Merck, known as MSD outside the United States and Canada, announced that the US Food and Drug Administration (FDA) has approved Isentress HD, a new 1200 mg once-daily dose of the company’s integrase inhibitor, Isentress (raltegravir), to be administered orally as two 600 mg film-coated tablets with or without food, in combination with other antiretroviral agents, for the treatment of HIV-1 infection in adults, and paediatric patients weighing at least 40 kg, who are treatment-naïve or whose virus has been suppressed on an initial regimen of Isentress 400 mg given twice daily.

“Isentress has been used as a component of treatment regimens for patients diagnosed with HIV-1 for almost a decade,” said Dr. Michael S. Saag, associate dean for global health, and director of the Center for AIDS Research at the University of Alabama at Birmingham School of Medicine. “The addition of a convenient once-daily version with a comparable efficacy and safety profile at 48 weeks to the existing twice-daily version of Isentress provides physicians with a new therapeutic option for some patients with HIV-1 infection.”

Isentress and Isentress HD do not cure HIV-1 infection or AIDS. Severe, potentially life-threatening and fatal skin reactions have been reported. This includes cases of Stevens-Johnson syndrome, hypersensitivity reaction, and toxic epidermal necrolysis. Immediately discontinue treatment with Isentress or Isentress HD and other suspect agents if severe hypersensitivity, severe rash, or rash with systemic symptoms or liver aminotransferase elevations develop and monitor clinical status, including liver aminotransferases closely.

The FDA approval of once-daily Isentress HD (raltegravir) is supported by data from the pivotal phase 3 ONCEMRK trial. At Week 48, 89 percent (N=531) of treatment-naïve HIV-1 infected patients receiving Isentress HD 1200 mg (2 x 600 mg) once a day achieved viral suppression of HIV-1 RNA <40 copies/mL compared to 88 per cent (N=266) of patients receiving Isentress 400 mg twice a day, each in combination therapy with emtricitabine + tenofovir disoproxil fumarate, with a treatment difference of 0.5 per cent, and a 95 per cent confidence interval of -4.2, 5.2. This was consistent across demographic groups at initiation of therapy and a variety of patient populations, including those with high viral load (HIV-1 RNA >100,000 copies/mL).

“Because of improvements in the effectiveness of antiretroviral therapies and with appropriate access to care, HIV infection can now be managed as a chronic disease,” said Carl Schmid, deputy executive director of the AIDS Institute. “For people living with HIV, having a wide range of effective therapies is important because it provides options to fit patients’ individual needs and lifestyles.”

In ONCEMRK, through 48 weeks, the rate of discontinuation of therapy due to adverse events was low (1 per cent in patients receiving Isentress HD 1200 mg once daily and 2 per cent in patients receiving Isentress 400 mg twice daily). There were no drug-related clinical adverse reactions of moderate to severe intensity occurring in =2 per cent of patients in either treatment group. Clinical adverse reactions of all intensities (mild, moderate, and severe) occurring in =2 per cent of patients on Isentress HD or Isentress included abdominal pain, diarrhea, vomiting, and decreased appetite. Treatment-emergent viral mutations leading to any drug resistance were detected in less than 1 per cent (4/531) of those treated with Isentress HD once daily.

Isentress HD can be co-administered with a wide range of antiretroviral agents and non-antiretroviral agents. The potential for drug-drug interactions must be considered prior to and during therapy. The co-administration of Isentress HD with aluminum and/or magnesium-containing antacids, calcium carbonate antacids, rifampin, tipranavir/ritonavir, etravirine, and other strong inducers of drug metabolizing enzymes (e.g., carbamazepine, phenobarbital, and phenytoin) is not recommended.

“Isentress HD exemplifies Merck’s unwavering commitment to innovation in HIV therapy, and we are pleased to be able to offer this option to a broad range of appropriate adult and pediatric patients weighing at least 40 kg who are living with HIV,” said Dr. Eliav Barr, senior vice president, global clinical development, infectious diseases and vaccines, Merck Research Laboratories.

According to a company press release,the price of Isentress HD will be the same as Isentress twice daily. Merck anticipates Isentress HD to be available in pharmacies in approximately four weeks.

The ONCEMRK study is an ongoing phase 3 multicenter, double-blind, randomized, active comparator-controlled clinical trial designed to evaluate the efficacy and safety of once-daily Isentress HD 1200 mg, given as two 600 mg oral tablets, compared to twice-daily Isentress 400 mg, each in combination therapy with emtricitabine + tenofovir disoproxil fumarate in previously untreated adults with HIV-1 infection with HIV-1 RNA =1000 copies/mL. The primary efficacy objective was the proportion of patients achieving HIV-1 RNA <40 copies/mL at Week 48.

Approved in 2007, Isentress was the first integrase inhibitor developed for the treatment of HIV-1 infection. Isentress is one of the regimen options recommended by the Department of Health and Human Services – in combination with other antiretroviral agents – as a first-line therapy in treatment-naïve HIV-1 infected adults. Isentress chewable tablets and oral suspension, each in combination therapy, are approved to treat pediatric patients aged at least four weeks of age, and weighing less than 20 kg.

Isentress works by inhibiting the insertion of HIV-1 DNA into human DNA by the integrase enzyme and has demonstrated rapid antiviral activity. Inhibiting integrase from performing this essential function limits the ability of the virus to replicate and infect new cells.

Isentress is approved as part of combination therapy in 112 countries for treatment of HIV-1 infection in adult patients. Isentress, in combination therapy, for use in children and adolescents with HIV-1 aged two years and older has also been approved for use in 69 countries, and Isentress oral suspension for infants at least four weeks of age is approved for use in 33 countries.