# EDGAR Filing Document

**Accession Number:** 0002137706
**File Stem:** 0002137706-26-000003
**Filing Date:** 2026-6
**Character Count:** 7588
**Document Hash:** 0f1b1e0835cf557594c69cc08d7dc0ce
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0002137706-26-000003.hdr.sgml**: 20260616

**ACCESSION NUMBER**: 0002137706-26-000003

**CONFORMED SUBMISSION TYPE**: 4

**PUBLIC DOCUMENT COUNT**: 1

**CONFORMED PERIOD OF REPORT**: 20260612

**FILED AS OF DATE**: 20260616

**DATE AS OF CHANGE**: 20260616

**REPORTING-OWNER**: 

**OWNER DATA:**
- **COMPANY CONFORMED NAME:** Hahn Stephen M.
- **CENTRAL INDEX KEY:** 0002137706

**ORGANIZATION NAME:**

**FILING VALUES:**
- **FORM TYPE:** 4
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-39980
- **FILM NUMBER:** 261094913

**MAIL ADDRESS:**
- **STREET 1:** C/O SENSEI BIOTHERAPEUTICS, INC.
- **STREET 2:** 1405 RESEARCH BLVD, SUITE 125
- **CITY:** ROCKVILLE
- **STATE:** MD
- **ZIP:** 20850
**ISSUER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Sensei Biotherapeutics, Inc.
- **CENTRAL INDEX KEY:** 0001829802
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**BUSINESS ADDRESS:**
- **STREET 1:** 701 TILLERY STREET #12 #1010
- **CITY:** AUSTIN
- **STATE:** TX
- **ZIP:** 78702
- **BUSINESS PHONE:** 512-200-2982

**MAIL ADDRESS:**
- **STREET 1:** 1405 RESEARCH BLVD, SUITE 125
- **CITY:** ROCKVILLE
- **STATE:** MD
- **ZIP:** 20850

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## FORM 4

### STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

[ ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

[ ] Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

---

| | | |
|:---|:---|:---|
| **1. Name and Address of Reporting Person**<sup>*</sup><br>Hahn Stephen M.<br><sub>(Last) (First) (Middle)</sub><br>C/O FAETH THERAPEUTICS, INC.<br>701 TILLERY STREET #12 #1010<br><sub>(Street)</sub><br>AUSTIN, TX 78702<br><sub>(City) (State) (Zip)</sub> | **3. Date of Earliest Transaction (Month/Day/Year)**<br>2026-06-12 | **5. Relationship of Reporting Person(s) to Issuer**<br>(Check all applicable)<br>[X] Director [ ] 10% Owner<br>[ ] Officer (give title below) [ ] Other (specify below)<br>_ _ |
| **2. Issuer Name and Ticker or Trading Symbol**<br>Sensei Biotherapeutics, Inc. [ FTH ] | **4. If Amendment, Date of Original Filed (Month/Day/Year)**<br>  | **6. Individual or Joint/Group Filing (Check Applicable Line)**<br>[X] Form filed by One Reporting Person<br>[ ] Form filed by More than One Reporting Person |

---

## Table I - Non-Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | 3. Transaction Code (V) | 3. Transaction Code (V) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | Code | V | Amount | (A) or (D) | Price | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| Common Stock | 2026-06-15 |  | C |  | 44763<sup>(1)</sup> | A | <sup>(2)(3)</sup> | 44763 | D |  |

---

## Table II - Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | 4. Transaction Code (V) | 4. Transaction Code (V) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 6. Date Exercisable and Expiration Date | 6. Date Exercisable and Expiration Date | 7. Title and Amount of Underlying Securities | 7. Title and Amount of Underlying Securities | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | Code | V | (A) | (D) | Date Exercisable | Expiration Date | Title | Amount or Number of Shares | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| Stock Option (right to buy) | $13 | 2026-06-12 |  | A<sup>(4)</sup> |  | 25000 |  | <sup>(4)</sup> | 2036-06-11 | Common Stock | 25000 | $0 | 25000 | D |  |
| Series B Preferred Stock<sup>(1)</sup> | <sup>(2)(3)</sup> | 2026-06-15 |  | C |  |  | 44.763 | <sup>(2)(3)</sup> | <sup>(2)(3)</sup> | Common Stock | 44763<sup>(1)</sup> | <sup>(2)(3)</sup> | 0 | D |  |

---

### Footnotes:

(1) Subject to certain conditions set forth in the Certificate of Designation of Preferences, Rights and Limitations of the Series B Preferred Stock, each share of Series B Preferred Stock is convertible into 1,000 shares of the Issuer's Common Stock and has no expiration date.

(2) Pursuant to February 17, 2026 Agreement and Plan of Merger (the "Merger Agreement"), by and among the Issuer, Sapphire First Merger Sub, Inc., a Delaware corporation and a wholly owned subsidiary of the Issuer ("First Merger Sub"), Sapphire Second Merger Sub,
LLC, a Delaware limited liability company and wholly owned subsidiary of the Issuer ("Second Merger Sub"), Faeth Holdings Therapeutics, Inc. ("HoldCo") and Faeth Therapeutics, LLC, a Delaware limited liability company and wholly owned subsidiary of HoldCo ("Faeth"), First Merger Sub merged with and into HoldCo, with HoldCo surviving the first merger as a wholly owned subsidiary of the Issuer, and immediately following the first merger, HoldCo merged with and into Second Merger Sub, with Second Merger Sub surviving the second merger as a wholly owned subsidiary of the Issuer (such mergers, the "Merger").

(3) Footnote continued: Upon the closing of the Merger, shares of outstanding common stock of HoldCo were converted into the right to receive shares of the Issuer's Series B Preferred Stock.

(4) The shares subject to the option vest and become exercisable in 36 equal monthly installments over a three year period such that the option is fully vested on the third anniversary of the date of grant, or June 12, 2029, subject to the Reporting Person's continuous service with the Issuer as of each such vesting date.

**Signature:** /s/ Josiah Craver, Attorney-in-Fact  
**Date:** 2026-06-16

### Remarks:

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.

**Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.**