— Christine M. Kukka, Project Manager, HBV Advocate
The antiviral tenofovir is emerging as one of the
most potent and effective antiviral medications, with an extremely low
rate of drug resistance. However, the antiviral appears to be less
effective in patients who have developed resistance to the antiviral
adefovir (Hepsera).
Researchers suggest that HBV
with mutations that can "resist" adefovir may also be able to continue
to replicate despite tenofovir treatment.
Turkish researchers, reporting in the February issue of the journal of Antiviral Therapy,
treated three groups of patients with tenofovir to see what effect
adefovir-resistance had on tenofovir's ability to lower viral load.
Forty-four of the patients had never been treated with antivirals, 30
had adefovir resistance and the third group of 24 had simply failed to
respond well to adefovir treatment.
The 44 previously untreated
patients experienced the fastest declines in HBV DNA, with 77.2%
achieving undetectable HBV DNA within 12 months.
The two groups, who had
previously been treated with adefovir had weaker responses to
tenofovir. Only 60% of those with documented adefovir resistance
achieved undetectable viral load after 12 months, while 75% of the
adefovir nonresponders cleared viral load.
HBV DNA decline is slower in
adefovir-experienced patients, researchers noted. "The clinical
significance of this slow response may be important in patients with
critical liver (disease) and high viral load," they wrote. "Optimal
combination treatment (tenofovir plus entecavir) could be considered in
these patients."(1)
In a related study published in the January issue of the journal Gut Liver,
South Korean researchers studied 17 patients who had developed
resistance to other antivirals. Four were treated with tenofovir and 13
were treated with a combination of tenofovir and lamivudine
(Epivir-HBV) for 42 months. The doctors monitored viral load, HBeAg
status, and kidney function.
After treatment, the average HBV
DNA level decreased to undetectable after 48 months. HBeAg loss was
seen in two patients. Five patients experienced a resurgence in HBV DNA
because they did not take the daily antiviral pills as prescribed. No
kidney damage was documented.(2)
Labels: Adeforvir resistance, trenofovir
