Upstream Bio, Inc. (UPB) Institutional Ownership

Ownership Summary

Upstream Bio, Inc. (NASDAQ:UPB) is held by 138 institutional investors per 13F filings through March 2026.

• Their combined ownership stood at 82.2% of outstanding shares in March 2026, down from 94.1% in December 2025.
• They increased total shares held in Upstream Bio by 17.7% from last quarter, and the number of investors in UPB increased 72.5% annually.
• Activity in UPB broke down as 92 buyers, 34 sellers, and 12 unchanged among 138 total holders.
• Institutional investors collectively held 44.64Mn shares in Upstream Bio as of March 2026, up by 6.71Mn shares quarter on quarter, and down 2.67Mn shares year over year.
• As of March 31, 2026, the biggest holder of Upstream Bio is FMR LLC at 8.1Mn shares, representing 14.91% of shares outstanding.
• The largest buyers of Upstream Bio for the quarter ending March 2026 were VANGUARD CAPITAL MANAGEMENT LLC (1.87Mn), Federated Hermes, Inc. (979.28K), Y-Intercept (Hong Kong) Ltd (954.07K), SEB Asset Management AB (878.47K), D. E. Shaw & Co., Inc. (793.39K).
• The largest sellers of Upstream Bio for the quarter ending March 2026 were UBS Group AG (1.57Mn), Altshuler Shaham Ltd (961.48K), State Street Corp (613.88K), TCG Crossover Management, LLC (562.82K), WELLINGTON MANAGEMENT GROUP LLP (552.38K).
• According to Business Quant data, leading holders of UPB for March 2026 are FMR LLC (8.1Mn), ORBIMED ADVISORS LLC (5.69Mn), BlackRock, Inc. (3.37Mn), Decheng Capital LLC (2.72Mn), Enavate Sciences GP, LLC (2.46Mn), VANGUARD CAPITAL MANAGEMENT LLC (1.87Mn), Y-Intercept (Hong Kong) Ltd (1.0Mn), Federated Hermes, Inc. (979.76K), GEODE CAPITAL MANAGEMENT, LLC (950.62K), MILLENNIUM MANAGEMENT LLC (937.32K).