Gain Therapeutics, Inc. (NASDAQ:GANX) ("Gain", or the "Company"), a clinical-stage biotechnology company leading the discovery and development of the next generation of allosteric small molecule therapies, today announced the presentation of a poster at the International Congress of Parkinson’s Disease and Movement Disorders, being held October 4-8, 2026, in Seoul, Korea. The poster outlines long-term open-label extension (OLE) data from the Phase 1b clinical study of rexaceract showing stabilization of MDS-UPDRS scores over 360 days (12 months) of dosing, supporting the disease-modifying potential in Parkinson’s disease (PD).

A PDF of the poster presented at the MDS Congress is available on the Science and Technology section of the Company’s website at https://gaintherapeutics.com/science-and-technology/posters/.

The poster, titled, "Long-Term Open-Label Data on the GCase Modulator GT-02287 (Rexaceract) in People with Parkinson’s Disease," will be presented on-site by the Company’s Chief Scientific Officer Joanne Taylor, Ph.D. The data, which includes safety, tolerability, and clinical scores from the Phase 1b nine-month study extension support continued development of rexaceract for PD.

Average MDS-UPDRS scores from baseline (Day 0) to 12 months (Day 360) in all participants who completed dosing regimen by August 31, 2026, and had evaluable MDS-UPDRS scores at each time point

As of August 31, 2026, 12 of the 13 evaluable patients have completed the full 12-month administration of rexaceract in the OLE with one additional participant scheduled to complete dosing in November 2026.

In the 12 evaluable participants, MDS-UPDRS motor scores were stable over the 12-month study period with rexaceract, demonstrating no clinically meaningful progression of motor symptoms on the MDS-UPDRS Parts II and III. A clinically meaningful change in PD disease progression is generally accepted to be an increase in MDS-UPDRS Part II and III together of approximately 6 points over a year, which also is the mean annual rate of disease progression among individuals with early PD. Part II of the MDS-UPDRS is patient-reported motor aspects of experiences of daily living and assesses the impact of Parkinson’s disease on activities such as eating, dressing, walking, and other everyday functions. Part III is a clinician-assessed motor examination, evaluating features such as tremor, rigidity, bradykinesia, speech, and gait.

The Company expects to submit a new Phase 2 study protocol to the U.S. Food and Drug Administration (FDA) in the coming weeks, informed by insights provided by the Phase 1b study results and recent discussion with potential partners, and initiate the Phase 2 clinical trial of rexaceract in people with Parkinson’s disease in 1Q27.