BioWorld International Correspondent

LONDON - GW Pharmaceuticals plc published fresh data showing its cannabis-based medicine Sativex provides effective long-term treatment of central neuropathic pain in multiple sclerosis, with no evidence that patients were increasing the dose to maintain the effect.

Stephen Wright, the company's R&D director, said this is an important addition to the findings from short-term trials. "The results confirm that Sativex is able to provide substantial relief from pain for a long period of time to patients who have previously failed to obtain benefit from other available treatments."

Wright added, "We believe this study shows that Sativex is able to meet a real medical need."

The data comes from an open label extension of a short-term randomized controlled trial. Pain scores for 66 patients who completed the extension trial showed sustained improvement over two years. At the end of the two years the mean pain score was 2.9 (a severity assessed as mild), compared to a mean on entry to the short-term trial of 6.5.

Sativex is self-administered as a sub lingual spray. There was no evidence of tolerance, with dosing remaining stable over the two years, and there were no additional safety issues. This is the longest period to have been studied in this indication.

Investigator David Rog, consultant neurologist at the Greater Manchester Neurosciences Centre, said, "Long Term use of Sativex provides sustained benefit in around of half of patients with multiple sclerosis and central neuropathic pain."

In addition, Porton Down, UK-based GW recently completed recruitment into a 339 patient Phase III study in this indication, with results expected in 2008.

Despite its progress in building the data file for Sativex in a number of indications, GW has had problems convincing the regulators in Europe.

In July the company's shares fell 27 pence to 65 pence and it was forced to withdraw the European submission of Sativex in treating spasticity in multiple sclerosis and conduct another trial. Since then the shares have drifted further down to 57 pence.

Stefan Hamill, analyst at Clear Capital in London, said the findings on tolerance removed one of the key issues hanging over the company. "This is significant as it offsets one of the main concerns about long-term use of Sativex, of drug dependence and dose escalation."

Hamill added that this data bode well for further results expected in 2008. "The market is overly pessimistic about GW and has largely focused on the negatives, whilst a body of positives has been developing."

While the UK regulator has dragged its heels, Sativex is approved for treating neuropathic pain in multiple sclerosis in Canada and the FDA has given the green light to U.S. Phase III studies.

Although Sativex is not a blockbuster, it has the potential to be a lucrative niche market, Hamill told BioWorld International.

Beyond this, knowledge is building that the cannabinoid system offers a range of targets in addition to the central nervous system, and to date most of these are undrugged.

Along with good relationships with key academics, GW has a deal with Otsuka Pharmaceutical Co Ltd of Japan to develop further cannabinoids in a range of central nervous system and oncology indications.