programmed cell death 1
programmed cell death 1
Overview
Programmed cell death 1 (PD-1) is an immune checkpoint receptor encoded by the PDCD1 gene and expressed primarily on activated T cells. It plays a central role in maintaining peripheral immune tolerance by dampening T-cell activation after engagement with its ligands, especially Programmed Death-Ligand 1 (PD-L1) and PD-L2. Through this inhibitory signaling axis, PD-1 helps limit excessive immune responses, but it can also be exploited by tumour cells and other suppressive elements of the tumour microenvironment to evade immune destruction.
Clinically, PD-1 has become a major therapeutic target in oncology. Antibodies such as pembrolizumab, nivolumab, cemiplimab, and camrelizumab block PD-1 signaling and can restore antitumour T-cell activity. However, response is variable, resistance is common, and treatment can cause immune-related adverse events. Recent research has therefore focused on PDCD1 genetic variation, combination strategies with CTLA-4 or LAG-3 blockade, radiotherapy, and mechanisms of T-cell dysfunction involving regulatory T cells, dendritic cells, cytotoxic T cells, and pathways such as CXCL-CXCR2 and TGF-β/VEGF.
Recent Publications Focus
Below is a summary of the newest research publications targeting programmed cell death 1 (sorted by publication date).
PD-1 checkpoint inhibitors continue to demonstrate transformative clinical efficacy across multiple cancer types through strategic combination approaches. Bispecific antibodies simultaneously targeting PD-1 and vascular endothelial growth factor (VEGF) combined with chemotherapy showed improved progression-free survival compared to PD-1 monotherapy alone in advanced squamous non-small cell lung cancer [42218899]. The antibody-drug conjugate sacituzumab tirumotecan combined with PD-L1 inhibitors showed promising antitumor activity as first-line therapy for PD-L1-positive advanced NSCLC [42214392]. A multi-modal regimen (TRIDENT) combining low-dose immunomodulatory radiotherapy, high-dose radiotherapy, and PD-1 blockade achieved notably durable overall survival in advanced NSCLC through activation of antitumor neutrophil programming and enhanced CD8+ T-cell function [42091852]. These clinical advances underscore the importance of rational combination strategies to maximize therapeutic benefit.
Overcoming primary and acquired resistance to PD-1 blockade remains a critical challenge, spurring investigation into multiple resistance mechanisms and resensitization strategies. PKC signaling was identified as a prognostic biomarker of anti-PD-1 resistance, with PKC inhibition inducing immunogenic pyroptotic cell death, promoting PD-L1 degradation, and enhancing CD8+ T-cell recruitment [42234523]. In hepatocellular carcinoma, WNK4 expression in cancer-associated fibroblasts mediated anti-PD-1 resistance through cysteine metabolic reprogramming, with targeting the WNK4-HMGB1-p53 axis potentially restoring PD-1 responsiveness [42253146]. The multikinase inhibitor lenvatinib reduced immunosuppressive CD206+CD163+ macrophages when combined with PD-1 blockade, with high macrophage infiltration paradoxically predicting superior response to combination therapy in gastric cancer [42044259]. Small-molecule activators were shown to restore T-cell fitness and synergize with checkpoint blockade: the covalent MKK3 activator arvenin I revived exhausted T-cells [42342561], while glycolytic inhibition combined with PD-L1-targeted nanoparticles enhanced immunotherapy efficacy in triple-negative breast cancer [41633299].
Novel molecular and spatial mechanisms for enhancing PD-1 blockade efficacy have emerged from preclinical and translational studies. Receptor-tethered cytosolic modulators that locally inhibit Src family kinases within the cytoplasmic microdomain of PD-1 suppressed phosphorylation and restored T-cell activity through spatial precision signaling control [42329051]. GSK-3 inhibition promoted T-cell differentiation programs that synergized with PD-1 blockade to generate "super-armed" CD8+ T cells with enhanced cytotoxic capacity and metabolic adaptability [42156357]. Salmonella-trained natural killer cells demonstrated superior efficacy compared to checkpoint blockade alone in preventing metastasis [42237539], while engineered bacteria co-expressing PD-1 and lactate oxidase enabled multifunctional immunotherapy through metabolic reprogramming and checkpoint inhibition [41740575]. Neutrophil-arming nanoplatforms that degrade neutrophil extracellular traps synergized with anti-PD-1 therapy [41587524], and galectin-9 blockade overcame ATR inhibitor-induced immune evasion in combination with PD-1 targeting [41651398]. Bispecific approaches targeting PD-1 and additional immune checkpoints showed clinical activity: anti-LAG-3 (fianlimab) combined with anti-PD-1 (cemiplimab) demonstrated preliminary efficacy across multiple cancer types [42028885], and simultaneous CHI3L1 and PD-1 targeting showed greater antifibrotic efficacy than monotherapy in pulmonary fibrosis [42048160].
Advances in understanding PD-1 as a molecular target and identifying predictive biomarkers have emerged from molecular and imaging studies. The N-terminal loop of PD-1 exhibits temperature-dependent conformational dynamics that significantly affect nivolumab binding affinity, with complex stability markedly reduced at elevated temperatures [42199044]. A bispecific immuno-PET probe targeting both PD-1 and VEGF demonstrated specific tumor uptake and enhanced retention compared to monospecific probes [42026833]. Early pembrolizumab plasma levels measured after the first treatment cycle emerged as a prognostic biomarker in real-world NSCLC patients [42097413], while single nucleotide polymorphisms in the PDCD1 gene were evaluated for their impact on progression-free survival [41965156]. Dual targeting of PD-1/PD-L1 and CTLA-4 in colorectal cancer highlighted synergistic mechanisms by which these pathways jointly suppress antitumor T-cell responses [41925220].
While PD-1 checkpoint inhibitors have revolutionized cancer immunotherapy, their use is accompanied by potentially severe immune-related adverse events requiring careful clinical recognition and management. A fatal case demonstrated concurrent immune-related myasthenia gravis and myocarditis in a cholangiocarcinoma patient receiving the PD-L1 inhibitor durvalumab, highlighting life-threatening autoimmune complications [42384108]. Immunotherapy-associated autoimmune hemolytic anemia was documented as a rare but serious immune-related toxicity in melanoma and cervical cancer patients receiving PD-1 inhibitors [41944848], and bilateral optic neuritis emerged as a recognized immune-related adverse event following nivolumab treatment [40744524]. These complications underscore the importance of early recognition and aggressive intervention in managing severe immune-related adverse events during PD-1-directed immunotherapy.