How does olaparib work (its mechanism of action)?
Olaparib is a PARP inhibitor. It blocks poly(ADP-ribose) polymerase (PARP) enzymes involved in repairing DNA damage, especially single-strand DNA breaks. When PARP is inhibited, damaged DNA accumulates and replication forks collapse, leading to double-strand breaks.
This DNA repair failure becomes especially harmful in tumors with existing defects in homologous recombination repair (for example, BRCA1 or BRCA2 mutations). As a result, cancer cells are more sensitive to olaparib than normal cells—a concept often described as “synthetic lethality” between PARP inhibition and homologous recombination deficiency.
What happens to DNA inside the cell when PARP is blocked?
By inhibiting PARP’s role in DNA break repair, olaparib disrupts multiple DNA-damage repair steps that PARP normally helps coordinate. The downstream effect is increased genomic instability and cancer cell death when the tumor cannot efficiently repair the resulting double-strand breaks.
Why does olaparib work better in BRCA-mutated or homologous recombination–deficient cancers?
Cells with homologous recombination defects already struggle to repair double-strand DNA breaks. PARP inhibition pushes the cell toward double-strand breaks it cannot properly resolve, making those cancer cells disproportionately vulnerable.
Does olaparib target a specific PARP subtype?
Olaparib is a PARP inhibitor that acts on PARP enzymes, with its clinical mechanism centered on impairing PARP-mediated DNA repair processes. The key therapeutic effect comes from the inability of cancer cells to survive replication-associated DNA damage.
Mechanism of action vs. what patients actually feel
The mechanism itself does not determine side effects directly, but the same pathway (DNA damage and replication stress) underlies olaparib’s anticancer effect. Treatment can still affect normal rapidly dividing tissues, contributing to adverse effects seen in practice (such as fatigue or effects on blood counts), because they also rely on DNA repair and cell division.
Where olaparib fits in the DNA repair pathway (practical framing)
Olaparib interferes with PARP-dependent DNA repair (often linked to base excision repair and single-strand break repair). Tumors that already have impaired homologous recombination repair cannot compensate, so DNA damage accumulates and the tumor’s growth is suppressed.
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