This clinical trial is designed to test whether a single image-guided intracerebral administration of inhibitory nerve cells, called interneurons (NRTX-1001), into subjects with drug-resistant unilateral mesial temporal lobe epilepsy (MTLE), with or without mesial temporal sclerosis (MTS), is safe (frequency of adverse events) and effective (seizure frequency). NRTX-1001 comprises human interneurons that secrete a neurotransmitter, gamma-aminobutyric acid (GABA).
Key Inclusion Criteria: 1. Male or Female, age ≥18 to ≤75 2. Focal seizures, clinically defined as unilateral MTLE 3. Has failed to achieve seizure control despite adequate trials of at least 2 ASDs at appropriate doses 4. Currently on stable doses (at least 1 month prior to Screening) of approved ASDs 5. Single seizure focus confirmed within one hippocampus 6. Seizure frequency averages ≥4 per 28-day period, including at least 2 clinical focal seizures per 28-day period with objective manifestations or more severe types, over the 6 months prior to the Screening Visit. (Phase 1/2 only) 7. Disabling seizure frequency of ≥2 per 28-day period averaged over 3 months prior to the Screening visit and over a prospective 10-week baseline period prior to Randomization (Phase 3 Only) Key Exclusion Criteria: 1. Epilepsy due to other medical conditions and/or progressive neurologic disease 2. Evidence of seizure focus outside of the hippocampus or evidence of seizures of non- focal origin. 3. Significant other medical conditions which would impair safe participation 4. History of status epilepticus in the 3 years prior to screening. 5. Primary or secondary immunodeficiency 6. Suicide attempts in the past year 3 years 7. Severe psychiatric disorders 8. Prior lobectomy or LITT procedure 9. MRI indicating potential malignant lesion 10. Pregnancy, or currently breastfeeding.