---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-26-377485"
form_type: "8-K"
ticker: "UPB"
cik: "0002022626"
company_name: "Upstream Bio, Inc."
filed_at: "2026-09-01T11:05:15+00:00"
generated_at: "2026-09-01T11:10:07.909598+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.8
calibrated_materiality_score: 0.8
confidence: "high"
source: SEC EDGAR
---

# Upstream Bio announces Phase 3 plans for verekitug in severe asthma and CRSwNP

## Summary
- Phase 3: 400mg verekitug SC every 12 weeks vs placebo; one trial each in severe asthma and CRSwNP.
- ~1,500 patients total across both trials; broad populations, no biomarker restriction.
- Primary endpoints: asthma AAER over 48 weeks; CRSwNP co-primary NPS and NCS at 48 weeks.
- Trials to start Q1 2027; BLA submission expected with supportive results; potential launch as early as 2030.
- Based on productive End-of-Phase 2 FDA meetings; data from 500+ treated patients.

## SEC filing metadata
- accession: 0001193125-26-377485
- form_type: 8-K
- ticker: UPB
- cik: 0002022626
- company_name: Upstream Bio, Inc.
- filed_at: 2026-09-01T11:05:15+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.8
- calibrated_materiality_score: 0.8
- confidence: high
- sec_items: 7.01, 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/2022626/000119312526377485/0001193125-26-377485-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/2022626/000119312526377485/upb-20260901.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-26-377485
- JSON: https://secwatch.observer/filing/0001193125-26-377485.json
- Plain text: https://secwatch.observer/filing/0001193125-26-377485.txt

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