Pfizer's Antiretroviral Maraviroc Reduces Viral Loads

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Pfizer's Antiretroviral Drugs Maraviroc

Pharmaceutical company Pfizer on Tuesday at the 47th Interscience Conference on Antimicrobial Agents and Chemotherapy in Chicago presented results of a new long-term study of its antiretroviral drug maraviroc, AFP/Yahoo! Newsreports. According to the company, data from a 48-week study showedthat nearly three times as many HIV-positive people who took maravirocin combination with a traditional treatment regimen achievedundetectable levels of HIV, compared with those receiving only thetraditional regimen (AFP/Yahoo! News, 9/19). Pfizer alsosaid that CD4+ T cell counts significantly were increased among peopletaking maraviroc, compared with participants who took only the standardregimen (AP/Yahoo! Finance News, 9/18).

FDAin August approved maraviroc, which belongs to a new class ofantiretrovirals that could provide an alternative to HIV-positivepeople who have developed resistance to multiple drugs. FDA gaveexpedited approval of maraviroc for use in combination with otherantiretrovirals. Maraviroc works by blocking a protein, called CCR5, onhuman immune system cells that HIV uses as a portal to enter and infectthe cell. Pfizer has proposed using the drug to treat people withadvanced HIV or AIDS who have not responded to other medications. FDAapproved maraviroc on the condition that the drug's label include ablack-box warning -- the strongest possible advisory. The drug alsowill have a warning about an increased risk of heart attack. FDA alsois requiring Pfizer to conduct further research into the drug'slong-term side effects (Kaiser Daily HIV/AIDS Report, 8/7).


Pfizeron Tuesday said the side effects recorded among participants who tookmaraviroc resembled those experienced by participants who received onlythe traditional regimen, the AP/Yahoo! Finance Newsreports. The most common side effects reported included diarrhea,nausea, fatigue and headache. Pfizer also said that maraviroc, soldunder the brand name Selzentry, is now on the market across the U.S.and that the company is working with private and public payers tosecure coverage and reimbursement, the AP/Yahoo! Finance News reports (AP/Yahoo! Finance News,9/18). "The safety and durability of response seen with Selzentry our study is reassuring," Jacob Lalezari, director of Quest Clinical Research at the University of California, said, adding, "This drug is an important new weapon for clinicians who treat HIV" (AFP/Yahoo! News, 9/19).

J&J Presents Data on Antiretroviral Prezista

Johnson & Johnsonon Tuesday at the ICAAC conference announced that its antiretroviraldarunavir, sold under the brand name Prezista, proved as effective in alate-stage trial as Abbott Laboratories' antiretroviral Kaletra in reducing HIV viral loads among people not previously treated for the virus, Reutersreports. For the study, researchers gave Prezista, a once-dailyprotease inhibitor, to participants along with Abbott's Norvir and Gilead Science'sTruvada. A separate group of people was given Kaletra and Truvada. Thestudy showed that HIV decreased to undetectable levels after 48 weeksamong 84% of patients taking experimental 800mg doses of Prezista,compared with 78% of those on Kaletra.

The trial was the first to test Prezista among people who previously have not taken other antiretrovirals, Reutersreports. Abbott spokesperson Ilke Arici said the study's findings aresomewhat questionable because the trial design did not reflect how thedrugs are distributed in real-life medical settings, Reutersreports. Arici said many participants were given a soft gel form ofKaletra, which she said is less effective than a new tablet formulationnow widely available in the U.S. J&J spokesperson Pam Van Houtensaid that most participants taking Kaletra began on the soft gel formbut later were switched to tablets after they became available. VanHouten said J&J plans to seek FDA approval by the end of 2007 forthe use of Prezista by people never previously treated for HIV(Pierson, Reuters, 9/18).

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