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OA10 - EGFR Mutations (ID 382)
- Event: WCLC 2016
- Type: Oral Session
- Track: Biology/Pathology
- Presentations: 1
OA10.01 - Comprehensive Genomic Profiling and PDX Modeling of EGFR Exon 20 Insertions: Evidence for Osimertinib Based Dual EGFR Blockade (ID 4375)
11:00 - 12:30 | Author(s): S.D. Airhart
EGFR exon 20 insertion mutations (EGFRex20ins) comprise a subset of EGFR activating alterations relatively insensitive to 1[st] and 2[nd] generation EGFR-TKIs. Comprehensive genomic profiling (CGP) integrated with PDX modeling may identify new EGFR-inhibition strategies for EGFRex20ins.
EGFRex20ins and co-occurring genomic alterations were identified by hybrid-capture based CGP performed on 14,483 consecutive FFPE lung cancer specimens to a mean coverage depth of >650X for 236 or 315 cancer-related genes plus 47 introns from 19 genes frequently rearranged in cancer. An EGFRex20ins(N771_P772>SVDNP)/EGFR-amplified tumor (24 copies) from this cohort was implanted subcutaneously into the flank of NOD.Cg-Prkdc[scid]Il2rg[tm1Wjl]/SzJ (NSG) mice for tumor growth inhibition studies (TGI) with vehicle, erlotinib (50 mg/kg PO daily), osimertinib (25 mg/kg PO daily), and osimertinib (25 mg/kg PO daily) plus cetuximab (10 mg/kg IV, 2x/week) administered for 21 days.
CGP identified 263/14,483 cases (1.8%) with EGFRex20ins, which represent 12% (263/2,251) of EGFR activating mutations in this series. 90% (237/263) were NSCLC-adenocarcinoma, 9% (23/263) were NSCLC-NOS, and 1% (2/263) were sarcomatoid carcinoma. Over 60 unique EGFRex20ins were identified, most commonly D770_N771>ASVDN (21%) and N771_P772>SVDNP (20%); 6% (15/263) harbored EGFR A763_Y764insFQEA, an EGFRex20ins typically sensitive to erlotinib. Among EGFRex20ins cases, EGFR-amplification occurred in 22% (57/263). Putative co-occurring driver alterations including EGFR (ex19del and L858R), Her2, MET and KRAS tended to be mutually exclusive, occurring only in 5% (12/263) of cases. The most common co-occurring alterations affected TP53 (56%), CDKN2A (22%), CDKN2B (16%), NKX2-1 (14%) and RB1 (11%). Average tumor mutation burden was low (mean 4.3 mutations/Mb, range 0-40.3 mutations/Mb). Clinical outcomes to 1st and 2nd generation EGFR-TKIs were obtained for a subset of cases with various EGFRex20ins, and 0/6 patients had responses. However, robust TGI was observed with combination osimertinib and cetuximab in a highly EGFR-amplified PDX model with a conserved EGFRex20ins (N771_P772>SVDNP) not associated with response to earlier generation EGFR-TKI, and was superior to vehicle, erlotinib or osimertinib alone (D21 mean tumor size 70 mm vs. 1000, 800, 225 mm respectively; p-values all <0.001).
Diverse EGFRex20ins were detected in 12% of EGFR-mut NSCLC. Available clinical outcomes data demonstrated lack of response to 1[st] and 2[nd] generation EGFR-TKIs. Identification of co-occurring EGFR-amplification in 22% of cases led to testing of a dual EGFR blockade strategy with an EGFR monoclonal antibody and osimertinib, which demonstrated exceptional tumor growth inhibition in an EGFRex20ins PDX minimally responsive to erlotinib. These findings can rapidly be translated into an ongoing clinical trial of osimertinib and necitumumab.
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