More specifically, amino acid substitutions occur in the tyrosine-methionine-aspartate- aspartate (YMDD) motif of the DNA polymerase of the virus, which renders the drug much less effective.

• 更具体的说，病毒DNA聚合酶中的酪氨酸-蛋氨酸-天门冬氨酸-天门冬氨酸（YMDD）基序中发生氨基酸取代，导致药物失效。