SCHEDULE: TCG Crossover Reports 3.9% Stake in Upstream Bio

TCG Crossover Fund I, L.P., TCG Crossover GP I, LLC, and Chen Yu have reported a combined beneficial ownership of 3.9% in Upstream Bio, Inc. common stock.

Summary

• TCG Crossover Fund I, L.P., TCG Crossover GP I, LLC, and Chen Yu (collectively, the Reporting Persons) beneficially own 2,117,103 shares of Upstream Bio, Inc. common stock.
• This ownership represents 3.9% of Upstream Bio, Inc.'s total outstanding common stock.
• The percentage is calculated based on 54,038,591 shares of Common Stock outstanding, as reported in Upstream Bio's Form 10-Q filed on November 5, 2025.
• The Reporting Persons have shared voting and shared dispositive power over these 2,117,103 shares.
• This filing is Amendment No. 1 to the original Schedule 13G, which was initially filed on February 14, 2025.
• The Reporting Persons certify that the securities were not acquired and are not held for the purpose of changing or influencing the control of the issuer.

Sentiment

Score: 6

Explanation: The filing indicates a continued significant, albeit passive, institutional investment in Upstream Bio, which can be viewed as a vote of confidence from TCG Crossover. However, it's a routine ownership disclosure and doesn't provide new operational or financial insights.

Positives

• A significant institutional investor group maintains a substantial, albeit passive, stake in Upstream Bio, indicating continued interest and confidence in the company.

Future Outlook

NA

Management Comments

• The securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under §§ 240.14a-11.

Industry Context

This filing reflects a passive investment by a crossover fund in a biotechnology company, a common strategy for funds investing in both private and public markets, often seen in the life sciences sector where companies transition from private funding to public markets.

Stakeholder Impact

• Shareholders: The continued significant stake by TCG Crossover may provide some reassurance regarding institutional interest in the company.

Key Dates

Keywords

Upstream Bio, TCG Crossover, Schedule 13G, beneficial ownership, common stock, institutional investment, passive investment, equity stake, SEC filing, 91678A107