Combinatorial completeness in cancer immunotherapy: a structural framework for addressing the seven failure modes of immune-mediated tumor control

Cancer immunotherapy has produced dramatic clinical successes since the FDA approval of ipilimumab in 2011 — but the successes remain concentrated in a minority of tumor types (melanoma, MSI-high colorectal cancer, high-PD-L1 NSCLC, others) and a minority of patients within those types. The structural reason for this pattern is that anti-tumor immunity has multiple failure modes, contemporary single-agent immunotherapies typically address only one or two of these, and tumor types differ in which failure modes are limiting. This paper proposes a structural framework — seven failure modes of immune-mediated tumor control — to organize intervention evaluation, combinatorial protocol design, and prediction of where in the clinical trial landscape combinatorial-complete protocols could produce qualitatively better outcomes. The seven modes are: (1) insufficient antigen presentation; (2) lack of T cell priming and dendritic cell engagement; (3) physical exclusion of T cells; (4) T cell exhaustion in the tumor microenvironment; (5) active immune suppression by the tumor microenvironment; (6) insufficient persistence of immune response; and (7) tumor heterogeneity and immune escape. For each mode the paper identifies the mechanism, contemporary intervention categories, FDA-approved agents where they exist, the clinical evidence base supporting mode-specific intervention, and the pattern of where the mode is dominant as a failure mechanism across cancer types. The framework's central observation is that the historical Coley mixed bacterial vaccine engaged Modes 1, 2, 5, 6, 7 strongly and Mode 3 partially, but engaged Mode 4 essentially not at all — a structurally distinctive pattern from contemporary checkpoint inhibitors, which provide strong Mode 4 engagement but limited engagement of the other modes. The framework predicts that combinatorial protocols engaging all seven modes simultaneously will produce qualitatively different outcomes from protocols engaging subsets of modes. The paper provides a 0–1 mode scoring methodology, worked examples for the historical Coley protocol, contemporary checkpoint combinations, ANKTIVA plus BCG (FDA-approved 2024 for NMIBC), TIL therapy, and in situ vaccination paradigms, and tumor-type case studies for melanoma, NMIBC, triple-negative breast cancer, pancreatic cancer, and microsatellite-stable colorectal cancer. This is a preprint and has not yet been peer-reviewed. Companion paper: "Combinatorial-complete immunotherapy protocols: three proposed trial designs testing the seven-mode framework in immunotherapy-refractory cancers" (Paper 4 of this series).