GW Pharmaceuticals became the latest casualty in the embattled biotechnology sector on Tuesday, after the pioneer of cannabis-based medicine saw its shares fall by more than a quarter after the failure of a critical clinical trial.

The company said a final stage trial for Sativex, its lead drug hope, to treat neuropathic pain in multiple sclerosis patients had shown a high response rate but narrowly failed to show significant benefits because of an unexpectedly large placebo response.