Next-generation integrase inhibitors : where to after raltegravir?

The integrase enzyme facilitates the incorporation of HIV-1 proviral DNA into the host cell genome and catalyses a function vital to viral replication. Inhibitors of this enzyme represent the newest class of antiretroviral drugs in our armamentarium to treat HIV-1 infection. Raltegravir, an integrase strand transfer inhibitor, was the first drug of this class approved by the US FDA; it is a potent and well tolerated antiviral agent. However, it has the limitations of twice-daily dosing and a relatively modest genetic barrier to the development of resistance. These qualities have prompted the search for agents with once-daily dosing, a more robust barrier to resistance, and a resistance profile of limited overlap with that of raltegravir. We review a series of integrase inhibitors that are in clinical or advanced pre-clinical studies. Elvitegravir, recently approved by the FDA as part of the elvitegravir/cobicistat/tenofovir disoproxil fumarate/emtricitabine fixed-dose combination pill has the benefit of being part of a one-pill, once-daily regimen, but suffers from extensive cross-resistance with raltegravir. Dolutegravir is the most advanced second-generation integrase inhibitor, and it boasts good tolerability, once-daily dosing with no need for a pharmacological enhancer, and relatively little cross-resistance with raltegravir. S/GSK1265744 has been developed into a long-acting parenteral agent that shows a high barrier to resistance in vitro and the potential for an infrequent dosing schedule. BI 224436 is in early clinical trials, but is unlikely to demonstrate cross-resistance with other integrase inhibitors. The inhibitors of the lens epithelium-derived growth factor (LEDGF)/p75 binding site of integrase (LEDGINs) are extremely early in development. Each of these contributes a new benefit to the class and will extend the treatment options for patients with HIV-1 infection.