**11. What are PARP inhibitors?**

Poly (ADP-ribose) polymerase (*PARP*) is a protein mediated the DNA double strand break repair, which was first identified in early sixties and first PARP inhibitor was discovered in 1980 as a chemotherapy sensitizer [17].

Following figure illustrates the normal action of the PARP proteins to aid the understanding of how the PARP inhibitors work (**Figure 3**).

In 2005 and 2006, inhibiting PARP enzymes was first observed to be highly effective against cancers with homologous recombination deficiencies [19], are being utilised in the clinical setting to manage recurrent ovarian cancers. However, PARPi – Niraparib also show significant clinical benefit in patients without HR deficiencies [20]. There are currently three FDA-approved PARP inhibitors for recurrent ovarian cancer – Olaparib, Rucaparib and Niraparib.

### **Figure 3.**

*Function of PARP proteins in DNA damage repair. Source: An update on PARP inhibitors—Moving to the adjuvant setting [18].*
