EMPIRE (NSABP FC-13): a biomarker-driven phase II platform trial evaluating cemiplimab-based immunotherapy in microsatellite-stable colorectal cancer with ctDNA-defined minimal residual disease.

Microsatellite-stable (MSS) colorectal cancer (CRC), which accounts for approximately 85% of cases annually, has demonstrated limited responsiveness to immune checkpoint blockade in the metastatic setting. Circulating tumor DNA (ctDNA) enables sensitive detection of minimal residual disease (MRD) following curative-intent therapy and identifies patients at high risk of recurrence who may benefit from additional treatment. The EMPIRE (NSABP FC-13) study is a multicenter, open-label, randomized phase II platform trial evaluating cemiplimab-based immunotherapy in patients with MSS CRC and ctDNA-defined MRD after definitive surgery and chemotherapy. Eligible patients have postoperative ctDNA positivity in the absence of radiographic recurrence and are allocated to one of three treatment arms: cemiplimab monotherapy; cemiplimab plus fianlimab (a lymphocyte activation gene-3 inhibitor); or cemiplimab plus REGN7075 (an EGFR×CD28 costimulatory bispecific antibody). The primary endpoint is ctDNA clearance at 12 weeks assessed by tumor-informed assay, with secondary endpoints including recurrence-free survival, safety and tolerability, longitudinal ctDNA kinetics, and patterns of recurrence. Arms 2 and 3 use single-stage phase II designs, whereas Arm 1 follows a Simon two-stage design with early futility stopping. The study integrates comprehensive correlative analyses to characterize mechanisms of response and resistance.Clinical trial registration: The http://www.clinicaltrials.gov identifier is NCT07058012.