Nucleoside/Nucleotide Reverse Transcriptase Inhibitors (NRTIs)

When the hepatitis B virus (HBV) infects a liver cell, it copies its own genetic code into the cell’s DNA. It does this using an enzyme (reverse transcriptase) from the cell’s RNA. In this way, the cell is then “programmed” to create new copies of HBV.

NRTIs, sometimes called “nucleoside analogues” or “nukes,” contain faulty versions of the building blocks (nucleotides) used by reverse transcriptase to convert RNA to DNA. When reverse transcriptase uses these faulty building blocks, the new DNA cannot be built correctly. In turn, HBV’s genetic material cannot be incorporated into the healthy genetic material of the cell and prevents the cell from producing new virus.

While nucleotide analogues (Hepsera and Viread) are technically different from nucleoside analogues, they act very much the same way. In order for nucleoside analogues to work, they must undergo chemical changes (phosphorylation) to become active in the body. Nucleotide analogues bypass this step because they are already chemically activated.

Last Reviewed: March 4, 2019