A Phase I-II Study to Test the Safety and Efficacy of PD1 (AB122) and Adenosine Receptor (AB928) Antagonists With Chemotherapy After Short-Course Radiation for Rectal Cancer.

This study tests a combination of two immunotherapy drugs — AB122 (a PD-1 blocker) and AB928 (an adenosine receptor blocker) — given alongside chemotherapy after short-course radiation for rectal cancer that has not yet spread. The goal is to improve outcomes and potentially avoid the need for major surgery. **You may be eligible if...** - You are 18 or older - You have confirmed rectal cancer (adenocarcinoma) - Your tumor is located within 5 cm of the anal opening and can be removed by standard rectal surgery - Your cancer has not spread to distant organs - You have never had prior pelvic radiation or chemotherapy for rectal cancer - Your physical health is good (ECOG score 0–1) **You may NOT be eligible if...** - Your cancer has spread (distant metastases) - You have had prior radiation to the pelvis or prior chemotherapy for rectal cancer - You have active autoimmune disease or are on immunosuppressive therapy - You have significant infections or serious medical conditions - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.