This study is testing a new treatment, **Rina-S**, for ovarian cancer that doesn't respond well to platinum-based chemotherapy. The purpose is to see if **Rina-S** works better than standard chemotherapy treatments. Participants will have a 50% chance of receiving **Rina-S** or one of four approved chemotherapy drugs. All participants will get an active treatment, not a placebo (a fake treatment). To join, participants must have a specific type of ovarian cancer and have tried 1 to 4 other treatments before, including platinum chemotherapy. They should not have had certain other treatments or have certain medical conditions that could interfere with the study. **Key Points:** - The study is worldwide, offering a 50:50 chance of receiving either **Rina-S** or standard treatment. - Participants must have specific prior treatments and no recent history of other cancers. - The study involves active treatment, no placebos, and standard medical care. This study is an opportunity to explore a new potential treatment while still receiving active care. Participants should consider their previous treatments and existing health conditions when deciding to partake.