UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): June 11, 2021

Sensei Biotherapeutics, Inc.

(Exact Name of Registrant as Specified in its Charter)

Registrant’s telephone number, including area code: (240) 243-8000

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Securities Exchange Act of 1934:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company   ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.   ☐

On June 11, 2021, Sensei Biotherapeutics, Inc. (the “Company”) notified Anupama Hoey that her employment as Chief Business Officer of the Company would terminate, effective as of June 18, 2021. In accordance with her employment agreement, previously filed as Exhibit 10.15 to the Company’s Registration Statement on Form S-1 (File No. 333-252138), contingent upon Ms. Hoey’s execution of a separation agreement, including a release of claims and compliance with certain restrictive covenants, Ms. Hoey will be entitled to severance benefits specified therein.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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