WEDNESDAY, April 26 (HealthDay News) -- A rare variant of the hepatitis B virus (HBV) can be resistant to the reverse-transcriptase inhibitor adefovir after initial resistance to lamivudine, according to a report in the April 27 issue of the New England Journal of Medicine.
Oliver Schildgen, Ph.D., of the University of Bonn in Germany, and colleagues describe three cases of primary resistance to the back-up drug adefovir in patients with a rare HBV variant (the rtI233V mutation). The patients had all become resistant to lamivudine.
The first patient was a 52-year-old man with chronic HBV who developed resistance to lamivudine within three months. After becoming resistant to tenofovir after nine months, he was switched to adefovir, with negative results, then back to tenofovir, with positive results.
The second and third patients were a 56-year-old liver transplant patient and his 52-year-old wife. Both were switched to adefovir after developing resistance to lamivudine, but did not significantly improve until treated with tenofovir.
"Some naturally occurring HBV strains are primarily resistant to adefovir," the authors write, noting "the rapid and strong effect of tenofovir in all three patients."
One author has received consulting and lecture fees from Gilead and GlaxoSmithKline, manufacturers of the inhibitors. The University of Bonn has a patent application pending on a system for the detection of HBV resistance mutations.
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