CAR T-cell therapy failure in solid tumors as a problem of temporal signal integration

Even though chimeric antigen receptor (CAR) T-cell therapy has revolutionized treatment for hematologic malignancies, its efficacy against solid tumors remains limited. Traditional explanations invoke antigen heterogeneity, immunosuppressive Tumor Micro Environments (TME), or CAR specificity. We propose that these are symptoms of a deeper, unifying issue: a temporal mismatch between transient antigen accessibility, CAR signaling integration, and metabolic constraints in the TME. Many conventional CAR designs and protocols assume static antigen presentation and unlimited signaling capacity, which rarely occurs in vivo. Recognizing CAR T-cell activation as a time-dependent, energy-limited process, we suggest that CAR ineffectiveness in solid tumors may result from misalignment of antigen exposure windows, the time required for CAR signaling integration, and metabolic constraints that shorten the effective T-cell activation. A central priority for future studies should hence be the development and validation of robust temporal monitoring tools for CAR T-cell antigen engagement and signaling integration in both preclinical models and clinical trials. Integrating these dynamics into a unified framework suggests new strategies, including time-synchronized CAR delivery, conditional activation systems, and metabolic support, to potentially improve CAR efficacy in solid tumors.