Go / no-go decision for Phase 2 development of ATRC-101 in late 2023
• Multiple oncology clinical candidates expected to be nominated in 2023
• IND filings for additional oncology programs targeted in late 2024 and early 2025

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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 anti-tumor	The active B cell response at the	Synthesized novel antibodies	Hit Antibodies binding
immune response	single-celllevel		non-autologous tumor tissue

Clinical Candidates

against novel targets

Hit Antibodies

Weaponization

Target Identification

Optimization

Naked optimized	Bi-specific	Antibody drug
antibodies	antibodies	conjugates

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Atreca's Platform Leverages B Cell Biology for Discovery

B cell responses driven by antigens in infectious disease, autoimmunity, and cancer*

Follicular	Processed	Follicular
dendritic cell	helper T cell
	tumor antigen
		Plasmablast
		B cells
Naïve or
memory
B cell

Evolving

B cells

Germinal center

Atreca proprietary antibody repertoire generation and analyses

Clonal family

Before treatment course

Antibody repertoire

After treatment course

•

•

Plasmablasts express antibodies targeting antigens being processed by an active immune response

Clonal families of plasmablast antibodies are generated in germinal centers during an adaptive immune response

Foundational patents granted in multiple jurisdictions that feature composition of matter claims directed to libraries of native pairs of

antibody heavy and light chain sequences generated from plasmablasts using nucleotide barcoding at the single-cell level

*DeFalco J, et al. Clin Immunol. 2018;187:37-45.

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