The Food and Drug Administration has approved Viread (tenofovir disoproxil fumarate), a new antiviral drug indicated for treatment of HIV-1 infection in combination with other antiretroviral medicines. Tenofovir disoproxil fumarate is the first nucleotide analog approved for HIV-1 treatment. Nucleotides are similar to nucleoside analogs, and block HIV replication in the same manner.
The introduction of potent antiviral drugs and the combined use of these drugs has markedly reduced replication of HIV in many patients and has improved survival rates. Yet because HIV mutates rapidly, resistance to one or more of these potent drugs may develop over time, necessitating the development of new drugs to treat these resistant virus strains.
FDA based its approval of tenofovir disoproxil fumarate on two clinical studies involving more than 700 patients who had previously been treated with antiretroviral agents, but showed signs of continued HIV replication despite drug therapy. The two clinical studies were a placebo-controlled 24-week study and a controlled dose-ranging 48-week clinical trial. Patients who received tenofovir disoproxil fumarate showed significant decreases in the quantities of HIV RNA in their blood compared to patients who received a placebo with the standard antiretroviral regimen.
Because the approval of tenofovir disoproxil fumarate was based on clinical trials involving patients who were previously treated with antiretrovirals, the risk-benefit ratio for untreated patients has yet to be determined. Furthermore, there are no study results to show long-term inhibition of the clinical progression of HIV by tenofovir.
Tenofovir disoproxil fumarate is available as a 300 mg tablet to be taken orally, with a meal. The use of tenofovir disoproxil fumarate should be considered for treating adult patients with HIV strains that are expected to respond to tenofovir as assessed by laboratory testing or treatment history.
The most frequently reported adverse events among patients in the clinical trials were mild to moderate gastrointestinal problems including diarrhea, nausea, vomiting and flatulence. Lactic acidosis and hepatomegaly with steatosis (severe liver enlargement and excess fat in the liver) have also occurred among patients treated with nucleoside analogues alone, or in combination with antiretrovirals. These are severe and possibly fatal conditions.
Viread is the brand name for tenofovir disoproxil fumarate and is marketed by Gilead Sciences, Inc. of Foster City, CA.