UK drug giant GlaxoSmithKline has ended a Phase IIb study of an HIV drug discovered by Japan’s Ono Pharmaceuticals - ONO-4128/873140 - following the emergence of potential safety issues, it was revealed yesterday.

The UK group has received reports of elevated liver function test values in these clinical trials and, after review of these findings with the US Food and Drug Administration, has terminated trials of the agent in treatment-naive patients.

According to Ono, GSK plans to continue its ongoing Phase III studies involving treatment-experienced patients, but will make changes to its protocol including patient inclusion/exclusion criteria. Participants will be monitored closely for signs or symptoms of liver toxicity and/or elevations in liver function tests.

ONO-4128/873140, which was discovered by Ono and licensed to GSK under an agreement signed in December 2002, appears to block the entry of HIV into human cells through a new mechanism of action that is totally different from those of currently available antiretroviral drugs, the Japanese group noted.

Under the terms of the groups’ agreement, GSK holds exclusive worldwide development, manufacturing and commercialisation rights for ONO-4128 and certain associated compounds. In return, Ono will receive clinical and regulatory milestone payments related to the drug’s progress, as well as royalties based on total worldwide annual net sales.