Highly purified cannabidiol ( CBD ) in CDKL5 deficiency disorder ( CDD ): Open‐label prospective study

Abstract Objective CDKL5 deficiency disorder (CDD) is an early‐onset developmental and epileptic encephalopathy characterized by frequent drug‐resistant seizures, cerebral visual impairment, motor dysfunction, and sleep and gastrointestinal disturbances. Preliminary evidence suggests that highly purified cannabidiol (CBD) may reduce seizure frequency, but data on its effects on comorbidities are lacking. This study aimed to evaluate the efficacy and safety of CBD in individuals with CDD. Methods We conducted a prospective, open‐label, single‐center study including patients with CDD aged >1 year. Outcomes included motor seizure frequency, caregiver‐ and clinician‐rated Clinical Global Impression (CGI), and changes in sleep, motor abilities, and EEG at 3, 6, and 12 months. CBD plasma levels were measured with High‐Performance Liquid chromatography–Mass Spectrometry (HPLC‐MS). Results Eight of nine patients (all females; median age 10 years, range 1–24) completed the study, with a retention rate at 12 months of 8/9 (89%). One discontinued at 6 months due to a skin rash. A > 50% seizure reduction was observed in 8/9 patients at 3 months, 6/9 at 6 months, and 1/8 at 12 months. Seven patients showed some degree of vigilance improvements, three in motor performance, and two in sleep and constipation. All caregivers reported at least minimal overall improvement (CGI score 3) at 3 months, and three reported marked improvement (CGI score 2), with a peak at 3 months. Five patients showed adverse events during the trial, but none were considered serious. The median CBD dose at all time‐points was 15.6 mg/kg/day (IQR 10.0–18.9) corresponding to a plasma dose of 69.9 ng/mL (IQR 29.8–114.6) and the median concentration/dose ratio was 4.7 (IQR 2.7–6.8). Significance The safety and efficacy of highly purified CBD in CDD were consistent with previous reports in the literature, with possible benefits beyond seizure control. Further studies are warranted to assess non‐seizure outcomes and compare long‐term efficacy across treatment options. Plain Language Summary We studied nine girls with CDKL5 deficiency disorder who had frequent, hard‐to‐treat seizures. They received cannabidiol for up to 1 year, added to their usual medicines. Most children had fewer seizures in the first months of treatment. Some families also noticed better alertness, eye contact, movement, sleep, or constipation. Side effects were usually mild and manageable. Although seizure frequency often returned to baseline by the end of the study, most families chose to continue cannabidiol. Because this was a small study without a placebo group, these results are preliminary, and larger controlled trials are needed.