Raltegravir (Isentress) for MDR- HIV

This drug looks more potent than virtually anything we have ever seen....

FDA approves Isentress to treat multi-drug-resistant HIV.

Isentress (raltegravir) is a twice-daily tablets as a treatment for patients who have strains of the HIV virus resistant to multiple antiretroviral drugs.Isentress is the first of a new class of antiretroviral drugs called integrase inhibitors, which work to prevent the virus from inserting its DNA into human DNA, thereby stunting its ability to replicate and infect new cells."

According to Merck, other HIV drugs "inhibit two other enzymes critical to the HIV replication process -- protease and reverse transcriptase." But Isentress "is the only approved treatment which inhibits the integrase enzyme." This approval was based on data from a 24-week study of about 700 patients with multi-drug-resistant HIV.

"More than 150,000 Americans taking HIV medicines have a hard-to-treat form of the virus and may benefit from the new drug," according to Merck. In studies, researchers found that Isentress "reduced the virus to less than could be detected after four months in 61 to 62 percent of patients who got the medicine in combination with other anti-HIV drugs." However, the virus load was reduced in only "33 to 36 percent" of patients who were receiving placebo "along with their most effective therapies." The FDA pointed out that "[a]dding Isentress to drugs already on the market can slow the advance of HIV." FDA advisers also noted that "[s]ide effects included rashes, diarrhea, nausea, and headaches." And while "more patients taking Isentress developed cancers, the drug didn't appear to pose an increased risk," they stated.

Meanwhile, the Wall Street Journal (10/13, Dooren) noted, "Isentress was approved as part of the FDA's accelerated-approval mechanism, which is aimed at getting life-saving treatments to market faster by allowing companies to submit less clinical data than usually required." As part of the accelerated approval process, Merck must continue studying Isentress after it goes on the market in order to gain full approval.

"The Merck drug has been closely watched since human testing began in 2005 because it was the first AIDS medicine to block...integrase, that is crucial in the process HIV uses to replicate."

The recommended dosage is a 400-mg tablet taken twice a day. It is estimated that Isentress will cost "$27 per day, or $9,850 per year," and may be available in pharmacies within the next two weeks. A comparable drug, Pfizer's Selzentry (maraviroc), "sells for at least $10,600 a year."

Martin Delaney, founder of San Francisco's Project Inform -- a leading AIDS drug advocacy organization -- and an activist in a group called the Fair Pricing Coalition, said that "Merck is not charging as much as he had feared." He added that Isentress "falls in the middle of the high end for AIDS drugs. For us, that is a victory."

University of California professor, Dr. Warner Greene, noted "This drug looks more potent than virtually anything we have ever seen." Dr. Greene also stated that "he believes...[Isentress] will prove safe because there are no known biological reasons why the drug might cause cancer." The Chronicle pointed out that Dr. Greene has said that "he has no economic ties to Merck."

Isentress and Selzentry "are considered breakthroughs for another reason: they are the first new classes of oral HIV medicines to reach the market in more than 10 years."