BANGKOK – Interim results of long-term, open-label extension trials of add-on prescription cannabidiol in patients with Dravet syndrome or Lennox-Gastaut syndrome show sustained, clinically meaningful seizure reductions with no new safety concerns, , reported at the International Epilepsy Congress.
“Overall, this is a very promising and sustainable result that we were happy to see,” said Dr. Patel, chief of child neurology at Nationwide Children’s Hospital in Columbus, Ohio.
Epidiolex is the brand name for the plant-derived, highly purified cannabidiol (CBD) in an oil-based oral solution at 100 mg/mL. Dr. Patel has been involved in the medication’s development program since the earliest open-label compassionate use study, which was followed by rigorous phase 3, double-blind, placebo-controlled randomized trials, eventually leading to Food and Drug Administration marketing approval for the treatment of Dravet syndrome and Lennox-Gastaut syndrome in patients 2 years of age or older.
“On June 25th, 2018, history was made: for the first time in United States history, a plant-based derivative of marijuana was approved for use as a medication, and it was also the first FDA-approved treatment for Dravet syndrome,” Dr. Patel noted at the congress sponsored by the International League Against Epilepsy.
A total of 96% of the 289 children with Dravet syndrome who completed the 14-week, double-blind, controlled randomized trials enrolled in the open-label, long-term extension, during which they were on a median of three concurrent antiepileptic drugs along with a mean modal dose of CBD at 22 mg/kg/day. Although the target maintenance dose of CBD was 20 mg/kg/day, as advised in the product labeling, physicians could reduce or increase the dose up to 30 mg/kg/day.
“In the initial compassionate-use study, our site could go up to 50 mg/kg/day,” according to Dr. Patel. “We have plenty of data showing efficacy and continued safety beyond the FDA-recommended dose.”
In the open-label extension study, the median reduction from baseline in monthly seizure frequency assessed in 12-week intervals up to a maximum of week 72 was 44%-57% for convulsive seizures and 49%-67% for total seizures. More than 80% of patients and/or caregivers reported improvement in the patient’s overall condition as assessed on the Subject/Caregiver Global Impression of Change scale.
The pattern of adverse events associated with CBD has been consistent across all of the studies. The most common side effects are diarrhea in about one-third of patients, sleepiness in one-quarter, and decreased appetite in about one-quarter. Seven percent of patients discontinued the long-term extension trial because of adverse events.
Seventy percent of patients remained in the long-term extension study at 1 year.
Twenty-six patients developed liver transaminase levels greater than three times the upper limit of normal, and of note, 23 of the 26 were on concomitant valproic acid. None met criteria for severe drug-induced liver injury, and all recovered either spontaneously or after a reduction in the dose of CBD or valproic acid. But this association between CBD, valproic acid, and increased risk of mild liver injury has been a consistent finding across the clinical trials program.
“This is a very important clinical pearl to take away,” commented Dr. Patel, who is also a pediatric neurologist at Ohio State University.
The interim results of the long-term, open-label extension study of add-on CBD in patients with Lennox-Gastaut syndrome are similar to the Dravet syndrome study. Overall, 99% of the 368 patients with Lennox-Gastaut syndrome who completed the 14-week, double-blind, randomized trials signed up for the open-label extension. During a median follow-up of 61 weeks, the median percent reduction in seizure frequency as assessed in serial 12-week windows was 48%-70% for drop seizures and 48%-63% for total seizures. Twenty-four percent of patients withdrew from the study. Eighty-eight percent of patients or caregivers reported an improvement in overall condition when assessed at weeks 24 and 48. Forty-seven patients developed elevated transaminase levels – typically within the first 2 months on CBD – and 35 of them were on concomitant valproic acid.