A marijuana plant. Picture: REUTERS
A marijuana plant. Picture: REUTERS

An experimental medication that could become the first drug derived from a marijuana plant approved in the US, received a boost from Food and Drug Administration (FDA) staff.

The treatment’s maker, UK company GW Pharmaceuticals, provided "substantial evidence" of the drug’s effectiveness, FDA staff said in a report released Tuesday. The medication would treat seizures associated with two rare forms of epilepsy that typically affect children, according to the report.

Although the medication appears to have an increased risk of liver injury, it could be managed, the report said.

"The risk-benefit profile established by the data in the application appears to support approval of cannabidiol," FDA staff wrote.

GW Pharma’s US depositary receipts rose 4.5% to $126 in early trading in New York.

Later this week, a meeting of outside agency advisers will weigh in on the treatment.

The drug is made from a compound in the marijuana plant called cannabidiol, a different chemical from tetrahydrocannabinol, or THC, which gives marijuana its euphoric effect.

The treatment, which GW Pharma hopes to market under the name Epidiolex, is produced in the UK from a plant that has been bred to have a high cannabidiol, or CBD, content, CEO Justin Gover said in an interview earlier in April month. The chemical is purified and made into a strawberry-flavoured oral solution, he said.

Approval could help pave the way for other cannabis-based drugs, Gover said.

"Epidiolex, if approved, will mark a sea change in the acceptability of cannabinoids as therapy," he said.

Twenty-nine states and Washington DC have passed laws legalising medical marijuana. FDA approval would provide patients with a consistent therapy that would be likely to be covered by insurance, Gover said.

The pharmaceutical company is seeking to sell the oral solution to treat seizures associated with two forms of epilepsy — Lennox-Gastaut and Dravet syndromes — in patients aged two years or older. Both are considered severe forms of epilepsy that begin in childhood. The syndromes are resistant to many treatments and as many as 20% of children with Dravet syndrome die before reaching adulthood, according to the National Institutes of Health.

The FDA has approved a few drugs made from synthetic cannabinoids, including Insys Therapeutics’ Syndros for loss of appetite in people with HIV/AIDS and nausea caused by chemotherapy. Insys is developing a cannabidiol oral solution for a severe type of epileptic seizure known as infantile spasms, and childhood epilepsy defined by staring spells where the child is notaware or responsive.

The FDA is expected to decide whether to approve GW Pharma’s drug by June 27. The agency will first discuss the drug with advisers on Thursday.

GW Pharma is studying the medication to treat other diseases, including infantile spasms.