UPB

Business Context and Reporting Period

Company: Upstream Bio, Inc. (Nasdaq: UPB)
Filing Type: Form 10-K (Annual Report)
Reporting Period: Fiscal year ended December 31, 2025
Business Overview: Upstream Bio is a clinical-stage biotechnology company developing verekitug, a monoclonal antibody targeting the Thymic Stromal Lymphopoietin (TSLP) receptor. The company focuses on severe respiratory disorders, specifically severe asthma, chronic rhinosinusitis with nasal polyps (CRSwNP), and chronic obstructive pulmonary disease (COPD). Verekitug is the only known antagonist in clinical development targeting the TSLP receptor.

Key Financial Metrics

Note: The company has no product sales revenue. Revenue is derived solely from a collaboration agreement with Maruho Co., Ltd. for research and development cost reimbursements.

Material Changes vs. Prior Period

• Net Loss Increase: Net loss increased by $80.6 million (128%) from 2024 to 2025, driven primarily by a $73.8 million increase in R&D expenses.
• R&D Expense Surge: R&D expenses more than doubled to $136.8 million. Key drivers included:
  • COPD Program: $31.5 million increase due to the initiation of the Phase 2 VENTURE trial.
  • Asthma Program: $19.6 million increase due to continued Phase 2 and long-term extension (LTE) studies.
  • Manufacturing: $16.4 million increase for Phase 3 clinical material development.
• Interest Income: Increased by $4.8 million to $16.9 million due to higher cash balances and interest rates on short-term investments.
• One-Time Income Removal: The $2.9 million gain from the change in fair value of the preferred stock tranche right liability recorded in 2024 was not present in 2025 as the liability was settled in April 2024.

Guidance, Outlook, and Risks

Clinical Progress and Outlook

• Positive Phase 2 Results: Reported positive top-line results for CRSwNP (September 2025) and severe asthma (February 2026).
• Phase 3 Timeline: Plans to initiate dosing in Phase 3 trials for severe asthma and CRSwNP in Q1 2027.
• COPD Development: Initiated Phase 2 trial (VENTURE) in July 2025.
• Liquidity: Management believes existing cash and investments ($341.5 million) are sufficient to fund operations through 2027.

Key Risks and Contingencies

• Capital Requirements: The company expects to continue incurring significant losses and will require additional funding to support Phase 3 trials and potential commercialization. Failure to raise capital could force delays or program reductions.
• Regulatory Uncertainty: Success depends on obtaining FDA and EMA approval for verekitug. Clinical trial results may not be replicated in larger Phase 3 studies.
• Third-Party Dependence: Reliance on third-party manufacturers (e.g., WuXi Biologics) for drug supply. The filing notes potential risks related to the "BIOSECURE Act" and U.S. government restrictions on certain biotechnology providers.
• Intellectual Property: Success depends on maintaining patent protection and defending against third-party infringement claims.

Investor Verification Checklist

• Cash Runway: Verify the sufficiency of the $341.5 million cash balance against the projected burn rate for Phase 3 trials in 2027.
• Phase 3 Design: Confirm the specific endpoints and patient population criteria for the planned Q1 2027 Phase 3 trials in asthma and CRSwNP.
• Manufacturing Supply Chain: Assess the impact of potential U.S. government restrictions (BIOSECURE Act) on the company's relationship with WuXi Biologics and other third-party manufacturers.
• Revenue Sustainability: Evaluate the terms of the Maruho agreement to understand the duration and limits of the current collaboration revenue stream.
• Patent Expiry: Review the expiration dates of the core patent families (2034, 2037, 2042) to assess the commercial exclusivity window.