Gabapentin Extended-Release - Depomed: Gabapentin ER, Gabapentin Gastric Retention, Gabapentin GR

Depomed is developing an extended-release (ER) oral formulation of gabapentin, a GABA receptor agonist commonly used for the treatment of epilepsy and seizures, neuropathic pain and hot flushes. Gabapentin ER is based on the company's proprietary AcuForm drug delivery technology, which is part of the Gastric Retention (GR) family of technologies; this offers improved drug absorption and bioavailability compared with the existing immediate-release formulation of gabapentin (Neurontin), making gabapentin ER suitable for twice-daily dosing. The product is in clinical development for the treatment of postherpetic neuralgia and diabetic neuropathies in the US. Additionally, Depomed has commenced a phase II trial of gabapentin ER in postmenopausal patients with hot flushes. Depomed's AcuForm platform is based on polymer technology that provides targeted drug delivery for a variety of compounds. Following ingestion, AcuForm tablets swell and are retained for 6-8 hours in the stomach, enabling controlled and prolonged release of gabapentin to the upper intestinal tract; this extends the time of drug delivery to the small intestine for complete and safe elimination via the lower intestinal track. Gabapentin ER is available for licensing. Depomed acquired exclusive development and commercialisation rights to gabapentin ER in September 2003 via its subsidiary, Depomed Development Ltd (DDL). Depomed is not required to pay upfront license fees, but will make royalty and milestone payments to DDL upon successful commercialisation of gabapentin ER. Gabapentin ER was originally developed by DDL, a joint venture between Depomed and Elan established in January 2000 to design products using the GR family of technologies. However, in efforts to restructure joint venture relationships, Elan withdrew from operational involvement of DDL in September 2003, and Depomed has gained full ownership of DDL. Depomed sublicensed exclusive rights to a US patent (held by the University of Rochester) covering the use of gabapentin in the treatment of hot flushes from PharmaNova in October 2006. Under the agreement, Depomed paid PharmaNova an upfront fee of US dollars 500 000. PharmaNova is also entitled to milestone payments and royalties on sales of gabapentin ER in this indication only. Depomed has reported significant safety and efficacy benefits from gabapentin ER in its phase II trial. This study was initiated in February 2005 following positive results from a phase I trial in which gabapentin ER demonstrated a pharmacokinetic profile suitable for twice-daily dosing. In two pharmacokinetic studies, gabapentin ER achieved improved bioavailability at higher doses. This result supports Depomed's development of a once- or twice-daily product with potentially fewer adverse events. The basic US patents relating to gabapentin expired in 2000. Depomed holds exclusive rights to a US patent (No. 6 310 098) held by the University of Rochester covering the use of gabapentin to treat hot flushes.Additionally, Depomed was issued a US patent (No. 6 723 340) in May 2004 that covers proprietary polymer combinations (as used in AcuForm tablets) to create improved formulations of existing drugs.