Nucleoside analogues act by mimicking the natural nucleosides that make up DNA and RNA. Once inside the cell, they undergo phosphorylation to become active triphosphate forms. These active forms are then incorporated into the growing DNA or RNA chain by polymerases. Due to structural differences from natural nucleosides, they can cause premature chain termination, faulty base pairing, or trigger DNA repair mechanisms, ultimately leading to cell death or the inhibition of viral replication.
