---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-23-168524"
form_type: "8-K"
ticker: null
cik: "0001718852"
company_name: "Prometheus Biosciences, Inc."
filed_at: "2023-06-16T23:59:59+00:00"
generated_at: "2026-06-13T22:54:43.849640+00:00"
event_type: "m_and_a"
sentiment: "neutral"
materiality_score: 1.0
calibrated_materiality_score: 1.0
confidence: "high"
source: SEC EDGAR
---

# Merck completes acquisition of Prometheus Biosciences for $200/share

## Summary
- Merger closed June 16, 2023; Prometheus stockholders received $200 cash per share.
- Prometheus becomes wholly owned subsidiary of Merck; trading suspended, delisting from Nasdaq initiated.
- All prior directors and executive officers replaced by Merck designees; charter and bylaws amended.

## SEC filing metadata
- accession: 0001193125-23-168524
- form_type: 8-K
- cik: 0001718852
- company_name: Prometheus Biosciences, Inc.
- filed_at: 2023-06-16T23:59:59+00:00
- event_type: m_and_a
- sentiment: neutral
- materiality_score: 1.0
- calibrated_materiality_score: 1.0
- confidence: high
- sec_items: 2.01, 3.01, 3.03, 5.01, 5.02, 5.03, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/d466468d8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-23-168524
- JSON: https://secwatch.observer/filing/0001193125-23-168524.json
- Plain text: https://secwatch.observer/filing/0001193125-23-168524.txt

## Key facts
- Executive change
  Martin Hendrix, Ph.D. resigned as Director at Prometheus Biosciences, Inc..
  - Action: resigned
  - Role: Director
  source text: each of the directors of Prometheus (Mark C. McKenna, Helen C. Adams, Fred Hassan, Martin Hendrix, Ph.D., James Laur, Joseph C. Papa, Judith L. Swain, M.D. and Mary Szela) resigned from the board of directors of Prometheus.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm
- Executive change
  Rita Karachun was appointed as Director at Prometheus Biosciences, Inc..
  - Action: became
  - Role: Director
  source text: At the Effective Time, Jon Filderman, Rita Karachun and Aaron Rosenberg, each a director of Merger Sub immediately prior to the Effective Time, became directors of Prometheus.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm
- Executive change
  Keith W. Marshall, Ph.D. departed as Executive Officer at Prometheus Biosciences, Inc..
  - Action: ceased
  - Role: Executive Officer
  source text: Mark C. McKenna, Keith W. Marshall, Ph.D. and Mark Stenhouse ceased to be executive officers of Prometheus.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm
- Executive change
  Aaron Rosenberg was appointed as Director at Prometheus Biosciences, Inc..
  - Action: became
  - Role: Director
  source text: At the Effective Time, Jon Filderman, Rita Karachun and Aaron Rosenberg, each a director of Merger Sub immediately prior to the Effective Time, became directors of Prometheus.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm
- Executive change
  Mary Szela resigned as Director at Prometheus Biosciences, Inc..
  - Action: resigned
  - Role: Director
  source text: each of the directors of Prometheus (Mark C. McKenna, Helen C. Adams, Fred Hassan, Martin Hendrix, Ph.D., James Laur, Joseph C. Papa, Judith L. Swain, M.D. and Mary Szela) resigned from the board of directors of Prometheus.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm
- Executive change
  Mark C. McKenna resigned as Director at Prometheus Biosciences, Inc..
  - Action: resigned
  - Role: Director
  source text: each of the directors of Prometheus (Mark C. McKenna, Helen C. Adams, Fred Hassan, Martin Hendrix, Ph.D., James Laur, Joseph C. Papa, Judith L. Swain, M.D. and Mary Szela) resigned from the board of directors of Prometheus.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm
- Executive change
  Jon Filderman was appointed as Director at Prometheus Biosciences, Inc..
  - Action: became
  - Role: Director
  source text: At the Effective Time, Jon Filderman, Rita Karachun and Aaron Rosenberg, each a director of Merger Sub immediately prior to the Effective Time, became directors of Prometheus.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm
- Executive change
  Fred Hassan resigned as Director at Prometheus Biosciences, Inc..
  - Action: resigned
  - Role: Director
  source text: each of the directors of Prometheus (Mark C. McKenna, Helen C. Adams, Fred Hassan, Martin Hendrix, Ph.D., James Laur, Joseph C. Papa, Judith L. Swain, M.D. and Mary Szela) resigned from the board of directors of Prometheus.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm
- Executive change
  Helen C. Adams resigned as Director at Prometheus Biosciences, Inc..
  - Action: resigned
  - Role: Director
  source text: each of the directors of Prometheus (Mark C. McKenna, Helen C. Adams, Fred Hassan, Martin Hendrix, Ph.D., James Laur, Joseph C. Papa, Judith L. Swain, M.D. and Mary Szela) resigned from the board of directors of Prometheus.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm
- Executive change
  Mark C. McKenna departed as Executive Officer at Prometheus Biosciences, Inc..
  - Action: ceased
  - Role: Executive Officer
  source text: Mark C. McKenna, Keith W. Marshall, Ph.D. and Mark Stenhouse ceased to be executive officers of Prometheus.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm
- Executive change
  Judith L. Swain, M.D. resigned as Director at Prometheus Biosciences, Inc..
  - Action: resigned
  - Role: Director
  source text: each of the directors of Prometheus (Mark C. McKenna, Helen C. Adams, Fred Hassan, Martin Hendrix, Ph.D., James Laur, Joseph C. Papa, Judith L. Swain, M.D. and Mary Szela) resigned from the board of directors of Prometheus.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm
- Executive change
  Joseph C. Papa resigned as Director at Prometheus Biosciences, Inc..
  - Action: resigned
  - Role: Director
  source text: each of the directors of Prometheus (Mark C. McKenna, Helen C. Adams, Fred Hassan, Martin Hendrix, Ph.D., James Laur, Joseph C. Papa, Judith L. Swain, M.D. and Mary Szela) resigned from the board of directors of Prometheus.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm
- Executive change
  Mark Stenhouse departed as Executive Officer at Prometheus Biosciences, Inc..
  - Action: ceased
  - Role: Executive Officer
  source text: Mark C. McKenna, Keith W. Marshall, Ph.D. and Mark Stenhouse ceased to be executive officers of Prometheus.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm
- Executive change
  James Laur resigned as Director at Prometheus Biosciences, Inc..
  - Action: resigned
  - Role: Director
  source text: each of the directors of Prometheus (Mark C. McKenna, Helen C. Adams, Fred Hassan, Martin Hendrix, Ph.D., James Laur, Joseph C. Papa, Judith L. Swain, M.D. and Mary Szela) resigned from the board of directors of Prometheus.
  evidence_url: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm
- M&A Transactions
  Prometheus Biosciences, Inc. underwent a change of control involving Merck & Co., Inc. for $200.00 per share in cash (closed 2023-06-16).
  - Action: change of control
  - Counterparty: Merck & Co., Inc.
  - Consideration: $200.00 per share in cash
  - Closing: 2023-06-16
  source text: to demand and have properly and validly demanded their appraisal rights under Delaware law, was canceled and extinguished and automatically converted into the right to receive $200.00 per share in cash (the “Merger Consideration”), without interest and subject to any applicable withholding taxes. In addition, at the Effective Time, (i) each outstanding
  evidence_url: https://www.sec.gov/Archives/edgar/data/1718852/000119312523168524/0001193125-23-168524-index.htm

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