UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2019 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-38266 SPERO THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) ( State or other jurisdiction of inco ...

1 Company Presentation Cantor Global Healthcare Conference October 3, 2019 Forward-looking Statements 2 This presentation contains forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995 regarding, among other things, the initiation, timing, progress and results of the Company's preclinical studies and clinical trials and its research and development programs, including management's assessment of such results; regulatory activities, including the Company's expectation t ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2019 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM TO Commission File Number 001-38266 SPERO THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) ( State or other jurisdiction of incorporat ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2019 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM TO Commission File Number 001-38266 SPERO THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) ( State or other jurisdiction of incorpora ...

SPER® 1 Company(Presentation Oppenheimer(Healthcare(Conference( March(20,(2019 Forward'looking-Statements 2 This presentation contains forward0looking statements as defined in the Private Securities Litigation Reform Act of 1995 regarding, among other things, the initiation, timing, progress and results of the Company's preclinical studies and clinical trials and its research and development programs, including management's assessment of such results; the anticipated timing of the opening of sites to suppor ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2018 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM TO Commission File Number 001-38266 SPERO THERAPEUTICS, INC. (Exact name of registrant as specified in its Charter) | Delaware | 46-4590683 | | --- | --- | | ( Sta ...

SPER® 1 Company(Presentation Cowen(and Company(Health(Care(Conference( March(12,(2019 Forward'looking-Statements 2 This presentation contains forward0looking statements as defined in the Private Securities Litigation Reform Act of 1995 regarding, among other things, the initiation, timing, progress and results of the Company's preclinical studies and clinical trials and its research and development programs, including management's assessment of such results; the anticipated timing of the opening of sites to ...