Targeting the EGFR with small-molecule inhibitors is a confirmed valid strategy in cancer therapy. Since the FDA approval of the first EGFR-TKI, erlotinib, great efforts have been devoted to the discovery of new potent inhibitors. Until now, fourteen EGFR small-molecule inhibitors have been globally approved for the treatment of different types of cancers. Although these drugs showed high efficacy in cancer therapy, EGFR mutations have emerged as a big challenge for these drugs. In this review, we focus on the EGFR small-molecule inhibitors that have been approved for clinical uses in cancer therapy. These drugs are classified based on their chemical structures, target kinases, and pharmacological uses. The synthetic routes of these drugs are also discussed. The crystal structures of these drugs with their target kinases are also summarized and their bonding modes and interactions are visualized. Based on their binding interactions with the EGFR, these drugs are also classified into reversible and irreversible inhibitors. The cytotoxicity of these drugs against different types of cancer cell lines is also summarized. In addition, the proposed metabolic pathways and metabolites of the fourteen drugs are discussed, with a primary focus on the active and reactive metabolites. Taken together, this review highlights the syntheses, target kinases, crystal structures, binding interactions, cytotoxicity, and metabolism of the fourteen globally approved EGFR inhibitors. These data should greatly help in the design of new EGFR inhibitors.

Globally Approved EGFR Inhibitors: Insights into Their Syntheses, Target Kinases, Biological Activities, Receptor Interactions, and Metabolism

Immunotherapy targeting coinhibitory receptors has been highly successful in treating a wide variety of malignancies; however, only a subset of patients exhibits durable responses. The first FDA-approved immunotherapeutics targeting coinhibitory receptors PD1 and CTLA4, alone or in combination, significantly improved survival but were also accompanied by substantial toxicity in combination. The third FDA-approved immune checkpoint inhibitor targets LAG3, a coinhibitory receptor expressed on activated CD4+ and CD8+ T cells, especially in settings of long-term antigenic stimulation, such as chronic viral infection or cancer. Mechanistically, LAG3 expression limits both the expansion of activated T cells and the size of the memory pool, suggesting that LAG3 may be a promising target for immunotherapy. Importantly, the mechanism(s) by which LAG3 contributes to CD8+ T-cell exhaustion may be distinct from those governed by PD1, indicating that the combination of anti-LAG3 and anti-PD1 may synergistically enhance antitumor immunity. Clinical studies evaluating the role of anti-LAG3 in combination with anti-PD1 are underway, and recent phase III trial results in metastatic melanoma demonstrate both the efficacy and safety of this combination. Further ongoing clinical trials are evaluating this combination across multiple tumor types and the adjuvant setting, with accompanying translational and biomarker-focused studies designed to elucidate the molecular pathways that lead to improved antitumor T-cell responses following dual blockade of PD1 and LAG3. Overall, LAG3 plays an important role in limiting T-cell activation and has now become part of the repertoire of combinatorial immunotherapeutics available for the treatment of metastatic melanoma. 

Molecular Pathways and Mechanisms of LAG3 in Cancer Therapy

Long non-coding RNA mediated drug resistance in breast cancer.

Tyrosine kinase inhibitors (TKIs) are the standard of care for patients with non-small cell lung cancer (NSCLC) that harbor mutations of the epidermal growth factor receptor (EGFR) gene. First-line therapy for these patients is often osimertinib, a third-generation EGFR TKI. Erlotinib, gefitinib, afatinib, and dacomitinib are first- and second-generation TKIs that are also available. However, almost all patients eventually develop disease progression due to TKI-acquired resistance. The mechanisms of resistance after TKI exposure often involve EGFR or its downstream pathways. While a frequently utilized strategy for combating acquired resistance to EGFR TKIs remains standard platinum-based chemotherapy, clinical investigation of promising novel agents targeting common resistance mechanisms such as MET, HER2, and HER3 is of increased interest. In this review, we discuss the mechanisms of resistance to TKIs in EGFR-mutant NSCLC, examine current treatment standards, and discuss novel developing therapies. Both EGFR-dependent (involving secondary mutations in EGFR) and EGFR-independent (mutations that bypass EGFR signaling and histologic transformation) resistance mechanisms are considered. Several novel treatment strategies are emerging to overcome these resistance mechanisms, as the understanding and identification of specific EGFR-TKI resistance mechanisms continues to improve. The treatments in development aim to target or bypass the mechanisms of resistance, including MET-, HER2-, and HER3-directed therapies. In patients with acquired TKI resistance, molecular profiling at the time of initial progression may help identify relevant mechanisms of resistance. Clinical trial participation is vital to continued investigation for EGFR-mutant NSCLC. 

http://www.lungcancerjournal.info/article/S016950022200441X/pdf

Treatment strategies and outcomes for patients with EGFR-mutant non-small cell lung cancer resistant to EGFR tyrosine kinase inhibitors: Focus on novel therapies.

The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) osimertinib has significantly prolonged progression-free survival (PFS) in patients with EGFR-mutant lung cancer, including those with brain metastases. However, despite striking initial responses, osimertinib-treated patients eventually develop lethal metastatic relapse, often to the brain. Although osimertinib-refractory brain relapse is a major clinical challenge, its underlying mechanisms remain poorly understood. Using metastatic models of EGFR-mutant lung cancer, we show that cancer cells expressing high intracellular S100A9 escape osimertinib and initiate brain relapses. Mechanistically, S100A9 upregulates ALDH1A1 expression and activates the retinoic acid (RA) signaling pathway in osimertinib-refractory cancer cells. We demonstrate that the genetic repression of S100A9, ALDH1A1, or RA receptors (RAR) in cancer cells, or treatment with a pan-RAR antagonist, dramatically reduces brain metastasis. Importantly, S100A9 expression in cancer cells correlates with poor PFS in osimertinib-treated patients. Our study, therefore, identifies a novel, therapeutically targetable S100A9-ALDH1A1-RA axis that drives brain relapse.Treatment with the EGFR TKI osimertinib prolongs the survival of patients with EGFR-mutant lung cancer; however, patients develop metastatic relapses, often to the brain. We identified a novel intracellular S100A9-ALDH1A1-RA signaling pathway that drives lethal brain relapse and can be targeted by pan-RAR antagonists to prevent cancer progression and prolong patient survival. This article is highlighted in the In This Issue feature, p. 873. 

/pdf/targeting-s100a9-aldh1a1-retinoic-acid-signaling-to-suppress-1gim6b1n.pdf

Targeting S100A9–ALDH1A1–Retinoic Acid Signaling to Suppress Brain Relapse in <i>EGFR</i>-Mutant Lung Cancer

Summary The discovery that mutations in the EGFR gene are detected in up to 50% of lung adenocarcinoma patients, along with the development of highly efficacious epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), has revolutionized the treatment of this frequently occurring lung malignancy Indeed, the clinical success of these TKIs constitutes a critical milestone in targeted cancer therapy Three generations of EGFR-TKIs are currently approved for the treatment of EGFR mutation-positive non-small cell lung cancer (NSCLC) The first-generation TKIs include erlotinib, gefitinib, lapatinib, and icotinib; the second-generation ErbB family blockers include afatinib, neratinib, and dacomitinib; whereas osimertinib, approved by the FDA on 2015, is a third-generation TKI targeting EGFR harboring specific mutations Compared with the first- and second-generation TKIs, third-generation EGFR inhibitors display a significant advantage in terms of patient survival For example, the median overall survival in NSCLC patients receiving osimertinib reached 386 months Unfortunately, however, like other targeted therapies, new EGFR mutations, as well as additional drug-resistance mechanisms emerge rapidly after treatment, posing formidable obstacles to cancer therapeutics aimed at surmounting this chemoresistance In this review, we summarize the molecular mechanisms underlying resistance to third-generation EGFR inhibitors and the ongoing efforts to address and overcome this chemoresistance We also discuss the current status of fourth-generation EGFR inhibitors, which are of great value in overcoming resistance to EGFR inhibitors that appear to have greater therapeutic benefits in the clinic

Acquired resistance to third-generation EGFR-TKIs and emerging next-generation EGFR inhibitors.

Background Transarterial chemoembolization (TACE) stands for the most commonly utilized therapy for hepatocellular carcinoma (HCC) worldwide. This study was to explore the potential predictive and prognostic roles of LAG-3 and PD-L1 as serum biomarkers in HCC patients underwent TACE treatment. Methods A total of 100 HCC patients receiving TACE as well as 30 healthy controls were enrolled in the study. Serum LAG-3 and PD-L1 levels were determined at baseline and 3 day after TACE using enzyme-linked immunosorbent assay (ELISA). Results We found serum levels of LAG-3 and PD-L1 were significantly elevated in HCC patients compared with healthy controls. Interestingly, patients with low pre-TACE and post-TACE levels of LAG-3 but not PD-L1 had a high probability of achieving an objective response (OR) after TACE treatment. Additionally, high pre-TACE LAG-3 level was correlated with poor disease outcome, and the patients with both high serum LAG-3 and PD-L1 level had the shorter overall survival (OS) than patients who are either PD-L1 or LAG-3 high or both PD-L1 and LAG-3 low. High pre-TACE serum LAG-3 level was positively associated with more cirrhosis pattern, advanced BCLC stage, pre-TACE alanine aminotransferase (ALT) level, and pre-TACE aspartate aminotransferase (AST) level. Furthermore, in 50 patients who underwent TACE, the serum LAG-3 level was significantly decreased at 3 day after TACE. Conclusion Both pre-TACE and post-TACE serum LAG-3 levels could serve as powerful predictors for tumor response of TACE, and high pre-TACE serum LAG-3 level was an indicator for poor prognosis in HCC.

/pdf/serum-lag-3-predicts-outcome-and-treatment-response-in-2c2gzejkdc.pdf

Serum LAG-3 Predicts Outcome and Treatment Response in Hepatocellular Carcinoma Patients With Transarterial Chemoembolization.

Tumor mutation burden (TMB) is associated with immune infiltration, while its underlying mechanism in hepatocellular carcinoma (HCC) remains unclear. A long noncoding RNA (lncRNA)-related competitive endogenous RNA (ceRNA) network can regulate various tumor behaviors, and research about its correlation with TMB and immune infiltration is warranted. Data were downloaded from TCGA and ArrayExpress databases. Cox analysis and machine learning algorithms were employed to establish a lncRNA-based prognostic model for HCC. We then developed a nomogram model to predict overall survival and odds of death for HCC patients. The association of this prognostic model with TMB and immune infiltration was also analyzed. In addition, a ceRNA network was constructed by using DIANA-LncBasev2 and the starBase database and verified by luciferase reporter and colocalization analysis. Multiplex immunofluorescence was applied to determine the correlation between ULBP1 and PD-L1. An eight-lncRNA (SLC25A30-AS1, HPN-AS1, LINC00607, USP2-AS1, HCG20, LINC00638, MKLN1-AS and LINC00652) prognostic score model was constructed for HCC, which was highly associated with TMB and immune infiltration. Next, we constructed a ceRNA network, LINC00638/miR-4732-3p/ULBP1, that may be responsible for NK cell infiltration in HCC with high TMB. However, patients with high ULBP1 possessed a poorer prognosis. Using multiplex immunofluorescence, we found a significant correlation between ULBP1 and PD-L1 in HCC, and patients with high ULBP1 and PD-L1 had the worst prognosis. In brief, the eight-lncRNA model is a reliable tool to predict the prognosis of HCC patients. The LINC00638/miR-4732-3p/ULBP1 axis may regulate immune escape via PD-L1 in HCC with high TMB.

/pdf/tumor-mutation-burden-associated-linc00638-mir-4732-3p-ulbp1-3kha1vokv3.pdf

Xiaojing Du

Papers

Acquired resistance to third-generation EGFR-TKIs and emerging next-generation EGFR inhibitors.

Serum LAG-3 Predicts Outcome and Treatment Response in Hepatocellular Carcinoma Patients With Transarterial Chemoembolization.

Tumor Mutation Burden-Associated LINC00638/miR-4732-3p/ULBP1 Axis Promotes Immune Escape via PD-L1 in Hepatocellular Carcinoma.