Shares in the company have been gaining after positive trial results of its experimental drug Epidiolex, and have notched up gains of more than 50 percent this year, shrugging off early declines.

GW Pharma's drug reduced the incidence of seizures in people suffering from rare forms of epilepsy, Lennox-Gastaut syndrome and Dravet syndrome.

The company, which was founded in 1998 with the aim of capitalizing on the medical benefits of cannabis, said the American Depositary Shares would be sold at $90 per share.

GW Pharma has had a rocky time on the London stock market, and in 2013 opted for a dual listing on the Nasdaq, where it has raised more than $500 million from U.S. investors.

The company's stock was down 2 percent at 600.5 pence on the London Stock Exchange on Wednesday.

(Reporting by Mamidipudi Soumithri in Bengaluru; Editing by Sunil Nair)