Net sales of restless legs syndrome (RLS) treatment Horizant (gabapentin enacarbil) Extended-Release Tablets in the United States in the fourth quarter grew 34% compared to the third quarter of 2013, which was the first full quarter of XenoPort’s commercialization of Horizant. The total number and the trajectory of growth of Horizant prescribed tablets achieved all-time highs. Horizant prescribed pill counts increased 27% nationwide for the fourth quarter ending December 31, 2013, compared to the third quarter of 2013. In territories where manufacturer XenoPort is actively promoting Horizant, total prescribed pills for the fourth quarter ending December 31, 2013, increased by 39% compared to the third quarter of 2013. This compares to no growth in non-promoted territories.

In its fourth quarter and year-end 2013 financial results, XenoPort also reported positive top-line results of a Phase 4 clinical trial that evaluated lower doses of gabapentin enacarbil for the treatment of moderate-to-severe primary RLS in adults. The study was conducted by XenoPort’s former commercial partner, GSK, as part of the post-marketing commitments imposed by the FDA in connection with its approval of Horizant for the treatment of adult patients with moderate-to-severe primary RLS. The most common adverse reactions in adult patients with moderate-to-severe primary RLS taking Horizant are somnolence/sedation, dizziness, headache, nausea, and fatigue.

“We…believe we have made progress in commercializing Horizant,” says Ronald W. Barrett, PhD, chief executive officer of XenoPort, in a release. “In only two full quarters of promotion, we believe we have demonstrated the potential of our targeted educational efforts and we continue to receive positive feedback from physicians who prescribe Horizant. We will continue to closely monitor our progress in increasing the value of Horizant through these commercialization efforts.”