---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-26-255467"
form_type: "8-K"
ticker: "CTMX"
cik: "0001501989"
company_name: "CytomX Therapeutics, Inc."
filed_at: "2026-06-03T20:15:15+00:00"
generated_at: "2026-06-03T20:44:07.285201+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.75
calibrated_materiality_score: 0.75
confidence: "high"
source: SEC EDGAR
---

# CytomX and Regeneron expand collaboration; CytomX to receive $37M in target nomination payments

## Summary
- Amendment No. 4 adds up to eight new collaboration programs; Regeneron nominates first two.
- CytomX receives $37M aggregate target nomination payments for the two nominated programs.
- Total potential milestones under expanded agreement are up to approximately $4 billion.
- Royalty rates on global net sales unchanged; program selection period extended.

## SEC filing metadata
- accession: 0001193125-26-255467
- form_type: 8-K
- ticker: CTMX
- cik: 0001501989
- company_name: CytomX Therapeutics, Inc.
- filed_at: 2026-06-03T20:15:15+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.75
- calibrated_materiality_score: 0.75
- confidence: high
- sec_items: 1.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1501989/000119312526255467/0001193125-26-255467-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1501989/000119312526255467/d66030d8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-26-255467
- JSON: https://secwatch.observer/filing/0001193125-26-255467.json
- Plain text: https://secwatch.observer/filing/0001193125-26-255467.txt

## Key facts
- Material Agreements
  CytomX Therapeutics, Inc. amended Amendment No. 4 with Regeneron Pharmaceuticals, Inc. valued at Total potential target nomination payments and preclinical, clinical, regulatory and commercial mile (effective 2026-05-31).
  - Action: amendment
  - Agreement: collaboration
  - Counterparty: Regeneron Pharmaceuticals, Inc.
  - Value: Total potential target nomination payments and preclinical, clinical, regulatory and commercial mile
  - Effective: 2026-05-31
  source text: On May 29, 2026, the Company and Regeneron entered into Amendment No. 4 to the Agreement (“Amendment No. 4”), effective May 31, 2026
  evidence_url: https://www.sec.gov/Archives/edgar/data/1501989/000119312526255467/0001193125-26-255467-index.htm

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