High-grade serous ovarian cancer (HGSOC) is a difficult-to-treat disease, mainly due to the lack of treatments for preventing tumour relapse following the primary surgery. In the last few years, a new class of compounds termed PARP inhibitors (PARPi) have emerged as highly promising drugs that prolong dramatically the relapse-free interval in HGSOC patients. Because of their mechanism of action, PARPi are currently given to a subgroup of patients whose cancer is defective in a specific mechanism of DNA repair. However, even within this subgroup there are patients who fail to respond, while, on the other hand, a significant fraction of patients, who are not identified as DNA repair-defective, do show very good response. Unfortunately, at the moment we have no means to identify in advance patients who are likely to benefit from PARPi and, hence, could receive a personalised treatment. Our consortium will implement innovative, patient-derived experimental models and cutting-edge technologies to design novel tools for the prediction of PARPi response, thus helping to tailor the therapies and to defeat HGSOC recurrence.