This clinical trial is focused on studying the effects of a medication called niraparib in patients with advanced ovarian cancer. Ovarian cancer is a type of cancer that begins in the ovaries, which are part of the female reproductive system. The study is specifically looking at patients who have a type of ovarian cancer known as homologous recombination deficiency, which means their cancer cells have trouble repairing DNA damage. The treatment being tested is niraparib tosylate monohydrate, which is taken as a capsule by mouth. This medication is being compared to a placebo, which looks like the medication but does not contain the active ingredient.

The purpose of the study is to evaluate how effective niraparib is in maintaining the response to initial chemotherapy treatment in patients with advanced ovarian cancer. Patients who have responded well to their first round of chemotherapy, which is a common cancer treatment using drugs to kill cancer cells, will be given either niraparib or a placebo. The study will monitor how long patients remain free from cancer progression, which means the cancer does not get worse, after starting the study treatment.

Participants in the study will take the study medication for up to 36 months, or until their cancer progresses or they experience unacceptable side effects. Throughout the study, patients will have regular check-ups to monitor their health and the status of their cancer. The study aims to provide valuable information on whether niraparib can help keep ovarian cancer from returning or worsening after initial treatment.