Overcoming PARP inhibitor resistance in ovarian cancer.

Ovarian cancer (OC) is one of the most lethal tumors in women, mostly diagnosed at advanced stages. Standard of care is based on surgery and platinum-based chemotherapy which provides high rates of response, although most patients will relapse. Poly(ADP-ribose) polymerase inhibitors (PARPi) have recently been incorporated in the treatment strategy for high-grade OC, particularly for those with defects in DNA repair pathways (homologous repair deficiency (HRd)). However, some tumor cells may not respond and some others will develop mechanisms of resistance to adapt. The most known mechanism of PARPi resistance is the reversion of HRd to homologous repair proficiency driven by epigenetic and genetic changes. Ongoing research is exploring different agents that are trying to re-sensitize tumor cells,overcome or bypass resistance to PARPi. Current investigations are focused on agents that target replication stress and DNA repair pathways, improve drug delivery, and target other cross-talk pathways. A crucial challenge in practice will be to identify and select patients for the appropriate therapy or combination strategies. However, efforts are needed to decrease overlapping toxicity and define the correct schedule timing of dosing to maximize the therapeutic index.