Sensei Biotherapeutics Reports Full Year 2022 Financial Results and Recent Business Highlights - Investigational New Drug (IND) application submitted for lead candidate SNS-101, a conditionally active VISTA-blocking anti

Sensei Biotherapeutics Reports Full Year 2022 Financial Results and Recent Business Highlights

- Investigational New Drug (IND) application submitted for lead candidate SNS-101, a conditionally

active VISTA-blocking antibody -

- New collaborations with Regeneron, the National Cancer Institute and Washington University in

St. Louis will support development of SNS-101 -

- Company anticipates advancing a second

TMAb program to IND-enabling studies following successful candidate selection -

- Strong balance sheet with cash runway into the second half of 2025 -

BOSTON, MA March 28, 2023 Sensei Biotherapeutics, Inc. (Nasdaq: SNSE), an immuno-oncology company focused on

the discovery and development of next-generation therapeutics for cancer patients, today reported financial results for full-year 2022 and provided recent business updates.

Over the last year the team has worked with urgency to test the biological rationale for our lead product candidate,

SNS-101, as a potentially transformative therapeutic option for patients with solid tumors, said John Celebi, President and Chief Executive Officer of Sensei Biotherapeutics. We remain

committed to the belief that VISTA has tremendous potential as an immune checkpoint target and continue to take steps to prioritize the advancement of SNS-101. We are pleased that, despite industry headwinds,

our work has culminated in the recent submission of an IND to begin a Phase 1/2 clinical trial with the support of our partners. We re also excited about the overall progress of programs generated through our TMAb platform, including SNS-102 and SNS-103, and look forward to advancing other conditionally active antibodies that

ignite and deploy the immune system s full potential to fight cancer.

Added Mr. Celebi, Following the streamlining and realignment

of the Company s resources to support its key indications and programs, including reductions in operating expenses, employee-related costs and occupancy costs, our programs are supported by a healthy cash position that provides runway into the

second half of 2025. We are confident in our strategy and expect to continue achieving critical near-term milestones across our pipeline.

Highlights and Milestones

Sensei continues to advance SNS-101, a conditionally active antibody

targeting the immune checkpoint VISTA (V-domain Ig suppressor of T cell activation), which is implicated in resistance to

PD-1/PD-L1 therapy and whose expression correlates with poor survival across numerous cancers. Recent updates for SNS-101

Collaborations Supporting SNS-101

Sensei recently announced three collaborations key to the development of SNS-101 and the planned Phase 1/2 clinical trial in solid tumors:

Additional TMAb Platform Updates

Through its proprietary

Tumor Microenvironment Activated biologics (TMAb) platform, Sensei is also advancing several pH-sensitive antibodies, including SNS-102 targeting VSIG4 (V-Set and Immunoglobulin Domain Containing 4) and SNS-103 targeting ENTPDase1 (ecto-nucleoside triphosphate diphosphohydrolase-1, also

Year End 2022 Financial Results

Cash Position: Cash, cash equivalents and marketable securities were $107.1 million as of December 31, 2022, as compared to

$147.6 million as of December 31, 2021. Sensei expects its current cash balance to fund operations into the second half of 2025.

Development (R&D) Expenses: R&D expenses were $30.4 million for the year ended December 31, 2022, compared to $21.7 million for the year ended December 31, 2021. The increase in R&D expenses was primarily

attributable to increased manufacturing and early development activities for the Company s lead program SNS-101, partially offset by a decrease in clinical trial expenses.

General and Administrative (G&A) Expenses: G&A expenses were $19.8 million for the year ended December 31, 2022, compared to

$15.8 million for the year ended December 31, 2021. The increase in G&A expense was primarily attributable to external professional services and personnel costs.

Net Loss: Net loss was $48.6 million for the year ended December 31, 2022, compared to $36.8 million for the year ended

Condensed Statements of Operations

(Unaudited, in thousands except share and per share data)

Selected Condensed Balance Sheet Data

(Unaudited, in thousands)

About Sensei Biotherapeutics

Sensei Biotherapeutics (Nasdaq: SNSE) is an immuno-oncology company focused on the discovery and development of next-generation therapeutics for cancer

patients. Through its TMAb (Tumor Microenvironment Activated biologics) platform, Sensei develops conditionally active therapeutics designed to disable immunosuppressive signals or activate

immunostimulatory signals selectively in the tumor microenvironment to unleash T cells against tumors. Sensei s lead investigational candidate is SNS-101, a conditionally active antibody designed to block

the V-domain Ig suppressor of T cell activation (VISTA) checkpoint selectively within the low pH tumor microenvironment, where VISTA acts as a suppressor of T cells by binding the receptor PSGL-1. The company is also developing SNS-102, a conditional binding monoclonal antibody targeting V-Set and Immunoglobulin Domain

Containing 4 (VSIG-4), as well as SNS-103, also a conditionally active monoclonal antibody targeting ecto-nucleoside triphosphate

diphosphohydrolase-1 (ENTPDase1), also known as CD39. For more information, please visit www.senseibio.com, and follow the company on Twitter @SenseiBio and LinkedIn.

Cautionary Note Regarding Forward-Looking Statements

Any statements contained in this press release that do not describe historical facts may constitute forward-looking statements as that term is defined in the

Private Securities Litigation Reform Act of 1995. These statements may be identified by words and phrases such as believe , designed to, expect , may , plan , potential ,

will , and similar expressions, and are based on Sensei s current beliefs and expectations. These forward-looking statements include expectations regarding the development and potential therapeutic benefits of Sensei s product

candidates, the expected safety profile of Sensei s product candidates, the availability of data from Sensei s preclinical studies, the timing of selection of product candidates, and its belief that its existing cash and cash equivalents

will be sufficient to fund its operations at least into the first quarter of 2025. These statements involve risks and uncertainties that could cause actual results to differ materially from those reflected in such statements. Risks and uncertainties

that may cause actual results to differ materially include uncertainties inherent in the development of therapeutic product candidates, such as the risk that any one or more of Sensei s product candidates will not be successfully developed or

commercialized; the risk of delay or cessation of any planned clinical trials of Sensei s product candidates; the risk that prior results, such as signals of safety, activity or durability of effect, observed from preclinical trials, will not

be replicated or will not continue in ongoing or future studies or clinical trials involving Sensei s product candidates; the risk that Sensei s product candidates or procedures in connection with the administration thereof will not have

the safety or efficacy profile that we anticipate; risks associated with Sensei s dependence on third-party suppliers and manufacturers, including sole source suppliers, 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 risks and uncertainties that are described in Sensei s Quarterly Report on

Form 10-Q filed with the U.S. Securities and Exchange Commission (SEC) on or about November 8, 2022 and Sensei s other Periodic Reports filed with the SEC. Any forward-looking

statements speak only as of the date of this press release and are based on information available to Sensei as of the date of this release, and Sensei assumes no obligation to, and does not intend to, update any forward-looking statements, whether

as a result of new information, future events or otherwise.

Senior Director, Investor Relations

Sensei Biotherapeutics

Ten Bridge Communications