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J. Zaretsky



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    ORAL 31 - PD1 Axis Inhibition (ID 143)

    • Event: WCLC 2015
    • Type: Oral Session
    • Track: Treatment of Advanced Diseases - NSCLC
    • Presentations: 1
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      ORAL31.05 - High Intratumoral T Cell Infiltration Correlated with Mutational Load and Response to Pembrolizumab in Non-Small Cell Lung Cancer (ID 2728)

      16:45 - 18:15  |  Author(s): J. Zaretsky

      • Abstract
      • Presentation
      • Slides

      Background:
      Responses to PD-1 blockade have been induced in approximately 20% of advanced non-small cell lung cancer (NSCLC) patients with progressive disease after standard therapy [Garon, NEJM 2015]. One challenge is to understand how the immune response was initiated in responding patients. Tumor mutational burden has been associated with response to PD-1 checkpoint inhibitors in NSCLC [Rizvi, Science, 2015]. In addition, studies in melanoma patient-derived tumor specimens revealed that responses to PD-1/L1 blockade rely on pre-therapy tumor infiltration of activated T effector cells [Tumeh, Nature, 2014]. We hypothesize that clonal T cell infiltration is correlated with tumor mutational load and clinical response with PD-1 blockade.

      Methods:
      We studied tumor specimens in NSCLC patients treated with pembrolizumab at UCLA on the KEYNOTE -001 clinical trial. All patients signed informed consent for the trial as well as separate specimen acquisition protocols. Responses were classified by the investigators according to irRC. DNA was extracted and whole exome sequencing was performed at the UCLA Immunogenetics Core. DNA from the same patient’s PBMC or other non-cancerous tissue was sequenced for baseline comparison. Immunohistochemistry (IHC) was done for CD8 (Clone C8/144B, Dako), CD4 (Clone SP35, Cell Marque) and PD-L1 (Clone SP142, Spring Bioscience).

      Results:
      We report results from 27 patients (14 responders, and 13 nonresponders). Significantly higher density of pre-dosing CD8+ cells (percentage of CD8+ nucleated cells) in the tumors of the responding patients was observed (mean of 17.7% in responders vs 5.6% in non-responders, p=0.02 by unpaired t test) suggestive of a pre-existing immune response. Mutational load in 5 patients (3 responders and 2 nonresponders) showed a trend towards correlation with response (mean of 19 nonsynonymous somatic mutations per MB in responders vs 6 in nonresponders, p=0.33). Interestingly, a strikingly significant correlation between mutational load and CD8 expression was observed (R[2]=0.96, p=0.003). In addition, pre-dosing tumor PD-L1 expression demonstrated a trend towards correlation with response (mean of 72.1% in responders vs 51.5% in nonresponders, p=0.07) but not with CD8 tumor infiltration (R[2]=0.05, p=0.28). No significant association of CD4+ T cell tumor infiltration with response (mean of 37.4% CD4 + cells in responders vs 27.0% in nonresponders, p=0.32) was observed.

      Conclusion:
      We observed strong correlation of pre-dosing intratumoral T cell infiltration with response and mutational load in NSCLC patients treated with pembrolizumab. Our results have direct implications for the design and interpretation of ongoing and planned immunotherapy studies for NSCLC and evaluation of potential predictive biomarkers to select patients most likely to benefit.

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