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N.R. Smith

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    MINI 16 - EGFR Mutant Lung Cancer 2 (ID 130)

    • Event: WCLC 2015
    • Type: Mini Oral
    • Track: Treatment of Advanced Diseases - NSCLC
    • Presentations: 1
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      MINI16.09 - Design, Execution, and Preliminary Biomarker Results from Paired Tumor Biopsy Cohorts of the AZD9291 AURA Trial (ID 941)

      16:45 - 18:15  |  Author(s): N.R. Smith

      • Abstract
      • Slides

      Epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) exhibits sensitivity to EGFR tyrosine kinase inhibitors (TKIs) such as erlotinib and gefitinib; however, acquired resistance eventually develops in most patients. The most common mechanism of TKI resistance is a second-site mutation in the EGFR kinase domain, T790M. AZD9291 is an oral, potent, irreversible EGFR-TKI with potency against both T790M resistance and sensitizing EGFR mutations. In the ongoing Phase I AURA study (NCT01802632), AZD9291 induced durable responses in patients with acquired resistance to EGFR-TKIs. We report results of paired biopsy cohorts of the AURA trial, reviewing modulation of key molecular biomarkers of AZD9291 activity in patient tumor samples.

      Two cohorts of patients on the AURA trial were consented for collection of paired tumor biopsies. These patients had a pre-study tumor biopsy with T790M positive tumor status confirmed by central laboratory EGFR testing (Cobas™ EGFR Mutation Test). Following 8 to 15 days of once daily AZD9291 treatment (80 or 160 mg), a post-dose tumor biopsy was obtained. Baseline and post-dose tumor tissue was processed for routine histology and pathologic evaluation. More than 100 viable tumor cells per sample were required for subsequent biomarker scoring. Formalin-fixed paraffin-embedded tumor biopsies were profiled by immunohistochemistry with a suite of key pathway and tumor-relevant markers (phospho[p]-EGFR, pERK, pAKT, pS6, PD-L1, CD8). Matching plasma pharmacokinetic samples were also obtained for PK-PD correlations.

      As of February 2015, 58 potential patients with an evaluable baseline biopsy were identified as candidates for post-dose biopsy collection. Sixteen of these patients did not proceed to an on-study biopsy as the identified lesions had regressed too substantially or were no longer considered suitable for re-biopsy, one patient was medically excluded from re-biopsy, and one patient’s sample was not available. In total, 40 patients supplied matched pre- and on-treatment biopsies. As of March 2015, paired tumor samples were available for QC from 26 of these 40 patients. Ten of these 26 biopsy specimens subsequently failed QC due to inadequate tumor content, leaving 16 paired tumor samples available for biomarker analyses, of which five have thus far been evaluated. AZD9291 treatment resulted in the inhibition of EGFR pathway components in the majority of post-treatment tumor biopsies. Tissue biomarker analyses are ongoing and updated data on evaluable biopsy pairs will be reported at the time of the congress.

      The completion of a paired biopsy cohort within the AURA trial was challenging due to the rapid onset of anti-tumor effects of AZD9291. Approximately 29% (17/58) of potentially eligible patients were unsuitable for the post-dose biopsy procedure due to tumor regression and 38% (10/26) of available post-dose biopsies were found to contain too little tumor for analysis. In the evaluable tumor pairs, pharmacodynamic modulation of the EGFR pathway was evident. Further biomarker analyses, including evidence of modulation of immune system markers, may help inform future combination strategies.

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