Merck Sharp & Dohme’s novel HIV drug Isentress has been launched in the UK, providing doctors with an important new weapon in the fight against the disease.

Isentress (raltegravir) is the first in a new class called integrase inhibitors to hit the market, and has been cleared for use in combination with other antiretrovirals against HIV-1 infection in adults who continue to exhibit viral replication despite prior therapy.

The drug has a unique mode of action in that it targets integrase, one of three enzymes essential for HIV replication. By preventing the action of integrase, which basically inserts the viral DNA into that of the host cell, Isentress affects the ability of the virus to replicate, thereby preventing the infection of other cells.

Isentress’ anti-HIV capabilities have been clearly demonstrated in clinical trials, which showed that, when the drug was combined with optimised background therapy, the majority of patients who were resistant to other therapies experienced significant reductions in viral load and increases in CD4 cell counts.

There are currently around 73,000 people living with HIV in the UK, many of which quickly develop resistance to their treatment regimens. But, sccording to Dr Mark Nelson, Director of HIV Services, Chelsea and Westminster Hospital in London: “When used as part of individually tailored combination therapy, raltegravir will be an important step forward in our fight against HIV”, and analysts believe that the drug could well achieve blockbuster status in a couple of years’ time.