As of September 29, 2026, Upstream Bio's top three insider holders are Upstream Llc Ai (TenPercentOwner, 5.49Mn shares), Advisors Llc Orbimed (Director, 4.55Mn shares), Erez Chimovits (Director, 4.55Mn shares).
| # | Insider | Position | Direct | Indirect | Total | Share of Insiders | Last Filed |
|---|---|---|---|---|---|---|---|
| 1 | Upstream Llc Ai | TenPercentOwner | 5,494,410 | 0 | 5,494,410 | 35.1% | 17 Oct, 2024 |
| 2 | Advisors Llc Orbimed | Director, TenPercentOwner | 0 | 4,554,873 | 4,554,873 | 29.1% | 17 Oct, 2024 |
| 3 | Erez Chimovits | Director, TenPercentOwner | 0 | 4,554,873 | 4,554,873 | 29.1% | 17 Oct, 2024 |
| 4 | Biomedical Innovation Master Investors (Cayman) Ii L.P. Wellington | TenPercentOwner | 894,733 | 0 | 894,733 | 5.7% | 15 Oct, 2024 |
| 5 | Everett Rand Sutherland | Chief Executive Officer | 68,717 | 0 | 68,717 | 0.4% | 17 Sep, 2026 |
| 6 | Aaron Deykin | Chief Medical Officer | 32,302 | 0 | 32,302 | 0.2% | 17 Sep, 2026 |
| 7 | Michael Gray | Cfo And Coo | 27,942 | 0 | 27,942 | 0.2% | 17 Sep, 2026 |
| 8 | Adam Houghton | Chief Business Officer | 22,901 | 0 | 22,901 | 0.1% | 17 Sep, 2026 |
| 9 | Allison Ambrose | General Counsel | 15,563 | 0 | 15,563 | 0.1% | 17 Sep, 2026 |
Each row is that insider’s most recently reported position, from Form 4 filings over the last 60 months — which is why this total does not tie to the quarterly series above, where a quarter counts only the insiders who filed in it. Shares held through a fund or institutional portfolio are counted on the institutional ownership page instead.
| Date | Insider | Position | Transaction | Shares | Price | Value | Shares Held After | Ownership |
|---|---|---|---|---|---|---|---|---|
| 16 Sep, 2026 | Michael Gray | Cfo And Coo | Disposed S | 853 | $5.49 | $4.68K | 27,942 | Direct |
| 16 Sep, 2026 | Everett Rand Sutherland | Chief Executive Officer | Disposed S | 2,095 | $5.49 | $11.50K | 68,717 | Direct |
| 16 Sep, 2026 | Allison Ambrose | General Counsel | Disposed S | 485 | $5.49 | $2.66K | 15,563 | Direct |
| 16 Sep, 2026 | Adam Houghton | Chief Business Officer | Disposed S | 700 | $5.49 | $3.84K | 22,901 | Direct |
| 16 Sep, 2026 | Aaron Deykin | Chief Medical Officer | Disposed S | 895 | $5.49 | $4.91K | 32,302 | Direct |
| 16 Jun, 2026 | Everett Rand Sutherland | Chief Executive Officer | Disposed S | 2,095 | $6.10 | $12.78K | 70,812 | Direct |
| 16 Jun, 2026 | Adam Houghton | Chief Business Officer | Disposed S | 700 | $6.10 | $4.27K | 23,601 | Direct |
| 16 Jun, 2026 | Allison Ambrose | General Counsel | Disposed S | 477 | $6.10 | $2.91K | 16,048 | Direct |
| 16 Jun, 2026 | Michael Gray | Cfo And Coo | Disposed S | 853 | $6.10 | $5.20K | 28,795 | Direct |
| 16 Jun, 2026 | Aaron Deykin | Chief Medical Officer | Disposed S | 895 | $6.10 | $5.46K | 33,197 | Direct |
| 09 Jun, 2026 | Liam Ratcliffe | Director | Acquired A | 17,096 | $0.00 | $0 | 17,096 | Direct |
| 09 Jun, 2026 | Daniella Beckman | Director | Acquired A | 17,096 | $0.00 | $0 | 17,096 | Direct |
| 09 Jun, 2026 | Marcella K. Ruddy | Director | Acquired A | 17,096 | $0.00 | $0 | 17,096 | Direct |
| 09 Jun, 2026 | Erez Chimovits | Director | Acquired A | 17,096 | $0.00 | $0 | 17,096 | Direct |
| 09 Jun, 2026 | Ronald C Jr Renaud | Director | Acquired A | 17,096 | $0.00 | $0 | 17,096 | Direct |
| 09 Jun, 2026 | Harold Edward Fleming | Director | Acquired A | 17,096 | $0.00 | $0 | 17,096 | Direct |
| 16 Mar, 2026 | Aaron Deykin | Chief Medical Officer | Disposed S | 894 | $9.29 | $8.31K | 32,687 | Direct |
| 16 Mar, 2026 | Adam Houghton | Chief Business Officer | Disposed S | 699 | $9.29 | $6.49K | 24,301 | Direct |
| 16 Mar, 2026 | Everett Rand Sutherland | Chief Executive Officer | Disposed S | 2,093 | $9.29 | $19.44K | 72,907 | Direct |
| 16 Mar, 2026 | Allison Ambrose | General Counsel | Disposed S | 475 | $9.29 | $4.41K | 16,525 | Direct |