Upstream Bio, Inc. (UPB) Insider Ownership

Historic Ownership Trends

Data spanning the past 90 days through December 12, 2025 reveals that Upstream Bio's three principal insider shareholders consist of TenPercentOwner Upstream Llc Ai (5.49Mn shares), Director Advisors Llc Orbimed (4.55Mn shares), Director Erez Chimovits (4.55Mn shares).

Top Direct Holders

Insider ownership data is derived from the last 60 months of Form 4 SEC filings.
Holder Position Shares Report Date
Upstream Llc Ai 5,494,410 17 Oct, 2024
Advisors Llc Orbimed 4,554,873 17 Oct, 2024
Erez Chimovits 4,554,873 17 Oct, 2024
Biomedical Innovation Master Investors (Cayman) Ii L.P. Wellington 894,733 15 Oct, 2024

* Please note that the shares above only reflect shares from the fund portfolio and the institutional portfolio. Shares from the personal portfolio are excluded from this Institutional Ownership Page. See these insiders' latest transactions here on Insider Page.

Recent Insider Transactions

Detailed insider trading activity based on Form 4 SEC filings.
Download Data
Transaction Date Insider Name Security Class Transaction Type Shares Traded Price Shares Remaining Ownership Code
15 Oct, 2024 Erez Chimovits Common Stock A 721,956 - 973,716 I C
15 Oct, 2024 Upstream Llc Ai Common Stock A 1,175,000 $17.00 1,175,000 D P
15 Oct, 2024 Advisors Llc Orbimed Common Stock A 721,956 - 973,716 I C
15 Oct, 2024 Biomedical Innovation Master Investors (Cayman) Ii L.P. Wellington Common Stock A 894,733 - 894,733 D C
15 Oct, 2024 Upstream Llc Ai Common Stock A 3,147,000 - 4,322,000 D C
15 Oct, 2024 Erez Chimovits Common Stock A 165,000 $17.00 1,138,716 I P
15 Oct, 2024 Advisors Llc Orbimed Common Stock A 165,000 $17.00 1,138,716 I P
15 Oct, 2024 Advisors Llc Orbimed Common Stock A 2,887,833 - 3,894,873 I C
15 Oct, 2024 Erez Chimovits Common Stock A 2,887,833 - 3,894,873 I C
15 Oct, 2024 Upstream Llc Ai Common Stock A 1,172,410 - 5,494,410 D C
15 Oct, 2024 Erez Chimovits Common Stock A 660,000 $17.00 4,554,873 I P
15 Oct, 2024 Advisors Llc Orbimed Common Stock A 660,000 $17.00 4,554,873 I P