Anesiva, Inc. announced that the US Food and Drug Administration (FDA) has granted orphan drug status to product candidate 4975 for the treatment of a painful condition in the foot known as interdigital neuroma in patients who fail conservative treatments, such as foot pads, NSAID (non-steroidal anti-inflammatory drugs) and injections of corticosteroids, that would otherwise require removing or chemically destroying the nerve that causes the pain.

Orphan drug designation is granted by the FDA to encourage companies to develop products that treat rare diseases and conditions and includes incentives such as market exclusivity for seven years, tax credits on qualified clinical trial expenses and a waiver of the FDA prescription drug user fees, a com0pany release stated.

"4975 has shown great promise in a number of indications, and the potential to treat the serious pain associated with interdigital neuroma, sometimes referred to as Morton's neuroma, offers an important opportunity for us. There are no drugs approved to treat this unmet medical need. This condition afflicts approximately 200,000 new patients in the United States each year with about half of them failing conservative therapy," said John P. McLaughlin, chief executive officer of Anesiva. "The long duration of action following a single localized administration of 4975 offers a unique treatment option to patients with various types of post-surgical, neuropathic and musculoskeletal pain conditions by providing pain relief for several weeks following a single injection without the side effects associated with other pain medications."

Interdigital neuroma is highly painful and has been described as feeling like walking on a hot pebble or having a hot poker thrust between the toes. This type of post-traumatic neuropathic pain is most often caused by compression of the nerves between the foot bones from running, wearing high narrow shoes and excessive standing. Treatment for interdigital neuroma currently includes orthotics, non-steroidal pain relievers and steroid injections, which fail in approximately 50 per cent of patients. Surgical removal of the neuroma may lead to lengthy painful rehabilitation, and like other treatment options that chemically destroy the affected nerve, result in permanent numbness in that portion of the foot. In some instances, the neuroma regrows causing a return of this painful condition.

Data from a Phase 2 clinical trial in patients with interdigital neuroma who previously failed treatments with conservative options, such as orthotics and steroid injections, demonstrated that 4975 produced a statistically significant reduction in foot pain for four weeks following a single injection when compared to placebo treatment.

4975 is long acting, with the potential to provide pain relief for weeks or months after just a single localized treatment. It is a non-opioid TRPV1 agonist with a unique mechanism of action that provides a long-lasting, localized effect on C-fibers and blocks the transmission of aching, throbbing pain caused by major surgical procedures. Because it selectively acts on pain-sensing nerve endings, 4975 does not affect other nerve fibers necessary for sensory or motor sensations, such as those needed to sense temperature or pressure.

In clinical studies to date, 4975 has not had the side effects often associated with other conventional pain medications and has been shown to be well tolerated. opioid drugs, such as morphine, which are commonly used agents to relieve pain in post-surgical and musculoskeletal pain conditions, have significant side effects including sedation, respiratory depression, euphoria, and nausea and vomiting during acute use, and constipation and physical dependence during chronic use.