NRTI Emtriva receives FDA approval

The Food and Drug Administration has approved Emtriva (FTC, emtricitabine), a new nucleoside reverse transcriptase inhibitor (NRTI) to be used in combination with other antiretroviral agents.

Emtriva is indicated for adults 18 and older. Safety and effectiveness in pediatric patients have not been established. In antiretroviral-treatment-experienced patients, Emtriva may be considered for adults with HIV strains that are expected to be susceptible to Emtriva as assessed by genotypic or phenotypic testing.

The recommended dose of Emtriva is one 200 mg capsule daily, with or without food.

The FDA based its approval on data from two 48 week clinical trials. The first trial was a double-blind, active-controlled multicenter study comparing Emtriva (200 mg once daily) administered in combination with didanosine and efavirenz vs. stavudine, didanosine, and efavirenz in 571 antiretroviral patients.

The proportion of patients who achieved and maintained confirmed HIV RNA < 400 copies/mL (< 50 copies/mL) through week 48 was 81% (78%) for the Emtriva, didanosine, and efavirenz group vs. 61% (59%) for the stavudine, didanosine, and efavirenz group, respectively.

The mean increase from baseline in CD4 cell count was 168 cells/mm3 for the Emtriva arm compared to 134 cells/mm3 for the control arm.

The second trial was an open-label, active-controlled multicenter study comparing Emtriva to lamivudine, in combination with stavudine or zidovudine and a protease inhibitor or NNRTI in 440 treatment experienced patients who were on lamivudine-containing triple-antiretroviral drug regimen for at least 12 weeks prior to study entry, and had HIV-1 RNA * 400 copies/mL.

The proportion of patients who achieved confirmed HIV RNA < 400 copies/mL (< 50 copies/ mL) through week 48 was 77% (67%) for the Emtriva group vs. 82% (72%) for the lamivudine group. The mean increase from baseline in CD4 cell count was 29 cells/mm3 for the Emtriva arm compared to 61 cells/mm3 for the lamivudine arm.

The most common adverse events that occurred in patients receiving Emtriva with other antiretroviral agents in clinical trials were headache, diarrhea, nausea, and rash, which generally were of mild to moderate severity.

Approximately 1% of patients discontinued participation in the clinical studies due to these events. With the exception of skin discoloration, which was reported with higher frequency in the Emtriva-treated group, all other adverse events were reported with similar frequency in Emtriva and control treatment groups.

Skin discoloration, manifested by hyperpigmentation (excess pigmentation) on the palms and/or soles, was predominantly observed in non-Caucasian patients. The mechanism and clinical significance are unknown.

It is recommended that all patients with HIV be tested for the presence of chronic hepatitis B virus (HBV) before initiating antiretroviral therapy.

Emtriva is not indicated for the treatment of chronic HBV infection, and the safety and efficacy of Emtriva have not been established in patients co-infected with HBV and HIV. "Flare-ups" of hepatitis B, where the illness can return in a worse way than before, have been reported in patients after the discontinuation of Emtriva. Patients co-infected with HIV and HBV should be closely monitored with both clinical and laboratory follow-up for at least several months after stopping treatment.

As with other NRTIs, Emtriva may cause lactic acidosis (buildup of an acid in the blood), serious liver problems called hepatotoxicity, with liver enlargement (hepatomegaly), and fat in the liver (steatosis).

Emtriva is a product of Gilead Sciences in Foster City, CA.