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Primo N. Lara

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    MA09 - EGFR & MET (ID 128)

    • Event: WCLC 2019
    • Type: Mini Oral Session
    • Track: Targeted Therapy
    • Presentations: 1
    • Now Available
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      MA09.02 - In Vivo, Ex Vivo and Early Clinical Activity of EGFR Monoclonal Antibody and Osimertinib in EGFR Exon 20 Insertion NSCLC (Now Available) (ID 968)

      15:15 - 16:45  |  Author(s): Primo N. Lara

      • Abstract
      • Presentation
      • Slides


      EGFR Exon 20 insertions (Ex20Ins) are the 3rd most common class of EGFR activating mutation, but patients with NSCLC harboring EGFR Ex20Ins lack effective approved EGFR-TKIs. Newer-generation TKIs and combination strategies with EGFR-monoclonal antibodies (moAbs) may enhance activity against EGFR Ex20Ins.


      Xenografts derived from CRISPR-modified H2073 cells with Ex20Ins (A763_Y764InsFQEA, D770_N771InsSVD or V769_D770InsASV) and Ex20Ins patient-derived xenografts (PDXs) (D770_N771InsSVD, A797_V769dupASV, D770_N771_InsG, H773_V774_InsNPH) were treated with vehicle, osimertinib , cetuximab, and osimertinib+cetuximab. Ex20Ins spheroid models (D770_N771InsSVD and M766_A767InsASV) were treated with cetuximab at fixed dose and increasing concentrations of osimertinib. Ex20Ins PDX (A763_Y764InsFQEA) was also treated with afatinib and erlotinib; Ex20Ins PDX (D770_N771InsSVD) was treated with these combinations plus afatinib+cetuximab. Immunoblotting for pharmacodynamic studies of on-target and downstream proteins, phospho-proteins and apoptosis markers were performed at relevant timepoints for D770_N771InsSVD PDX and CRISPR model. A phase 1 clinical trial with a dose expansion cohort in Stage IV EGFR Ex20Ins NSCLC is currently open to accrual at osimertinib 80 mg qd and the EGFR-moAb necitumumab 800 mg IV D1 and D8 of 21D cycle with response assessment by RECIST 1.1 (NCT02496663).


      The combination of osimertinib and cetuximab achieved significant tumor growth inhibition compared to osimertinib alone across PDX and CRISPR cell line xenograft models (p=0.05), except for the A763_Y764InsFQEA PDX model where osimertinib alone and osimertinib+cetuximab were equivalently effective (both p<0.001 compared to control). Spheroid models for D770_N771InsSVD and M766_A767InsASV showed significantly increased cytotoxicity from the addition of cetuximab across multiple doses of osimertinib. Osimertinib+cetuximab was superior to erlotinib, cetuximab, afatinib and afatinib+cetuximab in a D770_N771InsSVD PDX model (p<0.001). In this model, inhibition of p-EGFR, p-ERK, p-HER2 and increased caspase 3 cleavage were noted, consistent with significant tumor growth inhibition. In the phase 1 EGFR Ex20Ins expansion cohort of necitumumab in combination with osimertinib, 6/18 patients enrolled with 4 patients evaluable for response; 2 patients achieved a partial response and median PFS was 5.3 months.


      In vivo and ex vivo modeling in CRISPR cell line xenografts, PDXs and organoids demonstrated preclinical activity of dual EGFR blockade with osimertinib and EGFR monoclonal antibody in the 5 most common EGFR Ex20Ins representing a frequency of ~60% of detectable EGFR Ex20Ins in clinical practice. Osimertinib alone was as active as osimertinib plus cetuximab in A763_Y764InsFQEA, consistent with known sensitivity of this proximal insertion to single-agent EGFR-TKI. In a phase 1 study, osimertinib and the EGFR moAb necitumumab demonstrates preliminary clinically activity in EGFR Ex20Ins NSCLC.

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