Research ArticleCancer

Integrated molecular analysis of tumor biopsies on sequential CTLA-4 and PD-1 blockade reveals markers of response and resistance

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Science Translational Medicine  01 Mar 2017:
Vol. 9, Issue 379, eaah3560
DOI: 10.1126/scitranslmed.aah3560

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Checking on checkpoint inhibitors

Immune checkpoint blockade has greatly improved the success of treatment in melanoma and other tumor types, but it is expensive and does not work for all patients. To optimize the likelihood of therapeutic success and reduce the risks and expense of unnecessary treatment, it would be helpful to find biomarkers that can predict treatment response. Roh et al. studied patients treated with sequential checkpoint inhibitors targeting CTLA-4 and then PD-1. In these patients, the authors discovered that a more clonal T cell population specifically correlates with response to PD-1 blockade, but not CTLA-4, which may help identify the best candidates for this treatment. In addition, increased frequency of gene copy number loss was correlated with decreased responsiveness to either therapy.

Abstract

Immune checkpoint blockade produces clinical benefit in many patients. However, better biomarkers of response are still needed, and mechanisms of resistance remain incompletely understood. To address this, we recently studied a cohort of melanoma patients treated with sequential checkpoint blockade against cytotoxic T lymphocyte antigen–4 (CTLA-4) followed by programmed death receptor–1 (PD-1) and identified immune markers of response and resistance. Building on these studies, we performed deep molecular profiling including T cell receptor sequencing and whole-exome sequencing within the same cohort and demonstrated that a more clonal T cell repertoire was predictive of response to PD-1 but not CTLA-4 blockade. Analysis of CNAs identified a higher burden of copy number loss in nonresponders to CTLA-4 and PD-1 blockade and found that it was associated with decreased expression of genes in immune-related pathways. The effect of mutational load and burden of copy number loss on response was nonredundant, suggesting the potential utility of a combinatorial biomarker to optimize patient care with checkpoint blockade therapy.

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