Isentress (raltegravir) tablets, an integrase inhibitor from Merck & Co, Inc, was as effective as efavirenz at maintaining viral load suppression to undetectable levels (less than 50 copies/mL) and at improving CD4 counts in previously untreated (treatment-naïve) patients through 144 weeks in a phase-II study still underway. Both medicines were administered in combination with two other anti-HIV medicines, tenofovir and lamivudine. These results were presented at the fifth International AIDS Society's (IAS) Conference on HIV Pathogenesis, Treatment & Prevention in Cape Town, South Africa.

"We are encouraged that these data demonstrate the efficacy and tolerability profile of Isentress, with less effect on lipid levels, for up to 144 weeks," said Martin Markowitz, study investigator and clinical director of the Aaron Diamond AIDS Research Center in New York. "It is important for patients at any stage of HIV to have treatment options like Isentress that are effective and have a demonstrated tolerability profile in order to help them manage their disease."

On July 8, Isentress was approved by the US Food and Drug Administration (FDA) for use in treatment-naïve adult patients in combination with other antiretroviral (ARV) medicines for the treatment of HIV-1 infection. In markets outside the United States, where Isentress is approved for treatment-experienced patients, the use of Isentress in treatment-naïve patients is investigational. The expanded indication in the United States for Isentress was based on analyses of plasma HIV-1RNA levels through 48 weeks in three double-blind controlled studies. Two of these studies were conducted in clinically advanced, three-class antiretroviral (NNRT, NRTI, PI) treatment-experienced adults and one was conducted in treatment naïve adults. The use of other active agents with Isentress is associated with a greater likelihood of treatment response. The safety and efficacy of Isentress have not been established in paediatric patients.

In addition, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMEA) is expected to issue an opinion soon regarding an expanded marketing authorisation of Isentress in the European Union for patients starting HIV therapy for the first time, as well as all treatment-experienced patients, when used in combination with other antiretroviral medicines for the treatment of HIV-1 infection in adult patients.

Isentress is a first-in-class integrase inhibitor. Isentress works by inhibiting the insertion of HIV-1 DNA into human DNA by the integrase enzyme and has demonstrated rapid antiviral activity.