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Fabiola Cecchi



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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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      P1.13-43 - Molecular and Imaging Predictors of Response to Ado-Trastuzumab Emtansine in Patients with HER2 Mutant Lung Cancers: An Exploratory Phase 2 Trial (ID 14068)

      16:45 - 18:00  |  Author(s): Fabiola Cecchi

      • Abstract

      Background

      Ado-trastuzumab emtansine is a HER2 targeted antibody drug conjugate (ADC) that has demonstrated clinical activity in patients with HER2 mutant lung cancers, independent of HER2 protein expression. We hypothesize that the degree of HER2 homo- and/or heterodimerization may lead to preferential trastuzumab binding and internalization, and may serve as a predictor of response to HER2 ADC.

      a9ded1e5ce5d75814730bb4caaf49419 Method

      Patients with metastatic HER2 mutant lung cancers were enrolled in a phase 2 trial of ado-trastuzumab emtansine, treated at 3.6mg/kg IV every 3 weeks. The primary endpoint was overall response rate (ORR) using RECIST v1.1. An expansion cohort included patients assessed using PERCIST, with pre-treatment 89Zr-trastuzumab PET/CT as correlative HER2-targeted imaging. HER2 mutation was identified by next generation sequencing (NGS), and tumors with adequate tissue were subsequently tested by fluorescence in situ hybridization (FISH), immunohistochemistry (IHC), quantitative protein mass spectrometry, as well as quantitative HER2-HER3 heterodimerization by fluorescence lifetime imaging microscopy - Förster resonance energy transfer (FLIM-FRET).

      4c3880bb027f159e801041b1021e88e8 Result

      A total of 35 patients with HER2 mutant lung cancers were treated across 2 cohorts. ORR was 44% (8/18, 95% CI 22-69%) for RECIST cohort, and 46% (6/13, 95% CI 19-75%) for PERCIST cohort with 4 patients awaiting response assessment. Responders were seen across mutation subtypes (A775_G776insYVMA, G776delinsVC, V659E, S310F, L755P). Concurrent HER2 amplification was observed in 6 of 35 (17%) patients by either NGS or FISH. IHC ranged from 0 to 3+ and did not predict response. HER2 protein expression was low or absent in 15/18 cases tested by mass spectrometry. HER3 overexpression was seen in 7/18 cases tested and among them 5/6 evaluable patients had a partial response. FLIM-FRET efficiency was tested positive for HER2-HER3 heterodimer, which has been shown to be affected by the symmetrical heterodimer interface mutations (Claus et al, 2018), in 3 patients thus far and 1 of them had a partial response. Pre-treatment 89Zr-trastuzumab PET/CT showed increased uptake in 3/8 patients tested to date, and all 3 patients subsequently had partial metabolic response.

      8eea62084ca7e541d918e823422bd82e Conclusion

      This study confirmed the efficacy of ado-trastuzumab emtansine in patients with HER2 mutant lung cancers. HER2-containing dimers as indicated by HER3 overexpression or FLIM-FRET efficiency, and HER2-targeted imaging with 89Zr-trastuzumab PET/CT, may predict response to HER2 ADCs.

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