GW Pharmaceuticals’ cannabis-based epilepsy treatment, Epidiolex, scored a favorable review from FDA staff Tuesday, ahead of an advisory committee meeting scheduled later this week. The company provided “substantial evidence” of the drug’s effectiveness in treating two rare forms of epilepsy.

“Although the review is still ongoing, the risk-benefit profile established by the data in the application appears to support approval of cannabidiol for the treatment of seizures associated with LGS [Lennox-Gastaut syndrome] and DS [Dravet syndrome,]” the agency said in a report. GW was up 10% Tuesday morning on the news.

Both syndromes tend to appear in childhood, have a higher mortality rate than other types of epilepsy and are difficult to treat. They do not respond to many of the drugs typically used to treat epilepsy—for example, patients in GW’s phase 3 LGS trial had previously been treated with an average of nine antiepileptic drugs.

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Epidiolex is a purified form of cannabidiol derived from plants. How, exactly, it wards off seizures is unknown, but it does not appear to interact with cannabinoid receptors, and both preclinical and clinical data show it does not look to have abuse potential, the report said.

Although an increased risk of liver injury was flagged, the FDA team thinks this can be managed “with inclusion of relevant language in labeling, education of prescribers regarding the risk of transaminase elevation and need for monitoring of liver enzyme levels, and further characterization of the risk in the post-market setting.”

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The drug’s PDUFA date is June 27. Its approval could help smooth the path for other biotechs working on cannabis-based treatments, including Therapix, whose Tourette’s medication succeeded in phase 2, and GB Sciences, which has candidates for Parkinson’s and chronic pain in the works.

“Epidiolex, if approved, will mark a sea change in the acceptability of cannabinoids as therapy,” GW Pharma CEO Justin Gover told Bloomberg.

GW already markets Sativex outside the U.S. for the treatment of spasticity due to multiple sclerosis. Its pipeline includes candidates for glioblastoma and schizophrenia, as well as one being tested in epilepsy and autism spectrum disorders. The latter, a cannabidivarin dubbed GWP42006, recently failed a midstage trial in focal seizures.