Long-term efficacy and safety of cannabidiol in patients with treatment-resistant epilepsies: 4-year results from the expanded access program

Objective: Cannabidiol (CBD) expanded access program (EAP), initiated in 2014, provided add-on CBD to patients with treatment-resistant epilepsy (TRE) at 35 US epilepsy centers. Prior publications reported results through December 2016; herein, we present efficacy and safety results through January 2019.

Methods: Patients received plant-derived highly purified CBD (Epidiolex®; 100 mg/mL oral solution), increasing from 2-10 mg/kg/d to tolerance or maximum 25-50 mg/kg/d dose, depending on the study site. Efficacy endpoints included percentage change from baseline in median monthly convulsive and total seizure frequency and ≥50%, ≥75%, and 100% responder rates across 12-week visit windows for up to 192 weeks. Adverse events (AEs) were documented at each visit.

Results: Of 892 patients in the safety analysis set, 322 (36%) withdrew; lack of efficacy (19%) and AEs (7%) were the most commonly reported primary reasons for withdrawal. Median (range) age was 11.8 years (0-74.5), and patients were taking a median (range) 3 (0-10) antiseizure medications (ASMs) at baseline; most common ASMs were clobazam (47%), levetiracetam (34%), and valproate (28%). Median top CBD dose was 25 mg/kg/d; median exposure duration was 694 days. Median percentage reduction from baseline ranged from 50%-67% for convulsive seizures and 46%-66% for total seizures. Convulsive seizure responder rates (≥50%, ≥75%, and 100% reduction) ranged from 51%-59%, 33%-42%, and 11%-17% of patients across visit windows, respectively. AEs were reported in 88% of patients and serious AEs in 41%; 8% withdrew because of an AE. There were 20 deaths during the study deemed unrelated to treatment by the investigator. Most common AEs (≥20% of patients) were diarrhea (33%), seizure (24%), and somnolence (23%).

Significance: Add-on CBD was associated with sustained seizure reduction up to 192 weeks with an acceptable safety profile and can be used for long-term treatment of TREs.