By Pat Anson, Editor

A British drug maker has announced more disappointing results from clinical studies on the use of a medical marijuana spray to treat cancer pain.

GW Pharmaceuticals (NASDAQ: GWPH) said results from two new Phase III studies showed that its Sativex oral spray worked no better than a placebo in treating cancer pain. That was the same finding the company reported in January from an earlier study involving nearly 400 patients in the United States, Mexico and Europe.

However, patients in the U.S. did show “statistically significant improvement” in their pain levels when Sativex was taken along with an opioid pain medication. GW and its partner, Otuska Pharmaceutical, have requested a meeting with the U.S. Food and Drug Administration to explain that finding. Sativex is getting a “fast track” review from the agency as a treatment for cancer pain.

"In light of the missed primary endpoint in the first trial earlier this year, these additional results are not a surprise. Nevertheless, we are encouraged by data across the trials which consistently show positive outcomes for U.S. patients when analysed as a separate cohort," said Justin Gover, GW's Chief Executive Officer.

"We believe that this finding may provide important guidance in determining the optimal target patient population for Sativex and look forward to a discussion with the FDA on a potential path forward."

Sativex is composed primarily of two cannabinoids, CBD and THC, which are administered in an oral spray. Sativex is already being sold in Europe, Canada and Mexico to treat muscle tightness and contractions caused by multiple sclerosis. Canada also allows Sativex to be used for the treatment of neuropathic pain and advanced cancer pain.

The spray is not currently approved for use in the U.S. for any condition. It is estimated that over 400,000 cancer patients in the U.S. suffer from pain that is not well controlled by opioid pain medications.

"While the results overall have been disappointing, and not necessarily wholly consistent with clinical experience, nonetheless they suggest that Sativex may have a useful role in the treatment of certain subgroups of patients with advanced cancer pain who have exhausted opioid treatments," stated Dr. Marie Fallon, Professor of Palliative Care, University of Edinburgh and a principal investigator in the Phase III program.

"In particular, the U.S. patients enrolled in this program showed a useful therapeutic benefit whereas results in European patients were generally not favorable. These U.S. patients were less frail, hence the Sativex intervention was subjected to less ‘noise,’ providing clearer results and valuable guidance in determining the optimal target patient population for Sativex. This is a patient population with a significant unmet need and I believe that this important observation for Sativex warrants further investigation."

Cancer patients in all three studies were given Sativex or a placebo spray 3-to-10 times a day over a 5-week period. Patients remained on opioid therapy during the studies. Sativex was well tolerated, with the only side effects in some patients being dizziness and somnolence.

GW is developing other cannabis-based medicines to treat epilepsy, glioma, ulcerative colitis, type-2 diabetes, and schizophrenia.