NIMBLE-CRC: NeoImmunoModulation Before Leveraging Excision in Colorectal Rectal Cancer

This is a Phase II, single-arm, open-label trial evaluating the feasibility, safety, and preliminary activity of neoadjuvant Zanzalintinib (a VEGFR-targeting TKI) and Retifanlimab (an anti-PD-1 antibody) in patients with resectable stage II-III mismatch repair-proficient (pMMR) colon cancer. The study's primary objective is to determine the proportion of patients able to undergo curative-intent surgery within 14-35 days after completing two cycles (6 weeks) of neoadjuvant therapy. Secondary objectives include assessment of safety/tolerability and rates of pathologic response, including tumor regression grade (TRG). Two-year relapse-free survival (RFS) will also be evaluated.

This trial builds on emerging evidence from neoadjuvant immunotherapy studies-including in pMMR tumors-and the recently positive readout of STELLAR-303, which evaluated Zanzalintinib plus a PD-(L)1 inhibitor in refractory metastatic colorectal cancer. With a favorable safety profile, short treatment window, and rapid post-treatment pathologic readout, this study provides a low-risk opportunity to test whether immunotherapy-based neoadjuvant strategies can improve outcomes and potentially redefine management in early-stage, pMMR colon cancer.