Neuropathic pain a lucrative drug target

By ASTARA MARCH

WASHINGTON, Sept. 19 (UPI) -- The company that can develop an effective, easy-to-use drug specifically for neuropathic pain should enjoy outstanding revenues, industry analysts predict.

Datamonitor PLC, a business information company in London, reported this outlook in a statement released last week. The company looked at seven major markets -- including the United Kingdom, the United States, Japan, France, Germany, Italy and Spain -- and found that among $2.5 billion in sales for pain drugs, not one compound has been developed specifically for neuropathic pain use.

Unlike nociceptive pain, which is a message from an injured area of the body to the brain that subsides when the injury heals, neuropathic pain seems to be generated by the nerves themselves. There usually is no active injury present when the pain is experienced, and it often grows worse over time.

Remedies for nociceptive pain, such as NSAIDs and opioids, do not work for neuropathic pain, which is only marginally affected by opioids and responds best to anti-convulsants and tricyclic anti-depressants that block the brain's neurotransmitters.

The classic example of neuropathic pain is phantom-limb syndrome after amputation. Although a part of the body has been removed, the patient often experiences what feels like stabs of pain throughout the missing extremity (neuropathic pain is often described as stabbing, searing or burning).

Diabetes, AIDS, multiple sclerosis, fibromyalgia, chronic-fatigue syndrome, reflex sympathetic dystrophy, Lyme disease and shingles (caused by a virus similar to chickenpox) also produce neuropathic pain, and people with these problems will form a large part of the projected neuropathic pain drug market.

As of June 2005 only five drugs had been approved by the Food and Drug Administration to treat neuropathic pain:

• gabapentin, marketed by Pfizer as Neurontin, the gold-standard drug used in over 50 percent of cases and originally developed to treat depression;

• lidocaine, marketed by Endo Pharmaceuticals as Lidoderm, a local anesthetic;

• carbamazepine, originally marketed by Novartis as Tegretol, an anti-convulsant;

• duloxetine, an anti-depressant marketed as Cymbalta by Eli Lilly, and

• pregabalin, also marketed by Pfizer as Lyrica, another anti-depressant.

Neurontin recently lost its patent protection in the United States, and a number of generic versions are now available.

Most of these drugs need to be taken four times a day, opening a space for a pharmaceutical that requires less from the patient.

"Patients with neuropathic pain usually require several upward titrations of their pain medications before adequate pain control is achieved," said Clare Churchill, a healthcare analyst for Datamonitor, in the company's statement. "This can be particularly difficult if the patient must go through a difficult administration method a number of times before any results are seen."

Because many neuropathic-pain patients also are being treated for other conditions -- and therefore already must endure challenging pharmaceutical regimens -- Churchill said medication that could be taken orally once a day and would not negatively interact with other drugs would be ideal.

Datamonitor reported there are at least 97 compounds in development for the treatment of neuropathic pain, making it one of the most active pipelines in the central nervous system area. The company's analysis showed competition is centered on improved dosing formulations, but any serious drug would need to be at least equivalent in safety and efficacy to gabapentin and would need to demonstrate proven pain-reduction ability of greater than 50 percent in a significant majority of patients.

Dr. Michael Ferrante, director of the Pain and Spine Care Center at the UCLA Medical Center in Los Angeles, said he would be delighted to see new pharmaceuticals developed for neuropathic pain in the near future.

"Neurontin was a great step forward because it had a low side-effect profile and produced very quick results," Ferrante told United Press International. "Cymbalta, the newest medication, is more effective, but carries a significant risk of nausea. Lyrica is five times as effective as Neurontin, with a similar low side-effect profile, but is listed as a scheduled medication because it can potentially cause euphoria."

Ferrante said there is a strong need for an effective drug against neuropathic pain that has a low risk of side effects.

"People have been suffering for years with neuropathic pain, which is terribly debilitating," he said. "We need a home run for them."

Churchill said pharmaceutical companies also should consider devoting time and money to explore the pain-drug market in Japan, where neuropathic pain currently is treated with nerve blocks and vitamin B alone.

"Educating Japanese physicians on the use of the few current medications for neuropathic pain will be expensive and challenging," she said, "but the company that can do this effectively will reap a huge reward. There are a lot of sales out there."

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