Discovered by XenoPort, arbaclofen placarbil (AP) is a patented, oral new chemical entity that utilizes naturally-occurring, high-capacity nutrient transporters in the gastrointestinal tract to generate active, efficient absorption into the body. Once absorbed, AP is rapidly converted to the R-isomer of baclofen, a generic drug that is racemic (a mixture of the R- and S-isomer). Baclofen is a selective GABA-B agonist. XenoPort currently holds all rights to this product candidate.

AP is being developed as a potential treatment for patients with spasticity.

Spasticity

The pathophysiology of spasticity is unknown, but it is believed to result from an imbalance of inhibitory and excitatory functioning within the central nervous system. Patients with spasticity may experience abnormal increases in muscle tone that are associated with loss of range of motion, increased muscle stretch reflexes, weakness and problems with coordination. Common complications of spasticity include joint and muscle contracture, pain and difficulty performing activities of daily living. Racemic baclofen is approved in the United States for the treatment of patients with spasticity. The pharmacokinetic profile of baclofen in the blood after administration of AP shows more constant exposure to baclofen and less severe peaks and troughs of drug blood levels than racemic baclofen. As such, we believe the use of AP for the treatment of spasticity could provide more continuous exposure to R-baclofen and thereby potentially offer better treatment benefit.