Second new class of HIV drug given thumbs up
HIV drug, looks likely to win approval in the near future,
following a recommendation to regulators.
The Antiviral Drugs Advisory Committee of the US Food and Drug Administration (FDA) last week voted unanimously to recommend accelerated FDA approval of Isentress (raltegravir). Although the regulators are not bound to follow the committee's advice, they generally do. Isentress is set to be the first integrase inhibitor to market. Moreover, it will represent the second new class of HIV drugs approved this year - after a decade in which no new types of drug were launched. The first in the other new class of drugs is Pfizer's Selzentry (maraviroc), which was passed by the FDA last month and has also been recommended for approval in Europe. Isentress blocks integrase, an enzyme produced by HIV to enable viral DNA to integrate with human genetic material. In effect, this prevents the virus from replicating and although there are established antiretroviral drugs that inhibit two other enzymes critical to the HIV replication process - protease and reverse transcriptase - there are currently no approved drugs that inhibit integrase. "Despite the availability of various treatment options, the HIV epidemic continues, so there remains a need for new therapeutic approaches," said Dr Peter Kim, president of Merck Research Laboratories. "This positive recommendation signals an important step forward for the treatment of patients living with HIV." There are 40 million people infected with HIV worldwide with the majority in sub-Saharan Africa, according to the Joint United Nations Programme on HIV/AIDS (UNAIDS). On the other hand, Selzentry works by blocking the virus' predominant entry route into uninfected cells - the chemokine (C-C motif) receptor 5 (CCR5), leading to it being called an 'entry inhibitor'. Both Isentress and Selzentry are designed to be used with other antiretrovirals in patients who have become resistant to multiple established drugs, although they are also being tested in treatment-naïve patients. Although both drugs are the first in their respective classes, they won't be the last. Isentress is not the only integrase inhibitor in clinical development. Gilead Sciences' elvitegravir (GS-9137) is an integrase inhibitor hot on the heels of Isentress - it completed Phase II trials early this year. HIV can quickly develop resistance to drugs and so the more drugs within a class, the better. However, a recent trial uncovered some cross resistance between patients who received both elvitegravir and Isentress (in that order), which suggests the first drug to market could retain a large portion of the market even once follow-up drugs are approved. The key to snatching some of this market will be finding a compound that works in patients resistant to other integrase inhibitors.
