MK-0518 belongs to a new class of investigational antiretroviral therapy agents called integrase inhibitors that inhibit the insertion of the HIV viral DNA into human DNA.
The phase II trial data show comparable viral load reduction to below 50 copies/mL of HIV RNA between the MK-0518 regimen and a regimen containing Bristol-Myers Squibb’s Sustiva (efavirenz).
The interim results show that 85% to 95% of patients taking MK-0518 twice daily plus tenofovir (marketed by Gilead as Viread) and lamivudine (marketed by GlaxoSmithKline as Epivir) achieved this viral load reduction, compared to 92% of patients taking Sustiva once daily plus tenofovir and lamivudine.
This effect was observed at all four doses of MK-0518 studied (100mg, 200mg, 400mg and 600mg administered orally twice daily), in treatment-naive HIV-infected patients with documented genotypic susceptibility to tenofovir, lamivudine and efavirenz.
Moreover, patients on the MK-0518-based regimen achieved HIV RNA reductions to levels less than 50 copies/mL earlier than patients on the efavirenz-based regimen.
Both treatment regimens were generally well-tolerated. Clinical adverse experiences were mild to moderate, with nausea, dizziness and headache reported most frequently.