This phase II trial studies how well pembrolizumab and HER2Bi-armed activated T cells work in treating patients with castration resistant prostate cancer that has spread to other places in the body. Monoclonal antibodies, such as pembrolizumab, may interfere with the ability of tumor cells to grow and spread. HER2Bi-armed activated T cells are made using T cells and may target and kill cancer cells. Giving pembrolizumab and HER2Bi-armed activated T cells may work better in treating patients with castration resistant prostate cancer.

PRIMARY OBJECTIVES:

I. To estimate the clinical efficacy of 8 infusions of HER2 HER2Bi-armed activated T cells (BATs) (up to 10^10/infusion) twice per week for 4 weeks in combination with pembrolizumab once every 3 weeks starting with one dose 3 weeks before the 1st BATs infusion, by assessing the percentage of patients free of clinical progression at 6 months after registration.

SECONDARY OBJECTIVES:

I. Evaluate phenotype, cytokine profiles and IFN-gamma enzyme-linked immunosorbent spots (ELISpots), cytotoxicity and antibodies directed at laboratory prostate cancer cell lines for proof of principle of immune system activation and to correlate with clinical outcomes of response, progression free survival (PFS), and overall survival (OS).

II. Evaluate the magnitude of change in tumor infiltrating T cells, PD-1 expression, and the Th1/Th2 ratio in prostate cancer tumor tissue before and after immunotherapy and correlate it with the clinical outcomes of response, PFS, and OS.

OUTLINE:

Patients receive pembrolizumab intravenously (IV) over 30 minutes every 3 weeks. Treatment repeats every 3 weeks for up to 6 months in the absence of disease progression or unacceptable toxicity. Beginning at least 1 week after pembrolizumab, patients receive HER2Bi-armed activated T cells IV over 5-15 minutes 2 times a week for 4 weeks in the absence of disease progression or unacceptable toxicity.

After completion of study treatment, patients are followed up every 3 months.

Inclusion Criteria:

• Be willing and able to provide written informed consent/assent for the trial

• Have histologically confirmed prostate adenocarcinoma, with metastases

• Progression by either PSA, Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria for measurable disease or new areas of metastases on bone scan or symptom progression related to prostate cancer despite castrate levels of testosterone; (level < 50 ng/ml)

• Be agreeable to continue to maintain castrate levels of testosterone

• At least 2 weeks should have elapsed since any immunosuppressive therapy

• At least 4 weeks since prior chemotherapy for metastatic disease or at least 2 weeks since prior androgen targeting agents such as ketoconazole, abiraterone, enzalutamide, etc.

• Discontinue anti-androgens prior to therapy; at least 6 weeks since last dose of bicalutamide or nilutamide and at least 4 weeks from last dose of flutamide

• Have normal bone marrow, renal and hepatic function as deemed by the treating physician and approved by the clinical principal investigator (PI) Dr. Vaishampayan

• Not have concurrent anti-cancer therapy

• Not have concurrent immunosuppressive therapy or medical condition likely to cause immunosuppression

• Have life expectancy > 6 months

• Have a performance status of 0 or 1 on the Eastern Cooperative Oncology Group (ECOG)/Zubrod performance scale

• Agree to use an adequate method of contraception starting with the first dose of study therapy through 120 days after the last dose of study therapy

  • Note: Abstinence is acceptable if this is the usual lifestyle and preferred contraception for the subject

• Within 10 days of treatment registration: Absolute neutrophil count (ANC) >= 1,500 /mcL

• Within 10 days of treatment registration: Platelets >= 100,000 / mcL

• Within 10 days of treatment registration: Hemoglobin >= 9 g/dL or >= 5.6 mmol/L without transfusion or erythropoietin (EPO) dependency (within 7 days of assessment)

• Within 10 days of treatment registration: Serum creatinine =< 1.5 X upper limit of normal (ULN) OR measured or calculated creatinine clearance (glomerular filtration rate [GFR] can also be used in place of creatinine or creatinine clearance [CrCl]) >= 60 mL/min for subject with creatinine levels > 1.5 X institutional ULN

• Within 10 days of treatment registration: Serum total bilirubin =< 1.5 X ULN OR direct bilirubin =< ULN for subjects with total bilirubin levels > 1.5 ULN

• Within 10 days of treatment registration: Aspartate aminotransferase (AST) (serum glutamic-oxaloacetic transaminase [SGOT]) and alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase [SGPT] =< 2.5 X ULN OR =< 5 X ULN for subjects with liver metastases

• Within 10 days of treatment registration: Albumin >= 2.5 mg/dL

• Within 10 days of treatment registration: International normalized ratio (INR) or prothrombin time (PT) =< 1.5 X ULN unless subject is receiving anticoagulant therapy as long as PT or partial thromboplastin time (PTT) is within therapeutic range of intended use of anticoagulants

• Within 10 days of treatment registration: Activated partial thromboplastin time (aPTT) =< 1.5 X ULN unless subject is receiving anticoagulant therapy as long as PT or PTT is within therapeutic range of intended use of anticoagulants

Exclusion Criteria:

• Is currently participating and receiving study therapy or has participated in a study of an investigational agent and received study therapy or used an investigational device within 4 weeks of the first dose of treatment
• Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy (> 10 mg of prednisone daily or equivalent steroid doses) or any other form of immunosuppressive therapy within 7 days prior to the first dose of trial treatment
• Has a known history of active TB (Bacillus tuberculosis)
• Has hypersensitivity to pembrolizumab or any of its excipients
• Has had a prior anti-cancer monoclonal antibody (mAb) within 4 weeks prior to study day 1 or has not recovered (i.e. =< grade 1 or at baseline) from adverse events due to agents administered earlier; Note: Subjects with =\