SEC Form 4 · accession 0001193125-26-394318
Upstream Bio, Inc. · UPB
Statement of changes in beneficial ownership, as filed. Original on EDGAR ↗
Reporting owner
Allison Ambrose
Officer — General Counsel
Period of report
Sep 16, 2026
Accepted (ET)
Sep 17, 2026 · 4:05 pm EDT
Rule 10b5-1 plan
box not checked
Issuer CIK
0002022626
Table I — non-derivative securities
| Security | Date | Code | Shares | Price | A/D | Owned after | D/I | Nature of ownership |
|---|---|---|---|---|---|---|---|---|
| Common Stock | Sep 16, 2026 | S | 485 | $5.49 | D | 15,563 | D |
Table II — derivative securities
No Table II lines on this filing.
Explanation of responses
- F1The Issuer has adopted a "sell-to-cover" policy to satisfy the tax withholding obligations of the Reporting Person. The sales reported on this Form 4 represent the number of shares required to be sold by the Reporting Person to cover tax withholding obligations in connection with the vesting of restricted stock units. Such sales were automatic and not at the discretion of the Reporting Person.