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): September 5, 2025

MERSANA THERAPEUTICS, INC.

(Exact name of registrant as specified in its charter)

Delaware

001-38129

04-3562403

(State or other jurisdiction
of incorporation)

(Commission

File Number)

(IRS Employer

Identification No.)

840 Memorial Drive Cambridge, Massachusetts		02139
(Address of Principal Executive Offices)		(Zip Code)

Registrant’s telephone number, including area code: (617) 498-0020

Not Applicable

(Former name or former address, if changed since last report)

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 (see General Instruction A.2. below):

¨ 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 Symbol(s)	Name of each exchange on which registered
Common Stock, $0.0001 par value	MRSN	The Nasdaq Stock Market LLC

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. ¨

Item 3.01 Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing.

On September 5, 2025, Mersana Therapeutics, Inc. (the “Company”) received written notice (the “Notice”) from the Listing Qualifications Department of The Nasdaq Stock Market LLC (“Nasdaq”) notifying the Company that the Company is not in compliance with Nasdaq Listing Rule 5450(b)(2)(A) (the “MVLS Rule”), which requires the Company to maintain a minimum Market Value of Listed Securities (“MVLS”) of $50.0 million. The Notice is only a notification of deficiency, not of imminent delisting, and has no current effect on the listing of the Company’s common stock, which continues to trade on The Nasdaq Global Select Market under the symbol “MRSN.”

In accordance with the MVLS Rule, the Company has a period of 180 calendar days, or until March 4, 2026 (the “Compliance Date”), to regain compliance with the MVLS Rule. To regain compliance, the Company’s MVLS must close at $50.0 million or more for a minimum of ten consecutive business days prior to the Compliance Date. In the event the Company does not regain compliance with the MVLS Rule prior to the Compliance Date, Nasdaq will notify the Company that its securities are subject to delisting. At that time, the Company will have the opportunity to appeal the delisting determination to a Nasdaq hearings panel. The Company intends to monitor its MVLS and consider its available options to regain compliance with the MVLS Rule. However, there can be no assurance that the Company will be able to regain compliance with the MVLS Rule or maintain compliance with other Nasdaq listing rules.

SIGNATURES

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.

	MERSANA THERAPEUTICS, INC.

Date: September 5, 2025	By:	/s/ Brian DeSchuytner
		Brian DeSchuytner
		Senior Vice President, Chief Operating Officer and Chief Financial Officer

Mersana Therapeutics, Inc. 8-K