Neurona Therapeutics presented updated long-term clinical data from its ongoing Phase 1/2 trials of rezanecel (NRTX-1001) at the 2026 American Academy of Neurology Annual Meeting in April, reporting a median disabling seizure reduction of 97% in the post-month-13 observation window for patients in the low-dose Cohort 1. The figures reinforce the durability signal that has made rezanecel one of the most closely watched pipeline candidates in refractory epilepsy, a disease area that has seen limited paradigm-shifting advances despite more than 30 approved antiseizure medications.

Rezanecel is a one-time, allogeneic cell therapy comprising human embryonic stem cell-derived GABAergic interneurons — specifically a subtype that approximates the caudal ganglionic eminence-derived interneurons that regulate hippocampal excitatory activity. The therapeutic rationale is grounded in the observation that hippocampal interneuron loss is a consistent histopathological feature of mesial temporal sclerosis, the structural abnormality associated with mesial temporal lobe epilepsy (MTLE), the most common form of drug-resistant focal epilepsy. Rather than suppressing seizures through pharmacological modulation of synaptic transmission, rezanecel aims to physically restore the inhibitory circuit deficits that underpin seizure generation.

As of the AAN presentation, 31 participants had been dosed across both open-label studies, receiving either a low or high dose of rezanecel via stereotactic injection into the hippocampus ipsilateral to the seizure onset zone. Patients in the primary efficacy window of months 7 to 12 post-treatment achieved a median 92% reduction in disabling seizures from baseline in the low-dose cohort. Among patients with follow-up extending beyond month 13, that reduction deepened to 97%. Neurona has not reported seizure freedom rates separately, but the magnitude and persistence of the response — in patients who had failed a median of five prior antiseizure medications — is without obvious precedent in the published Phase 1 literature for this indication.

The tolerability profile has been consistent with surgical intervention of this type: peri-procedural headache and transient neurological symptoms dominated the adverse event picture, with no evidence of graft-related malignancy or immune rejection, the latter reflecting the immunologically privileged nature of the central nervous system.

Neurona has announced plans to initiate the Phase 3 EPIlepsy Cell Therapy (EPIC) trial in the second half of 2026. The study is designed as a randomised, sham-controlled, double-blind trial in adults with drug-resistant MTLE. The sham-controlled design addresses a methodological challenge that has historically complicated surgical epilepsy trials: separating placebo effect from true treatment response in patients who are aware they received an intervention.

The cell therapy approach to epilepsy represents a fundamentally different paradigm from both pharmacotherapy and ablative surgery. For patients who have exhausted medical options and are not candidates for resection, it offers a potential path to durable seizure control without permanent structural tissue removal.