Boundless Bio, Inc. filed a Form 425 communication on October 26, 2026, relating to its proposed merger with Serapha Bio, Inc. under an Agreement and Plan of Merger and Reorganization dated June 22, 2026, as amended August 28, 2026.

Key Highlights

  • Merger structure: Boulder Merger Sub Corp., a wholly owned subsidiary of Boundless Bio, will merge with and into Serapha Bio, with Serapha surviving as a wholly owned subsidiary of Boundless Bio.
  • Merger Agreement amendment: The original Agreement and Plan of Merger and Reorganization, dated June 22, 2026, was amended by Amendment No. 1 dated August 28, 2026.
  • Registration statement filed: Boundless Bio has filed a Form S-4 (File No. 333-299369) with the SEC that includes a proxy statement and prospectus, which had not yet been declared effective as of the filing date.
  • Key risk identified: The filing notes a lawsuit filed by Beam Therapeutics Inc. against Serapha, YolTech Therapeutics, and two individuals affiliated with YolTech Therapeutics, relating to SERP-01.
  • Lead asset: Serapha's pipeline centers on SERP-01, with a Phase 2/3 clinical trial initiation referenced as a forward-looking milestone for the treatment of alpha-1 antitrypsin deficiency (AATD).
  • Stockholder approvals required: Closing of the proposed merger is conditioned on approval from stockholders of both Boundless Bio and Serapha, among other conditions.

Boundless Bio and Serapha Bio Merger Terms and Disclosed Risks

According to the filing, Boundless Bio, Inc. (NASDAQ:BOLD) published a Form 425 communication on October 26, 2026, filed pursuant to Rule 425 under the Securities Act of 1933 and deemed filed pursuant to Rule 14a-12 under the Securities Exchange Act of 1934. The filing relates to a proposed merger in which Boulder Merger Sub Corp., a Delaware corporation and wholly owned subsidiary of Boundless Bio, would merge with and into Serapha Bio, Inc., a Delaware corporation, leaving Serapha as a wholly owned subsidiary of Boundless Bio upon completion.

The communication, published by Serapha on October 26, 2026, references forward-looking statements concerning SERP-01, Serapha's lead candidate targeting alpha-1 antitrypsin deficiency. These statements, the filing notes, are subject to the cautionary language of the Private Securities Litigation Reform Act of 1995 and encompass expectations about Phase 2/3 trial initiation, AAT level thresholds, reduction of toxic Z-AAT, and potential regulatory approvals. The filing cautions that the ongoing investigator-initiated trial is conducted by third parties outside Serapha's control, involves a limited number of patients, and "is not designed to support regulatory approval."

Among the risks disclosed, the filing identifies the lawsuit by Beam Therapeutics Inc. against Serapha, YolTech Therapeutics, and two individuals affiliated with YolTech, as well as Serapha's reliance on intellectual property licensed from YolTech Therapeutics. Additional disclosed risks include the possibility that anticipated ownership percentages of the combined company or the cash dividend to pre-merger Boundless Bio stockholders "may change based on adjustments at or prior to closing," and the need for substantial additional funding for the combined company. The S-4 registration statement had not been declared effective by the SEC as of the filing date.

What Was Disclosed

Boundless Bio filed a Form 425 communication disclosing details of its proposed merger with Serapha Bio, including the merger structure, the status of the Form S-4 registration statement, identified litigation risks, and forward-looking statements about SERP-01's clinical development in AATD.