ABSTRACT NUMBER: ESOC2026LB196 INTRA-ARTERIAL ALLOGENIC MESENCHYMAL STEM CELLS (NCS-01) FOLLOWING THROMBECTOMY: PHASE 1 SAFETY, FEASIBILITY, AND EXPLORATORY EFFICACY SIGNALS

Abstract Background and aims Despite treatment advances, a significant proportion of treated patients remain disabled after acute ischaemic stroke (AIS). Endovascularly delivered intra-arterial (IA) mesenchymal stem cells (MSCs) may lead to benefit via paracrine-mediated recovery post reperfusion. We aimed to test the safety and exploratory efficacy of dose escalation of NCS-01, an allogeneic bone-marrow-derived MSC sub-population, delivered IA post-thrombectomy. Methods This phase 1/2, dose-escalation, multi-centre study (NCT03915431) enrolled anterior circulation AIS patients within 48 hours of onset following successful thrombectomy. Two Phase 1 cohorts (n=4 each) were randomised 3:1 (NCS-01 vs sham) at single doses of 1x 107 and 3 x 107 cells respectively, administered via microcatheter in the ipsilateral terminal ICA or proximal MCA. Safety, including early neurological deterioration (END), new ischaemia on MRI, and treatment-related adverse events (TRAEs) & exploratory efficacy included infarct volume reduction,NIHSS and mRS were measured over 12 months. Results Interim analysis included eight patients (median age 65.5; 5M, 3F, median NIHSS 11) from five centres. Follow-up to 12 months was completed by one patient in Cohort 1 and all four in Cohort 2. No END, new ischaemia, sICH, or TRAEs occurred in treated or sham groups. Infarct volume decreased from baseline by 41, 77 & 86% in the treated group and 20% in the sham patient. NIHSS and mRS showed serial improvement over 12 months in both groups (Figure). Conclusions IA NCS-01 post-reperfusion is feasible, appears safe and may be showing a promising proof-of-concept signal of clinical activity. These interim results support the continued completion of the trial. Conflict of interest Figure 1 - belongs to Results