Nucleoside analog inhibiting DNA synthesis

Nucleoside analogues are synthetic compounds structurally similar to natural nucleosides but modified so that when metabolized intracellularly into their active triphosphate forms they can be incorporated into growing strands of DNA during replication. Their incorporation leads primarily to chain termination because they lack the chemical groups required for addition of subsequent nucleotides. This mechanism effectively inhibits both cellular and viral DNA synthesis depending on the context. They are widely used therapeutically both as chemotherapeutic agents against cancer cells—where they disrupt rapidly dividing cells—and as antivirals targeting viruses such as HIV, hepatitis B/C viruses, and herpes simplex virus by inhibiting their specific polymerases or reverse transcriptases. The incorporation causes stalling at replication forks triggering cellular responses including checkpoint activation mediated by proteins like Chk1 and ATM kinase signaling pathways that lead either to repair attempts or apoptosis if damage is irreparable[1][2][4]. Despite their efficacy, these drugs have notable side effects including bone marrow suppression due mainly to mitochondrial toxicity[2]. Resistance mechanisms involve altered recognition/sensing pathways at stalled forks[1]. This target is best understood not as a single molecule but rather a class defined by its shared mechanism—nucleotide mimicry causing inhibition/termination during nucleic acid synthesis—and thus represents an important therapeutic concept across oncology and infectious disease pharmacology.

Other names

Nucleoside analogsnucleoside antimetabolitesantiviral nucleosideschemotherapy nucleosides

Drugs in this class are phosphorylated intracellularly to their active triphosphate forms which: Are incorporated into nascent DNA strands by cellular or viral polymerases. Act as chain terminators due to lack of necessary chemical groups for further elongation. Cause stalling of replication forks leading to activation of cell cycle checkpoints such as Chk1 pathway. Trigger phosphorylation events like H2AX phosphorylation indicating DNA damage response.