Pfizer Inc. announced that the US Food and Drug Administration's (FDA) Antiviral Drugs Advisory Committee voted (10 to 4) to recommend the approval of Selzentry (maraviroc) tablets for use in treatment-naïve adult patients with CCR5-tropic HIV-1 virus as part of combination therapy.

"Pfizer is pleased that the Committee has recognized the effectiveness and safety profile of maraviroc in patients who are starting HIV therapy," said Dr. Howard Mayer, Pfizer's executive director and disease area leader, antivirals. "Today's discussion marks an important step in expanding available treatment options for patients with HIV infection and we look forward to working with the FDA to further address the points raised by the panel."

Selzentry was granted accelerated approval in August 2007 and full approval in November 2008 by the FDA for use in treatment-experienced adult patients with only CCR5-tropic HIV-1 virus in combination with other antiretroviral therapies. Selzentry is an oral medicine that blocks viral entry to human cells. Rather than fighting HIV inside white blood cells, Selzentry prevents the virus from entering uninfected cells by blocking its predominant entry route, the CCR5 co-receptor.

In making its decision, the Advisory Committee reviewed 48- and 96-week efficacy and safety data from the ongoing phase 3 MERIT (Maraviroc versus Efavirenz Regimens as Initial Therapy) trial and MERIT ES (analysis of the MERIT study with the enhanced sensitivity Trofile assay).

Results of MERIT at 48-weeks showed that Selzentry plus Combivir (zidovudine/lamivudine) was as effective as Sustiva (efavirenz) plus zidovudine/lamivudine at reducing viral load for the co-primary endpoint of <400 copies/mL, but did not show non-inferiority for the co-primary endpoint of <50 copies/mL at 48-weeks. Safety results at 96-weeks showed that among those patients who remained on therapy, less than half the number of malignancies were observed in patients taking Selzentry compared to those taking efavirenz. Additionally, no new safety signals were identified in association with Selzentry at 96-weeks. The most frequently reported adverse events were nausea, headache, dizziness, diarrhoea, fatigue, upper respiratory tract infection, and vomiting. Patients were screened into the study using the original Trofile assay which is no longer available.

MERIT ES is a retrospective analysis, which utilized the enhanced sensitivity Trofile™ assay in screening samples from the MERIT trial. Results of MERIT ES at 48-weeks showed that treatment-naïve patients with CCR5-tropic HIV-1 taking Selzentry plus zidovudine/lamivudine experienced comparable virologic suppression to undetectable levels (<50 copies/mL) to those taking efavirenz plus zidovudine/lamivudine. The enhanced sensitivity Trofile assay used in the MERIT ES analysis has been the only available version of the Trofile assay since June 2008.

The FDA often seeks the advice of its Advisory Committees when evaluating potential treatments, but is not required to follow its recommendation. Through the joint venture with GlaxoSmithKline, which is expected to close in the fourth quarter of 2009, Pfizer remains committed to the expansion of Selzentry/Celsentri's current indications to include appropriate treatment-naïve populations throughout the world.

At the end of 2006, an estimated 1.1 million people in the US were living with HIV infection. The Centers for Disease Control and Prevention (CDC) estimates that in 2006 approximately 56,300 people were newly infected with HIV in the US (the most recent year that data are available).

Selzentry has been approved for use in treatment-experienced adult patients with only CCR5-tropic HIV-1 virus detectable in combination with other antiretroviral therapies, in several other markets around the world including the US, Canada and the European Union.

Maraviroc is marketed under the trade name Selzentry in the US and Celsentri in all other countries in which it is approved.