Adage Capital Management, L.P., along with managing members Robert Atchinson and Phillip Gross, filed a Schedule 13G with the SEC on November 12, 2026, disclosing beneficial ownership of shares in Xilio Therapeutics, Inc. as of September 30, 2026.

Key Highlights

  • Beneficial ownership: Each reporting person beneficially owns 464,598 shares of Xilio Therapeutics common stock, par value $0.0001 per share.
  • Percent of class: The 464,598 shares represent 7.06% of outstanding common stock, calculated based on 6,580,153 shares outstanding as of August 10, 2026.
  • Shared voting and dispositive power: All 464,598 shares are held with shared voting power and shared dispositive power; sole voting and sole dispositive power are each reported as 0.
  • Triggering date: The event requiring this filing occurred on September 30, 2026.
  • Three reporting persons: Adage Capital Management, L.P. (investment adviser and limited partnership), Robert Atchinson, and Phillip Gross are each named as reporting persons.
  • Shares held through: Common stock is directly held by Adage Capital Partners, L.P., with Adage Capital Management, L.P. acting as investment manager, according to the filing.

Adage Capital Management Reports Ownership Position in Xilio Therapeutics as of September 30, 2026

According to the Schedule 13G filed November 12, 2026, Adage Capital Management, L.P. ("ACM"), a Delaware limited partnership based at 200 Clarendon Street, 52nd Floor, Boston, Massachusetts 02116, serves as the investment manager of Adage Capital Partners, L.P. ("ACP"), which directly holds the reported shares of Xilio Therapeutics, Inc. common stock. The filing identifies ACM's type as investment adviser and limited partnership ("IA, PN").

Robert Atchinson and Phillip Gross are each identified as reporting persons in their capacity as managing members of entities in the Adage Capital organizational structure, including Adage Capital Advisors, L.L.C. and Adage Capital Partners GP, L.L.C., the general partner of ACP, and Adage Capital Partners, L.L.C., the general partner of ACM. Both individuals are citizens of the United States and are classified as "HC, IN" (holding company and individual) under the filing's reporting person type designations.

The filing states that the percentage of class (7.06%) was calculated based on 6,580,153 shares of common stock outstanding as of August 10, 2026, as reported in Xilio Therapeutics' Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2026, filed with the SEC on August 12, 2026. The filing also states that it "should not be construed in and of itself as an admission by any Reporting Person as to beneficial ownership of the securities reported herein." The issuer's principal executive offices are located at 828 Winter Street, Suite 300, Waltham, Massachusetts 02451. The CUSIP number for the reported securities is 98422T209.

What Was Disclosed

Adage Capital Management, L.P., Robert Atchinson, and Phillip Gross filed a Schedule 13G disclosing aggregate beneficial ownership of 464,598 shares of Xilio Therapeutics, Inc. common stock, representing 7.06% of the class, with all voting and dispositive power held on a shared basis.