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AI brief of an SEC Form 8-K · Boundless Bio, Inc. (BOLD)

Boundless Bio to merge with private Serapha Bio; holders to own about 3.7% combined

Mixed Impact 5 of 5 m&a Written later

Boundless Bio agreed on June 22, 2026 to an all-stock merger with privately held Serapha Bio, a clinical-stage company developing an in vivo base editing therapy for Alpha-1 Antitrypsin Deficiency. Boundless stockholders are expected to own about 3.69% of the combined company, and the company's CEO, Zachary Hornby, steps down effective July 1, 2026, which affects shareholders' stake and the company's management.

Key points

  • Merger agreement dated June 22, 2026; the combined company is expected to operate as Serapha Bio and trade as AATD, subject to Nasdaq approval
  • Pre-merger Boundless holders expected to own about 3.69% and Serapha holders about 96.31% of the combined company, fully diluted
  • Boundless may pay a pre-closing cash dividend; the press release says about $44 to $48 million, and the press release states the BBI-940 program will not be advanced
  • CEO Zachary Hornby steps down July 1, 2026; Chief Legal Officer Jessica Oien to serve as principal executive officer; closing expected in Q4 2026

The filing

CompanyBoundless Bio, Inc. (BOLD)
Form8-K, current report
Filed with the SECJun 23, 2026, 8:30 AM ET
Accession number0001193125-26-278570

Items reported: 1.01 Material Definitive Agreement2.05 Exit / Restructuring Costs3.02 Unregistered Equity Sale5.01 Change in Control5.02 Director / Officer Change7.01 Regulation FD Disclosure8.01 Other Events

Read the filing on SEC.gov ↗

Written by AI on Nov 9, 2026, 11:43 AM ET, from this filing only. Written later: this filing was briefed after the fact, when past filings were added to the site, so the brief may be read with hindsight; the filing itself is the record of what was known on June 23, 2026.

Briefs are written by AI from the filing text and can contain mistakes — open the filing before acting on anything. Impact (1-5) and tone are the AI's reading of the filing for shareholders, not a price forecast. Not investment advice.