UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 7, 2025 SPERO THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-38266 46-4590683 (State or other jurisdiction of incorporation) (Commission File Number) (I.R.S. Employer Identification No.) 675 Massachusetts Avenue, 14th Floor Cambridge, Massachusett ...