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Barrier-matched, pharmacodynamic (PD)-gated immunotherapy development in MSS/pMMR colorectal cancer
Chanchan Shan1, Jian Zhang2, Liyuan Zhang3
1Department of Oncology, Jiangyuan Hospital Affiliated to Jiangsu Institute of Nuclear Medicine, Wuxi, Jiangsu, China; The Second Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China.
Abstract:
Immune checkpoint inhibitors (ICIs) have transformed treatment for deficient mismatch repair/high microsatellite instability (dMMR/MSI-H) colorectal cancer (CRC), but durable benefit remains uncommon in microsatellite-stable/proficient mismatch repair (MSS/pMMR) disease. Negative combination trials may reflect heterogeneous resistance programs tested without adequate biological stratification or prospective pharmacodynamic verification. This narrative and critical Review examines MSS/pMMR CRC through tissue-level immune-desert, immune-excluded, and immune-suppressed contexts, with active liver metastasis treated as a putative organ-context modifier rather than a validated predictive phenotype. We develop a hypothesis-generating, barrier-matched, pharmacodynamic (PD)-gated approach for future trials, not routine care. The workflow separates Tier 1 core stratification-liver-metastasis status, disease burden, core genomics, and baseline plasma circulating tumor DNA (ctDNA)-from Tier 2 tissue-based immune-spatial assessment required for mechanism-matched allocation to most non-hepatic barriers. Therapeutic modules are aligned with the dominant resistance context and reassessed after short induction using prespecified GO/ADAPT/STOP rules. For spatial or tissue-based mechanisms, GO requires a barrier-specific readout when tissue assessment is feasible; ctDNA is a complementary systemic-response signal and cannot by itself establish barrier engagement. Mixed or lesion-discordant phenotypes and inadequate tissue remain exploratory unless a prespecified dominance rule is met. A prototype master protocol would combine mechanism-defined cohorts, contemporaneous controls where feasible, early barrier-specific PD conversion as the primary biological endpoint, 6-month progression-free survival as the primary clinical endpoint, and prespecified expansion, futility, safety, and adaptation rules. Prospective validation is needed before this approach can inform practice.
Insights
This review proposes a new pharmacodynamic-gated approach for microsatellite-stable/proficient mismatch repair colorectal cancer (MSS/pMMR CRC) trials. It matches therapies to resistance contexts, aiming for better outcomes in this challenging cancer type.
Area of Science:
- Oncology
- Immunotherapy
- Colorectal Cancer Research
Background:
- Immune checkpoint inhibitors (ICIs) show limited efficacy in microsatellite-stable/proficient mismatch repair (MSS/pMMR) colorectal cancer (CRC).
- Previous combination trials failed due to a lack of biological stratification and pharmacodynamic (PD) verification.
- Understanding diverse resistance mechanisms in MSS/pMMR CRC is crucial for advancing treatment.
Purpose of the Study:
- To critically review MSS/pMMR CRC resistance contexts (immune-desert, -excluded, -suppressed).
- To propose a hypothesis-generating, barrier-matched, pharmacodynamic (PD)-gated approach for future clinical trials.
- To outline a framework for stratifying patients and matching therapies to specific resistance mechanisms.
Main Methods:
- Categorization of MSS/pMMR CRC into distinct immune contexts based on tissue analysis.
- Development of a tiered stratification workflow incorporating clinical, genomic, and spatial immune data.
- Proposal of a master protocol integrating mechanism-defined cohorts and PD endpoints.
Main Results:
- Identified distinct tissue-level immune contexts influencing treatment response in MSS/pMMR CRC.
- Proposed a novel workflow stratifying patients based on core data and tissue-based immune-spatial assessment.
- Outlined a PD-gated trial design with mechanism-matched therapeutic modules and adaptive rules.
Conclusions:
- A barrier-matched, PD-gated strategy is proposed for future MSS/pMMR CRC trials.
- This approach aims to improve therapeutic efficacy by aligning treatments with specific resistance mechanisms.
- Prospective validation is required before this strategy can guide clinical practice.
