Viread (tenofovir disoproxil fumarate)

Viread (tenofovir disoproxil fumarate) is an oral nucleotide analogue DNA polymerase inhibitor. DNA polymerase is the enzyme that is necessary for the virus to replicate in liver cells.

Viread is specifically indicated for the treatment of chronic hepatitis B in adults. Viread has not been evaluated in patients with decompensated liver disease.

Viread is supplied as a tablet designed for oral administration. The recommended initial dose of the drug is 300 mg once daily taken orally, without regard to food.

The dosing interval of Viread should be adjusted in patients with baseline creatinine clearance <50 mL/min using the following recommendations:
Creatinine Clearance <50 mL/min recommended 300 mg dosing interval is every 24 hours.
Creatinine Clearance 30-49 mL/min recommended 300 mg dosing interval is every 48 hours.
Creatinine Clearance 10-29 mL/min recommended 300 mg dosing interval is every 72 to 96 hours.

In hemodialysis patients the recommended 300 mg dosing interval is every 7 days or after a total of approximately 12 hours of dialysis.

FDA Approval
FDA approval of Viread was based on the results of two phase III clinical trials.

HBeAg-Negative Chronic Hepatitis B
This randomized, double-blind, active-controlled study, dubbed Study 0102, enrolled 375 subjects with HBeAg- (anti-HBe+) Hepatitis B and compensated liver function. At baseline, the mean Knodell necroinflammatory score was 7.8; mean plasma HBV DNA was 6.9 log10 copies/mL; and mean serum ALT was 140 U/L. The subjects received Viread 300 mg or Hepsera 10 mg and were measured for complete response at 48 weeks. Complete response was defined as serum HBV DNA levels below 400 copies/mL and histologic improvement characterized by at least a two point reduction in the Knodell necroinflammatory score with no concurrent worsening of fibrosis. This was observed in 71% of the subjects who received Viread compared to 49% of the subjects who received Hepsera. Histological Response was observed in 72% of the Viread group and 69% of the Hepsera group; HBV DNA reductions <400 copies/mL (<69 IU/mL) occurred in 93% and 63% of the Viread and Hepsera arms, respectively and normalized ALT was observed in 76% and 77% of the Viread and Hepsera arms, respectively.

HBeAg-Positive Chronic Hepatitis B
This randomized, double-blind, active-controlled study, dubbed Study 0103, enrolled 266 subjects with HBeAg+ nucleoside-naïve Hepatits B and compensated liver function. At baseline, subjects had a mean Knodell necroinflammatory score of 8.4; mean plasma HBV DNA was 8.7 log10 copies /mL; and mean serum ALT was 147 U/L. The subjects received Viread 300 mg or Hepsera 10 mg and evaluated for complete response at 48 weeks. Complete response was observed in 67% of the subjects who received Viread and 12% of the subjects who received Hepsera. Histological response was seen in 74% and 68% of the Viread and Hepsera arms, respectively; HBV DNA levels <400 copies/mL (<69 IU/mL) was observed in 76% of the Viread arm and 13% of the Hepsera arm and normalized ALT was reached in 68% and 54% of the Viread and Hepsera arms, respectively. In addition, HBeAg Loss/Seroconversion was seen in 20%/19% and 16%/16% of the Viread and Hepsera arms, respectively and HBsAg Loss/Seroconversion was seen in 3%/1% and 0/0 of the Viread and Hepsera arms, respectively.

Adverse events associated with the use of Viread may include, but are not limited to, the following:

• nausea
• abdominal pain
• diarrhea
• headache
• dizziness
• fatigue
• nasopharyngitis
• back pain
• skin rash

Viread (tenofovir disoproxil fumarate) is an oral nucleotide analogue DNA polymerase inhibitor.Tenofovir diphosphate inhibits the activity of HBV polymerase by competing with the natural substrate deoxyadenosine 5’-triphosphate and, after incorporation into DNA, by DNA chain termination. Tenofovir diphosphate is a weak inhibitor of mammalian DNA polymerases a, ß, and mitochondrial DNA polymerase gamma.

Matthews GV, Avihingsanon A, Lewin SR, Amin J, Rerknimitr R, Petcharapirat P, Marks P, Sasadeusz J, Cooper DA, Bowden S, Locarnini S, Ruxrungtham K, Dore GJ A randomized trial of combination hepatitis B therapy in HIV/HBV coinfected antiretroviral naïve individuals in Thailand. Hepatology 2008 Aug 11

Del Poggio P, Zaccanelli M, Oggionni M, Colombo S, Jamoletti C, Puhalo V Low-dose tenofovir is more potent than adefovir and is effective in controlling HBV viremia in chronic HBeAg-negative hepatitis B. World Journal of Gastroenterology 2007 Aug 14;13(30):4096-9

Santos SA, Uriel AJ, Park JS, Lucas J, Carriero D, Jaffe D, Dieterich DT Effect of switching to tenofovir with emtricitabine in patients with chronic hepatitis B failing to respond to an adefovir-containing regimen. European Journal of Gastroenterology & Hepatology 2006 Dec;18(12):1247-53

van Bömmel F, Zöllner B, Sarrazin C, Spengler U, Hüppe D, Möller B, Feucht HH, Wiedenmann B, Berg T Tenofovir for patients with lamivudine-resistant hepatitis B virus (HBV) infection and high HBV DNA level during adefovir therapy. Hepatology 2006 Aug;44(2):318-25

Delaney WE 4th, Ray AS, Yang H, Qi X, Xiong S, Zhu Y, Miller MD Intracellular metabolism and in vitro activity of tenofovir against hepatitis B virus. Antimicrobial Agents and Chemotherapy 2006 Jul;50(7):2471-7.

For additional information regarding Viread or Hepatitis B, please visit the Viread web page.