This study is researching an experimental CAR T cell therapy called 27T51, referred to as study drug. The study drug is a MUC16 targeting immune cell therapy focused on adult female participants with recurrent or difficult to treat epithelial ovarian, primary peritoneal or fallopian tube cancer.

This study has two (2) major parts:

Phase 1a Dose Escalation and Phase 1b Dose Expansion. The aim of the dose escalation part will be to test the safety of 27T51 in a small number of participants to find the highest dose given to humans without unacceptable side effects. The aim of the dose expansion part will be to test 27T51 at the established dose level(s) from the dose escalation part and may include other medications given in combination with 27T51.

Information collected from this study will help researchers understand more fully whether this immune cell therapy, also known as CAR T cell therapy, can be safely used to treat solid tumors such as ovarian cancer.

Former Sponsor 2seventy bio

Key Inclusion Criteria:

1. Eastern Cooperative Oncology Group (ECOG) performance status ≤ 1
2. Histological diagnosis of epithelial ovarian, primary peritoneal, or fallopian tube cancer according to World of Health Organization (WHO) 2020 classification
3. Recurrent or refractory epithelial ovarian, primary peritoneal, or fallopian tube cancer, as described in the protocol
4. Serum cancer antigen (CA) 125 ≥ 2 × upper limit of normal (ULN) as assessed at the local lab by a 510(k) cleared test at screening
5. Participants must have at least 1 measurable tumor lesion as defined by the response evaluation criteria in solid tumors (RECIST) 1.1.
6. Expected survival ≥ 3 months

Key Exclusion Criteria:

1. Inadequate cardiovascular, renal and hepatic function, as described in the protocol
2. Absolute lymphocyte count (ALC) < 100 cells/μL at time of leukapheresis
3. History of Grade ≥ 2 hemorrhage within 30 days, or inadequate coagulation parameters, as described in the protocol
4. Known history or presence of clinically relevant central nervous system (CNS) pathology, as described in the protocol
5. Ongoing or recent (within 2 years) evidence of significant autoimmune disease that required treatment with systemic immunosuppressive treatments, which may suggest risk for immune related adverse events (AEs)
6. Treatment with any cellular or gene therapy

Note: Other protocol-defined Inclusion/Exclusion criteria apply

All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing.

When Regeneron has:

• received marketing authorization from major health authorities (e.g., FDA, European Medicines Agency (EMA), Pharmaceuticals and Medical Devices Agency (PMDA), etc.) for the product and indication or has globally discontinued development of the product for all indications on or after April 2020 and has no plans for future development
• made the study results publicly available (e.g., scientific publication, scientific conference, clinical trial registry)
• the legal authority to share the data, and
• ensured the ability to protect participant privacy

Qualified researchers can submit a proposal for access to individual patient or aggregate level data from a Regeneron-sponsored clinical trial through Vivli. Regeneron's Independent Research Request Evaluation Criteria can be found at: https://www.regeneron.com/sites/default/files/Regeneron-External-Data-Sharing-Policy-and-Independent-Research-Request-Evaluation-Criteria.pdf