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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): August 6, 2026

REPLIMUNE GROUP, INC.

(Exact name of registrant as specified in its charter)

Delaware |  | 001-38596 |  | 82-2082553
(State or other jurisdiction of incorporation) |  | (Commission File Number) |  | (IRS Employer Identification Number)

500 Unicorn Park Drive

Suite 303

Woburn, MA 01801

(Address of principal executive offices, including Zip Code)

Registrant’s telephone number, including area code: (781) 222-9600

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 Symbol(s) |  | Name of each exchange on which registered
Common Stock, par value $0.001 per share |  | REPL |  | The Nasdaq Stock Market LLC (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. ¨

| Item 8.01 | Other Events.

On August 6, 2026, Replimune Group, Inc. (the “Company”) issued a press release announcing that the U.S. Food and Drug Administration has granted accelerated approval for TUDRIQEVTM (vusolimogene oderparepvec-wtpg), previously referred to as RP1, in combination with nivolumab for the treatment of adults with unresectable advanced cutaneous melanoma who experienced disease progression on an anti-PD-1 antibody-based regimen. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial(s). A copy of the press release is filed as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated by reference herein. In addition, the Company posted to its website a corporate presentation in connection with the approval. A copy of the corporate presentation is attached hereto as Exhibit 99.2 and is incorporated by reference herein.

| Item 9.01 | Financial Statements and Exhibits.

Exhibit No. |  | Description
99.1 |  | News Release dated August 6, 2026
99.2 |  | Company Presentation dated August 6, 2026
104 |  | Cover page interactive data file (formatted as Inline XBRL)

SIGNATURES

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

| REPLIMUNE GROUP, INC.
Date: August 6, 2026 | By: | /s/ Sushil Patel
|  | Sushil Patel
|  | Chief Executive Officer