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Yuichi Sesumi

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    P1.13 - Targeted Therapy (Not CME Accredited Session) (ID 945)

    • Event: WCLC 2018
    • Type: Poster Viewing in the Exhibit Hall
    • Track:
    • Presentations: 1
    • Moderators:
    • Coordinates: 9/24/2018, 16:45 - 18:00, Exhibit Hall
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      P1.13-42 - Activity of Novel HER2 Inhibitor, Poziotinib, for HER2 Exon 20 Mutations in Lung Cancer and Mechanism of Acquired Resistance (ID 12717)

      16:45 - 18:00  |  Author(s): Yuichi Sesumi

      • Abstract


      Oncogenic HER2 mutations are present in 2-4% of adenocarcinoma of the lung. However, clinical trials of HER2 inhibitors such as afatinib or neratinib has been unsatisfactory. Recently, a novel HER2 inhibitor, poziotinib has been developed and clinical trial results are being expected. Here, we evaluated poziotinib in comparison with pre-existing TKIs using Ba/F3 system. We also derived resistant clones against poziotinib and investigated their resistant mechanism.

      a9ded1e5ce5d75814730bb4caaf49419 Method

      We introduced three common HER2 mutations into Ba/F3 cells (i.e. G776delinsVC (VC), A775_G776insYVMA (YVMA) and P780_Y781insGSP (GSP)) which account for 13, 72, 9% of HER2 mutations in human lung cancer, respectively. We defined sensitivity index (SI) as an IC90divided by trough concentration of a given drug at the recommended dose for humans in the literature, as a surrogate for drug activity in humans. Poziotinib activity was compared with 8 TKIs (afatinib, osimertinib, erlotinib, neratinib, lapatinib, dacomitinib, irbinitinib, and AZ5104). In addition, we created resistant clones by exposing poziotinib in the presence of N-ethyl-N-nitrosourea (ENU) and HER2 secondary mutations were searched.

      4c3880bb027f159e801041b1021e88e8 Result

      All drugs but lapatinib showed the highest activity against VC (Table). In contrast, YVMA was most resistant in all but neratinib and poziotinib. For most common YVMA, poziotinib was the only drug that had SI of less than 10 (Table). Furthermore, poziotinib was most potent for VC and GSP except dacomitinib for GSP (Table). We established 19 poziotinib-resistant clones, all of which harbored C805S secondary mutation of the HER2 gene homologous to C797S of the EGFR gene.

      Ctrough [nM] YVMA VC GSP
      Afatinib 69 28 5.4 12
      Dacomitinib 166 20 4.4 6.6
      Erlotinib 2969 337 22 98
      Osimertinib 400 40 4.5 30
      Neratinib 100 11 11 28
      Lapatinib 516 133 117 91
      Poziotinib 20 6.0 2.7 10
      Irbinitinib 520 34 33 16
      AZ5104 50 60 8.0 48

      8eea62084ca7e541d918e823422bd82e Conclusion

      Poziotinib showed the most potent activity against HER2 exon 20 mutations. We also found that secondary C805S HER2 mutation was the common mechanism of acquired resistance, which most likely inhibit covalent binding of poziotinib with HER2.