Cost regulators in Scotland have given the green light for the expanded use of Merck Sharp & Dohme’s HIV drug Isentress, granting a wider range of patients access to the drug on the country’s National Health Service.

Back in 2008, the Scottish Medicines Consortium OK’d the use of Isentress (raltegravir) in combination with other antiretrovirals in patients who continue to exhibit viral replication despite previous treatment, and restricted to those with triple class resistant HIV-1 infection.

Now, the agency has expanded the criteria for its use on the NHS, only restricting it to patients who are intolerant or resistant to non-nucleoside reverse transcriptase inhibitors (NNRTIs) or protease inhibitors (PIs) or when they are unable to take these therapies because of potential drug-drug interactions.

Isentress 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 is able to interfere with the ability of the virus to replicate, thereby preventing the infection of other cells.

The SMC’s decision to expand the drug’s use was based on clinical trial data demonstrating that, after 48 weeks of treatment, almost double the amount of patients taking Isentress plus optimised background therapy achieved a reduction in HIV viral load to less than 50 copies/ml compared to placebo (62% versus 33%, respectively).

In addition, data also showed that Isentress-based therapy was as effective as Bristol-Myers Squibb’s Sustiva (efavirenz) in reducing viral load in treatment-naïve patients, but that patients taking MSD’s drug had significantly fewer side effects, thereby offering a potential advantage over its rival.

'Good news'
According to Professor Clifford Leen, Consultant Physician Infectious Diseases, Western General Hospital, Edinburgh, the SMC’s move is “great news” for the 5,882 patients diagnosed with HIV in the country.

“Many patients are on regimens with older antiretroviral drugs and a significant number have tolerability issues, such as gastrointestinal side effects and lipid abnormalities [and] the approval by the SMC means that more patients can now access a new drug from a different class if a change is required,” he explained.