Cancer Advisor

PD-1 and PD-L1 checkpoint inhibitors can produce remarkably durable responses in some patients. However, resistance remains one of the central challenges in modern oncology. A tumor may never respond to immunotherapy in the first place, or it may respond initially and later progress. The reason is important: blocking PD-1 or PD-L1 removes one immune-suppressive signal, but it does not guarantee that the immune system can recognize, enter, survive within, and destroy every cancer cell. This article explains the major biological mechanisms behind primary and acquired immunotherapy resistance , why PD-L1 alone cannot reliably predict response, how tumor evolution and the tumor microenvironment contribute to treatment failure, and what strategies researchers and oncologists are investigating to overcome resistance. Bottom line: PD-1/PD-L1 resistance is not a single disease mechanism. It is a systems problem involving tumor genetics, antigen presentation, T-cell function...

Originally compiled for translational precision oncology tracking. References to clinical registries provided inline. Pembrolizumab (Keytruda) has fundamentally shifted the treatment paradigm for advanced malignancies by blocking the Programmed Death-1 (PD-1) receptor. However, clinical data shows that up to 60–70% of patients experience either primary resistance (lack of initial response) or adaptive secondary resistance (progression after a period of response). Accumulating clinical evidence points to the Tumor Microenvironment (TME) as the principal driver of this therapeutic failure. This review synthesizes the cell-extrinsic and cell-intrinsic mechanisms within the TME that neutralize cytotoxic T-cell activity and maps out strategic metabolic and microenvironmental interventions to restore anti-PD-1 sensitivity. 1. Introduction: The Mechanism of Immune Checkpoint Blockage (ICB) The therapeutic rationale behind pembrolizumab relies on a simple premise: unmask...