Phase 1 Study Evaluating Safety and Tolerability of SL-T10, GX-I7, and Pembrolizumab Triple Combination in mCRPC.

Inclusion Criteria:

1. Male patients 19 years of age or older at the date of written informed consent.
2. Patients with histopathologically or cytologically confirmed adenocarcinoma of theprostate, documented by bone or soft tissue lesions.
3. Patients with castration-resistant prostate cancer with a blood testosterone level ofless than 50 ng/dL at the screening visit.
4. patients with metastatic castration-resistant prostate cancer (mCRPC) who meet thefollowing criteria (based on PCWG3.0 modified RECIST 1.1)

1. Prior taxane therapy for metastatic prostate cancer or confirmed refusal or inadequacyof such therapy 2) Patients who have received prior docetaxel and at least one of thefollowing agents: abiraterone acetate or enzalutamide before or after docetaxel treatment
2. Patients with progression of prostate cancer during/after prior therapy, in theinvestigator's judgment, with either of the following, in the internal or externalcastration state

1. PSA progression defined as at least 2 PSA level increases (≥1 week interval betweeneach test) and a PSA level of ≥2 ng/mL at Screening
2. Advanced soft tissue disease as defined by RECIST 1.1
3. Progressive bone disease defined as ≥2 new lesions on bone scan (per PCWG3)
4. Patients who are on androgen deprivation therapy (ADT) of any kind (patients who havenot undergone bilateral orchiectomy must begin internal castration therapy, such asluteinizing hormone-releasing hormone (LHRH) agonists, LHRH antagonists, or anti-androgenicagents, at least 4 weeks prior to Baseline and must continue for the entire duration of thestudy)

Exclusion Criteria:

1. patient has an active autoimmune disease or is receiving systemic steroid therapy orin immunosuppressive status.
2. Patient has history of chemotherapy, radiation chemotherapy, biological therapy,immunotherapy, or radiation therapy within 4 weeks prior to the screening visit (Incase of nitrosoureas or mitomycin, 6 weeks prior to the screening visit)