Niraparib is a potent and highly selective poly-ADP ribose polymerase (PARP) inhibitor.

It is approved as a maintenance treatment for epithelial ovarian cancer which has demonstrated response to platinum chemotherapy.

We review the scientific basis of PARP inhibition, chronologically detailing preclinical and clinical data which have led to the approvals to date.

We also discuss ongoing trials and the biological rationale for combination treatments, with a focus on the cGAS/stimulator of interferon genes (STING) pathway and immune checkpoint inhibitors.

The review also highlights practical challenges faced by clinicians, such as limitations of current strategies in defining biomarkers, particularly with regard to homologous recombination deficiency status.