Spero Therapeutics, Inc.

SPRO·NASDAQ·$2.86Share Price as of 11/2·$166MMarket Cap as of 11/2

Financials

10-QQ2 ended 06/30/2608/12/26 10-QQ1 ended 03/31/2605/13/26 10-KFY 202503/26/26 10-QQ3 ended 09/30/2511/13/25 10-QQ2 ended 06/30/2508/12/25

Disclosures

8-KCurrent report10/27/26 8-KCurrent report08/28/26 8-KCurrent report08/12/26 8-KCurrent report07/14/26 8-KCurrent report06/25/26

Prospectuses and Registrations

S-8Registration of securities for employees10/28/26 S-3Shelf registration08/28/26 S-8Registration of securities for employees06/23/26 S-8Registration of securities for employees08/12/25 S-8Registration of securities for employees08/05/24

Proxies

DEF 14ADefinitive proxy04/27/26 DEFA14AAdditional proxy materials04/27/26 PRE 14APreliminary proxy04/13/26 DEF 14ADefinitive proxy04/28/25 DEFA14AAdditional proxy materials04/28/25

Ownership

Form 3Initial insider ownership08/06/26 Form 4Insider transaction08/06/26 Form 4Insider transaction06/25/26 Form 4Insider transaction06/25/26 Form 4Insider transaction06/25/26

Other

EFFECTRequest for effectiveness09/10/26 ARSAnnual report to shareholders04/27/26 ARSAnnual report to shareholders04/28/25 ARSAnnual report to shareholders04/16/24 EFFECTRequest for effectiveness03/22/24