Selzentry was originally approved for treatment-experienced patients in 2007. Pfizer, Selzentry’s manufacturer, applied for its expanded use in September after receiving results from study 1026.

Study 1026 compared a 300 mg dose of Selzentry given twice daily in combination with Combivir (zidovudine/lamivudine) to treatment of Combivir and Sustiva (efavirenz) in treatment-naïve patients. Sustiva is an effective antiretroviral already approved as an option for patients undergoing treatment for the first time.

Selzentry specifically targets HIV strains that use a protein, called CCR5, to enter human T cells. Other strains of HIV use the CXCR4 protein and are not susceptible to the effects of Selzentry. It has been suggested that treatment-naïve patients are the most appropriate group to receive Selzentry because most are infected with CCR5-using HIV only.

Pfizer initially applied for Selzentry approval after week 48 results became available from study 1026. The reviewing FDA committee determined that the results showed a significant rate of virologic failure, or reemergence of a high viral load, observed in participants taking Selzentry. As a result, the committee recommended waiting for the completion of the study at week 96 to monitor the long-term changes in viral load. These results are considered to be a more accurate assessment of the efficacy of Selzentry use in treatment-naive patients and are included in Pfizer’s recent application.

A more sensitive test to determine the type of protein, CCR5 or CXCR4, used by a patient’s HIV strain was developed during the course of the study. This test established that 44 percent of the virological failures seen were due to improper administration to individuals infected with CXCR4-using HIV.

The results from week 96 indicated that Selzentry was both safe and effective as a first-line treatment. Participants taking Selzentry showed similar changes in viral load and CD4 cell counts to those taking Sustiva. The Antiviral Drugs Advisory Committee has now voted to recommend approval of Selzentry for use in treatment-naïve patients.

For more information, please read the Antiretroviral Drugs Advisory Committee Briefing Document available on the FDA Web site, as well as the press release on the Pfizer Web site.