Atara Biotherapeutics : Goldman Sachs 45th Annual Global Healthcare Conference

UNLEASHING THE PROMISE OF CELL THERAPY FOR CANCER AND AUTOIMMUNE DISEASES

JUNE 12, 2024

Nasdaq: ATRA

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Forward-Looking Statements

This presentation and the accompanying oral presentation contain forward-looking statements made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. All statements other than statements of historical facts contained in this presentation, including statements regarding our future results of operations and financial position, future transactions, business strategy, commercial partners, product, product candidates, correspondence and discussions with regulatory authorities, regulatory submissions, regulatory approvals, the initiation, timing, progress and results of preclinical studies and clinical trials and our research and development programs, ability to sell, manufacture or otherwise commercialize our product and product candidates, research and development costs, timing and likelihood of success, plans and objectives of management for future operations, any milestone and/or royalty payments, our ability to obtain and maintain intellectual property protection for our product and product candidates, and the sufficiency of Atara's cash, cash equivalents, short-term investments to fund its planned operations are forward-looking statements of Atara Biotherapeutics, Inc. ("Atara" or the "Company"). These statements 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. In some cases you can identify these statements by forward-looking words such as "believe," "may," "will," "estimate," "continue," "anticipate," "intend," "could," "would," "project," "predict," "plan," "expect" or the negative or plural of these words or similar expressions. These forward-looking statements are subject to risks and uncertainties, including those discussed in Atara's filings with the Securities and Exchange Commission (SEC), including in the "Risk Factors" and "Management's Discussion and Analysis of Financial Condition and Results of Operations" sections of the Company's most recently filed periodic reports on Form 10-K and Form 10-Q and subsequent filings and in the documents incorporated by reference therein. These risks and uncertainties include, without limitation, risks and uncertainties associated with the costly and time- consuming pharmaceutical product development process and the uncertainty of clinical success; the COVID-19 pandemic, and the wars in Ukraine and the Middle East, which may significantly impact (i) our business, research, clinical development plans and operations, including our operations in Southern California, Denver and at our clinical trial sites, as well as the business or operations of our third- party manufacturer, contract research organizations or other third parties with whom we conduct business, (ii) our ability to access capital, and (iii) the value of our common stock; the impact of future and pending legislation and regulations; the use of our information technology and communication systems and cybersecurity attacks; the sufficiency of our cash resources and need for additional capital, and other factors that may cause our or our industry's actual results, levels of activity, performance or achievements to be materially different from those anticipated by the forward-looking

statements. Because forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified and some of which are beyond our control, you should not rely on these forward-looking statements as predictions of future events. The events and circumstances reflected in our forward-looking statements may not be achieved or occur and actual results could differ materially from those projected in the 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.

Certain information contained in this presentation and statements made orally during this presentation relate to or are based on studies, publications, surveys and other data obtained from third-party sources and Atara's own internal estimates and research. While Atara believes these third-party studies, publications, surveys and other data to be reliable as of the date of this presentation, it has not independently verified, and makes no representation as to the adequacy, fairness, accuracy or completeness of, any information obtained from third-party sources. In addition, no independent source has evaluated the reasonableness or accuracy of Atara's internal estimates or research and no reliance should be made on any information or statements made in this presentation relating to or based on such internal estimates and research.

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Differentiated Allogeneic T-Cell Immunotherapy Pipeline

Program

Indication

Target

Preclinical

Phase 1

Phase 2

Phase 3

Registration

Next Milestone

ATA3219

(Oncology)

ATA3219

(Autoimmune)

ATA3431

Tab-cel® or EbvalloTM (tabelecleucel)

ATA188

Non-Hodgkin's Lymphoma (NHL)	CD19						Q4 2024: Initial NHL Ph 1
					clinical data expected
Lupus Nephritis (LN)							H1 2025: Initial LN Ph 1
	CD19						clinical data expected
Systemic Lupus Erythematosus
					H2 2025: Initial SLE Ph 1
(SLE) without lymphodepletion
						clinical data expected
B-cell malignancies	CD19/CD20						IND targeted for H2 2025
Autoimmune disease
RR EBV+ PTLD following HCT	EBV		ALLELE	Study		EU Approved	Q2 2024: BLA submitted
and SOT*
Multi-Cohort(Label-Expansion):	EBV	EBVision Study				Ongoing enrollment
EBV+ cancers(1)
Progressive MS	EBV(2)						Evaluating strategic
	EMBOLD Study				options following
							completion of the study

Excluding EbvalloTM in EU, these investigational agents are not approved by any regulatory agencies and efficacy and safety have not been established

EBV+ PTLD: Epstein-Barr Virus Associated Post-Transplant Lymphoproliferative Disease; RR: rituximab relapsed/refractory; HCT: allogeneic hematopoietic cell transplant; SOT: solid organ transplant;

NHL: non-Hodgkin's lymphoma

Atara has entered into an agreement with Pierre Fabre to commercialize tab-cel® for EBV+ cancers worldwide

*Indication pursued as monotherapy for treatment of adult and pediatric patients two years of age and older with Epstein-Barr virus positive post-transplant lymphoproliferative disease (EBV+ PTLD) who have received at least one prior therapy. For solid organ transplant patients, prior therapy includes chemotherapy unless chemotherapy is inappropriate

Other programs: EBV vaccine and other hematological malignancies and solid tumor AlloCAR T programs

1. Phase 2 multi-cohort initiated in Q3 2020, with possible indications including EBV+ PTLD with CNS involvement, front-linetreatment in EBV+ PTLD including front line with CNS involvement, EBV+ PID/AID LPD, and other potential EBV-associated diseases

(2) Targeted antigen recognition technology; Phase 2 Randomized Controlled Trial

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Atara Is Leveraging T-Cell Biology to Develop Differentiated, Off-the-Shelf CAR T Programs

Atara Overview

• Unique allogeneic cell therapy platform leveraging EBV T-cell biology and next gen CAR T construct
• First company to obtain regulatory approval for an allogeneic T-cell immunotherapy with tabelecleucel (tab-cel® or EbvalloTM) EMA approval
• U.S. tab-cel BLA submitted in Q2 2024
• Pierre Fabre global tab-cel partnership: $640M potential consideration + significant royalties
• Cash runway into 2027 enables key pipeline readouts

Atara's Allogeneic CAR T Programs

Hematological Malignancies

Hematological Malignancies

ATA3219	ATA3431
CD19 CAR:	CD19/20 CAR:
Initial NHL Ph1 Data Expected	IND Targeted for H2
Q4 2024	2025

B-cell Driven Autoimmune Diseases

ATA3219

Initial LN Ph1 Data Expected H1 2025

Initial SLE Without LD Data Expected H2 2025

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Atara Is the Most Advanced Allogeneic Cell Therapy Company

Differentiated

Platform

Supportive

Clinical Data

Based on natural biology of EBV T cells

First and only approved allogeneic T-cell therapy with EbvalloTM

First allogeneic T-cell therapy BLA submission to FDA

Robust allogeneic T-cell experience with favorable safety profile in 600+ patients

Pioneered the use of allogeneic T-cell therapy with no lymphodepletion Third party clinical data reinforce attributes of Atara's CAR T platform

Operating	Proven EBV T-cell scaled up manufacturing process, efficient supply and distribution
Experience	network
	Over a decade of real-world experience across clinical, regulatory, manufacturing and
	supply
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Innovating Next-Gen CAR T Leveraging the Only Allogeneic T-cell Platform With an Approved Product

Allogeneic EBV T-Cell (EBVALLOTM)

Next-gen Allogeneic CAR T

Healthy

Donor Cells

EBV TCR

Chimeric Antigen Receptor

CAR

EBV TCR

Manufacturing

	Viral Vector
EBV T Cell	EBV CAR T Cell

• No gene editing of the TCR or MHC
• Minimal HLA matching (only 2 of 10 alleles)
• No lymphodepletion
• Favorable safety profile in 600+ patients with outpatient experience
• Robust manufacturing with biologic-like COGM

• Retain features of EBV T cells
• Does not require complex gene edits
• Leverages novel CD3ζ signaling domain (1XX)
• CAR-targetedactivity - can be modified to express single or dual targets

EBV = Epstein-Barr Virus; HLA = Human Leukocyte Antigen; CAR = Chimeric Antigen Receptor; TCR = T-cell Receptor; MHC = major histocompatibility complex

Tab-cell® (EbvalloTM) is approved in the European Union

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Atara's Allogeneic CAR T Platform Designed to Improve Patient Journey and Expand Access Versus Autologous Cell Therapies

Current Autologous CAR T Patient Journey

Apheresis

• Time consuming, extra logistics, requirement to stop treatment

Lymphodepletion

• Chemotherapy side effects
• Infection risk
• Safety risks in women of child-bearing age
• Genotoxic
• Added cost and complexity

CAR T Treatment

• 2-5weeks-long process to engineer and deliver autologous CAR T cells
• 30+ minute infusion

Post Infusion Monitoring

• 1-2weeks inpatient monitoring at hospital
• Cytokine release syndrome
• Neurotoxicity

Atara T Cells Offer Unique Potential Advantages in the Allogeneic Field (as evaluated in tab-cel & ATA188 clinical development studies)

Off-the-Shelf	No Lymphodepletion	5-10 Minute Infusion	1-2 Hours Monitoring
(No Patient Apheresis)

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Atara's CAR T Platform Closely Retains Autologous T-Cell Biology While Offering the Benefits of an Allogeneic Approach

Atara's Allogeneic CAR T Platform

Atara's CAR Platform

	EBV
	Specificity		Partial HLA
Retained	2	3
Matching
TCR	1

5
Less
Differentiated	4	1XX Costimulatory

PhenotypeDomain

CAR

1. Tanchot et al, Science 1997. 2. Myers et al, Trends Immunology 2017. 3. Polic et al, PNAS 2001. 4. Curran ASTCT 2020, ASH 2023; 5. Atara clinical experience; Prockop et al, JCI 2020. 6. Feucht et al, Nature Medicine, 2018

Key Features

1• Retained TCR: Unedited TCR serves as a key T cell survival signal1,2,3 contributing to functional persistence3

2• EBV Specificity: Low GvHD risk due to TCR recognition of viral antigens

3• Partial HLA Matching: Enables allogeneic approach that avoids host versus graft rejection4,5

4• 1XX Costimulatory Domain: Novel CD3ζ signaling domain6 optimizes potency, expansion and mitigates T-cell exhaustion

5• Less Differentiated Phenotype: αβ T cell manufactured with less differentiated phenotype contributes to potency and durability of clinical response

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αβ = alpha beta; Graft-versus-host disease (GVHD)

Atara's CAR T Platform Offers Unique Advantages Versus Other Allogeneic Approaches in the Field

αβ T cell

Gene edited

αβ TCR

Gene Editing to Knockout TCR and Other Edits

NK cell

Lacks TCR

γδ T cell

γδ TCR

Invariant TCR

	Atara	αβ T Cell
	EBV CAR	NK Cell	γδ T Cell
	T Cell	Gene edited
	(αβ unedited)
Safety	600+ patients	Lower CRS/ICANS risk than auto CAR T
safely treated3
	(EBV Platform)
Expansion	Robust	Moderate	Minimal	Minimal-to-
(CAR preclinical)	Moderate

• Aggressive lymphodepletion often required
• Gene editing and/or stealth approaches to limit alloreactivity impact expansion and persistence1
• Minimal expansion drives need for high cell dose
• Non-physiologicstimulation leads to T cell exhaustion2

Persistence	Several	~3-4 weeks	Suboptimal	Suboptimal
Months3
	(EBV Platform)
Durability	Robust	Moderate	Suboptimal	Suboptimal
(CAR preclinical)

1. Wang et al, Nature CMI 2021. 2. Zhang et al, Nature Comm 2023. 3. Clinical experience with allo EBV T-cells
including tab-cel and ATA188; Prockop et al, JCI, 2020; Bhat et al, ISNI 2023	9
αβ = alpha beta; NK = natural killer; γδ = gamma delta

Novel 1XX Costimulatory Domain Proof of Concept in Both Oncology and Lupus Models

1XX Rationale and Design

1XX Pre-Clinical Proof Points

Challenge: Signaling via CD28 and CD3ζ domains overstimulate T cells, leading to exhaustion; 4-1BB slower to activate1

Solution: Modified CD3ζ costimulatory domain (1XX), including two inactivating ITAM mutations, drives physiologic levels of signaling2

• Avoids activation-induced cell death
• Reduces cytokine release syndrome
• Improves persistence

Oncology:

Rapid tumor eradication with 1XX in tumor model2

Lupus:

Functional benefit using two mutated ITAMs in lupus model3,4

CAR T	CAR T
CD28	1XX

Tumor burden (average radiance)

Days after T cell injection

Control	CAR T
PBS	Two mutated ITAMs

Reduced immune complex deposition in the

kidney (C3 / IgG) with CAR T 3

1. Salter et al, Sci Signal, 2018. 2. Feucht et al, Nature Medicine, 2018. 3. Jin et al, Cell Mol Immunol, 2021. 4. Kansal et al, Sci Transl Med, 2019. ITAM = Immunoreceptor Tyrosine Activation Motif; PBS = Phosphate Buffered

Saline; LD = lymphodepletion

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