GlaxoSmithKline has decided to terminate Phase III trials of aplaviroc (GW873140), a drug for HIV discovered by Japan's Ono Pharmaceuticals, after encountering additional cases of liver damage in patients taking the drug.

Last month, GSK terminated a Phase IIb trial of aplaviroc in patients who had not received prior treatment for HIV after two cases of severe liver toxicity were uncovered [[20/09/05a]], but said Phase III testing in treatment-experienced patients would continue. Ono said it has now stopped all studies of the drug, and had no plans at present to start any more, indicating that development of the drug may be terminated.

GSK had high hopes for aplaviroc, formerly known as 873140, as it used a different mode of action to currently available HIV treatments and so was unlikely to show any cross-resistance.

It belongs to the CCR5 inhibitor class of antiretroviral drugs, which are designed to block HIV from getting into host cells. Pfizer and Schering-Plough are also developing CCR5 inhibitors for HIV treatment, in Phase III and Phase II trials, respectively.