The quadruple immunotherapy for colorectal cancer (QuICC) trial for mismatch repair-proficient metastatic colorectal cancer.

[BACKGROUND] Despite successes in other malignancies, immune checkpoint blockade (ICB) has not demonstrated reproducible efficacy in mismatch repair-proficient (pMMR) colorectal cancer (CRC). Preclinical studies indicate that multitargeted combination immunotherapy may sensitize resistant tumors to immune-mediated killing. This trial was designed to test this hypothesis by combining agents to induce and augment an immune response in pMMR CRC.

[METHODS] In this single-center, phase 1/2 trial, eligible patients had pMMR, RECIST v1.1-measurable metastatic CRC, ≥2 prior lines of therapy, and no prior immunotherapy. The primary endpoint was objective response rate. Patients received triplet therapy: CV-301 (CEA/MUC-1 vaccine), N-803 (IL-15 receptor superagonist), bintrafusp alfa (bifunctional anti-PD-L1/TGFβ "trap"), or quadruplet therapy (adding PDS01ADC [tumor-targeted IL-12 immunocytokine]).

[RESULTS] Between September 2020 and September 2022, 32 patients enrolled in triplet (n = 12) and quadruplet (n = 20) therapy. The combinations had toxicity profiles consistent with each individual agent included. One complete response durable for 29+ months occurred in a patient with RAS wild-type CRC metastatic to lymph nodes who received quadruplet therapy.

[CONCLUSION] Quadruplet therapy produced one objective response in unselected mCRC patients (n = 20). There were no responses with triplet therapy (n = 12). The role of ICB-based combination immunotherapy in pMMR CRC remains unclear. NCT04491955.