Roche has announced results from a study demonstrating that the new boosted dosing regimen for its protease inhibitor Invirase(R) (saquinavir 1000 mg with ritonavir 100 mg twice-daily) has no significant interactions when it is co-administered with tenofovir disoproxil fumarate (300 mg once-daily).
Boosting Invirase 1000 mg with ritonavir 100 mg twice-daily, a new dosing strategy approved by the U.S. Food and Drug Administration (FDA) for use in HIV combination regimens, achieves therapeutic drug levels of saquinavir.
Roche is developing a 500 mg tablet formulation of Invirase that will cut daily pill count for the new twice-daily dosing regimen in half.
A filing for the 500 mg formulation is projected for submission to the FDA for review in 2004. "Clinical studies examining drug interactions between tenofovir and other anti-HIV drugs have shown some unexpected results, including a decrease in levels of a protease inhibitor, which could lead to inadequate viral suppression and possible resistance, or an increase in tenofovir drug levels, which could result in tenofovir-associated toxicity. Therefore, it is important that interactions between tenofovir and each anti-HIV drug be examined on a case-by-case basis," said Dr. Malte Schutz, Medical Director, Roche. "In this study, when tenofovir was taken in combination with Invirase and ritonavir, no interactions were observed, providing reassurance to physicians that these agents can be administered together in combination regimens without the need for dose adjustment."
Continued administration of Invirase therapy following loss of viral suppression may increase the likelihood of cross-resistance to other protease inhibitors. Invirase is not a cure for HIV infection or AIDS. Invirase does not prevent the transmission of HIV.