| Item 1. | |
| (a) | Name of issuer:
Sensei Biotherapeutics, Inc. |
| (b) | Address of issuer's principal executive offices:
1405 Research Boulevard, Suite 125, Rockville, Maryland 20850. |
| Item 2. | |
| (a) | Name of person filing:
This statement is filed by:
(i) Caligan Partners LP, a Delaware limited partnership ("Caligan"), which serves indirectly as the investment manager to Caligan Partners Master Fund LP, a Cayman Islands limited partnership (the "Caligan Fund"), and managed accounts (the "Caligan Accounts"), with respect to the shares of common stock, par value $0.0001 per share ("Common Stock"), of Sensei Biotherapeutics, Inc., a Delaware corporation (the "Company"), held, and issuable upon exercise of warrants held, by the Caligan Fund and Caligan Accounts; and
(ii) David Johnson, the Managing Partner of Caligan and Managing Member of Caligan Partners GP LLC, the general partner of Caligan ("Mr. Johnson"), with respect to the shares of Common Stock held, and issuable upon exercise of warrants held, by the Caligan Fund and Caligan Accounts.
Each of the foregoing is referred to as a "Reporting Person" and collectively as the "Reporting Persons." |
| (b) | Address or principal business office or, if none, residence:
The principal business address of each of the Reporting Persons is 780 Third Avenue, 30th Floor, New York, NY 10017. |
| (c) | Citizenship:
Caligan is a Delaware limited partnership. Mr. Johnson is a United States citizen. |
| (d) | Title of class of securities:
Common Stock, par value $0.0001 per share |
| (e) | CUSIP No.:
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| Item 3. | If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a: |
| (a) |  Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
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| (b) | Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
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| (c) | Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
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| (d) | Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
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| (e) |  An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
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| (f) | An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
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| (g) | A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
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| (h) | A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
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| (i) | A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
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| (j) | A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:
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| (k) | Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
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| Item 4. | Ownership |
| (a) | Amount beneficially owned:
The information required by Item 4(a) is set forth in Row 9 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
The percentages set forth in this Schedule 13G are calculated based upon an aggregate of 1,340,281 shares of Common Stock outstanding as of March 23, 2026, as reported in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2025, filed with the Securities and Exchange Commission on March 30, 2026. |
| (b) | Percent of class:
9.40% |
| (c) | Number of shares as to which the person has:
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| | (i) Sole power to vote or to direct the vote:
The information required by Item 4(c)(i) is set forth in Row 5 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
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| | (ii) Shared power to vote or to direct the vote:
The information required by Item 4(c)(ii) is set forth in Row 6 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
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| | (iii) Sole power to dispose or to direct the disposition of:
The information required by Item 4(c)(iii) is set forth in Row 7 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
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| | (iv) Shared power to dispose or to direct the disposition of:
The information required by Item 4(c)(iv) is set forth in Row 8 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
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| Item 5. | Ownership of 5 Percent or Less of a Class. |
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Not Applicable
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| Item 6. | Ownership of more than 5 Percent on Behalf of Another Person. |
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If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required.
See Item 2(a). |
| Item 7. | Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person. |
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Not Applicable
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| Item 8. | Identification and Classification of Members of the Group. |
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Not Applicable
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| Item 9. | Notice of Dissolution of Group. |
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Not Applicable
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