Titan Phase III trial for subdermal implant begins enrollment

A year after the FDA rejected Titan Pharmaceutical's ($TTNP) Probuphine subdermal implant for the treatment of opioid dependence, the company is knocking on the approval door once again. It announced July 21 that the first patients have enrolled in its Phase III trial designed to address the FDA's questions.

The implant delivers buprenorphine, which is currently available in sublingual tablet and oral formulations--a market with 2012 annual sales of about $1.5 billion in the U.S., according to Titan.

Fifteen trial sites have received Institutional Review Board approval, with another 6 planned; 5 patients have been enrolled so far out of an anticipated 180. The double-blind, double-dummy study will consist of two treatment arms. One group will continue to receive standard buprenorphine therapy delivered sublingually, while the treatment group will receive four investigational subdermal Probuphine implants.

Advantages of the delivery method include continuous dosing and improved patient compliance and retention, Titan says. "With more than 2 million people in the U.S. suffering from opioid dependence, there is a strong need for new treatments. If approved, Probuphine would be the first and only commercialized treatment of opioid dependence to provide continuous, around-the-clock blood levels of buprenorphine for 6 months following a single procedure," said Kate Glassman-Beebe, Titan's chief development officer, in a statement.

The product uses Titan's ProNeura drug delivery system. "The continuous drug delivery system consists of a small, solid rod made from a mixture of ethylene-vinyl acetate and a drug substance," Titan explains on its website. It is typically placed subdermally in the upper arm and delivers buprenorphine for 6 months. The company says that the delivery system has showed promise as a treatment for Parkinson's disease in nonclinical studies. 

Titan has granted Braeburn Pharmaceuticals North American commercial rights to Probuphine. The commencement of the trial occurs as the issue of prescription drug abuse moves into the national spotlight due to the now-overturned ban of the painkiller Zohydro ER in Massachusetts over concerns that it is easily abused.

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