GlaxoSmithKline plc (GSK) and XenoPort, Inc. (Nasdaq:XNPT) announced
today that the United States (US) Food and Drug Administration (FDA) has
approved Horizant® (gabapentin enacarbil) Extended-Release
Tablets for the management of postherpetic neuralgia (PHN) in adults.
The efficacy and safety of Horizant for the management of PHN was
evaluated in a single 12-week principal efficacy trial, plus two
supportive studies that all met their respective primary endpoints. The
three clinical studies involved 574 adult patients from the US, Canada
The recommended dosage for the management of PHN in adults is 600 mg
twice daily. Treatment should be initiated at a dose of 600 mg in
the morning for three days followed by 600 mg twice daily (1,200 mg/day)
beginning on day four. Doses must be adjusted in patients with impaired
renal function. In the 12-week, controlled study in patients with PHN,
somnolence and dizziness were the most frequently reported side effects.
Somnolence was reported in 10% of patients treated with 1,200 mg of Horizant
per day compared with 8% of patients receiving placebo. Dizziness was
reported in 17% of patients receiving 1,200 mg of Horizant per
day compared with 15% of patients receiving placebo.
In association with GSK's first commercial sale of the product after
approval for PHN, XenoPort is entitled to a milestone payment of $10
million from GSK.