---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-26-278570"
form_type: "8-K"
ticker: "BOLD"
cik: "0001782303"
company_name: "Boundless Bio, Inc."
filed_at: "2026-06-23T12:30:21+00:00"
generated_at: "2026-06-23T12:35:54.880521+00:00"
event_type: "m_and_a"
sentiment: "negative"
materiality_score: 0.9
calibrated_materiality_score: 0.9
confidence: "high"
source: SEC EDGAR
---

# Boundless Bio to merge with Serapha; Serapha equityholders to own ~96%

## Summary
- Pre-merger Serapha equityholders to own ~96.31% of combined company; Boundless Bio holders ~3.69% on fully diluted basis.
- Serapha raises $138M Series A preferred and $92M PIPE concurrently with merger agreement.
- Boundless Bio to cut ~75% of workforce; expects $3M-$5M in termination costs, substantially completed in Q3 2026.
- CEO Zachary Hornby, CSO Christian Hassig, CMO Robert Doebele to depart July 1, 2026; Jessica Oien appointed President and PEO.
- Boundless Bio discontinues BBI-940 clinical program due to poor oral bioavailability in KOMODO-1 trial.

## SEC filing metadata
- accession: 0001193125-26-278570
- form_type: 8-K
- ticker: BOLD
- cik: 0001782303
- company_name: Boundless Bio, Inc.
- filed_at: 2026-06-23T12:30:21+00:00
- event_type: m_and_a
- sentiment: negative
- materiality_score: 0.9
- calibrated_materiality_score: 0.9
- confidence: high
- sec_items: 1.01, 2.05, 3.02, 5.01, 5.02, 7.01, 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1782303/000119312526278570/0001193125-26-278570-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1782303/000119312526278570/d159021d8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-26-278570
- JSON: https://secwatch.observer/filing/0001193125-26-278570.json
- Plain text: https://secwatch.observer/filing/0001193125-26-278570.txt

## Key facts
- Executive change
  Zachary D. Hornby departed as President and Chief Executive Officer at Boundless Bio, Inc..
  - Action: cease
  - Role: President and Chief Executive Officer
  source text: effective July 1, 2026, Zachary D. Hornby will cease his role as President and Chief Executive Officer, and as a member of the board of directors of Boundless Bio.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1782303/000119312526278570/0001193125-26-278570-index.htm
- Executive change
  Jessica Oien was appointed as President and Principal Executive Officer at Boundless Bio, Inc..
  - Action: appointed
  - Role: President and Principal Executive Officer
  source text: effective July 1, 2026, Jessica Oien, Boundless Bio’s Chief Legal Officer and Corporate Secretary, was appointed to serve as Boundless Bio’s President and "principal executive officer," in addition to maintaining her current responsibilities as Chief Legal Officer and Corporate Secretary.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1782303/000119312526278570/0001193125-26-278570-index.htm
- Executive change
  Christian Hassig departed as Chief Scientific Officer at Boundless Bio, Inc..
  - Action: cease
  - Role: Chief Scientific Officer
  source text: effective July 1, 2026, Christian Hassig, Ph.D., will cease his role as Boundless Bio’s Chief Scientific Officer
  evidence_url: https://www.sec.gov/Archives/edgar/data/1782303/000119312526278570/0001193125-26-278570-index.htm

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.