Sutro Biopharma to cut one-third of staff in overhaul

Sutro Biopharma, Inc. reported a new organizational restructuring to focus on three preclinical antibody-drug conjugate (ADC) programs and its research and development collaborations.

Rhea-AI Filing Summary

Sutro Biopharma, Inc. reported a new organizational restructuring to focus on three preclinical antibody-drug conjugate (ADC) programs and its research and development collaborations. The company expects this restructuring, together with anticipated near-term milestone payments, to extend its cash runway into at least mid-2027. As part of the plan, Sutro intends to reduce its workforce by approximately one-third. The company estimates total cash payments and costs related to the program prioritization and workforce reduction will be approximately $4.1 million to $4.3 million, with a significant majority expected to be paid in the fourth quarter of 2025. Following prioritization of its ADC programs, Sutro expects initial clinical data from STRO-004, its next-generation Tissue Factor-targeting exatecan ADC, to be available in 2026.

Positive

• None.

Negative

• Sutro Biopharma plans to cut its workforce by approximately one-third and expects to incur about $4.1 million to $4.3 million in restructuring-related cash costs, signaling a materially disruptive cost-cutting effort.

Insights

Biotech equity analyst

Sutro cuts about one-third of staff to extend cash runway into mid-2027.

Sutro Biopharma is undertaking a significant restructuring to concentrate resources on three preclinical ADC programs and partnered R&D. The company links this move, along with expected milestone payments, to extending its cash runway into at least mid-2027, which may ease near-term funding pressures while narrowing its development focus.

The plan includes reducing the workforce by approximately one-third and incurring estimated restructuring-related cash payments and costs of about $4.1 million to $4.3 million, with most of this expected in the fourth quarter of 2025. This indicates a meaningful reset of the operating base, trading immediate charges and organizational disruption for lower ongoing expenses.

The company also highlights an expectation of initial clinical data from STRO-004, its next-generation Tissue Factor-targeting exatecan ADC, in 2026, tying the extended runway to a specific development milestone. Future disclosures in periodic reports may clarify whether cost savings and milestone receipts are tracking to support that timeline and how the reduced workforce affects execution.

8-K Event Classification

2 items: 2.05, 9.01

2 items

Item 2.05 Costs Associated with Exit or Disposal Activities Financial

The company committed to an exit plan involving layoffs, facility closures, or restructuring charges.

Item 9.01 Financial Statements and Exhibits Exhibits

Financial statements, pro forma financial information, or exhibit attachments filed with this report.

FAQ

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

What restructuring did Sutro Biopharma (STRO) announce?

Sutro Biopharma announced a further organizational restructuring to prioritize advancement of its three preclinical ADC programs and its research and development collaborations, along with a significant workforce reduction.

How much will Sutro Biopharma spend on its restructuring?

Sutro Biopharma estimates total cash payments and costs related to program prioritization and workforce reductions at approximately $4.1 million to $4.3 million, with a significant majority expected to be paid in the fourth quarter of 2025.

How will the restructuring affect Sutro Biopharmas cash runway?

The company expects that cost savings from the restructuring, together with certain anticipated near-term milestone payments, will extend its cash runway into at least mid-2027.

What workforce changes are included in Sutro Biopharmas plan?

As part of the corporate restructuring, Sutro Biopharma plans to reduce its workforce by approximately one-third.

When does Sutro Biopharma expect clinical data from STRO-004?

Following prioritization of its ADC programs, Sutro Biopharma expects initial clinical data to be available in 2026 from STRO-004, its next-generation Tissue Factor-targeting exatecan ADC.

What exhibit was filed with Sutro Biopharmas 8-K on restructuring?

The company filed Exhibit 99.1, a press release announcing the operational restructuring intended to extend its cash runway through key milestones.

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

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Accepted by SEC EDGAR 09/29/2025 - 05:15 PM Learn about SEC filing dates

0001382101false00013821012025-09-292025-09-29

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): September 29, 2025

SUTRO BIOPHARMA, INC.

(Exact name of registrant as specified in its charter)

Delaware	001-38662	47-0926186
(State or other jurisdiction of Incorporation)	(Commission File Number)	(IRS Employer Identification No.)

111 Oyster Point Blvd,

South San Francisco, California, 94080

(Address of principal executive offices) (Zip Code)

(650) 881-6500

(Registrant’s telephone number, including area code)

Not Applicable

(Former name or former address, if changed since last report)

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 Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common Stock, $0.001 par value		STRO		The Nasdaq Global Market

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. ☐

Item 2.05 Costs Associated with Exit or Disposal Activities

On September 29, 2025, Sutro Biopharma, Inc. (the “Company”) announced further organizational restructuring to prioritize the advancement of its three preclinical ADC programs and its research and development collaborations. The restructuring is expected to extend the Company’s runway into at least mid-2027 resulting from cost savings associated with the restructuring and certain expected near-term milestone payments. Following further prioritization of the ADC programs, the Company expects initial clinical data to be available from STRO-004, its next-generation Tissue Factor-targeting exatecan ADC, in 2026. As part of the corporate restructuring, the Company plans to reduce its workforce by approximately one-third.

The total cash payments and costs related to the further prioritization of the ADC programs and reducing the workforce are estimated to be approximately $4.1million to $4.3 million, with a significant majority of these amounts expected to be paid in the fourth quarter of 2025. These estimates are subject to a number of assumptions and actual results may differ. The Company may also incur additional costs not currently contemplated due to events that may occur as a result of, or that are associated with, the corporate restructuring.

A copy of the press release announcing the corporate restructuring is attached as Exhibit 99.1 to this Current Report on Form 8-K.

Item 9.01. Financial Statements and Exhibits

(d) Exhibits.

Exhibit Number		Description
99.1		Press Release issued by Sutro Biopharma, Inc. announcing operational restructuring intended to extend cash runway through key milestones.
104		Cover Page Interactive Data File (embedded within the Inline XBRL document)

Forward-Looking Statements

This Current Report on Form 8-K contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, and other federal securities laws. Any statements contained herein that do not describe historical facts, including, but not limited to, statements regarding anticipated preclinical and clinical development activities; timing of announcements of IND submissions, clinical results, trial initiation, and other regulatory filings; outcome of discussions with regulatory authorities; potential benefits of the Company’s product candidates and platform; potential business development and partnering transactions; potential market opportunities for the Company’s product candidates; the timing and receipt of anticipated future milestone payments; the Company’s expected cash runway; and the expected costs and cost reductions associated with the restructuring, are forward-looking statements that involve risks and uncertainties that could cause actual results to differ materially from those discussed in such forward-looking statements. Such risks and uncertainties include, among others, the risks identified in the Company’s filings with the SEC, including its Annual Report on Form 10-K for the fiscal year ended December 31, 2024, filed with the SEC on March 13, 2025. Any of these risks and uncertainties could materially and adversely affect the Company’s results of operations, which would, in turn, have a significant and adverse impact on the Company’s stock price. The Company cautions you not to place undue reliance on any forward-looking statements, which speak only as of the date they are made. The Company undertakes no obligation to update publicly any forward-looking statements to reflect new information, events or circumstances after the date they were made or to reflect the occurrence of unanticipated events.

SIGNATURE

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

	Sutro Biopharma, Inc.
Date: September 29, 2025	By:	/s/ David Pauling
		David Pauling
		General Counsel and Chief Administrative Officer