# EDGAR Filing Document

**Accession Number:** 0001829802
**File Stem:** 0001193125-26-234882
**Filing Date:** 2026-5
**Character Count:** 18425
**Document Hash:** e0e5cfe3cf1d4fca7ad163b9ec6a5940
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-26-234882.hdr.sgml**: 20260521

**ACCESSION NUMBER**: 0001193125-26-234882

**CONFORMED SUBMISSION TYPE**: 8-K

**PUBLIC DOCUMENT COUNT**: 13

**CONFORMED PERIOD OF REPORT**: 20260521

**ITEM INFORMATION**: Other Events

**ITEM INFORMATION**: Financial Statements and Exhibits

**FILED AS OF DATE**: 20260521

**DATE AS OF CHANGE**: 20260521

**FILER**: 

**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

**FILING VALUES:**
- **FORM TYPE:** 8-K
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-39980
- **FILM NUMBER:** 261009852

**BUSINESS ADDRESS:**
- **STREET 1:** 1405 RESEARCH BLVD, SUITE 125
- **CITY:** ROCKVILLE
- **STATE:** MD
- **ZIP:** 20850
- **BUSINESS PHONE:** (240) 243-8000

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

?xml version='1.0' encoding='ASCII'? 8-K

### 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): May 21, 2026

## Sensei Biotherapeutics, Inc.

#### (Exact Name of Registrant as Specified in its Charter)

---

| | | |
|:---|:---|:---|
| **Delaware** | **001-39980** | **83-1863385** |
| **(State or Other Jurisdiction**<br>**of Incorporation)** | **(Commission**<br>**File Number)** | **(IRS Employer**<br>**Identification No.)** |
| **1405 Research Blvd, Suite 125** | **1405 Research Blvd, Suite 125** |  |
| **Rockville, MD** | **Rockville, MD** | **20850** |
| **(Address of Principal Executive Offices)** | **(Address of Principal Executive Offices)** | **(Zip Code)** |
| **451 D Street, Suite 710** | **451 D Street, Suite 710** |  |
| **Boston, MA** | **Boston, MA** | **02210** |
| **(Former Address of Principal Executive Offices)** | **(Former Address of Principal Executive Offices)** | **(Zip Code)** |

---

#### 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:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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

---

| | | |
|:---|:---|:---|
| **Title of each class** | **Trading**<br>**symbol** | **Name of each exchange**<br>**on which registered** |
| Common Stock | SNSE | The Nasdaq Stock Market LLC |

---

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. ☐

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| | |
|:---|:---|
| **Item 8.01.** | **Other Events.** |

---

As previously announced, Sensei Biotherapeutics, Inc. (the "Company") will hold its 2026 annual meeting of stockholders ("Annual Meeting") of the Company on June 10, 2026, at 11:00 a.m. Eastern Daylight Time, unless postponed or adjourned to a later date. At the Annual Meeting, stockholders will be asked to approve, among other things, the issuance of shares of common stock, par value $0.0001 per share ("common stock"), of the Company upon conversion of Series B Non-Voting Convertible Preferred Stock, par value $0.0001 per shares ("Series B Preferred Stock"), which will (a) represent more than 20% of the shares of common stock outstanding and (b) result in the change of control of the Company pursuant to Nasdaq Listing Rules 5635(a) and 5635(b), respectively. In connection with the Annual Meeting, the Company is filing unaudited pro forma condensed consolidated financial information of the Company for the quarter ended March 31, 2026, presenting the historical consolidated financial position of the Company for the quarter ended March 31, 2026, adjusted to give effect to the conversion of the shares of Series B Preferred Stock into shares of common stock.

The unaudited pro forma condensed financial information, including the notes thereto, should be read in conjunction with the financial statements of the Company and the Company's management's discussion and analysis of financial condition and results of operations included in the Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 2026, filed with the Securities and Exchange Commission ("SEC") on May 15, 2026. Such unaudited pro forma condensed financial information is presented for illustrative purposes only and may not be an indication of the Company's financial condition following the conversion of the Series B Preferred Stock for several reasons. The unaudited pro forma condensed financial information has been derived from the historical unaudited financial statements of the Company for the quarter ended March 31, 2026, and certain adjustments and assumptions have been made regarding the Company after giving effect to the conversion of the Series B Preferred Stock. The information upon which these adjustments and assumptions have been made is preliminary, and these kinds of adjustments and assumptions are difficult to make with accuracy. Moreover, the unaudited pro forma condensed financial information does not reflect all costs that are expected to be incurred by the Company in connection with the conversion of the Series B Preferred Stock. As a result, the actual financial condition of the Company following the conversion of the Series B Preferred Stock may not be consistent with, or evident from, the unaudited pro forma condensed financial information. The assumptions used in preparing the unaudited pro forma condensed financial information may not prove to be accurate, and other factors may affect the Company's financial condition following the conversion of the Series B Preferred Stock. For more information, please see Exhibit 99.1 attached hereto and incorporated herein by reference.

For more information regarding the Annual Meeting, please refer to the Company's Definitive Proxy Statement, filed with the SEC on April 27, 2026.

---

| | |
|:---|:---|
| **Item 9.01** | **Financial Statements and Exhibits.** |

---

(d) Exhibits

---

| | |
|:---|:---|
| **Exhibit**<br>**Number** | **Exhibit Description** |
| 99.1 | [Unaudited Pro Forma Condensed Financial Information of Sensei Biotherapeutics, Inc. for the quarter ended March 31, 2026.](d162035dex991.htm) |
| 104 | The cover page from this Current Report on Form 8-K, formatted in Inline XBRL |

---

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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.

---

| | |
|:---|:---|
|  | **Sensei Biotherapeutics, Inc.** |
| Date: May 21, 2026 | /s/ Christopher W. Gerry |
|  | Christopher W. Gerry |
|  | President and General Counsel |

---

## Exhibit 99.1

**Exhibit 99.1** 

**SENSEI BIOTHERAPEUTICS, INC.** 

**UNAUDITED PRO FORMA CONDENSED FINANCIAL INFORMATION** 

On February 17, 2026, Sensei Biotherapeutics, Inc. (the "Company") acquired Faeth Holdings Therapeutics, Inc. ("Faeth HoldCo") and its wholly owned subsidiary Faeth Therapeutics, LLC ("Faeth Subsidiary" and, together with Faeth HoldCo, "Faeth Therapeutics" or "Faeth") pursuant to an Agreement and Plan of Merger (the "Merger Agreement"), dated as of February 17, 2026, by and among the Company, its merger subsidiaries, Faeth HoldCo and Faeth Subsidiary (such transaction, the "Acquisition").

Under the terms of the Merger Agreement, the Company issued to the stockholders of Faeth an aggregate of 10,497.0980 shares of Series B Non-Voting Convertible Preferred Stock, par value $0.0001 per share (the "Series B Preferred Stock"), representing 10,497,098 shares of common stock of the Company, par value $0.0001 per share ("Common Stock"), on an as-converted-to-common basis and without giving effect to any beneficial ownership limitations.

Concurrently with the acquisition of Faeth Therapeutics, on February 17, 2026, the Company entered into a Securities Purchase Agreement (the "Purchase Agreement") with new and returning investors to raise $200.0 million of gross proceeds in which investors were issued an aggregate of 14,440.395 shares of Series B Preferred Stock, or 14,440,395 on an as-converted-to-common basis and without giving effect to any beneficial ownership limitations, (the "PIPE Securities") at a price of $13,850 per share, or $13.85 per share on an as-converted-to-common basis, (collectively, the "Financing"). The Financing closed on February 20, 2026.

Subject to the receipt of stockholder approval of the Parent Stockholder Matters (as defined in the Merger Agreement), each share of Series B Preferred Stock will automatically convert into 1,000 shares of Common Stock, subject to certain beneficial ownership limitations established by each holder.

The following unaudited pro forma condensed financial information presents the historical consolidated financial position and results of operations of the Company, adjusted to give effect to the conversion of the Series B Preferred Stock into common stock (the "Conversion") that will automatically occur three business days subsequent to the expected affirmative vote for stockholder approval of the Parent Stockholder Matters. The vote for stockholder approval of the Parent Stockholder Matters is scheduled to occur on June 10, 2026. The unaudited pro forma condensed balance sheet gives pro forma effect to the Conversion as if it had been consummated on March 31, 2026. The unaudited pro forma condensed statement of operations for the three months ended March 31, 2026 gives effect to the Conversion as if it had occurred on January 1, 2026.

The unaudited pro forma condensed financial information is based on the assumptions and adjustments described in the accompanying notes. Accordingly, the pro forma adjustments are preliminary, subject to further revision as additional information becomes available and additional analyses are performed and have been made solely for the purpose of providing unaudited pro forma condensed financial information.

The unaudited pro forma condensed financial information, including the notes thereto, should be read in conjunction with the financial statements of the Company and the Company's management's discussion and analysis of financial condition and results of operations included in the Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 2026, filed with the Securities and Exchange Commission ("SEC") on May 15, 2026.

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**UNAUDITED PRO FORMA CONDENSED BALANCE SHEET** 

**AS OF MARCH 31, 2026** 

**(in thousands)** 

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | | **Transaction Accounting Adjustments** | **Transaction Accounting Adjustments** | |
|  |<br>**March 31,<br>2026** | **Conversion** | **Note**<br>**References** |<br>**Pro Forma As<br>Adjusted** |
|  **Assets** |  |  |  |  |
|  Current assets: |  |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Cash and cash equivalents | $152325 | $— |  | $152325 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Marketable securities | 50468 |  |  | 50468 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Prepaid expenses | 974 |  |  | 974 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Other current assets | 465 |  |  | 465 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total current assets | 204232 |  |  | 204232 |
|  Right-of-use assets - operating leases, net | 913 |  |  | 913 |
|  Right-of-use assets - financing leases, net |  |  |  |  |
|  Property and equipment, net | 69 |  |  | 69 |
|  Other non-current assets | 167 |  |  | 167 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total assets | $205381 | $— |  | $205381 |
|  **Liabilities, redeemable convertible preferred stock and stockholders' (deficit) equity** |  |  |  |  |
|  Current liabilities: |  |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Accounts payable and accrued expenses | $8982 | $— |  | $8982 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Compensation and employee benefits liabilities | 4169 |  |  | 4169 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Operating lease liabilities, current | 1021 |  |  | 1021 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Financing lease liabilities, current | 18 |  |  | 18 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total current liabilities | 14190 |  |  | 14190 |
|  Operating lease liabilities, non-current |  |  |  |  |
|  Other non-current liabilities | 1 |  |  | 1 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total liabilities | 14191 |  |  | 14191 |
|  Commitments and contingencies |  |  |  |  |
|  Series B redeemable convertible preferred stock | 328476 | (321856) | **A** | 6620 |
|  Stockholders' (deficit) equity: |  |  |  |  |
|  Common stock |  | 2 | **A** | 2 |
|  Additional paid-in capital | 316111 | 321854 | **A** | 637965 |
|  Accumulated deficit | (453373) |  |  | (453373) |
|  Accumulated other comprehensive (loss) income | (24) |  |  | (24) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total stockholders' (deficit) equity | (137286) | 321856 |  | 184570 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total liabilities, redeemable convertible preferred stock, and stockholders' (deficit) equity | $205381 | $— |  | $205381 |

---

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**UNAUDITED PRO FORMA CONDENSED STATEMENT OF OPERATIONS** 

**FOR THE THREE MONTHS ENDED MARCH 31, 2026** 

**(in thousands, except share and per share amounts)** 

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **For the Three Months Ended March 31, 2026** | **For the Three Months Ended March 31, 2026** | **For the Three Months Ended March 31, 2026** | **For the Three Months Ended March 31, 2026** |
|  | | **Transaction<br>Accounting<br>Adjustments** | | |
|  |<br>**Actual** | **Conversion** |<br>**Note<br>References** |<br>**Pro Forma As<br>Adjusted** |
|  Operating expenses: |  |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Research and development | $17957 | $— |  | $17957 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; General and administrative | 19713 |  |  | 19713 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Acquired in-process research and development | 132957 |  |  | 132957 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total operating expenses | 170627 |  |  | 170627 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Loss from operations | (170627) |  |  | (170627) |
|  Other income (expense), net: |  |  |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Interest income, net | 392 |  |  | 392 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Other (expense) income, net | (1) |  |  | (1) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Net loss | $(170236) | $— |  | $(170236) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Net loss per common share, basic and diluted | $(131.45) |  |  | $(6.62) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Weighted-average shares outstanding, basic and diluted | 1295052 | 24434920 | **A** | 25729972 |
|  **Comprehensive loss:** |  |  |  |  |
|  Net loss | $(170236) | $— |  | $(170236) |
|  Other comprehensive items: |  |  |  |  |
|  Unrealized (loss) gain on marketable securities | (25) |  |  | (25) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total other comprehensive (loss) income | (25) |  |  | (25) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total comprehensive loss | $(170261) | $— |  | $(170261) |

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**SENSEI BIOTHERAPEUTICS, INC.** 

**NOTES TO UNAUDITED PRO FORMA CONDENSED BALANCE SHEET** 

**Note 1. Transaction accounting adjustments for the Conversion** 

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;**A.** Reflects the expected conversion of 24,434.92 shares of Series B Preferred Stock into 24,434,920 shares
of common stock that will automatically occur three business days subsequent to the expected affirmative vote for the Conversion. The aforementioned vote is scheduled to occur on June 10, 2026. The transaction accounting adjustments reflecting
the Conversion do not reflect the conversion of shares of Series B Preferred Stock that are not expected to convert due to certain beneficial ownership limitations established by each holder based solely on the shares of Series B Preferred Stock
beneficially owned by the holders thereof. The number of shares of Series B Preferred Stock that ultimately convert into shares of common stock may be more or less than our expectations.