cetuximab

Overview

Cetuximab is a chimeric IgG1 monoclonal antibody targeting the extracellular domain of EGFR. It blocks ligand binding and recruits immune effectors (ADCC). Used clinically in EGFR-expressing HNSC and COAD/READ with wild-type RAS. Also used concurrently with radiotherapy in locally advanced HNSCC.

Evidence in the corpus

  • In preclinical radiosensitization studies, C-MMAE (cetuximab conjugated to MMAE via MC-VC linker, DAR ~3.7) selectively radiosensitized EGFR+ tumor cells (CAL-27, CALU3, A549, SCC-61) but not EGFR-low LN229 cells, while the antibody-only control (cetuximab alone) showed no significant radiosensitization effect — distinguishing receptor-mediated payload delivery from EGFR signal inhibition PMID:27698471.
  • C-MMAE accumulated in EGFR+ xenografts (CAL-27 HNSC; SCC-61, SCC-35, SQ-9G HNSC; A549 NSCLC; HCT-116 colon) by Cy5 fluorescence imaging after i.v. injection, persisting ≥72 h; LN229 (EGFR-low) did not accumulate C-MMAE PMID:27698471.
  • In CAL-27 (HNSC) xenografts, C-MMAE + IR (3 Gy × 2 fractions) produced significantly greater tumour-growth delay than cetuximab + IR, free MMAE + IR, or co-administered free MMAE + cetuximab + IR (P<0.0001 by day 35); co-administration of free payload + antibody was inferior to the conjugate, demonstrating that covalent coupling is required for tumour-restricted radiosensitization PMID:27698471.
  • The authors note that clinical trials adding cetuximab to cytotoxic chemoradiotherapy in NSCLC or HNSCC failed to improve outcomes (referenced as negative trials), motivating the ADC-delivery paradigm over signal inhibition alone PMID:27698471.
  • Used in combination with sotorasib (KRASG12C inhibitor) to treat KRASG12C-mutant colorectal cancer; KRASG12C amplification identified as a recurrent acquired resistance mechanism, with mTOR inhibition (AZD8055) proposed as a senolytic strategy after drug withdrawal PMID:36355783
  • EGFR amplification (16% of OSCC) was identified as the basis for cetuximab targeting in HNSCC, but downstream PI3K pathway alterations (HRAS, PIK3CA, BRAF, AKT1) may limit EGFR-inhibitor efficacy; no biomarker for cetuximab response was identified PMID:23619168
  • Cited as a monoclonal antibody targeting EGFR in NPC with limited benefit; used as reference for EGFR-targeted therapy including ADC comparisons PMID:24952746
  • KRAS, NRAS, and BRAF driver mutations were 100% concordant between primary and metastatic tumor sites in 69 MSS CRC trios, confirming that sequencing either site is equally valid for determining cetuximab eligibility PMID:25164765
  • Referenced as a largely unsuccessful therapeutic target in aggressive cutaneous squamous cell carcinoma (cSCC) via anti-EGFR monoclonal antibody therapy; cetuximab trials in cSCC noted alongside gefitinib in the context of the absence of actionable oncogenic drivers in whole-exome sequencing of 39 aggressive cSCC cases PMID:25303977
  • EGFR-targeting monoclonal antibody; noted as the last approved targeted therapy for HNSC (approved 2006); no new targeted therapies validated since, motivating routine NGS in recurrent/metastatic HNSC PMID:27442865
  • OncoKB Level 1 resistance biomarkers for cetuximab in COADREAD are hotspot KRAS and NRAS mutations (44% and listed frequency respectively in this 1,134-CRC MSK-IMPACT cohort); one acquired-resistance case carried EGFR S492R after 1.5 years of cetuximab, concurrent with ERBB2 amplification PMID:29316426

Resistance mechanisms

  • EGFR-low / EGFR-negative tumors (e.g., LN229 glioblastoma) do not accumulate C-MMAE and show no radiosensitization — receptor expression is the gating biomarker PMID:27698471.

Cancer types (linked)

Sources

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