Material Event (Form 8-K)

Item 8.01. Other Events.

On June 30, 2025, Gain Therapeutics, Inc. (the "Company") announced an update on the progress of its ongoing Phase 1b clinical study evaluating the safety and tolerability of GT-02287 in people with Parkinson's Disease with or without a GBA1 mutation. The study, which aimed to enroll 15-20 participants, reached 16 participants on June 30, 2025, despite a two-month delay in protocol implementation. In addition, the independent data monitoring committee met recently and recommended to continue the study with no changes in dose level, concluding no serious treatment emergent adverse events have occurred.

The faster-than-anticipated enrollment means all those participants will reach their 90-day visit in time to facilitate biomarker analysis of all cerebrospinal fluid ("CSF") samples taken by fourth quarter of 2025 instead of the first quarter of 2026. Based on the greater relevance of CSF biomarkers as proof of drug activity, and considering the new timeline, the Company is expected to provide full results on 90-day biomarker evidence from all CSF and blood samples together during 4Q 2025, which is also earlier than originally planned.

Additionally, to facilitate the continued interest on the part of clinicians and patients currently aware of the Phase 1b study in Australia, the Company will extend the screening window for participants through July 31, 2025. The Company is also planning to approach the local health authorities in Australia to extend the dosing period of the Phase 1b beyond the 90-day period currently allowed in the protocol. Long-term chronic toxicology studies required to support this extension of dosing are near completion, and the Company is expected to provide an update on the progress of the extension before the end of 3Q25. The Company believes that the extension of the Phase 1b will also better inform Phase 2 protocol design and planning for early 2026.