Raltegravir (Isentress)

Raltegravir (Isentress) is an HIV-1 integrase strand-transfer inhibitor with potent antiretroviral activity. It belongs to a new class of antiretrovirals called integrase inhibitors. The drug works against HIV's integrase protein, blocking its ability to integrate its genetic code into human cells.

Raltegravir (Isentress), formerly known as MK-0518, is the first licensed integrase inhibitor. It was given marketing approval in the US in 2007 and in Europe in early 2008 for use by treatment-experienced patients. Raltegravir’s approval was based upon the results from the BENCHMRK I and II studies that showed it had a durable anti-HIV effect in patients with limited treatment options.

The drug was approved for use in initial antiretroviral regimens by both the UK and US in 2009, based on 48-week data from the STARTMRK clinical trial. As an initial regimen, raltegravir (given in combination with tenofovir and emtricitabine) sustained viral suppression at rates equivalent to an efavirenz-based regimen.1

Other studies are looking at whether individuals who are virologically suppressed on a boosted protease inhibitor-based regimen can be safely switched to an NRTI-sparing regimen of raltegravir and atazanavir and at the safety and efficacy of raltegravir dosed once daily at 800mg.2


  1. Lennox JL et al. Safety and efficacy of raltegravir-based versus efavirenz-based combination therapy in treatment-naive patients with HIV-1 infection: a multicentre, double-blind randomised controlled trial. Lancet 374(9692): 796-806, 2009
  2. Mena A et al. A pilot study assessing Raltegravir (Isentress) QD versus BID in HIV patients inclluded in a simplification trial. 49th Interscience Conference on Antimicrobial Agents and Chemotherapy, San Franciso, abstract H-920, 2009