A Pilot Presurgical Trial of REGN5678 (Anti-PSMA x CD28) in Patients With High-risk, Localized Prostate Cancer Followed by Radical Prostatectomy

Inclusion Criteria: * Men ≥ 18 years of age * Histologically documented Gleason 8 or greater prostatic adenocarcinoma in at least 3 biopsy cores and at least 8 mm of disease on a single core of Gleason 8 or greater. Prostate biopsy within 3 months of screening is allowed for entry requirements. Prostate biopsy must be reviewed at MD Anderson Cancer Center. Patients with small cell, neuroendocrine, or transitional cell carcinomas or mixed histologies are not eligible * Eastern Cooperative Oncology Group (ECOG) performance status (PS) grade of 0 or 1 * No evidence of metastatic disease as documented by technetium-99m (99mTc) bone scan and by computed tomography (CT) or magnetic resonance imaging (MRI) scans. Imaging may be obtained up to 60 days prior to enrollment * Localized or locally advanced disease deemed by the surgeon to be resectable. Patients must be appropriate candidates for radical prostatectomy plus pelvic lymph node dissection * No prior treatment for prostate cancer including prior surgery (excluding transurethral resection of the prostate \[TURP\]), cryoablation, pelvic lymph node dissection, radiation therapy, hormonal therapy or chemotherapy * Hemoglobin ≥ 11 g/dL * Absolute neutrophil count ≥ 1.5 x 10\^9/L * Platelet count ≥ 100 x 10\^9/L * Serum creatinine ≤ 1.5 x upper limit of normal (ULN) or estimated glomerular filtration rate \> 50 mL/min/1.73 m\^2. A 24-hour urine creatinine collection may substitute for the calculated creatinine clearance to meet el…