Adenosine Signaling Modulation and Immune Checkpoint Inhibition With Hormone Sensitive Oligometastatic Prostate Cancer

This study is testing a combination of two drugs — GB1211 (which blocks adenosine, a molecule tumors use to avoid immune attack) and pembrolizumab (an immunotherapy) — in men with hormone-sensitive prostate cancer that has spread to a small number of sites (oligometastatic). **You may be eligible if...** - You are a man with confirmed prostate cancer (adenocarcinoma) - Your primary prostate tumor was treated with surgery and/or radiation - You have 1–3 new metastases (spread to bone or soft tissue) that developed after initial treatment - You are on hormone therapy (androgen deprivation therapy) **You may NOT be eligible if...** - Your cancer is castration-resistant (progressing despite very low testosterone) - You have more than 3 metastatic sites - You have active autoimmune disease - You have had prior immunotherapy for prostate cancer Talk to your doctor to see if this trial is right for you.