---
schema_version: "secwatch.filing_event.v1"
accession: "0002022626-25-000005"
form_type: "8-K"
ticker: "UPB"
cik: "0002022626"
company_name: "Upstream Bio, Inc."
filed_at: "2025-09-02T23:59:59+00:00"
generated_at: "2026-05-17T09:01:45.715618+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.78
calibrated_materiality_score: 0.78
confidence: "high"
source: SEC EDGAR
---

# Upstream Bio Phase 2 VIBRANT trial meets primary endpoint for verekitug in CRSwNP

## Summary
- Placebo-adjusted reduction in nasal polyp score of -1.8 (p<0.0001) at Week 24; key secondary endpoint nasal congestion score reduced -0.8 (p=0.0003).
- 76% reduction in need for surgery or systemic corticosteroids (p=0.03); no serious adverse events observed.
- Verekitug (100 mg every 12 weeks) generally well tolerated; company plans to engage regulators and present at upcoming medical conference.
- Additional top-line data for verekitug in severe asthma expected in coming months.

## SEC filing metadata
- accession: 0002022626-25-000005
- form_type: 8-K
- ticker: UPB
- cik: 0002022626
- company_name: Upstream Bio, Inc.
- filed_at: 2025-09-02T23:59:59+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.78
- calibrated_materiality_score: 0.78
- confidence: high
- sec_items: 7.01, 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/2022626/000202262625000005/0002022626-25-000005-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/2022626/000202262625000005/upb-20250902.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0002022626-25-000005
- JSON: https://secwatch.observer/filing/0002022626-25-000005.json
- Plain text: https://secwatch.observer/filing/0002022626-25-000005.txt

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