Failure to Satisfy Listing Rule (Form 8-K)

Item 3.01. Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing.

On October 2, 2025, Xilio Therapeutics, Inc. (the "Company") received approval from the Listing Qualifications Department (the "Staff") of the Nasdaq Stock Market LLC ("Nasdaq") to transfer the listing of the Company's common stock from The Nasdaq Global Select Market to The Nasdaq Capital Market. Effective as of the opening of business on October 6, 2025, the Company's common stock will be transferred to The Nasdaq Capital Market and will continue to trade under the symbol "XLO." The Nasdaq Capital Market is a continuous trading market that operates in substantially the same manner as The Nasdaq Global Select Market. All companies listed on The Nasdaq Capital Market must meet certain financial requirements and adhere to Nasdaq's corporate governance standards.

As previously disclosed on April 8, 2025, the Company received a letter from the Staff of Nasdaq notifying the Company of its failure to maintain the $1.00 minimum bid price required for continued listing on The Nasdaq Global Select Market under Nasdaq Listing Rule 5450(a)(1) (the "Minimum Bid Price Requirement"). In connection with the transfer to The Nasdaq Capital Market, Nasdaq granted the Company an additional 180 calendar day period, or until March 30, 2026, to regain compliance with the Minimum Bid Price Requirement.

During the additional 180 calendar day grace period, the Company's common stock must close at $1.00 or more for at least 10 consecutive business days to regain compliance with the Minimum Bid Price Requirement, unless the Staff exercises its discretion to extend this 10-dayperiod pursuant to Nasdaq Listing Rule 5810(c)(3)(H).

The Company is continuing to evaluate available options to regain compliance with the Minimum Bid Requirement.