# EDGAR Filing Document

**Accession Number:** 0001701108
**File Stem:** 0001193125-26-032004
**Filing Date:** 2026-1
**Character Count:** 6048
**Document Hash:** 9225479da838588c2f54598e1bae963c
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-26-032004.hdr.sgml**: 20260130

**ACCESSION NUMBER**: 0001193125-26-032004

**CONFORMED SUBMISSION TYPE**: 8-K

**PUBLIC DOCUMENT COUNT**: 12

**CONFORMED PERIOD OF REPORT**: 20260130

**ITEM INFORMATION**: Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers: Compensatory Arrangements of Certain Officers

**ITEM INFORMATION**: Other Events

**FILED AS OF DATE**: 20260130

**DATE AS OF CHANGE**: 20260130

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Spero Therapeutics, Inc.
- **CENTRAL INDEX KEY:** 0001701108
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 8-K
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-38266
- **FILM NUMBER:** 26584278

**BUSINESS ADDRESS:**
- **STREET 1:** 675 MASSACHUSETTS AVENUE
- **STREET 2:** 14TH FLOOR
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02139
- **BUSINESS PHONE:** 857-242-1600

**MAIL ADDRESS:**
- **STREET 1:** 675 MASSACHUSETTS AVENUE
- **STREET 2:** 14TH FLOOR
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02139

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Spero Therapeutics, LLC
- **DATE OF NAME CHANGE:** 20170316

?xml version='1.0' encoding='ASCII'? 8-K

### 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 30, 2026

## SPERO THERAPEUTICS, INC.

#### (Exact name of registrant as specified in its charter)

---

| | | |
|:---|:---|:---|
| **Delaware** | **001-38266** | **46-4590683** |
| **(State or other jurisdiction**<br> **of incorporation)** | **(Commission**<br> **File Number)** | **(I.R.S. Employer**<br> **Identification No.)** |
| **675 Massachusetts Avenue, 14<sup>th</sup> Floor** | **675 Massachusetts Avenue, 14<sup>th</sup> Floor** |  |
| **Cambridge, Massachusetts** | **Cambridge, Massachusetts** | **02139** |
| **(Address of principal executive offices)** | **(Address of principal executive offices)** | **(Zip Code)** |

---

#### Registrant's telephone number, including area code (857) 242-1600
Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

---

| | | |
|:---|:---|:---|
| **Title of each class** | **Trading**<br> **Symbol(s)** | **Name of each exchange**<br> **on which registered** |
| Common Stock, $0.001 par value | SPRO | The Nasdaq Global Select Market |

---

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

------

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| | |
|:---|:---|
| **Item 5.02** | **Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.**  |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b) On January 30, 2026, Ankit Mahadevia, MD notified the Board of Directors (the "Board") of Spero Therapeutics, Inc. (the "Company") of his intention to resign from the Board, including from his service on the Development Committee of the Board and from all officer and director positions he holds with any and all subsidiaries of the Company, effective as of January 30, 2026. Dr. Mahadevia's resignation is as a result of his other professional commitments and not the result of any dispute or disagreement with the Company or the Board on any matter relating to the Company's operations, policies or practices. The Company thanks Dr. Mahadevia for his years of service since the inception of the Company. The Company and Dr. Mahadevia intend to enter into a consulting agreement, pursuant to which Dr. Mahadevia will be available to provide support to the Company's management.

---

| | |
|:---|:---|
| **Item 8.01** | **Other Events.**  |

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On January 20, 2026, the Company received a letter (the "Letter") from the U.S. Securities and Exchange Commission (the "SEC") advising the Company that the SEC has concluded its investigation into the Company and that, based on the information as of the date of the Letter, the SEC does not intend to recommend an enforcement action against the Company at this time. The Letter was provided under the guidelines set out in the final paragraph of Securities Act Release No. 5310. The investigation was previously disclosed by the Company in its periodic reports under the Securities Exchange Act of 1934, as amended.

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#### SIGNATURE
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

---

| | | |
|:---|:---|:---|
| Date: January 30, 2026 | **SPERO THERAPEUTICS, INC.** | **SPERO THERAPEUTICS, INC.** |
|  | By: | /s/ Esther Rajavelu |
|  |  | Esther Rajavelu |
|  |  | President & Chief Executive Officer |

---