---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-26-125057"
form_type: "8-K"
ticker: "UPB"
cik: "0002022626"
company_name: "Upstream Bio, Inc."
filed_at: "2026-03-26T23:59:59+00:00"
generated_at: "2026-05-15T08:54:46.380173+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.8
calibrated_materiality_score: 0.8
confidence: "high"
source: SEC EDGAR
---

# Upstream Bio details Phase 3 strategy for verekitug; positive Phase 2 asthma and CRSwNP data

## Summary
- Phase 3 development plan for verekitug: high-dose quarterly regimen (up to 400 mg q12w) in severe asthma and CRSwNP; initiation in Q1 2027.
- Phase 2 VALIANT asthma trial met primary endpoint: AAER reduction 56% (p<0.0003) with 100 mg q12w; safety profile favorable.
- Phase 2 VIBRANT CRSwNP data: placebo-adjusted NPS reduction -1.95 (WOCF) and NCS reduction -0.96 at week 24.
- Cash position $341.5M as of Dec 31, 2025, expected to fund operations through 2027.
- Q4 2025 net loss $42.5M vs $21.2M a year ago; R&D expenses rose to $40.2M.

## SEC filing metadata
- accession: 0001193125-26-125057
- form_type: 8-K
- ticker: UPB
- cik: 0002022626
- company_name: Upstream Bio, Inc.
- filed_at: 2026-03-26T23:59:59+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.8
- calibrated_materiality_score: 0.8
- confidence: high
- sec_items: 2.02, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/2022626/000119312526125057/0001193125-26-125057-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/2022626/000119312526125057/upb-20260326.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-26-125057
- JSON: https://secwatch.observer/filing/0001193125-26-125057.json
- Plain text: https://secwatch.observer/filing/0001193125-26-125057.txt

## Key facts
- Earnings Releases
  Upstream Bio, Inc. reported financial results for the quarter and year ended December 31, 2025.
  - Period: the quarter and year ended December 31, 2025
  - Result: reported results
  source text: On March 26, 2026, Upstream Bio, Inc. (the “Company”) announced its financial results and business highlights for the quarter and year ended December 31, 2025.
  evidence_url: https://www.sec.gov/Archives/edgar/data/2022626/000119312526125057/0001193125-26-125057-index.htm

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