Sativex phase III neuropathic pain trials show benefits: GW Pharma
GW Pharmaceuticals plc announces preliminary results of two phase III studies of Sativex, its cannabinoid spray medicine, in peripheral neuropathic pain.
These studies are part of a programme to generate data for the future expansion of the use of Sativex in Europe beyond Multiple Sclerosis (MS) into other pain conditions.
The results of the study in patients with neuropathic pain characterised by allodynia show that patients taking Sativex obtain clinically important improvements in their management of pain and quality of sleep. In comparison with placebo, statistically significant improvements were seen for key outcome measures, including a positive result in the primary analysis of patient response, the outcome measure recommended by regulatory authorities.
The results of the study in patients with painful diabetic neuropathy show that patients taking Sativex obtained substantial improvements in their pain, indeed among the highest level of response seen in the published literature. There was an abnormally large placebo response in this study, which means that the data are more difficult to interpret categorically.
Dr Stephen Wright, GW's R&D Director, said, "Neuropathic pain is one of the most difficult types of chronic pain to treat. These studies focused on particularly high need patients, who were already taking the best available pain treatments, and yet still suffered severe pain. Even in this most difficult to treat population, Sativex has produced improvements over and above current treatments that are highly meaningful to the everyday lives of patients."
These two studies form part of a programme of neuropathic pain trials conducted to date by GW and reinforce the large body of positive data already generated. These data contribute significantly to a future regulatory filing in the use of Sativex as a treatment for neuropathic pain. GW intends to continue to add to this evidence base.
This multi-centre double-blind, randomised, placebo-controlled parallel group study in 246 patients examined the effect of Sativex in patients with neuropathic pain characterised by allodynia. Allodynia is the occurrence of pain in response to a normally non-painful stimulus (e.g. clothes touching against the skin). It is often intense and can occur in patients suffering from a range of conditions that damage the peripheral nerves (e.g. nerve lesions, post-herpetic neuralgia). Patients in this study were being treated with a range of currently available analgesics, which were maintained during the course of the study.
The results of this study confirm the efficacy of Sativex. The responder analysis of the primary endpoint (the proportion of patients obtaining a clinically meaningful improvement in pain relief), was statistically significantly in favour of Sativex (p=0.03) for the full Intention to Treat (ITT) population. In addition, two of the key pain-related secondary efficacy endpoints, the Patient's Global Impression of Change (p<0.03) and the assessment of sleep quality (p<0.01), were also statistically significantly in favour of Sativex. All the other secondary efficacy endpoints were in favour of Sativex.
European and US regulators recommend a responder analysis of the primary endpoint in pain studies as the key assessment of outcome. This analysis was positive and confirms that Sativex produces a clinically important benefit over and above currently available treatments in a meaningful proportion of otherwise treatment-resistant patients. An additional analysis of the mean endpoint data was strongly in favour of Sativex and approached statistical significance.
This multi-centre double-blind, randomised, placebo-controlled parallel group study in 297 patients examined the effect of Sativex in patients with painful diabetic neuropathy. Patients in this study were being treated with a range of currently available analgesics, which were maintained during the course of the study.
In this study, patients taking Sativex showed a 30% mean improvement in pain scores, among the highest level of response seen in the published literature. One third of Sativex patients achieved over a 50% improvement in pain. However, the study results are difficult to interpret due to an abnormally large response in the placebo group. As such, although all outcome measures compared to placebo are in favour of Sativex, they do not reach statistical significance.
With regard to safety, the pattern of adverse events in both studies was similar to that seen in other Sativex studies.
Peripheral neuropathic pain forms part of a regulatory strategy to obtain approvals for Sativex across major markets in a range of indications, including MS symptoms, central neuropathic pain and cancer pain. Sativex is the subject of an ongoing regulatory application in four selected European countries for the symptomatic relief of spasticity in MS. Upon initial approval, it is intended to extend the MS spasticity indication into other European countries through the mutual recognition procedure. Since the rules do not permit a parallel regulatory application in neuropathic pain, GW's regulatory strategy for this indication is to continue to build the clinical evidence base whilst the MS spasticity regulatory process is ongoing. Hence, additional confirmatory trials have been under preparation for some months and ethics committee approvals obtained. With the benefit of today's results, the designs of the additional studies can be finalised prior to their commencement. These studies will further contribute to a future regulatory submission in neuropathic pain.
Sativex is approved and marketed in Canada for the symptomatic relief of central neuropathic pain in MS, and is the subject of an ongoing regulatory submission in Canada for the relief of cancer pain.
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