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Tenofovir More Effective than Adefovir for Long-Term Treatment of Resistant Hepatitis B Virus: Presented at AASLD

By Crystal Phend

SAN FRANCISCO, CA -- November 23, 2005 -- Tenofovir (Viread) appears to be more effective and less affected by resistance mutations than adefovir for long term use in patients with lamivudine resistant hepatitis B, researchers said here at the American Association for the Study of Liver Diseases' (AASLD) annual meeting.

Tenofovir gives "fast and stable suppression of HBV DNA" compared to adefovir, said lead author Florian van Bömmel, MD, Physician, Department of Hepatology and Gastroenterology, Charité Campus Virchow Klinikum, Berlin, Germany.

Adefovir dipivoxil (Hepsera) is a nucleotide analogue that treats lamivudine resistant hepatitis B virus. Tenofovir is a nucleotide analogue that is approved for treatment of HIV and is also active against hepatitis B virus.

Recent research results showed the two drugs have different virological responsiveness after 1 year of therapy. In their study, Dr. van Bömmel and colleagues extended the comparison to almost 3 years for virological and immunological effectiveness and mutations in the hepatitis B virus polymerase gene.

In a presentation on November 14^th Dr. van Bömmel presented the retrospective study, which included 88 patients with lamivudine resistant hepatitis B who then received either tenofovir or adefovir.

One group of 35 patients switched directly to tenofovir at a dose of 300 mg and followed for 33 months. The 53 patients that switched to adefovir received 10 mg and were followed for an average of 4 months.

The two treatment groups had no significant differences in virus genotype, virus DNA levels at baseline, viral resistance at baseline or percentage of patients co-infected with HIV.

Patients were monitored for elevated liver enzymes and virus DNA once every 3 months.

At 12 months, 94% of patients on tenofovir had undetectable virus levels compared with 32% on adefovir. By 18 months, all of the tenofovir patients had undetectable levels compared with 35% of adefovir patients. At 24 months, tenofovir was still at 100% while adefovir reached 49% at undetectable levels.

No significant adverse effects were noted in either group and liver enzyme levels remained in normal ranges.

Variations in virus DNA levels according to mutations were not present in the tenofovir group but mutations did significantly lower suppression rates in the adefovir group at months 12 and 18.

The researchers concluded that tenofovir is superior to adefovir in this setting.

"Monotherapy with adefovir is not recommended," Dr. van Bömmel said.


[Presentation title: Long-Term Effect of Tenofovir in the Treatment of Lamivudine-Resistant Hepatitis B Virus Infections in Comparison to Adefovir. Abstract 184]

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