Sensei Biotherapeutics : Company Presentation November 2023

Conditionally Active Antibodies for Immuno-oncology

NOVEMBER 2023 | Nasdaq: SNSE

Disclaimer

This presentation has been prepared by Sensei Biotherapeutics, Inc. (the "Company," "we," "us") and is made for informational purposes only. The information set forth herein does not purport to be complete or to contain all of the information you may desire. Statements contained herein are made as of the date of this presentation unless stated otherwise, and neither the delivery of this presentation at any time, nor any sale of securities, shall under any circumstances create an implication that the information contained herein is correct as of any time after such date or that information will be updated or revised to reflect information that subsequently becomes available or changes occurring after the date hereof.

This presentation contains estimates and other statistical data made by independent parties and by us relating to market shares and other data about our industry. This presentation also contains "forward-looking" statements as that term is defined in the Private Securities Litigation Reform Act of 1995 that are based on our management's beliefs and assumptions and on information currently available to management. These forward-looking statements include, without limitation, expectations regarding the development and potential therapeutic benefits of our product candidates; the expected safety profile and pharmacokinetic profile of our product candidates, including SNS-101; the expected timing of clinical data from our Phase 1/2 clinical trial of SNS-101; the availability of data from our preclinical studies; the timing of discovery and selection of product candidates; and our belief that our existing cash and cash equivalents will be sufficient to fund our operations at least into the second half of 2025 and reach midway into Phase 2 clinical studies of SNS-101.

When used in this presentation, the words and phrases "designed to," "may," "believes," "intends," "seeks," "anticipates," "plans," "estimates," "expects," "should," "assumes," "continues," "could," "will," "future" and the negative of these or similar terms and phrases are intended to identify forward-looking statements. Forward-looking statements involve known and unknown risks, uncertainties and other 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. Risks and uncertainties that may cause actual results to differ materially include uncertainties inherent in the development of therapeutic product candidates, such as preclinical discovery and development, conduct of clinical trials and related regulatory requirements, including the risk of delay or cessation of any clinical trials of Sensei's product candidates, our reliance on third parties over which we may not always have full control, risks regarding the accuracy of our estimates of expenses, capital requirements and needs for additional financing, and other risk and uncertainties that are described in our Quarterly Report on Form 10-Q filed with the SEC on or about August 3, 2023 and our other Periodic Reports filed with the SEC. Forward-looking statements represent our management's beliefs and assumptions only as of the date of this presentation and include all matters that are not historical facts. Our actual future results may be materially different from what we expect. Except as required by law, we assume no obligation to update these forward-looking statements publicly, or to update the reasons actual results could differ materially from those anticipated in the forward-looking statements, even if new information becomes available in the future.

Certain information contained in this presentation relates to, or is based on, studies, publications, surveys and other data obtained from third-party sources and the Company's own internal estimates and research. While the Company believes these third-party sources 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, all of the market data included in this presentation involves a number of assumptions and limitations, and there can be no guarantee as to the accuracy or reliability of such assumptions. Finally, while we believe our own internal research is reliable, such research has not been verified by any independent source.

Engineered Selectivity to Extend the Clinical Reach of Immuno-oncology Agents

LEAD PROGRAM

SNS-101, a conditionally active antibody targeting VISTA

Initial Phase 1 data demonstrate well tolerated safety profile & potentially best-in- class pharmacokinetics (PK)

TMAb PLATFORM

Conditionally active antibodies designed to widen therapeutic window and enable druggability of promising oncology targets

EXPECTED MILESTONES

Initial PK & safety combination data in Q1 2024

Topline monotherapy data in Q2 2024

Topline combination data in 2024

FINANCIALS

Ended Q2 2023: $78.8M*

Cash runway into 2H 2025

Cash currently sufficient to reach midway into

Phase 2 clinical studies for SNS-101

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*Consists of cash, cash equivalents and marketable securities

Lack of Tumor Targeting is a Major Obstacle to IO Innovation

Industry Problem

Conventional antibodies target immune checkpoints that are highly expressed in normal tissues, resulting in:

Dose-limiting toxicities due to on-target/off-tumor action

Pharmacological sink effect requires higher and more frequent dosing

Suboptimal activity due to poor PK and dose-limiting toxicities

Sensei's Solution

Conditionally active antibodies are selectively targeted to the tumor microenvironment, potentially providing:

Little or no toxicity due to selective on-target/on-tumor action

Lower and less frequent doses by avoiding normal tissue binding

Powerful activity selectively focused on the tumor microenvironment

Only one new checkpoint inhibitor has been approved since the original CTLA-4 and PD-1/PD-L1 group

IpilimumabPembrolizumab

(anti-CTLA-4)(anti-PD-1)

2011

2014

Relatlimab

(anti-LAG-3)

2022

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TMAb Antibodies are Designed to Bind Selectively in the Tumor

Microenvironment

Lack of peripheral target engagement can improve safety and pharmacokinetic parameters while focusing action to the tumor microenvironment

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Innovative Pipeline of IO Drugs with Broad Commercial Potential

*Sensei has entered into a clinical supply agreement with Regeneron supporting the planned evaluation of SNS-101 in combination with Regeneron's anti-PD-1 therapy Libtayo® (cemiplimab) in a Phase 1/2 clinical trial in solid tumors.

*Sensei has entered into a Cooperative Research and Development Agreement (CRADA) with the National Cancer Institute. The goal of this collaborative effort is to further elucidate the role of VISTA in immune checkpoint resistance and expand the potential of SNS-101 as a combination therapy beyond anti-PD-1.

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SNS-101

VISTA is a Potent T cell Checkpoint Extensively Expressed on Myeloid Cells1

VISTA is a B7 family member that suppresses T cell function and is expressed extensively by myeloid cells

SNS-101 targets immunosuppressive function mediated by PSGL-1 and other receptors

VISTA has inherent pH sensitivity: its extracellular domain is uniquely rich in histidines2

SNS-101 has monovalent affinity of 0.218 nM at pH 6.0, with no observed binding at neutral pH

Myeloid lineage cell or

tumor cell (less common)

T-cell proliferation & activation

1. Lines et al. Cancer research vol. 74,7 (2014)	8
2. Johnston et al., Nature 2019

Historical Challenges Targeting VISTA-Positive Myeloid Cells Resulted in Early

Clinical Trial Termination

Dose-limiting toxicity

Grade 3 CRS-associated encephalopathy

• JNJ-61610588(CI-8993) was the first anti-VISTA antibody to be studied in clinical trials in 2016 (NCT02671955) 1
• Transient Cytokine Release Syndrome (CRS) observed in several patients at
  0.15 mg/kg
• Transient Grade 3 CRS-associated encephalopathy observed at 0.3 mg/kg, after which Janssen halted the study

Challenging PK profile

Non-linear PK, short t1/2

JNJ-61610588 Human Plasma Concentration

1 Curis, Inc., Corporate Presentation, Feb 2022

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SNS-101 is a Differentiated, pH-Sensitive Antibody Designed to Overcome the

Unique Challenges of VISTA

Differentiated Design and Mechanism

Rapidly Enrolling Phase 1/2 Clinical Trial

IgG1, Fc-active antibody designed to selectively block VISTA in the low-pH tumor microenvironment

Multi-center U.S. study as single agent and in combination with PD-1 inhibitor Libtayo®

	Potential Best-in-Class Safety and PK	No observed CRS or dose-limiting toxicity and no
	Profile Supported by Initial Clinical Data	evidence of target-mediated drug disposition*
	Achieving "Firsts" for the VISTA Field	First VISTA-blocking antibody administered at a dose
	anticipated to be therapeutically relevant without eliciting
		dose-limiting toxicity
	Approaching Near-Term Clinical	Anticipate initial combination PK/safety data in Q1 2024
	with topline monotherapy data in Q2 2024 and topline
	Milestones
	combination data in 2024

*As of safety cut-off date of October 3, 2023

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