Gene-edited T Regulatory Cells (CRG-150) for the Treatment of Relapsed/Refractory Malignancies

The goal of this Phase 1/2a interventional study is to evaluate the safety and tolerability of CRG-150 in relapsed/refractory HR+HER2- breast cancer, Triple Negative Breast Cancer (TNBC) and prostate cancer. The main questions it aims to answer are: Phase 1 * Incidence of DLTs * Incidence of CRG-150 related AEs and SAEs * Select the Recommended Phase 2 Dose (RP2D), as determined through the dose escalation process for the specified indications Phase 2a * HR+HER2- Breast Cancer and TNBC: Overall Response Rate (ORR) (CR+PR) using FDG PET/CT and RECIST 1.1 by Investigator assessment * Prostate Cancer: ORR per PCWG3-modified RECIST 1.1 by Investigator assessment Participants will be required to perform study procedures and assessments, and will also receive the following study treatments: • CRG-150 cells at the assigned dose

Inclusion Criteria: 1. Capable of understanding, and willing to comply with, and voluntarily sign and date an informed consent form (ICF). 2. Willing to adhere to the study visit schedule and other protocol requirements, including the required apheresis procedure/blood collection. 3. Is ≥18 years old at the time consent is obtained. 4. Must have one of the following metastatic cancer diagnoses: 1. HR+HER2- breast cancer 2. TNBC 3. Prostate cancer 5. Has received the following treatment lines for their disease, and in the opinion of the Investigator, the patient would unlikely tolerate or derive clinically meaningful benefit from available treatment options: 1. Metastatic HR+HER2- breast cancer * Patients previously treated for metastatic disease with at least two of the following: endocrine therapy (ET), CDK4/6 inhibitors, or antibody-drug conjugate, with disease progression or intolerance to therapy. * Prior chemotherapy is not required but does not exclude the patient from the study. 2. Metastatic TNBC (mTNBC, estrogen, progesterone, and human epidermal growth factor receptor 2 \[HER2\] negative) • Patients previously treated for metastatic disease with at least two of the following: immunotherapy, antibody-drug conjugate, or chemotherapy with disease progression or intolerance to therapy. 3. Metastatic prostate cancer (mPC) * Previously treated for advanced or metastatic disease with the following, alone or in combination, and have demonstrated disease progression by PCWG3 and/or RECIST 1.1 by Investigator judgment, OR is intolerant to therapy: * Patients previously treated for metastatic disease with at least two of the following: androgen deprivation therapy, oral androgen receptor pathway inhibitors, or taxane chemotherapy with disease progression or intolerance to therapy. * Patient will be allowed if they refuse or are considered unfit for taxane chemotherapy. 6. Has measurable disease as per RECIST 1.1 or bone-only disease (HR+HER2- breast cancer or TNBC only) OR by RECIST 1.1 or bone-only metastases with measurable prostate-specific antigen (PSA) (≥1 ng/mL) (mPC only). 7. Has an ECOG performance status of 0 or 1 at screening. 8. Has adequate organ function as defined by: 1. Hematological parameters: * Absolute neutrophil count (ANC) ≥1.0 × 109/L (1000/µL) * Platelet count (PLT) ≥50.0 × 109/L (50,000/µL) * Hemoglobin ≥7.0 g/dL * Absolute lymphocyte count (ALC) \>0.5 × 109/L (500/µL) 2. Renal: Calculated creatinine clearance must be ≥40 mL/min/1.73 m2 (by the Chronic Kidney Disease Epidemiology Collaboration 2021 equation). 3. Hepatic parameters: * Serum total bilirubin ≤1.5x upper limit of normal (ULN) (or \