The goal of this clinical trial is to learn if OPB-201 is safe in recurrent endometrial and platinum resistant ovarian cancer participants and also to find the optimal dose of OPB-201. Participants will have their own T cells modified in a laboratory and given back to them as OPB-201 in this one-time treatment. Participants will be in the hospital when they receive OPB-201 and then be checked at the clinical site frequently for the first few months.

A phase 1a/b study to evaluate the safety and efficacy of OPB-201, an autologous PReferentially expressed Antigen of MElanoma (PRAME) T cell receptor (TCR) T cell therapy in recurrent endometrial and platinum-resistant ovarian cancer.

Inclusion Criteria:

1. Age ≥ 18 years of age at the time of signing the informed consent form.
2. Histologically confirmed diagnosis of endometrial cancer, epithelial ovarian, peritoneal, or fallopian tube cancer based on local histopathological findings.
3. Received at least 1 prior line of systemic chemotherapy including a platinum-based chemotherapy.
4. Received prior therapy with a PARP inhibitor if the subject has a known germline or somatic BRCA1/2 mutation.
5. Measurable disease.
6. Consent to provide archived tumor tissue sample.
7. ECOG performance status of 0 or 1.
8. Adequate organ function.
9. HLA-A *02:01 or HLA-A *02:02
10. PRAME positive tumor

Exclusion Criteria:

1. Women of child-bearing potential who are pregnant or breastfeeding.
2. Uncontrolled bacterial, fungal, or viral infections.
3. Active infection requiring systemic therapy.
4. Bleeding or thrombotic disorders or at risk for severe hemorrhage.
5. Any form of primary immunodeficiency.
6. Had an allogenic tissue/solid organ transplant.
7. Active autoimmune disease.
8. Concurrent treatment with systemic high dose corticosteroids.
9. Unresolved acute effects of any prior therapy.
10. Other exclusions as stated in the protocol.

Female