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Preprint WatchStrongOctober 26th, 2026

Effects of panitumumab on the proteome of treated EGFRvIII glioblastoma cells and on their extracellular vesicles

Gateau, A.; Moeglen-Paget, B.; Durand, S.; Akil, H.; Humbert, G.; Bessette, B.; Lalloue, F.

Panitumumab reduces surface EGFRvIII on extracellular vesicles released by U87-EGFRvIII glioblastoma cells without a matching reduction in the parent cell lysate, and the resulting EV proteomic shift is proposed as a circulating biomarker of anti-EGFR treatment efficacy and of treatment escape.

Strong contradiction

3 prior failures

Three or more documented clinical failures match this mechanism, or a Phase 3 efficacy failure is on record.

This preprint proposes extracellular vesicle proteomics as a readout of anti-EGFR efficacy in EGFRvIII glioblastoma, reporting that panitumumab lowers surface EGFRvIII on vesicles released by U87-EGFRvIII cells without a matching fall in the parent cell lysate. The Claidex graph holds three EGFR failures that bear on the inference. In tak-186-mvc-101-egfr-cd3-cobra-solid-tumors-phase1-2-efficacy-failure an EGFR-directed T cell engager failed on efficacy in EGFR-expressing tumours, showing that antigen presence does not predict benefit. In fpi-2107-egfr-cmet-nsclc-dosimetry-uptake-failure an EGFR-directed radioconjugate failed because measured tumour uptake did not match the targeting hypothesis, which is the same class of gap between a molecular readout and a clinical effect that this preprint's biomarker would have to bridge. In bg-60366-egfr-cdac-nsclc-strategic-shutdown an EGFR degrader programme closed before producing efficacy data at all. The specific risk here is that a vesicle-borne marker tracks drug-induced trafficking rather than tumour response, and the preprint's own data separate the two compartments, with vesicle EGFRvIII falling while cellular EGFRvIII does not. Validation against clinical outcome rather than against target modulation is the step that would distinguish a response biomarker from a pharmacodynamic one.

Abstract excerpt

Glioblastoma (GB) is an aggressive brain tumor for which reliable biomarkers of therapeutic response are still needed. Extracellular vesicles (EVs) can carry molecular components derived from their parent cells, thereby providing information on changes associated with the tumor and treatments. Among potential biomarkers, epidermal growth factor receptor variant III (EGFRvIII), is found in more than 40% of GB patients and is associated with aggressive tumor behavior and therapeutic resistance. EGFRvIII has also been detected on the surface of EVs, suggesting its potential value for monitoring tumor-associated molecular changes. This study investigated the effects of panitumumab, an anti-EGFR monoclonal antibody, on the proteomic profiles of EVs derived from EGFRvIII cells. U87 and U87-EGFRvIII cells and their derived EVs were characterized before and after treatment. Our results demonstrate that panitumumab significantly reduced surface EGFRvIII on EVs derived from U87-EGFRvIII cells, whereas no significant decrease was observed in cell lysates. The proteomic analysis highlighted much more changes in EVs than in their parental cells after treatment, particularly in proteins associated with extracellular matrix organization and collagen. In conclusion, our results suggest that EVs derived from EGFRvIII cells could serve as a useful circulating biomarker for assessing treatment efficacy and for preventing treatment escape.

Matching Claidex post-mortems

3 of 3 indexed

This is an automated contradiction flag, not an editorial judgment on the preprint's quality. Flags identify where the preclinical literature and the clinical failure record diverge.