Neuropathic Pain

Neuropathic pain is a common and increasingly prevalent form of pain that is thought to involve an alteration in nervous system function or a reorganization of nervous system structure. It can be associated with nerve damage caused by trauma, diseases such as diabetes, shingles, irritable bowel syndrome, late-stage cancer or the toxic effects of chemotherapy. In many patients, damage to sensory nerves is accompanied by varying degrees of pain. The experience can range from mildly increased sensitivity to touch or temperature to excruciating pain. This kind of pain is extremely difficult to manage clinically because it fails to respond to most medications currently used to treat other forms of pain. According to Pharmaprojects, a healthcare publication, each year approximately 26 million people worldwide suffer from some form of neuropathic pain.

Drugs such as opioid painkillers and non-steroidal anti-inflammatory agents that are effective in treating inflammatory and acute pain usually are not effective in treating neuropathic pain. Opioid painkillers also have significant adverse side effects that limit their usefulness, including respiratory depression, nausea, vomiting, dizziness, sedation, mental clouding, constipation, urinary retention, and severe itching. In addition, prolonged use of opioid painkillers can lead to the need for increasing dosage and potentially addiction. Neurontin, previously the market leading treatment for neuropathic pain with sales of $2.7 billion in 2004, is now generic. Currently, the leading drugs approved for neuropathic pain indications include Lyrica, the successor to Neurontin and Cymbalta. Lyrica had worldwide sales of $291 million in 2005. Cymbalta, indicated for treatment of diabetic peripheral neuropathic pain as well as treatment of major depressive disorder, had worldwide sales of $680 million in 2005. We believe that there is a large unmet medical need for new therapies with improved efficacy and side effect profiles.

In collaboration with Allergan, we have discovered and are developing a new class of small molecule drug candidates that we believe may represent a significant breakthrough in the treatment of neuropathic pain. Our novel and selective alpha adrenergic agonists provide highly effective pain relief in a wide range of preclinical models, without the side effects of current pain therapies, including gastrointestinal, cardiovascular and respiratory effects, as well as sedation. Allergan has demonstrated that our drug candidates are highly potent and efficacious when administered orally in relevant animal models and are more efficacious than Neurontin in preclinical models at approximately 300-fold lower doses.

Allergan has completed Phase I clinical trials for two orally active, small molecule drug candidates and is currently conducting Phase II clinical trials in this program. Based on the preclinical profile of these drug candidates and the results of the Phase I clinical trials, we believe these drug candidates may represent a new class of highly effective and safe therapeutics for neuropathic pain.

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