Seoul – October 18, 2026 -- XellSmart's off-the-shelf Parkinson's cell therapy XS411 improved OFF-state motor scores by an average of more than 30 points at six months in all nine Phase I participants, and its 30-patient Phase II trial in China has completed enrollment.
The data were presented at the International Congress of Parkinson's Disease and Movement Disorders (MDS). The company says the results showed no dose-limiting toxicities, serious adverse events or adverse events related to XS411.
Phase I data show motor and imaging gains in nine patients
The single-arm, open-label trial used a 3+3 dose-escalation design across three cohorts. Participants had moderate-to-advanced disease, a mean duration of about 10 years, end-of-dose wearing-off and OFF-state Hoehn-Yahr stages of 3 to 4. Cells were transplanted into the bilateral posterior putamen.
Patients gained an average of more than five hours of good ON time per day at six months, defined as ON time without troublesome dyskinesia. PDQ-39 questionnaire results followed the same trend. Benefits continued through available follow-up, with a trend favoring the higher-dose group. Serial MRI showed no aberrant cellular overgrowth or tumor formation, and no graft-induced dyskinesia was observed.
Because open-label designs risk bias in clinician and patient ratings, the study added 18F-DOPA PET imaging. Scans showed elevated specific binding ratios in the putamen versus baseline, in areas consistent with the injection sites. XellSmart interprets this as evidence that the transplanted cells survive, engraft and differentiate.
Phase II trial enrolls all 30 patients under PROBE design
The registrational Phase II study is led by Beijing Tiantan Hospital. Sub-centers include Peking Union Medical College Hospital, the Second Affiliated Hospital of Soochow University and Jiangsu Province Hospital. Transplantation in the treatment group is complete and follow-up is ongoing.
The trial uses a Prospective Randomized Open-label Blinded Endpoint (PROBE) design with parallel arms and independent outcome assessment. XellSmart describes it as the world's first stem cell trial in Parkinson's disease built on this design. The company expects the data to support a pivotal Phase III registrational trial.
XS411 skips HLA matching, setting it apart from Kyoto's donor-line approach
XS411 is an allogeneic therapy made of iPSC-derived dopaminergic neural progenitor cells. It is designed for use without patient-specific HLA matching and is given with a standardized immunosuppressive regimen. XellSmart contrasts this with Kyoto University's iPSC therapy, the only conditionally approved Parkinson's cell product to date, which relies on HLA "super-donor" lines. The company says those lines face technical, cost and regulatory barriers to global deployment. It also notes that three of four pioneering international trials used embryonic stem cells, which carry ethical limits.
FDA Fast Track and China funding add two 2026 milestones
XS411 secured funding under China's National Major Innovative Drug Program. The XellSmart-led consortium includes Tongji University, NIFDC, Beijing Tiantan Hospital and Peking Union Medical College Hospital, and the project kicked off in June 2026.
In July 2026, after clinical trial clearance in China and the US, the FDA granted XS411 Fast Track Designation. XellSmart says this enables closer FDA communication on trial design and may open expedited pathways, including rolling review.
The Phase I data come from nine patients in an open-label, single-arm study, and the company acknowledges the bias risk of such designs. Phase II is intended to test efficacy under blinded endpoint assessment.