An experimental drug has been found to be effective at relieving neuropathic pain caused by shingles, and may also be useful in treating other types of neuropathy caused by diabetes, HIV and chemotherapy.
The new drug, called EMA401, was developed by Spinifex Pharmaceuticals, an Australian biotechnology company.
Shingles is caused when a dormant viral infection of a nerve is reactivated, resulting in a painful rash. In most cases, the rash lasts a few weeks, but in some cases the virus causes permanent nerve damage that results in a chronic neuropathic pain called post-herpetic neuralgia. Around one in 10 people with shingles has post-herpetic neuralgia. Once established, it usually lasts a lifetime.
In a Phase II clinical trial involving 183 patients with post-herpetic neuralgia, EMA401 was found to significantly reduce pain in 28 days and did not cause any serious side effects. The study, which was funded by Spinifex, is published in The Lancet.
“Conventional painkillers don’t tend to help people with severe chronic neuropathic pain and most available treatments have modest efficacy and/or are limited by side effects. We are therefore keen to find new ways of providing these people with some relief,” said lead author Professor Andrew Rice, from the Department of Surgery and Cancer at Imperial College London.
“A positive trial like this in such a challenging condition as post-herpetic neuralgia, for a drug that acts in a new way, is unusual and very exciting. We hope that the new drug will ultimately offer hope for patients who aren’t helped by current treatments.”
Patients in the study came from six different countries, ranged in age from 22 to 89 years, and suffered from post-herpetic neuralgia for at least six months.
Over half the patients who took 100 mg of EMA401 twice daily had “superior relief” from pain, compared to those who took a placebo. Fifty-eight percent found the drug effective, reducing their pain by at least 30 percent.
What makes EMA401 different from other drugs on the market is that it targets angiotensin II type 2 (AT2) receptor antagonists. This was the first clinical study to evaluate the efficacy of an AT2 receptor antagonist in treating neuropathic pain.
“Most importantly, their work identifies a possible new drug for the treatment of neuropathic pain with a novel mechanism of action, and thus offers hope for patients who have insufficient pain relief with presently available drugs,” said Nanna Finnerup, MD, of the Danish Pain Research Center at Aarhus University in a commentary also published in The Lancet.
Spinifex Pharmaceuticals now plans to conduct a larger trial, possibly testing higher doses of the drug for longer periods of time.
“There is a clear need for new treatments that bring patients pain relief with fewer side effects. In addition to post-herpetic neuralgia, we see broad potential for EMA401 to treat a range of chronic painful conditions such as pain due to osteoarthritis and diabetes,” said Tom McCarthy, CEO of Spinifex.
Spinifex’s development of EMA401 includes a clinical trial in the treatment of neuropathic pain in patients after cancer chemotherapy, which is being conducted at Imperial College London.