---
schema_version: "secwatch.filing_event.v1"
accession: "0001724521-26-000021"
form_type: "8-K"
ticker: "RCUS"
cik: "0001724521"
company_name: "Arcus Biosciences, Inc."
filed_at: "2026-04-20T23:59:59+00:00"
generated_at: "2026-05-15T05:20:48.427862+00:00"
event_type: "other_material"
sentiment: "negative"
materiality_score: 0.75
calibrated_materiality_score: 0.75
confidence: "high"
source: SEC EDGAR
---

# Arcus discontinues Phase 3 STAR-121 NSCLC trial; Gilead lets option rights lapse

## Summary
- STAR-121 evaluating domvanalimab + zimberelimab + chemo vs pembro + chemo in 1L metastatic NSCLC stopped by IDMC for futility.
- Zimberelimab + chemo showed comparable overall survival vs pembro + chemo; trial discontinued despite that.
- Gilead declines option continuation payment; option period ends July 14, 2026; loses rights to CCR6, CD89, CD40L programs.
- Gilead retains time-limited options for AB801 (AXL inhibitor), AB598 (anti-CD39), AB102 (MRGPRX2 antagonist), and TNF small molecule.
- Arcus retains full rights to casdatifan program except Taiho territories (Japan and certain Asian countries).

## SEC filing metadata
- accession: 0001724521-26-000021
- form_type: 8-K
- ticker: RCUS
- cik: 0001724521
- company_name: Arcus Biosciences, Inc.
- filed_at: 2026-04-20T23:59:59+00:00
- event_type: other_material
- sentiment: negative
- materiality_score: 0.75
- calibrated_materiality_score: 0.75
- confidence: high
- sec_items: 8.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1724521/000172452126000021/0001724521-26-000021-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1724521/000172452126000021/rcus-20260420.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001724521-26-000021
- JSON: https://secwatch.observer/filing/0001724521-26-000021.json
- Plain text: https://secwatch.observer/filing/0001724521-26-000021.txt

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