[SCHEDULE 13G] Sensei Biotherapeutics, Inc. Passive Investment Disclosure (>5%)

Sensei Biotherapeutics files a Schedule 13G reporting passive ownership.

Rhea-AI Filing Summary

Sensei Biotherapeutics files a Schedule 13G reporting passive ownership. Caligan Partners LP and David Johnson report beneficial ownership of 126,002 shares of common stock, representing 9.40% of the class based on 1,340,281 shares outstanding as of March 23, 2026. The filing notes the Reporting Persons also hold Series B Non‑Voting Convertible Preferred Stock convertible into 361,010 shares of common stock under the Certificate of Designation.

The statement is a joint filing by Caligan Partners (as investment manager) and Mr. Johnson (Managing Partner). Voting and dispositive power are reported as shared for 126,002 shares. The filing is presented as passive ownership under Schedule 13G.

Insights

Institutional Ownership Specialist

Caligan reports a single passive stake of 126,002 shares (9.40%) with convertible preferred exposure.

Caligan Partners LP and David Johnson jointly report beneficial ownership of 126,002 shares, equal to 9.40% of the outstanding common stock based on March 23, 2026. The filing classifies this position as passive under Schedule 13G and discloses shared voting and dispositive power for those shares.

The filing also discloses Series B Preferred convertible into 361,010 shares when conversion conditions in the Certificate of Designation are met. Timing and conversion mechanics are governed by that certificate; cash‑flow treatment and conversion timing are not specified in the provided excerpt.

Corporate Governance Analyst

Shared voting/dispositive power implies control is exercised jointly rather than solely by Mr. Johnson.

The cover data shows 0 sole voting and dispositive power and 126,002 shared voting and dispositive power. This indicates the stake is managed collectively by the reported entities rather than by a single individual.

Future disclosures (for example, a conversion of the Preferred Stock) would change the ownership profile; the Certificate of Designation sets conversion conditions and timing, which are not detailed here.

Key Figures

Shares beneficially owned: 126,002 shares Percent of class: 9.40% Shares outstanding: 1,340,281 shares +1 more

4 metrics

Shares beneficially owned 126,002 shares reported beneficial ownership by Caligan/Johnson

Percent of class 9.40% based on 1,340,281 shares outstanding as of March 23, 2026

Shares outstanding 1,340,281 shares outstanding as of <date>March 23, 2026</date> (source: Form 10‑K)

Convertible preferred conversion 361,010 shares shares issuable upon conversion of Series B Non‑Voting Convertible Preferred Stock

Key Terms

Schedule 13G, Series B Non‑Voting Convertible Preferred Stock, Shared dispositive power

3 terms

Schedule 13G regulatory

"Joint filing reporting passive beneficial ownership position"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

Series B Non‑Voting Convertible Preferred Stock financial

"Preferred Stock convertible into 361,010 shares of Common Stock"

Shared dispositive power regulatory

"Shared Dispositive Power 126,002.00 reported on cover page"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What stake does Caligan Partners report in Sensei Biotherapeutics (SNSE)?

Caligan Partners and David Johnson report beneficial ownership of 126,002 shares, representing 9.40% of the class based on March 23, 2026. The filing is a joint Schedule 13G reporting passive ownership.

Does the filing show voting or dispositive power for the reported shares?

The filing shows 0 sole voting and dispositive power and 126,002 shared voting and dispositive power. This indicates the position is managed jointly by the Reporting Persons.

Are there convertible securities disclosed in the Schedule 13G for SNSE?

Yes. The Reporting Persons hold Series B Non‑Voting Convertible Preferred Stock convertible into 361,010 shares of common stock under the Certificate of Designation. Conversion timing and mechanics are governed by that certificate.

What outstanding share count does the filing use to calculate percent ownership?

The percent ownership is calculated using 1,340,281 shares outstanding as of March 23, 2026, as reported in the company’s Form 10‑K for the fiscal year ended December 31, 2025.

Who filed the Schedule 13G for Sensei Biotherapeutics (SNSE)?

The statement was filed jointly by Caligan Partners LP (as investment manager to related funds and accounts) and David Johnson, Managing Partner of Caligan, on behalf of the referenced funds and accounts.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 05/15/2026 - 08:32 AM EDT Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Sensei Biotherapeutics, Inc.

(Name of Issuer)

Common Stock, par value $0.0001 per share

(Title of Class of Securities)

81728A207

(CUSIP Number)

03/31/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 81728A207

1

Names of Reporting Persons

Caligan Partners LP

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 126,002.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 126,002.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

126,002.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

9.40 %

12

Type of Reporting Person (See Instructions)

IA, PN

Comment for Type of Reporting Person: In addition to the shares of the Issuer's common stock (the "Common Stock") provided for in rows (6), (8) and (9), the Reporting Persons hold Series B Non-Voting Convertible Preferred Stock (the "Preferred Stock") that, when convertible, may be converted into 361,010 shares of Common Stock. The Preferred Stock will be convertible at such time as, and otherwise in accordance with the terms, provided in the Certificate of Designation governing such Preferred Stock.

SCHEDULE 13G

CUSIP Number(s): 81728A207

1

Names of Reporting Persons

David Johnson

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 126,002.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 126,002.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

126,002.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

9.40 %

12

Type of Reporting Person (See Instructions)

HC, IN

Comment for Type of Reporting Person: In addition to the shares of the Issuer's common stock (the "Common Stock") provided for in rows (6), (8) and (9), the Reporting Persons hold Series B Non-Voting Convertible Preferred Stock (the "Preferred Stock") that, when convertible, may be converted into 361,010 shares of Common Stock. The Preferred Stock will be convertible at such time as, and otherwise in accordance with the terms, provided in the Certificate of Designation governing such Preferred Stock.

SCHEDULE 13G

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 Number(s): 81728A207
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);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(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);
(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:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
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:
	(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.
	(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.
	(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.
	(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.
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	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.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Caligan Partners LP

Signature:	/s/ David Johnson
Name/Title:	David Johnson, Managing Partner
Date:	05/15/2026

David Johnson

Signature:	/s/ David Johnson
Name/Title:	David Johnson, Individually
Date:	05/15/2026

Exhibit Information

Exhibit 99.1: Joint Filing Agreement