1966P - Treatment with BLU-667, a potent and selective RET inhibitor, provides rapid clearance of ctDNA in patients with RET-altered non-small cell lung cancer (NSCLC) and thyroid cancer

BLU667, an investigational agent, is a potent and selective inhibitor of oncogenic rearranged during transfection (RET) alterations and predicted resistance mutations. Up to 90% of advanced medullary thyroid cancer (MTC) is characterized by single nucleotide variants and short insertions/deletions in the RET gene. In NSCLC, 1-2% of patients (pts) harbor rearrangements resulting in RET fusions. In the first-in-human ARROW study (NCT03037385), BLU-667 has demonstrated significant clinical activity in RET-altered NSCLC and MTC and has been well tolerated. Previous data has shown that early declines in circulating tumor DNA (ctDNA) may predict for treatment outcome. We investigated the change in ctDNA levels from baseline following treatment with BLU-667 and whether early changes in ctDNA during treatment were associated with clinical responses and outcomes.Blood was collected at baseline and prespecified time points during treatment. Plasma from 111 pts with locally documented RET-altered MTC and NSCLC were profiled with the Personal Genome Diagnostics PlasmaSELECT™ R64 sequencing panel.RET fusions were detected at baseline in 45/63 (71%) pts with NSCLC and RET mutations in 35/48 (73%) pts with MTC. Baseline ctDNA mutant allele fraction (MAF; MTC) or unique fusion reads (NSCLC) correlated with the sum of target lesions (p<0.01). BLU-667 led to rapid RET ctDNA declines in almost all pts and across all doses (60-600mg QD, 100-200mg BID). Eighty-one percent of pts with NSCLC and detectable ctDNA at baseline had undetectable RET ctDNA after 8 weeks of treatment. Clearance of RET fusions in NSCLC was observed for multiple fusion partners including CCDC6 and KIF5B. Forty-one percent of pts with MTC harboring somatic RET mutations also had undetectable RET ctDNA after 8 weeks. The correlation between changes in ctDNA levels and clinical outcomes are currently not mature and will be reported at the meeting.Treatment with BLU-667 led to a robust and rapid decline in ctDNA in almost all patients regardless of treatment dose or tumor diagnosis and in NSCLC irrespective of fusion partner studied.NCT03037385.Blueprint Medicines Corporation.Blueprint Medicines Corporation.G. Curigliano: Honoraria (self), Advisory / Consultancy, Speaker Bureau / Expert testimony: Seattle Genetics; Honoraria (self), Advisory / Consultancy, Speaker Bureau / Expert testimony, Travel / Accommodation / Expenses: Roche; Honoraria (self), Advisory / Consultancy, Speaker Bureau / Expert testimony: Novartis; Honoraria (self), Advisory / Consultancy, Speaker Bureau / Expert testimony: Lilly; Honoraria (self), Advisory / Consultancy, Speaker Bureau / Expert testimony: BMS; Honoraria (self), Advisory / Consultancy, Speaker Bureau / Expert testimony, Travel / Accommodation / Expenses: Pfizer. V. Subbiah: Advisory / Consultancy: MedImmune; Research grant / Funding (institution): Novartis (Inst), GlaxoSmithKline (Inst), NanoCarrier (Inst), Northwest Biotherapeutics (Inst), Genentech (Inst), Roche (Inst), Berg Pharma (Inst), Bayer AG (Inst), Incyte (Inst), Fujifilm (Inst), PharmaMar (Inst), D3 Oncology Solutions (Inst), Pfizer (Ins; Travel / Accommodation / Expenses: PharmaMar, Bayer AG. J.F. Gainor: Honoraria (self): Merck, Incyte, ARIAD Pharmaceuticals, Novartis, Pfizer; Advisory / Consultancy: Genentech, Bristol-Myers Squibb, Theravance, Loxo, Takeda, Array BioPharma, Amgen, Merck, Agios, Regeneron, Oncorus, Jounce Therapeutics; Research grant / Funding (institution): Merck (Inst), Novartis (Inst), Genentech (Inst), Bristol-Myers Squibb (Inst), Adaptimmune (Inst), AstraZeneca (Inst), ARIAD Pharmaceuticals (Inst), Jounce Therapeutics (Inst), Blueprint Medicines (Inst), Moderna Therapeutics (Inst), Tesaro (Inst), Alexo T. D.H. Lee: Honoraria (self): AstraZeneca, Boehringer-Ingelheim, Bristol-Myers Squibb, CJ Healthcare, Eli Lilly, Janssen, Merck, MSD, Mundipharma, Novartis, Ono, Pfizer, Roche, Samyang Biopharm and ST Cube; Advisory / Consultancy: Ministry of Food and Drug Safety, Korea, Health Insurance Review and Assessment Service, Korea, National Evidence-based Collaborating Agency, Korea, and National Cancer Control Planning Board, Korea. M.H. Taylor: Honoraria (self), Advisory / Consultancy: BMS, Eisai Inc, Array Biopharma, Bayer, LOXO, Blueprint, Arqule, Novartis; Speaker Bureau / Expert testimony: BMS, Eisai Inc; Research grant / Funding (institution): BioAtla; Travel / Accommodation / Expenses: BMS, Eisai Inc, Array Biopharma, Bayer, Loxo, Blueprint. V. Zhu: Honoraria (self), Speaker Bureau / Expert testimony: AstraZeneca, Roche-Foundation Medicine, Roche/Genentech, Takeda; Advisory / Consultancy, Shareholder / Stockholder / Stock options: TP Therapeutics. R.C. Doebele: Honoraria (self): Pfizer, AstraZeneca, ARIAD Pharmaceuticals, Guardant Health, Takeda Pharmaceuticals, Spectrum Pharmaceuticals, Trovagene; Advisory / Consultancy: Pfizer, OncoMed Pharmaceuticals, Trovagene, Ignyta, GreenPeptide, AstraZeneca; Research grant / Funding (institution): Ignyta (Inst); Travel / Accommodation / Expenses: Ignyta, ARIAD Pharmaceuticals, Guardant Health; Shareholder / Stockholder / Stock options: Rain Therapeutics; Licensing / Royalties: Other Intellectual Property: Licensing fees from Abbott Molecular for patent PCT/US2013/057495, licensing fees from Ignyta for biologic materials (Inst). G. Lopes: Advisory / Consultancy: Pfizer; Research grant / Funding (self): AstraZeneca; Research grant / Funding (institution): Merck Sharp & Dohme (Inst); EMD Serono (Inst), AstraZeneca (Inst), AstraZeneca, Blueprint Medicines (Inst), Tesaro (Inst), Bavarian Nordic (Inst), Novartis (Inst), G1 Therapeutics (Inst). E. Garralda: Research grant / Funding (self), Research grant / Funding (institution): Novartis; Travel / Accommodation / Expenses: BMS, Menarini, Glycotope; Licensing / Royalties: MSD. S.M. Gadgeel: Advisory / Consultancy: Pfizer, Genentech, ARIAD Pharmaceuticals, AstraZeneca, Bristol-Myers Squibb, AbbVie; Speaker Bureau / Expert testimony: AstraZeneca; Research grant / Funding (self), Research grant / Funding (institution): Merck; Research grant / Funding (institution): Pfizer (Inst), Merck, Genentech (Inst), Blueprint Medicines (Inst), ARIAD Pharmaceuticals (Inst), Takeda (Inst); Travel / Accommodation / Expenses: ARIAD Pharmaceuticals, Takeda. C.D. Turner: Full / Part-time employment: Blueprint Medicines Corporation. M. Palmer: Full / Part-time employment: Blueprint Medicines Corporation. S. Miller: Full / Part-time employment: Blueprint Medicines Corporation. All other authors have declared no conflicts of interest

Identifying and targeting ROS1 gene fusions in non-small cell lung cancer

Purpose: Oncogenic gene fusions involving the 3\u2032 region of ROS1 kinase have been identified in various human cancers. In this study, we sought to characterize ROS1 fusion genes in non-small cell lung cancer (NSCLC) and establish the fusion proteins as drug targets. Experimental Design: An NSCLC tissue microarray (TMA) panel containing 447 samples was screened for ROS1 rearrangement by FISH. This assay was also used to screen patients with NSCLC. In positive samples, the identity of the fusion partner was determined through inverse PCR and reverse transcriptase PCR. In addition, the clinical efficacy of ROS1 inhibition was assessed by treating a ROS1-positive patient with crizotinib. The HCC78 cell line, which expresses the SLC34A2-ROS1 fusion, was treated with kinase inhibitors that have activity against ROS1. The effects of ROS1 inhibition on proliferation, cell-cycle progression, and cell signaling pathways were analyzed by MTS assay, flow cytometry, and Western blotting. Results: In the TMA panel, 5 of 428 (1.2%) evaluable samples were found to be positive for ROS1 rearrangement. In addition, 1 of 48 patients tested positive for rearrangement, and this patient showed tumor shrinkage upon treatment with crizotinib. The patient and one TMA sample displayed expression of the recently identified SDC4-ROS1fusion, whereas twoTMAsamples expressed theCD74-ROS1 fusion and two others expressed the SLC34A2-ROS1 fusion. In HCC78 cells, treatment with ROS1 inhibitors was antiproliferative and downregulated signaling pathways that are critical for growth and survival. Conclusions: ROS1 inhibition may be an effective treatment strategy for the subset of patients with NSCLC whose tumors express ROS1 fusion genes. Clin Cancer Res; 18(17); 4570-9. \ua92012 AACR