This is a multi-center, open-label Phase 1/2 trial evaluating the safety and efficacy of AB-3028 in subjects with metastatic castration resistant prostate cancer (mCRPC).

This study is intended for subjects diagnosed with metastatic castration-resistant prostate cancer (mCRPC) and whose disease progressed after treatment with an androgen receptor pathway inhibitor (ARPI). The purpose of this study is to test the safety and efficacy of AB-3028 cells in subjects with metastatic castration-resistant prostate cancer. This treatment has not been approved by the Food and Drug Administration.

The goal of the Phase I portion of this study is to evaluate safety profile of AB-3028 and to determine the maximum tolerated dose or recommended phase 2 dose of AB-3028. The Phase 2 portion of the study will investigate the efficacy of AB-3028. T cells are part of the immune system that protect the body from infection and may help fight cancer. The T cells given in this study will come from the subject and will have a DNA cassette put in them that makes them able to recognize a priming antigen as well as Prostate-Specific Membrane Antigen (PSMA), two proteins found on prostate cancer tumor cells. These logic-gated T cells may help the body's immune system identify and kill cancer cells while sparing normal healthy tissues from toxicity.

The AB-3028 cells are given as a single intravenous infusion.

After completion of study treatment, subjects are followed with serial measurements of safety, tolerability and response.

This is a research study to obtain new information that may help people in the future.

Key Inclusion Criteria:

1. At least 18 years of age at time of signing informed consent form.

2. Histologically confirmed adenocarcinoma of the prostate, meeting all of the following criteria:

   • Documented progressive metastatic castration-resistant prostate cancer (mCRPC) based on PCWG3 criteria.

3. Prior prostate cancer treatment with at least 1 novel androgen receptor pathway inhibitor (ARPI) therapy.

   • PSMA+ by PSMA PET.

   • Measurable disease by RECIST 1.1 criteria, or evaluable disease via measurable PSA (≥ 1 ng/mL) per PCWG3 criteria.

4. Adequate organ functions.

Key Exclusion Criteria:

1. Any prior systemic therapy for CRPC within 14 days prior to scheduled protocol required leukapheresis.
2. Central nervous system (CNS) metastatic disease, leptomeningeal disease, or cord compression.
3. Unwillingness to participate in an extended safety monitoring period.