FDA Recommends Approval Of Merck's Antiretroviral Raltegravir

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Merck's Antiretroviral Raltegravir

An independent FDA panel of medical experts on Wednesday unanimously recommended accelerated approval of Merck's antiretroviral drug raltegravir, the Wall Street Journal reports (Corbett Dooren, Wall Street Journal,9/6). Merck in June announced that FDA granted priority review statusto raltegravir, an experimental integrase inhibitor. Raltegravireffectively decreases HIV viral loads after 24 weeks of use amongHIV-positive people who have not responded to other treatments,according to a study published in the April 14 online edition of thejournal Lancet. Raltegravir works by blocking an HIVenzyme called integrase. Integrase is one of the three enzymesnecessary for HIV to replicate in the body, and integrase inhibitorsstop HIV from inserting its genes into uninfected DNA. The other twoenzymes necessary for viral replication, reverse transcriptase andprotease, already are targeted by a variety of antiretrovirals.

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FDAlast week released a review of raltegravir ahead of the panel'smeeting. According to the FDA review, which was posted on the agency'sWeb site, raltegravir is effective at treating HIV-positive people whohave shown resistance to available treatments. Rash and increasedlevels of creatine in the blood were the most common side effects ofthe drug, according to the review. Other potential side effects includeliver injuries and cancer. In clinical trials, a higher number ofcancers were found among people taking raltegravir than among thosetaking a placebo, but the difference could be because of a lower rateof cancer among people in the placebo group, FDA said.

The panelwas asked whether raltegravir should be used only by people enrolled inclinical trials or by people "with few or no remaining treatmentoptions." In addition, FDA asked the panel if Merck should be requiredto conduct postmarketing studies on the drug. The agency is expected tomake a final decision about raltegravir in mid-October (Kaiser Daily HIV/AIDS Report, 9/4).

According to the Journal,the panel did not recommend which drugs should be used in combinationwith raltegravir or whether it should replace a drug in a standardthree-drug regimen to treat HIV (Wall Street Journal,9/6). Some panel members expressed concern over the increased number ofcancers among people taking raltegravir in clinical trials; however,representatives from Merck and FDA noted that the cancer rate wascomparable to that found among HIV-positive people with a highlydrug-resistant strain of the virus (Chong, Los Angeles Times,9/6). Some panel members recommended that FDA limit the drug's labelingfor people who have developed resistance to multiple treatment regimens(Dixon, Reuters,9/5). Several panel members also recommended that the agency requireMerck to conduct follow-up studies among people taking the drug for upto five years (Los Angeles Times, 9/5).

Merck saidthat if the drug is approved, it will be used in combination withstandard oral antiretrovirals by HIV-positive people who have developedresistance to their current treatments. Raltegravir will be sold underthe brand name Isentress (Kaiser Daily HIV/AIDS Report, 9/4).

Reprinted with permission from kaisernetwork.org. You can view theentire Kaiser DailyHIV/AIDS Report, search the archives, and sign up for email delivery at kaisernetwork.org/email . TheKaiser Daily HIV/AIDS Report is published for kaisernetwork.org, a free service ofThe Henry J. Kaiser Family Foundation.

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