An investigational Parkinson’s disease treatment licensed by GlaxoSmithKline (NYSE:GSK) is now slated for a fourth quarter new drug application with the U.S. regulators following positive late-stage clinical trial results.

British pharmaceutical giant GSK, which has its U.S. headquarters in Research Triangle Park,  is partnering with California-based Impax Pharmaceuticals, a division of Impax Laboratories (Nasdaq:IPXL) to develop the compound IPX066 in phase 3 clinical trials.

IPX066 is an extended release formulation of the combination drug carbidopa-levodopa. GSK said trial results show that the compound, being studied as a treatment for motor symptoms of Parkinson’s disease, worked better than an existing treatment, carbidopa-levodopa plus the drug entacapone.

Novartis (NYSE:NVS) markets that patented drug combination under the name Stalevo. Stalevo and entacopone, which is marketed as Comtan, together generated $600 million in 2010 sales, according to Novartis.

The IPX066 phase 3 study measured “off time,” the time when the medication has worn off and Parkinson’s symptoms return. IPX066 results showed a 33.5 percent decrease in off time. Stalevo only showed a 10 percent decrease in off time. For Parkinson’s patients, IPX066′s results translates into an 84 minute improvement. GSK said that full results from the trial will be presented at an upcoming scientific meeting.

A new Parkinson’s drug would be a win for GSK, which licensed rights to the Impax compound last December. The deal gave Impax an $11.5 million up front payment and potential payments up to $175 million if the drug candidate hits development and commercialization milestones.

Impax will also receive double-digit royalties on GSK’s sales of the drug. Impax will file the U.S. new drug application. GSK has the rights to worldwide commercialization rights for IPX066 except for the United States and Taiwan. GSK plans to file a marketing application for IPX066 in Europe in 2012.

Get the latest news alerts: Follow WRAL Tech Wire at Twitter.