Upstream Bio, Inc. — Director's Dealing 2024

Oct 17, 2024

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: Upstream Bio, Inc. (UPB)
CIK: 0002022626
Period of Report: 2024-10-15

Reporting Person: ORBIMED ADVISORS LLC (Director, 10% Owner)
Reporting Person: OrbiMed Capital GP VIII LLC (Director, 10% Owner)
Reporting Person: OrbiMed Advisors Israel II Ltd (Director, 10% Owner)
Reporting Person: OrbiMed Israel GP II, L.P. (Director, 10% Owner)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2024-10-15	Common Stock	C	721956	—	Acquired	973716	Indirect
2024-10-15	Common Stock	P	165000	$17	Acquired	1138716	Indirect
2024-10-15	Common Stock	C	2887833	—	Acquired	3894873	Indirect
2024-10-15	Common Stock	P	660000	$17	Acquired	4554873	Indirect

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2024-10-15	Series A redeemable convertible preferred stock	$	C	524500	Disposed		Common Stock (524500)	Indirect
2024-10-15	Series A redeemable convertible preferred stock	$	C	2098000	Disposed		Common Stock (2098000)	Indirect
2024-10-15	Series B redeemable convertible preferred stock	$	C	197456	Disposed		Common Stock (197456)	Indirect
2024-10-15	Series B redeemable convertible preferred stock	$	C	789833	Disposed		Common Stock (789833)	Indirect

Footnotes

F1: Each share of Series A redeemable convertible preferred stock and Series B redeemable convertible preferred stock automatically converted into shares of the Issuer's common stock on a one-for-1.049 basis immediately prior to the closing of the Issuer's initial public offering and have no expiration date.

F2: These securities are held of record by OrbiMed Israel Partners II, L.P. ("OIP II"). OrbiMed Israel GP II, L.P. ("Israel GP") is the general partner of OIP II, and OrbiMed Advisors Israel II Limited ("Advisors II") is the general partner of Israel GP. By virtue of such relationships, Israel GP and Advisors II may be deemed to have voting and investment power over the securities held by OIP II and, as a result, may be deemed to have beneficial ownership over such securities. Advisors II exercises voting and investment power through an investment committee comprised of Carl L. Gordon, David P. Bonita, and Erez Chimovits ("Chimovits"), each of whom disclaims beneficial ownership of the securities held by OIP II.

F3: These securities are held of record by OrbiMed Private Investments VIII, LP ("OPI VIII"). OrbiMed Capital GP VIII LLC ("GP VIII") is the general partner of OPI VIII, and OrbiMed Advisors LLC ("OrbiMed Advisors") is the managing member of GP VIII. By virtue of such relationships, GP VIII and OrbiMed Advisors may be deemed to have voting power and investment power over the securities held by OPI VIII and, as a result, may be deemed to have beneficial ownership over such securities. OrbiMed Advisors exercises voting and investment power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and W. Carter Neild, each of whom disclaims beneficial ownership of the securities held by OPI VIII.

F4: Each of Advisors II, Israel GP, OrbiMed Advisors, and GP VIII disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of its pecuniary interest therein, if any. OrbiMed Advisors, GP VIII. Advisors II, and Israel GP have designated a representative, Chimovits, an employee of OrbiMed Advisors and a director of Advisors II, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any such person or entity is a beneficial owner of such securities for the purpose of Section 16 of the Exchange Act, or for any other purpose.