Nine patients. No serious adverse events. An average gain of more than five hours of good ON time per day at six months. Those numbers, presented at the International Congress of Parkinson’s Disease and Movement Disorders, are the first clinical read on XS411, XellSmart’s allogeneic, HLA-independent cell therapy for Parkinson’s disease, and they arrive alongside confirmation that the company has finished enrolling its Phase II trial.
The Phase I single-arm study used a 3+3 dose-escalation design across three cohorts, all participants with moderate-to-advanced disease averaging roughly a decade since diagnosis. OFF-state MDS-UPDRS Part III scores dropped by more than 30 points from baseline at six months, a margin the company says clears published minimal clinically important difference thresholds. The open-label format is an inherent limitation for clinician-rated and patient-reported measures, but ¹⁸F-DOPA PET imaging, an established objective biomarker for dopaminergic engraftment, showed elevated tracer uptake in the putamen at injection sites, consistent with surviving, functional grafted cells. That imaging signal is the hardest evidence the company can offer at this stage that transplanted cells are doing what they are supposed to do.
The Phase II trial, led by Beijing Tiantan Hospital with three additional top-tier Chinese centers, enrolled all 30 planned participants and has completed transplantation in the treatment group. Its design is a PROBE framework, meaning randomized allocation and open-label treatment but blinded endpoint assessment by independent evaluators. XellSmart says this is the first stem cell trial in Parkinson’s disease built on that design. The blinded assessment structure matters because it is the element most likely to satisfy regulators when the company eventually seeks to run a confirmatory Phase III. Context worth noting: Japan conditionally approved Raguneprocel, an iPSC-derived dopaminergic therapy from Kyoto University, in February 2026, so the field is moving toward approval-stage decisions even as XS411 remains in Phase II.
XS411 requires no patient-specific HLA matching, which removes a logistical barrier that has complicated earlier allogeneic approaches. The practical test of that advantage will appear in the Phase II outcome data, particularly whether the standardized immunosuppression regimen keeps rejection rates low across a larger, more diverse patient group. That readout, not the current enrollment milestone, is what will determine whether the design holds up at scale.
XS411: the facts in one place
- Also written: XS411CN
- Sponsor: XellSmart Biopharmaceutical Co., Ltd.
- Mechanism: Allogeneic iPSC-derived dopaminergic neural progenitor cells transplanted into the putamen to replace lost dopamine-producing neurons and restore neurological function
- Indication studied: Primary Parkinson’s disease
- Phase: Phase I (US); Phase II (China)
- Enrollment: 9 (Phase I, China); 30 (Phase II, China)
- Headline result: Phase I (China): no serious adverse events; average gain of more than five hours of good ON time per day at six months; significant improvements in motor scores and quality of life
- Registry identifier: NCT07166757, NCT07080775
- Current status: Phase I ongoing in US following FDA IND approval January 2025; Phase II multicenter registrational trial in China completed enrollment July 2026; FDA Fast Track Designation granted July 28, 2026
- FDA IND approval: January 2025
- FDA Fast Track Designation: July 28, 2026
- Phase II multicenter trial launch announced: April 14, 2026
- Phase II enrollment completed: July 2026
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
