A Study of INCB123667 in Participants With Platinum-Resistant Ovarian Cancer With Cyclin E1 Overexpression

Inclusion Criteria: * Histological diagnosis of a high-grade serous epithelial ovarian, fallopian tube, or primary peritoneal cancer. * Have platinum-resistant disease: * Participants who have only had 1 line of platinum-based therapy must have received at least 4 cycles of a platinum-containing regimen. * Participants who have received 2 to 4 lines of platinum-based therapy must have progressed on or within 6 months after the last dose of platinum. * Willingness to undergo a pretreatment biopsy. Note: Tissue from a fresh pretreatment biopsy is preferred, however an archival sample is acceptable as long as the sample is no older than 5 years. * Received at least 1 and no more than 4 prior lines of systemic therapy following the initial diagnosis, after which single-agent therapy is considered an appropriate next therapeutic option. * Must have received bevacizumab unless there was a contraindication for its use. * If the tumor tests positive for FRα, participants must have received mirvetuximab soravtansine unless there is an exception for its use on medical grounds. Exclusion Criteria: * Have endometrioid, clear cell, mucinous, or sarcomatous histology, mixed tumors containing any of these histologies, or low-grade/borderline ovarian cancer. * Have primary platinum-refractory disease: either did not respond (CR or PR) to first-line platinum-containing therapy or progressed on or within 3 months after the last dose of the first line platinum-containing therapy. * The tumor tests positive for FRα but the participant has not received mirvetuximab soravtansine for any reason other than medical contraindication. * Clinically significant or uncontrolled cardiac disease within 6 months before the first dose of study drug. * Known active CNS metastases and/or carcinomatous meningitis. * Known additional malignancy that is progressing or requires active treatment. Other protocol-defined Inclusion/Exclusion Criteria may apply.