Next-generation DNA sequencing (NGS) results for tumours from phase II ABRAZO study of talazoparib after platinum or cytotoxic non-platinum regimens in patients (pts) with advanced breast cancer (ABC) and germline BRCA1/2 (gBRCA) mutations

Background Loss-of-function mutations in genes encoding components of the homologous recombination (HR) machinery are associated with tumor sensitivity to poly (ADP-ribose) polymerase (PARP) inhibitors. In ABRAZO, the PARP inhibitor talazoparib demonstrated encouraging efficacy in gBRCA-mutated ABC, both in pts whose cancer responded to prior platinum therapy (cohort 1) and in pts who had received ≥3 prior nonplatinum chemotherapy regimens for ABC (cohort 2). Methods Baseline tumor tissue (primary or metastatic sites) from enrolled pts was sequenced using the FoundationOne CDx NGS panel. 60/84 pts (71%) in the intent-to-treat population had available tumor tissue, which could be sequenced. Mutations summarized below were known or likely pathogenic single-nucleotide variants, insertions, deletions, or rearrangements. Additional exploratory computational analyses pertinent to HR deficiency were performed, including genomic loss of heterozygosity (gLOH) and somatic-germline-zygosity assessments. Results Tumor mutations in BRCA1 and BRCA2 were detected in 29 (48%) and 28 (47%) of 60 evaluable pts (no pts exhibited mutations in both BRCA1 and BRCA2). These mutations were most commonly single-nucleotide variants (BRCA1: 12 [20%] and BRCA2: 10 [17%]) or deletions (BRCA1: 11 [18%] and BRCA2: 12 [20%]). Mutations in other genes implicated in HR were comparatively rare, with mutations in CHEK2 (2 pts), ARID1A, ATR, BARD1, BRD4, BRIP1, FANCC, and STAG2 (each in single pts) detected. In addition to BRCA1/2, genes where mutations were detected in ≥ 10% of evaluable pts included TP53 (45%) and PIK3CA (12%). TP53 mutations were more commonly observed in BRCA1-mutated than in BRCA2-mutated tumors (22/29 [76%] compared with 4/28 [14%]). Associations of genetic/genomic events with progression-free survival will be presented. Conclusions NGS of tumors from the ABRAZO study of talazoparib in patients with gBRCA-mutated ABC revealed a complex mutational landscape. Exploratory correlative analyses are ongoing and will be reported. Clinical trial identification NCT02034916. Legal entity responsible for the study Pfizer Inc. Funding Pfizer Inc. Disclosure N.C. Turner: Advisory / Consultancy, Research grant / Funding (institution): Pfizer Inc.; Advisory / Consultancy, Research grant / Funding (institution): BioMarin. A..D. Laird: Full / Part-time employment: Pfizer Inc. M.L. Telli: Advisory / Consultancy, Research grant / Funding (institution): Pfizer Inc.; Advisory / Consultancy: AstraZeneca; Advisory / Consultancy, Research grant / Funding (institution): Tesaro; Advisory / Consultancy, Research grant / Funding (institution): PharmaMar; Advisory / Consultancy, Research grant / Funding (institution): Vertex; Research grant / Funding (institution): AbbVie; Research grant / Funding (institution): Biothera; Research grant / Funding (institution): Calithera Biosciences; Research grant / Funding (institution): Genentech; Research grant / Funding (institution): Medivation; Research grant / Funding (institution): Novartis; Research grant / Funding (institution): OncoSec; Research grant / Funding (institution): Sanofi. H.S. Rugo: Research grant / Funding (institution): Eisai; Research grant / Funding (institution): Genentech; Research grant / Funding (institution): GSK; Research grant / Funding (institution), Travel / Accommodation / Expenses: Lilly; Research grant / Funding (institution): MacroGenics; Research grant / Funding (institution): Merck; Research grant / Funding (institution): Novartis; Research grant / Funding (institution): OBI Pharma; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): Plexxikon; Travel / Accommodation / Expenses: Mylan; Travel / Accommodation / Expenses: Puma; Research grant / Funding (institution): Eisai; Research grant / Funding (institution): Genentech; Research grant / Funding (institution): GlaxoSmithKline; Research grant / Funding (institution), Travel / Accommodation / Expenses: Lilly; Research grant / Funding (institution): MacroGenics; Research grant / Funding (institution): Merck; Research grant / Funding (institution): Novartis; Research grant / Funding (institution): OBI Pharma; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): Plexxikon; Travel / Accommodation / Expenses: Mylan; Travel / Accommodation / Expenses: Puma. A. Mailliez: Honoraria (self), Advisory / Consultancy: AstraZeneca; Advisory / Consultancy: Tesaro; Advisory / Consultancy, Research grant / Funding (institution): PharmaMar; Advisory / Consultancy: Vertex; Research grant / Funding (institution): AbbVie; Research grant / Funding (institution): Biothera; Research grant / Funding (institution): Calithera Biosciences; Research grant / Funding (institution): Genentech; Research grant / Funding (institution): Medivation; Research grant / Funding (institution): Novartis; Research grant / Funding (institution): OncoSec; Research grant / Funding (institution): Pfizer Inc. J. Ettl: Honoraria (institution), Advisory / Consultancy: Lilly; Advisory / Consultancy, Travel / Accommodation / Expenses: Novartis; Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: Pfizer; Honoraria (institution), Advisory / Consultancy: Roche; Advisory / Consultancy: Tesaro; Advisory / Consultancy: Eisai; Research grant / Funding (institution), Travel / Accommodation / Expenses: Celgene; Honoraria (self): TEVA; Honoraria (self): AstraZeneca. J. Balmana: Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: AstraZenca; Advisory / Consultancy: Clovis; Advisory / Consultancy: Tesaro; Advisory / Consultancy: BMS; Research grant / Funding (institution), Travel / Accommodation / Expenses: PharMar. P.A. Fasching: Honoraria (self), Advisory / Consultancy: Roche; Honoraria (self), Advisory / Consultancy: Amgen; Honoraria (self), Advisory / Consultancy, Research grant / Funding (institution): Novartis; Honoraria (self), Advisory / Consultancy: Pfizer; Honoraria (self), Advisory / Consultancy: Celgene; Honoraria (self), Advisory / Consultancy: Puma; Honoraria (self), Advisory / Consultancy: Daiichi Sankyo; Honoraria (self), Advisory / Consultancy: Eisai; Honoraria (self), Advisory / Consultancy: Merck; Honoraria (self), Advisory / Consultancy: AstraZeneca; Honoraria (self), Advisory / Consultancy: Teva; Honoraria (self), Advisory / Consultancy: Hexal; Honoraria (institution), Speaker Bureau / Expert testimony: Myelo; Research grant / Funding (institution): BioNTech. S.A. Hurvitz: Research grant / Funding (institution): Ambryx; Research grant / Funding (institution): Amgen; Research grant / Funding (institution): Bayer; Research grant / Funding (institution): BI Pharma; Research grant / Funding (institution): Biomarin; Research grant / Funding (institution): Cascadian; Research grant / Funding (institution): Daiichi Sankyo; Research grant / Funding (institution): Dignitana; Research grant / Funding (institution): Genentech; Research grant / Funding (institution): GSK; Research grant / Funding (institution), Travel / Accommodation / Expenses: Lilly; Research grant / Funding (institution): Macrogenics; Research grant / Funding (institution): Medivation; Research grant / Funding (institution): Merrimack; Research grant / Funding (institution), Travel / Accommodation / Expenses: Novartis; Research grant / Funding (institution), Travel / Accommodation / Expenses: OBI Pharma; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): Pieris; Research grant / Funding (institution): PUMA; Research grant / Funding (institution): Roche. L.A. Albacker: Full / Part-time employment: Foundation Medicine Inc. G.M. Frampton: Full / Part-time employment: Foundation Medicine Inc. J. Chelliserry: Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer Inc. P. Bycott: Research grant / Funding (self), Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer Inc. U. Conte: Shareholder / Stockholder / Stock options, Full / Part-time employment: Pfizer Inc. A.M. Wardley: Honoraria (self), Advisory / Consultancy: AstraZeneca; Honoraria (self), Advisory / Consultancy: Lilly; Honoraria (self), Advisory / Consultancy: Novartis; Honoraria (self), Advisory / Consultancy, Speaker Bureau / Expert testimony, Research grant / Funding (institution): Roche. M.E. Robson: Honoraria (self), Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: AstraZeneca; Advisory / Consultancy: McKesson; Research grant / Funding (institution): AbbVie; Research grant / Funding (institution): BioMarin; Research grant / Funding (institution): Medivation; Research grant / Funding (institution): Myriad Genetics; Research grant / Funding (institution): Tesaro. All other authors have declared no conflicts of interest.