1 unchanged sentence
Evaluation of Disclosure Controls and Procedures
−Removed: Our management, with the participation of our Interim Chief Executive Officer and Chief Financial Officer (our principal executive officer and principal financial officer) evaluated the effectiveness of our disclosure controls and procedures as of December 31, 2024.
+Added: Our management, with the participation of our Chief Executive Officer and Chief Financial Officer (our principal executive officer and principal financial officer) evaluated the effectiveness of our disclosure controls and procedures as of December 31, 2025.
The term “disclosure controls and procedures,” as defined in Rules 13a-15(e) and 15d-15(e) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), means controls and other procedures of a company that are designed to ensure that information required to be disclosed by a company in the reports that it files or submits under the Exchange Act is recorded, processed, summarized and reported, within the time periods specified in the SEC’s rules and forms.
1 unchanged sentence
Management recognizes that any controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving their objectives and management necessarily applies its judgment in evaluating the cost-benefit relationship of possible controls and procedures.
−Removed: Based on the evaluation of our disclosure controls and procedures as of December 31, 2024, our Interim Chief Executive Officer and Chief Financial Officer concluded that, as of such date, our disclosure controls and procedures were effective at the reasonable assurance level.
+Added: Based on the evaluation of our disclosure controls and procedures as of December 31, 2025, our Chief Executive Officer and Chief Financial Officer concluded that, as of such date, our disclosure controls and procedures were effective at the reasonable assurance level.
Management’s Annual Report on Internal Controls Over Financial Reporting
9 unchanged sentences
Trading Arrangements
−Removed: None of our directors or officers adopted or terminated a Rule 10b5-1 trading arrangement or a non-Rule 10b5-1 trading arrangement (as defined in Item 408(c) of Regulation S-K) during fiscal year 2024.
+Added: On December 17, 2025 , Esther Rajavelu , President, Chief Executive Officer, Chief Financial Officer, Chief Business Officer and Treasurer , adopted a Rule 10b5-1 trading arrangement (as defined in Item 408(a) of Regulation S-K) (the “Trading Agreement”).
+Added: The Trading Agreement will terminate on December 17, 2026 unless terminated earlier pursuant to the terms of the Trading Agreement.
+Added: The aggregate number of shares to be sold under the Trading Agreement is 78,412 .
+Added: None of our other directors or officers adopted or terminated a Rule 10b5-1 trading arrangement or a non-Rule 10b5-1 trading arrangement (as defined in Item 408(c) of Regulation S-K) during the three months ended December 31, 2025.
Disclosure Regarding Foreign Jurisdictions that Prevent Inspections.
5 unchanged sentences
Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters.
−Removed: The response to this item is incorporated by reference from the discussion responsive thereto under the captions “Security Ownership of Certain Beneficial Owners and Management” and “Equity Compensation Plans and Other Benefits Plans” in our proxy statement for the 2025 Annual Meeting of Stockholders to be filed with the SEC within 120 days after the end of the fiscal year covered by this Annual Report on Form 10-K.
+Added: The response to this item is incorporated by reference from the discussion responsive thereto under the captions “Security Ownership of Certain Beneficial Owners and Management” and “Equity Compensation Plan Information” in our proxy statement for the 2026 Annual Meeting of Stockholders to be filed with the SEC within 120 days after the end of the fiscal year covered by this Annual Report on Form 10-K.
Certain Relationships and Related Transactions, and Director Independence.
−Removed: The response to this item is incorporated by reference from the discussion responsive thereto under the captions “Certain Relationships and Related Transactions” and “Management and Corporate Governance Matters” in our proxy statement for the 2025 Annual Meeting of Stockholders to be filed with the SEC within 120 days after the end of the fiscal year covered by this Annual Report on Form 10-K.
+Added: The response to this item is incorporated by reference from the discussion responsive thereto under the captions “Certain Relationships and Related Person Transactions” and “Management and Corporate Governance Matters” in our proxy statement for the 2026 Annual Meeting of Stockholders to be filed with the SEC within 120 days after the end of the fiscal year covered by this Annual Report on Form 10-K.
Principal Accountant Fees and Services.
−Removed: The response to this item is incorporated by reference from the discussion responsive thereto under the caption “Independent Public Accountants” in our proxy statement for the 2025 Annual Meeting of Stockholders to be filed with the SEC within 120 days after the end of the fiscal year covered by this Annual Report on Form 10-K.
+Added: The response to this item is incorporated by reference from the discussion responsive thereto under the caption “Independent Public Accounting Firm” in our proxy statement for the 2026 Annual Meeting of Stockholders to be filed with the SEC within 120 days after the end of the fiscal year covered by this Annual Report on Form 10-K.
Exhibits, Financ ial Statement Schedules.
41 unchanged sentences
(Exhibit 10.8)
−Removed: Consulting Agreement, dated June 13, 2023, by and between the Registrant and Ankit Mahadevia, M.D.
−Removed: (Exhibit 10.2)
−Removed: Amendment and Restated Employment Agreement, dated June 13, 2023, by and between the Registrant and Satyavrat Shukla
−Removed: (Exhibit 10.3)
−Removed: Interim Period Agreement, dated January 10, 2025, by and between the Registrant and Satyavrat Shukla
−Removed: (Exhibit 10.1)
−Removed: Retention Letter Agreement, dated November 13, 2024, by and between the Registrant and Satyavrat Shukla
−Removed: Employment Agreement, dated August 11, 2022, by and between the Registrant and Kamal Hamed, M.D.
−Removed: (Exhibit 10.5)
−Removed: Amendment to Employment Agreement, dated November 10, 2022, by and between the Registrant and Kamal Hamed, M.D.
−Removed: (Exhibit 10.8)
−Removed: Separation Agreement, dated July 30,2024 by and between the Registrant and Kamal Hamed, M.D.
−Removed: (Exhibit 10.1)
−Removed: Separation Agreement, dated July 30,2024 by and between the Registrant and Kamal Hamed, M.D.
+Added: Employment Agreement, dated January 1, 2020, by and between the Registrant and Timothy Keutzer.
(Exhibit 10.12)
3 unchanged sentences
(Exhibit 10.1)
−Removed: Retention Letter Agreement, dated November 13, 2024, by and between the Registrant and Timothy Keutzer
Employment Agreement, dated October 31, 2023, by and between the Registrant and Esther Rajavelu
2 unchanged sentences
(Exhibit 10.2)
−Removed: Retention Letter Agreement, dated November 13, 2024, by and between the Registrant and Esther Rajavelu
−Removed: Employment Agreement, dated November 6, 2020, by and between the Registrant and Tamara Joseph
−Removed: (Exhibit 10.13)
−Removed: Amendment to Employment Agreement, dated November 10, 2022, by and between the Registrant and Tamara Joseph
−Removed: (Exhibit 10.10)
−Removed: Separation Agreement, dated February 9, 2024, by and between the Registrant and Tamara Joseph
−Removed: (Exhibit 10.34)
−Removed: Consulting Agreement, dated February 9, 2024, by and between the Registrant and Tamara Joseph
−Removed: (Exhibit 10.34)
−Removed: Consulting Agreement, effective as of August 5, 2024, by and between the Registrant and John C.
−Removed: Pottage, Jr., M.D.
+Added: Amended and Restated Employment Agreement, dated April 28, 2025, by and between the Registrant and Esther Rajavelu
(Exhibit 10.10)
1 unchanged sentence
Pottage, Jr., M.D.
+Added: (Exhibit 10.28)
Lease Agreement, dated August 24, 2015, by and between the Registrant and U.S.
10 unchanged sentences
(Exhibit 10.4)
−Removed: Sublease, dated July 6, 2016, by and between the Registrant and Tetraphase Pharmaceuticals, Inc.
−Removed: (Exhibit 10.12)
Stock Purchase Agreement, dated June 6, 2016, by and among Spero Cantab, Inc., the Registrant, Spero Cantab UK Limited, PBB Distributions Limited, New Pharma License Holdings Limited, Cantab Anti-Infectives Ltd and Pro Bono Bio PLC, as amended by Amendment to Stock Purchase Agreement, dated July 18, 2017
(Exhibit 10.13)
−Removed: Assignment and License Agreement, dated May 9, 2016, by and among Spero Trinem, Inc., the Registrant and Vertex Pharmaceuticals Incorporated
−Removed: (Exhibit 10.14)
License Agreement, dated June 14, 2017, by and between the Registrant and Meiji Seika Pharma Co., Ltd., as supplemented by Addendum to License Agreement, dated June 14, 2017
8 unchanged sentences
(Exhibit 10.2)
+Added: Termination Letter, dated December 31, 2025, by and between Registrant and Pfizer Inc.
+Added: regarding termination of License Agreement
Exclusive License Agreement, dated September 21, 2022, by and between the Registrant and GlaxoSmithKline Intellectual Property (No.
8 unchanged sentences
(Exhibit 10.4)
−Removed: Share Purchase Agreement, dated September 21, 2022, by and between the Registrant and Glaxo Group Limited
−Removed: (Exhibit 10.4)
Controlled Equity Offering Sales Agreement, dated March 11, 2021, by and between the Registrant and Cantor Fitzgerald & Co.
(Exhibit 10.28)
−Removed: Form of Proprietary Information and Inventions Assignment Agreement
−Removed: (Exhibit 10.17)
Spero Therapeutics, Inc.
Insider Trading Policy, effective as of June 5, 2023
+Added: (Exhibit 19.1)
List of Subsidiaries of the Registrant
1 unchanged sentence
Consent of PricewaterhouseCoopers LLP, independent registered public accounting firm
−Removed: Certification of Principal Executive Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002
−Removed: Certification of Principal Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002
+Added: Certification of Principal Executive Officer and Principal Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002
Certification pursuant to 18 U.S.C.
21 unchanged sentences
Esther Rajavelu
−Removed: Interim Chief Executive Office
+Added: President, Chief Executive Officer, Chief Financial Officer, Chief Business Officer and Treasurer
POWER OF ATTORNEY
2 unchanged sentences
/s/ Esther Rajavelu
−Removed: Interim Chief Executive Officer, Chief Financial Officer, Chief Business Officer and Treasurer
+Added: President, Chief Executive Officer, Chief Financial Officer, Chief Business Officer, Treasurer, and Director
March 26, 2026
21 unchanged sentences
Compared sentence by sentence after normalising whitespace, quotation marks, case and digits, so re-formatting and restated figures do not read as changed language. Wording changes appear as one removal and one addition. The current filing and the prior one are authoritative.