XellSmart Biopharmaceutical presented clinical data for XS411, its off-the-shelf cell therapy candidate for Parkinson's disease, at the International Congress of Parkinson's Disease and Movement Disorders, the company said. An investigator presented the Phase I results during a session on clinical trials, pharmacology and medical management, and the same session covered completion of enrollment in a randomized, parallel-group Phase II trial in China that uses an open-label design with blinded endpoint assessment.
XS411 is an allogeneic therapy made from induced pluripotent stem cell-derived dopaminergic neural progenitor cells. It is designed for use without patient-specific human leukocyte antigen matching and is given with a standardized immunosuppressive regimen, and after transplantation into the putamen the cells are intended to differentiate into dopaminergic neurons.
Phase I results
The Phase I trial was single-arm and open-label, enrolling nine participants with moderate-to-advanced Parkinson's disease across three dose cohorts under a 3+3 dose-escalation design. Mean disease duration was about 10 years, and all participants had end-of-dose wearing-off and OFF-state Hoehn-Yahr stages of 3 to 4. The trial met its primary safety and tolerability objectives, with no dose-limiting toxicities, serious adverse events or adverse events considered related to XS411 reported during follow-up. Serial MRI showed no aberrant cellular overgrowth or tumor formation, and no graft-induced dyskinesia was observed.
OFF-state MDS-UPDRS Part III scores improved by an average of more than 30 points from baseline at six months, with a trend toward greater efficacy in the higher-dose group. Participants gained an average of more than five hours of good ON time per day at six months, defined as ON time without troublesome dyskinesia, and scores on the 39-item Parkinson's Disease Questionnaire followed the same trend. ¹⁸F-DOPA PET scans showed elevated specific binding ratios in the putamen compared with baseline, with signal increases that matched the injection sites; the release noted that open-label trials carry a risk of bias in clinician ratings and patient-reported outcomes, and presented the imaging as an objective measure alongside them.
Phase II design and sites
The Phase II study is led by Beijing Tiantan Hospital, with Peking Union Medical College Hospital, the Second Affiliated Hospital of Soochow University and Jiangsu Province Hospital as sub-centers. It uses a Prospective Randomized Open-label Blinded Endpoint design, which the company describes as the first Parkinson's disease stem cell therapy trial built around that design. All 30 planned participants have been enrolled, transplantation has been completed in the treatment group and follow-up is ongoing.
Funding and FDA designation
XS411 secured funding under China's National Major Innovative Drug Program through a XellSmart-led consortium that includes Tongji University, NIFDC, Beijing Tiantan Hospital and Peking Union Medical College Hospital, with work starting in June 2026. In July 2026, after clinical trial clearance in China and the United States, XS411 received FDA Fast Track Designation, which the company said allows more efficient communication with the agency on clinical strategy and trial design and may make the program eligible for expedited pathways including rolling review.
