The purpose of this study is to evaluate INCB123667 versus investigator's choice of chemotherapy in participants with platinum-resistant ovarian cancer with cyclin E1 overexpression.

Inclusion Criteria:

• Histological diagnosis of 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 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.

• Archival FFPE tumor tissue block or slides from a specimen no older than 5 years must be available. If not available, participant must be willing to undergo a pretreatment tumor biopsy.

• Received at least 1 and no more than 4 prior lines of systemic therapy following the initial diagnosis, after which single-agent chemotherapy is considered an appropriate next therapeutic option.

• Should have received prior treatment with bevacizumab unless there was a contraindication for its use.

• Should have received prior treatment with mirvetuximab soravtansine if the tumor is positive for FRα, unless there is an exception for its use on medical grounds.

• Measurable disease per RECIST v1.1.

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, defined as progression on or within 3 months after the last dose of first line platinum-containing therapy.
• Clinically significant or uncontrolled cardiac disease within 6 months before the first dose of study treatment.
• Known active CNS metastases and/or carcinomatous meningitis.
• Known additional malignancy that is progressing or requires active treatment, or history of other malignancy within 3 years before the first dose of study treatment.
• Clinically significant gastrointestinal abnormalities.

Other protocol-defined Inclusion/Exclusion Criteria may apply.

Incyte shares data with qualified external researchers after a research proposal is submitted. These requests are reviewed and approved by a review panel on the basis of scientific merit. All data provided is anonymized to respect the privacy of patients who have participated in the trial in line with applicable laws and regulations. The trial data availability is according to the criteria and process described on https://www.incyte.com/our-company/compliance-and-transparency

Data will be shared after the primary publication or 2 years after the study has ended for market authorized products and indications.

Data from eligible studies will be shared with qualified researchers according to the criteria and process described in the Data Sharing section of the www.incyteclinicaltrials.com website. For approved requests, the researchers will be granted access to anonymized data under the terms of a data sharing agreement.