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):October 6, 2025

4800 Montgomery Lane**, Suite 220**

Bethesda , Maryland 20814

(Address of principal executive offices) (Zip Code)

(301

)

500-1556

(Registrant’s telephone number, including area code)

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:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR§230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2).

Emerging growth company x

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. ¨

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

Item 8.01 Other Information

On October 6, 2025, Gain Therapeutics, Inc. (the “Company”) presented preliminary data from the Company’s ongoing Phase 1b clinical study of GT-02287 in people with Parkinson’s disease (“PD”) with or without a GBA1 mutation at the International Congress of Parkinson’s Disease and Movement Disorders.

Preliminary Findings

After 90 days of dosing, GT-02287 has been safe and generally well tolerated, with no treatment-emergent serious adverse events observed. A transient increase in alkaline phosphatase and other liver enzymes has been observed in some participants and normalized despite ongoing dosing. Of the 21 study participants, two are treatment-naïve, two are on deep brain stimulation, and 18 are on levodopa and/or dopamine agonists or other PD drugs.

Mean MDS-UPDRS scores at baseline were 5.8, 7.4, and 24.7 for Parts I, II, and III, respectively. Several participants experienced an improvement in their UPDRS Part II and III scores after 90 days of dosing with GT-02287 while mean Part I scores remained unchanged. The mean improvement in Parts II and III by Day 90, which was not observed by Day 30, suggests that GT-02287 has a disease-slowing effect, consistent with the preclinical models in vivo and the proposed mechanism of action of GT-02287, supporting continued development. The plasma pharmacokinetics (PK) profile was consistent across all 14 participants sampled, was within the projected therapeutics range, and comparable to exposures observed in healthy volunteers in the Phase 1 study.

At two different meetings, the data monitoring committee has recommended continuation of the study and more recently, Australian health authorities have approved the Phase 1b study extension for patients who can now be treated for up to 12 months.

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.