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No Bioequivalence Reported for Fixed-Dose Combination of Emtricitabine and Tenofovir Disoproxil Fumarate and Efavirenz
A bioequivalence study is required to demonstrate that a co-formulated product results in the same levels of medication in the blood as achieved when the individual products are dosed simultaneously as separate pills. Pending the results of the planned bioequivalence studies, Gilead and Bristol-Myers Squibb anticipate filing a New Drug Application with the U.S. Food and Drug Administration in the first half of 2006.
In December 2004, Gilead and Bristol-Myers Squibb announced the establishment of a U.S. joint venture to co-formulate the antiretrovirals Truvada and Sustiva in a fixed-dose regimen. If approved, the new product would be the first complete Highly Active Antiretroviral Therapy (HAART) treatment regimen for HIV available in a fixed-dose combination taken once daily. Fixed-dose combinations contain multiple medicines formulated together and may help simplify HIV therapy for patients and providers. The joint venture established by the two companies is the first of its kind in the field of HIV therapy.
Guidelines issued by the U.S. Department of Health and Human Services (DHHS) list the combination of emtricitabine, tenofovir disoproxil fumarate and efavirenz as one of the preferred non-nucleoside reverse transcriptase inhibitor (NNRTI)-based treatments for use in appropriate patients that have never taken anti-HIV medicines before. It is important that patients be aware that individual HIV medications must be taken as part of combination regimens, and that they do not cure HIV infection or prevent passing HIV to others.
Truvada combines Emtriva® (emtricitabine) and Viread® (tenofovir disoproxil fumarate) in one tablet taken once a day in combination with other antiretroviral agents. In the United States, Truvada is indicated in combination with other antiretroviral agents (such as non-nucleoside reverse transcriptase inhibitors or protease inhibitors) for the treatment of HIV-1 infection in adults. Safety and efficacy studies using Truvada tablets or using Emtriva and Viread in combination are ongoing.
Emtriva and Viread have each been studied as part of multi-drug regimens and have been found to be safe and effective. In clinical study 303 Emtriva and lamivudine (3TC) demonstrated comparable efficacy, safety and resistance patterns as part of multidrug regimens. These data, and those from study 903, in which lamivudine and tenofovir were used in combination, support the use of Truvada for the treatment of HIV-1 infection in treatment-naive adults. In treatment-experienced patients, the use of Truvada should be guided by laboratory testing and treatment history.
There are no study results demonstrating the effect of Truvada on clinical progression of HIV-1, and it is not recommended that Truvada be used as a component of a triple nucleoside regimen.
Truvada should not be used with Emtriva or Viread, or other drugs containing lamivudine, including Combivir®, Epivir®, Epivir-HBV®, Epzicom(TM) or Trizivir®. Two-hundred eighty-three patients have received combination therapy with Emtriva and Viread with either a non-nucleoside reverse transcriptase inhibitor or protease inhibitor for 24 to 48 weeks in ongoing clinical studies. Based on these limited data, no new patterns of adverse events were identified and there was no increased frequency of established toxicities. For additional safety information about Emtriva or Viread in combination with other antiretroviral agents, please see "About Emtriva" and "About Viread," below.
Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogues alone or in combination with other antiretrovirals. Viread, Emtriva and Truvada are not indicated for the treatment of chronic hepatitis B virus (HBV) infection and the safety and efficacy of these drugs has not been established in patients co-infected with HBV and HIV. Severe acute exacerbations of hepatitis B have been reported in patients who have discontinued Viread or Emtriva. Hepatic function should be monitored closely with both clinical and laboratory follow-up for at least several months in patients who discontinue Viread, Emtriva or Truvada and are co-infected with HIV and HBV. If appropriate, initiation of anti-hepatitis B therapy may be warranted.
Immune reconstitution syndrome has been reported in patients treated with combination antiretroviral therapy, including Viread. Changes in body fat have been observed in patients taking Viread, Emtriva, Truvada and other anti-HIV medicines. The cause and long term health effect of these conditions are unknown.
In the United States, Emtriva is indicated, in combination with other antiretroviral agents, for the treatment of HIV-1 infection in adults. This indication is based on analyses of plasma HIV-1 RNA levels and CD4 cell counts from controlled studies of 48 weeks duration in antiretroviral-naive patients and antiretroviral-treatment-experienced patients who were virologically suppressed on an HIV treatment regimen. In antiretroviral-treatment-experienced patients, the use of Emtriva may be considered for adults with HIV strains that are expected to be susceptible to Emtriva as assessed by genotypic or phenotypic testing.
Adverse events that occurred in more than five percent of patients receiving Emtriva with other antiretroviral agents in clinical trials include abdominal pain, asthenia (weakness), headache, diarrhea, nausea, vomiting, dizziness and rash (rash, pruritis, maculopapular rash, urticaria, vesiculobullous rash, pustular rash and allergic reaction). Approximately one percent of patients discontinued participation because of these events. All adverse events were reported with similar frequency in Emtriva and control treatment groups with the exception of skin discoloration which was reported with higher frequency in the Emtriva treated group. Skin discoloration, manifested by hyperpigmentation on the palms and/or soles, was generally mild and asymptomatic. The mechanism and clinical significance are unknown.
In the United States, Viread is indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection. This indication is based on analyses of plasma HIV-1 RNA levels and CD4 cell counts in controlled studies of Viread in treatment-naive adults and in treatment-experienced adults. There are no study results demonstrating the effect of Viread on clinical progression of HIV-1. The use of Viread should be considered for treating adult patients with HIV-1 strains that are expected to be susceptible to tenofovir as assessed by laboratory testing or treatment history.
Drug interactions have been observed when didanosine, atazanavir or lopinavir/ritonavir is co-administered with Viread and dose adjustments may be necessary. Data are not available to recommend a dose adjustment of didanosine for patients weighing less than 60 kg. Patients on atazanavir or lopinavir/ritonavir plus Viread should be monitored for Viread-associated adverse events which may require discontinuation. When co-administered with Viread, it is recommended that atazanavir 300 mg be given with ritonavir 100 mg. Atazanavir without ritonavir should not be co-administered with Viread.
Renal impairment, including serious cases, has been reported. Renal impairment occurred most often in patients with underlying systemic or renal disease or in patients taking concomitant nephrotoxic agents, though some cases have appeared in patients without identified risk factors. Decreases in bone mineral density (BMD) at the lumbar spine and hip and increases in biochemical markers of bone metabolism have been seen with the use of Viread. The clinical significance of changes in BMD and biochemical markers is unknown and follow-up is continuing to assess long-term impact. The most common adverse events and those occurring in more than five percent of patients receiving Viread with other antiretroviral agents in clinical trials include asthenia, pain, abdominal pain, headache, nausea, diarrhea, vomiting, rash (rash, pruritis, maculopapular rash, urticaria, vesiculobullous rash and pustular rash), flatulence, dizziness and depression. Less than one percent of patients discontinued participation because of gastrointestinal events.
Source: Gilead Sciences, Inc.