Upstream Bio, Inc.

UPB·NASDAQ·$8.21Share Price as of 11/2·$447MMarket Cap as of 11/2

Financials

10-QQ2 ended 06/30/2608/11/26 10-QQ1 ended 03/31/2605/13/26 10-KFY 202503/26/26 10-QQ3 ended 09/30/2511/05/25 10-QQ2 ended 06/30/2508/06/25

Disclosures

8-KCurrent report09/01/26 8-KCurrent report08/11/26 8-KCurrent report06/10/26 8-KCurrent report05/13/26 8-KCurrent report03/26/26

Prospectuses and Registrations

424B5Prospectus supplement03/26/26 S-8Registration of securities for employees03/26/26 S-3ASRAutomatic shelf registration11/05/25 S-8Registration of securities for employees03/12/25 424B4Prospectus10/11/24

Proxies

DEF 14ADefinitive proxy04/16/26 DEFA14AAdditional proxy materials04/16/26 DEF 14ADefinitive proxy04/17/25 DEFA14AAdditional proxy materials04/17/25

Ownership

SC 13G/ABeneficial ownership (amended)10/29/26 Form 4Insider transaction09/17/26 Form 4Insider transaction09/17/26 Form 4Insider transaction09/17/26 Form 4Insider transaction09/17/26

Other

ARSAnnual report to shareholders04/16/26 ARSAnnual report to shareholders04/17/25 SEC STAFF LETTERSEC staff letter10/16/24 CERTCEO/CFO certification10/10/24 EFFECTRequest for effectiveness10/10/24