Shares in DOV Pharmaceutical are expected to fall through the floor today after a drug to treat back pain, bicifadine, was no better than placebo in a Phase III trial.

Bicifadine failed to show any benefit on pain at all three of the doses tested in the study, and DOV shares lost more than 40% of their value in after-hours trading on the Nasdaq, after ending the day at $14.69.

The company said the poor performance of bicifadine in back pain could have been a result of a higher-than-expected placebo response or “the extent of patients’ reliability in taking their medication,” but added it was now sifting through the data to see what went wrong.

But despite the setback, DOV insisted it would press on with developing bicifadine for two other indications, osteoarthritis and neuropathic pain, currently in Phase II trials, and would continue its two Phase III trials in back pain to their conclusion.

Bicifadine is thought to have a novel mechanism of action in pain, enhancing and prolonging the actions of two neurotransmitters, serotonin and norepinephrine, by blocking the transporter molecule that terminates their physiologic action.

Its activity is thought to be more closely related to the mechanism of Lilly’s Cymbalta (duloxetine) - a serotonin and norepinephrine reuptake inhibitor that was approved as a treatment for neuropathic pain in 2004 - rather than conventional narcotic pain relievers or those which work by blocking prostaglandins.