(AIDSmeds.com)—GlaxoSmithKline (GSK) announced on December 18 that it has discontinued development of brecanavir, its experimental protease inhibitor, due to “insurmountable” problems developing a formulation for the drug.

Early studies, including a 24-week Phase II study, indicated that brecanavir held promise for HIV-positive people either starting therapy for the first time or those with virus resistant to other protease inhibitors.

According to press release issued by GSK, the decision to halt development of brecanavir was based on the company’s inability to develop a viable oral dosage formulation capable of delivering the desired drug levels in treatment-experienced patients.

“As in all of our drug development programs,“ the press release said, ”GSK investigated several formulations of brecanavir. We conducted extensive studies in an effort to identify a formulation that would maximize therapeutic benefit for people living with HIV, especially those who are heavily treatment-experienced. Ultimately, our formulation work could not overcome the limitations of the brecanavir molecule which make consistent delivery of target drug levels unachievable.”

GSK is in the process of notifying researchers associated with clinical trials of brecanavir. HIV-positive patients receiving brecanavir through these studies will be taken off the drug and directed to an approved HIV option or another experimental agent, if necessary.