---
schema_version: "secwatch.filing_event.v1"
accession: "0001599298-25-000137"
form_type: "8-K"
ticker: "SMMT"
cik: "0001599298"
company_name: "Summit Therapeutics Inc."
filed_at: "2025-09-08T23:59:59+00:00"
generated_at: "2026-05-17T07:36:22.150645+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.85
calibrated_materiality_score: 0.85
confidence: "high"
source: SEC EDGAR
---

# Ivonescimab HARMONi trial shows improved OS trend in longer follow-up; North American HR=0.70

## Summary
- Longer-term follow-up of Western patients: OS HR=0.78 (nominal p=0.0332); median OS 16.8 vs 14.0 months.
- North American patients: median OS not reached for ivonescimab vs 14.0 months for placebo (HR=0.70).
- Primary PFS analysis showed HR=0.52 (p<0.00001); median PFS 6.8 vs 4.4 months.
- Overall response rate higher with ivonescimab (45% vs 34%); median duration of response 7.6 vs 4.2 months.
- Safety profile manageable; TRAEs leading to discontinuation 7.3% (ivonescimab) vs 5.0% (placebo).

## SEC filing metadata
- accession: 0001599298-25-000137
- form_type: 8-K
- ticker: SMMT
- cik: 0001599298
- company_name: Summit Therapeutics Inc.
- filed_at: 2025-09-08T23:59:59+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.85
- calibrated_materiality_score: 0.85
- confidence: high
- sec_items: 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1599298/000159929825000137/0001599298-25-000137-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1599298/000159929825000137/smmt-20250907.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001599298-25-000137
- JSON: https://secwatch.observer/filing/0001599298-25-000137.json
- Plain text: https://secwatch.observer/filing/0001599298-25-000137.txt

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