Study on the efficacy and toxicity of pamiparib combined with tamoxifen in the treatment of patients with epithelial ovarian cancer with biochemical recurrence during first-line PARPi maintenance therapy.

TPS5621 Background: A high proportion of ovarian cancer patients tend to have elevated CA-125 1-6 months before imaging recurrence. The time between biochemical recurrence (i.e., only elevated CA-125 without imaging finding or clinical symptoms) to imaging recurrence can be considered a "window period", and if the “window period” can be extended, it may convert platinum-resistant relapsed patients to platinum-sensitive patients, and ultimately improving patient outcomes. The timing of treatment for the biochemical recurrent patients has been controversial. Tamoxifen, an anti-estrogenic drug, is considered an effective option for these patients. Pamiparib (BGB-290) is an investigational small molecule inhibitor of PARP1 and PARP2. According to OReO study(NCT03106987), the "PARPi after PARPi" strategy is effective in recurrent ovarian cancer patients previously treated with a PARP inhibitor. Therefore, we aim to further explore the use of PARP inhibitors in maintenance therapy for patients with ovarian cancer. Methods: This study (NCT05669768) will evaluate the efficacy and toxicity of pamiparib and tamoxifen in ovarian cancer patients with biochemical recurrence during first-line PARPi maintenance therapy. The included ovarian cancer patients are required to achieve No Evidence of Disease (NED) or demonstrated a response following platinum-based chemotherapy, with normalized CA-125 levels. First-line maintenance treatment with a PARP inhibitor is mandatory, with a minimum interval of ≥6 months to biochemical recurrence. The trial design is interventional, employing a Simon two-stage design to estimate sample size. The primary outcome of the study is the CA-125 response rate, which was assessed according to the GCIG criteria. 1 The secondary outcome was Time to First Subsequent Therapy (TFST). Patients undergo regular assessments for tumor markers and imaging throughout treatment. If persistent elevation of tumor markers or the detection of recurrent lesions or distant metastases is observed, the patient is promptly removed from the study group. Standardized antitumor therapy is then initiated based on the patient's condition. The total planned enrollment is 46 participants, utilizing a single-group assignment and an open-label design. 1 of planned 12 patients for the first stage of accrual have been enrolled. Reference: 1. Rustin GJ, Vergote I, Eisenhauer E, et al. Definitions for response and progression in ovarian cancer clinical trials incorporating RECIST 1.1 and CA 125 agreed by the Gynecological Cancer Intergroup (GCIG). Int J Gynecol Cancer. 2011;21(2):419-423. Clinical trial information: NCT05669768 .