DUETTE: A randomized phase II study to assess a second maintenance treatment with olaparib (ola) or ola+ceralasertib (cer), in patients (pts) with platinum-sensitive relapsed (PSR) epithelial ovarian cancer who have previously received PARP inhibitor maintenance treatment (NCT04239014).

TPS6104 Background: Ovarian cancer is the leading cause of death from gynecological cancers in the USA, and the fifth most common cause of cancer death in women. Ola is a PARPi approved for first-line maintenance treatment of BRCA-mutated advanced ovarian cancer in women who achieve a complete or partial response to platinum-based chemotherapy. Ola is also efficacious in combination with bevacizumab in the same population, independent of BRCA mutation status. Cer is a potent, oral, selective inhibitor of ATR. ATR is a critical DDR kinase that is activated in response to replication stress and stalled replication forks. There is no second maintenance standard of care for patients with PSR ovarian cancer who have previously received a PARPi in the maintenance setting. Pre-clinical models have shown that several mechanisms of PARPi resistance may be overcome by ATR inhibition, such as BRCA reversion, replication fork protection and DDR rewiring. DUETTE will select pts with tumor response or stable disease after second or third-line platinum-based treatment, with the expectation to enrich for non-BRCA reversion PARPi resistance mechanisms. The study will address the role of a second maintenance treatment following prior 1L or 2L maintenance, an emerging population of unmet need, and includes translational studies that aim to further our knowledge of clinical PARPi resistance mechanisms and predictors of treatment response. Methods: DUETTE is a global, multi-center, phase II study. 192 pts with PSR epithelial ovarian cancer who have previously received PARPi maintenance treatment, will be retreated with platinum and those who have not progressed after ≥ 4 cycles will be randomized (1:1:1) to 3 treatment arms: Arm 1, open-label: cer 160 mg once daily (qd) days 1 to 7 plus ola 300 mg twice daily (bd); Arm 2, blinded: ola monotherapy 300 mg bd and Arm 3, blinded: ola-placebo. Treatment is administered in 28-day cycles. All pts will be stratified by BRCA status (mutation or wildtype) and response to most recent line of platinum-based chemotherapy (CR/PR or SD). The primary endpoint is to assess the efficacy of maintenance ola monotherapy and cer+ola combination therapy compared with placebo by PFS using blinded, independent central review. Secondary endpoints are overall survival, PFS2, ORR, DoR, safety and tolerability. Enrolment is planned to start in April 2020.