An independent FDA panel of medical experts last month unanimously recommended accelerated approval of raltegravir, an experimental integrase inhibitor. Raltegravir effectively decreases HIV viral loads after 24 weeks of use among HIV-positive people who have not responded to other treatments, according to a study published in the April 14 online edition of the journal Lancet. Raltegravir works by blocking an HIV enzyme called integrase. Integrase is one of the three enzymes necessary for HIV to replicate in the body, and integrase inhibitors stop HIV from inserting its genes into uninfected DNA. The other two enzymes necessary for viral replication, reverse transcriptase and protease, already are targeted by a variety of antiretrovirals.
According to an FDA review of raltegravir released ahead of the independent panel's meeting, the drug is effective at treating HIV-positive people who have shown resistance to available treatments. Rash and increased levels of creatine in the blood were the most common side effects of the drug, according to the review. Other potential side effects include liver injuries and cancer. In clinical trials, a higher number of cancers was found among people taking raltegravir than among those taking a placebo, but the difference could be because of a lower rate of cancer among people in the placebo group, FDA said.
Merck said that if the drug is approved, it will be used in combination with standard oral antiretrovirals by HIV-positive people who have developed resistance to their current treatments. Raltegravir will be sold under the brand name Isentress. FDA is expected to make a final decision about raltegravir in mid-October.
According to the Journal, a "major factor" in the drug's financial prospects will be its price, which has not been determined but is "especially important" because of the recent availability of other antiretrovirals on the market. Merck has declined to comment on pricing ahead of an FDA decision, but the company said it has spent "hundreds of millions of dollars" to develop the drug. Lanny Cross -- former director of the New York AIDS Drug Assistance Program and a consultant for the National Alliance of State and Territorial AIDS Directors -- said that if Merck places the drug at the high end of the price range, "there's no way the system could handle that."
Martin Delaney, who has participated in price negotiations with Merck on behalf of the Fair Pricing Coalition, said that the company has shown sensitivity to patients' financial needs in the past but that Merck officials have been "arguing they need to get profitability." He added that Merck wants to price the drug in the range of Prezista, sold by the Johnson & Johnson subsidiary Tibotec Pharmaceuticals, and Bristol-Myers Squibb's Reyataz, both of which cost around $9,500 annually wholesale.
An additional factor that will influence the drug's prospects is whether physicians will prescribe it for people living with HIV in the early stages of treatment, the Journal reports. "Since the drug seems to be very effective and pretty well-tolerated, I think (there is) potential for it to move in and take territory" from some older antiretrovirals, Judith Feinberg -- head of the AIDS clinical-trials unit at the University of Cincinnati College of Medicine who served on the FDA advisory panel -- said. She added that some physicians might be uncomfortable prescribing raltegravir more regularly until further studies are complete. According to the Journal, Merck is conducting late-stage studies on the drug among HIV-positive people new to treatment. The company expects to have the results toward the end of 2008, the Journal reports.
Source: Kaiser Family Foundation