Introduction: B-cell malignancies may depend on the histone methyl transferase EZH2 to perpetuate a less differentiated state, with activating mutations of EZH2 being potential oncogenic drivers. Tazemetostat, a potent, selective EZH2 inhibitor, is in Phase 2 clinical development in relapsed or refractory (RR) Non-Hodgkin Lymphoma (NHL). Objective responses were observed in patients with EZH2 mutant or wild type (WT) tumors in the Phase 1 part of the Phase 1/2 study. The ongoing Phase 2 study enrolls patients with mutant or WT EZH2 havingRR Diffuse Large B-Cell Lymphoma (DLBCL) or Follicular Lymphoma (FL) to determine efficacy and safety. The primary endpoint is overall response rate. Here we report results of a molecular analysis of circulating tumor DNA (ctDNA) collected from patient's plasma and associations with preliminary response data, including the discovery of novel candidate molecular predictors of tazemetostat response.

Methods: Archived tumor and/or plasma-derived ctDNA samples were obtained during screening in the Phase 2 trial of tazemetostat in NHL (NCT01897571).Prospectively, archived tumor was analyzed for EZH2 hot spot mutations Y646X, A682G and A692V using the cobas® EZH2 Mutation Test (Roche Molecular Systems, in development). Retrospectively, next generation sequencing (NGS) was performed on archived tumor DNA (target coverage of 1,500X) and ctDNA (20,000X for somatic mutations and 5,000X for structural alterations) to identify somatic mutations, amplifications, and translocations in a panel of 62 genes commonly altered in NHL. Best objective overall response (Cheson 2007) on June 01, 2017 was used to generate three groups: responders (CR + PR; n = 43), progressive disease (PD; n = 66), and patients with either stable disease (SD) or unknown (UK) clinical response (n=76). Genetic alterations identified in ctDNA collected pre-dose, at variant allele frequencies greater than 0.5%, and associated with either the responder or PD groups (discovery case set, n=109) were identified using Fischer's exact test (two-tailed).

Results: Regardless of sample type or technology the concordance rate for detection of EZH2 status was > 95%. NGS and the cobas Test of archived tumor samples was > 99% concordant (n = 128) with 19 EZH2 mutant cases detected by the cobas Test. Concordance of EZH2 status between archived tumor detected by the cobasTestor NGS and ctDNA by NGS was 95% (n = 185). Consistent with published literature KMT2D (65% somatic sequence mutations) and BCL2 (55% of cases including amplification, translocations, somatic sequence mutations) were the most frequently altered genes in our patient population, with somatic sequence mutations in other chromatin modifying proteins CREBBP, HIST1H1E, EZH2, and EP300 occurring in 36, 23, 14 and 11% of patients respectively. With the exception of PIM1 (30% DLBCL and 6% FL) and TNFRSF14 (10% DLBCL and 29% FL) the top 5 genes identified had similar mutation frequencies between DLBCL (n=122) and FL (n=63) cases. Analysis of 109 discovery cases, including both DLBCL and FL patients revealed STAT6 mutations as the variant demonstrating the most significant association ( P <0.13) with clinical response (CR + PR) to tazemetostat. Further refinement of the analysis by disease cohort identified CREBBP ( P <0.10) and EZH2 ( P <0.07) associated with clinical response in DLBCL (n=76) and FL (n=33) respectively. In contrast mutations in ten genes including PIM1 , BCL6 , TP53 and HIST1H1E were affiliated (all P <0.06) with PD (i.e. lack of response to tazemetostat) across both the FL and DLBCL cohorts, with only BCL2 variants demonstrating significance through multiple test correction (adjusted P value = 0.04).

Conclusions: The molecular predictors identified in this ctDNA analysis contain genes previously described as potential predictors of tazemetostat response in archived tumor analysis such as STAT6 , EZH2 , TP53 and HIST1H1E . In addition to these genes, we were able to uncover variants in CREBBP , BCL2 , BCL6 and PIM1 that may offer new insights into potential mechanisms of response, or lack of response to tazemetostat. Moreover to identification of molecular predictors of response, plasma based ctDNA screening has been demonstrated to be a viable method to identify NHL patients with mutant EZH2 in the absence of tumor samples or with lesions in anatomical sites of high risk.

Disclosures

Daigle: Epizyme, Inc: Employment, Equity Ownership. McDonald: Epizyme, Inc: Employment, Equity Ownership, Research Funding. Morschhauser: Roche: Consultancy, Honoraria; Servier: Consultancy; Gilead: Consultancy; Janssen: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; Celgene: Consultancy, Honoraria. Salles: Roche/Genentech: Consultancy, Honoraria, Research Funding; Gilead: Honoraria, Research Funding; Mundipharma: Honoraria; Janssen, Celgene, Novartis, and Amgen: Consultancy, Honoraria. Ribrag: Roche: Honoraria, Other: travel, accommodation, expenses; Epizyme: Consultancy, Honoraria; Nanostring: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Esai: Honoraria, Research Funding; Pharmamar: Consultancy; BMS: Consultancy, Honoraria; Infinity: Consultancy, Honoraria; ArgenX: Research Funding; MSD: Consultancy, Honoraria; Servier: Consultancy, Honoraria. Tilly: Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Honoraria; Karyopharm: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Honoraria; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Immunogen: Honoraria. Gerecitano: Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees; Arcus Medica: Consultancy, Membership on an entity's Board of Directors or advisory committees; Royal Bank of Canada: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees; Merck: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Orexo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Aratana: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees; Mass Medical International: Honoraria, Membership on an entity's Board of Directors or advisory committees; Samus Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees. Johnson: Epizyme, Inc: Consultancy, Honoraria, Research Funding. Radford: GlaxoSmithKline: Equity Ownership; Novartis: Speakers Bureau; AztraZeneca: Equity Ownership; Seattle Genetics: Speakers Bureau; ADC Therapeutics: Research Funding; Takeda: Research Funding, Speakers Bureau. Dickinson: GlaxoSmithKline: Honoraria, Research Funding. Opat: Janssen: Consultancy, Honoraria, Speakers Bureau; Roche: Consultancy, Honoraria, Research Funding, Speakers Bureau; Gilead: Consultancy, Honoraria, Research Funding, Speakers Bureau; Beigene: Research Funding; Mundipharma: Consultancy; Amgen: Research Funding. Jurczak: Nordic Nanovector: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sandoz Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Research Funding; Spectrum: Membership on an entity's Board of Directors or advisory committees, Research Funding; Jagiellonian University: Employment; Gilead: Research Funding; Servier: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Research Funding; Celtrion: Research Funding; Acerta Pharma: Research Funding; Pharmacyclics: Research Funding; Pfizer: Research Funding; Morphosys: Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Research Funding. Cartron: Celgene: Consultancy, Employment; Sanofi, BMS, Jansen, celgene, Roche, Gilead: Equity Ownership; Roche: Consultancy, Equity Ownership, Honoraria, Research Funding. Lamy: Roche: Consultancy, Honoraria. Zinzani: Celgene, Janssen, Gilead, Roche, Takeda, BMS, MSD, Sandoz, Servier, Mundipharma: Speakers Bureau; Merck: Consultancy, Other: Advisory board; ​Celgene, Roche, Janssen, Gilead, Takeda, BMS, MSD, Servier, Sandoz, Mundipharma: Honoraria. Assouline: Janssen: Honoraria; Paladin: Speakers Bureau; Bristol Myer Squibb: Speakers Bureau; Novartis Canada Inc.: Honoraria; Pfizer: Speakers Bureau. Morin: Epizyme, Inc: Consultancy. Wu: Roche: Employment, Equity Ownership. Sausen: Personal Genome Diagnostics: Employment. Clawson: Epizyme, Inc: Employment, Equity Ownership. Ho: Epizyme, Inc: Employment, Equity Ownership. Miao: Epizyme, Inc: Employment, Equity Ownership. Blakemore: Epizyme Inc.: Employment, Equity Ownership.

Topics:
circulating tumor dna, diffuse large b-cell lymphoma, follicular lymphoma, massively-parallel genome sequencing, neoplasms, bcl-2 protein, protein p53, screening, antigens, cancer

Author notes

*

Asterisk with author names denotes non-ASH members.

© 2017 by The American Society of Hematology
2017
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