[8-K] Xilio Therapeutics, Inc. Reports Material Event

Rhea-AI Filing Summary

Xilio Therapeutics (XLO) furnished an Item 7.01 update, providing two press releases with new and updated clinical and preclinical data. The company highlighted Phase 2 results related to high plasma tumor mutational burden for vilastobart in combination with atezolizumab in microsatellite stable metastatic colorectal cancer.

Additional disclosures included portfolio updates: preclinical findings from its masked T cell engager platform and programs, updated Phase 1 data for efarindodekin alfa, and Phase 2 circulating tumor DNA data for vilastobart. These data were presented in poster sessions at the Society for Immunotherapy of Cancer 40th Annual Meeting. The information, including Exhibits 99.1 and 99.2, was furnished—not filed—under Regulation FD and is not subject to Section 18 liabilities nor incorporated by reference unless specifically stated.

Insights

Biotech disclosure analyst

Informational Reg FD update; data furnished, not filed.

Xilio Therapeutics released clinical and preclinical data snapshots via press releases, including Phase 2 vilastobart plus atezolizumab in MSS metastatic colorectal cancer and updates across its masked T cell engager platform. The data were presented at the SITC 40th Annual Meeting.

The company furnished this information under Item 7.01, which signals a Regulation FD communication. Furnished materials are expressly not subject to Section 18 liabilities and are not incorporated into other filings unless specifically referenced.

No financial impacts, guidance, or transactional terms are disclosed in the excerpt. Any implications for the programs hinge on the detailed results contained in Exhibits 99.1 and 99.2.

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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): November 7, 2025

Xilio Therapeutics, Inc.

(Exact Name of Registrant as Specified in Charter)

Delaware		001-40925		85-1623397
(State or Other Jurisdiction of Incorporation)		(Commission File Number)		(IRS Employer Identification No.)

828 Winter Street, Suite 300 Waltham, Massachusetts		02451
(Address of Principal Executive Offices)		(Zip Code)

Registrant’s telephone number, including area code: (857) 524-2466

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 (see General Instruction A.2. below):

☐ 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, par value $0.0001 per share		XLO		Nasdaq Capital 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 7.01. Other Events.

On November 7, 2025, Xilio Therapeutics, Inc. (the “Company”) issued a press release announcing new data related to high plasma tumor mutational burden from its ongoing Phase 2 clinical trial evaluating vilastobart in combination with atezolizumab in patients with microsatellite stable metastatic colorectal cancer, a copy of which is furnished as Exhibit 99.1 to this Current Report on Form 8-K.

Also on November 7, 2025, the Company issued a press release announcing updated data across its portfolio, including preclinical data for the Company's masked T cell engager platform and programs, as well as updated Phase 1 data for efarindodekin alfa, and Phase 2 data related to circulating tumor DNA for vilastobart, a copy of which is furnished as Exhibit 99.2 to this Current Report on Form 8-K.

These data are presented in poster presentations at the Society for Immunotherapy of Cancer (SITC) 40thAnnual Meeting. The information in Item 7.01 of this Current Report on Form 8-K, including Exhibit 99.1 and Exhibit 99.2, is being furnished and shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Exchange Act or the Securities Act of 1933, as amended, except as expressly set forth by specific reference in such filing.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits.

Exhibit Number		Description
99.1		Press release issued by Xilio Therapeutics, Inc. on November 7, 2025
99.2		Press release issued by Xilio Therapeutics, Inc. on November 7, 2025
104		Cover Page Interactive Data File (formatted as Inline XBRL with applicable taxonomy extension information contained in Exhibits 101)

SIGNATURES

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.

	XILIO THERAPEUTICS, INC.
Date: November 7, 2025	By:	/s/ Caroline Hensley
		Caroline Hensley
		Chief Legal Officer

FAQ

What did Xilio Therapeutics (XLO) announce in this 8-K?

The company furnished two press releases with new and updated data, including Phase 2 vilastobart plus atezolizumab results and broader portfolio updates.

Which programs were included in XLO’s data update?

Vilastobart (Phase 2, including ctDNA), efarindodekin alfa (Phase 1), and preclinical data for the masked T cell engager platform.

Where were the data presented?

In poster presentations at the Society for Immunotherapy of Cancer (SITC) 40th Annual Meeting.

Are the press releases considered filed or furnished?

They are furnished under Item 7.01 and are not deemed filed, nor subject to Section 18, unless specifically incorporated by reference.

What exhibits were included with the 8-K?

Exhibit 99.1 and Exhibit 99.2 contain the press releases; Exhibit 104 is the cover page Inline XBRL data file.

What exchange and symbol does Xilio trade under?

Common stock trades on the Nasdaq Capital Market under the symbol XLO.