Introduction:Myeloid/lymphoid neoplasmswith fibroblast growth factor receptor 1 rearrangement (MLN FGFR1) are aggressive hematologic neoplasms caused by various reciprocal translocations involving chromosome band 8p11, resulting in tyrosine kinase fusion genes (eg, ZMYM2::FGFR1 from t[8;13][p11;q12] or BCR::FGFR1 from t[8;22][p11;q11]) and constitutive FGFR1 activationand downstream signaling. Pemigatinib is a potent and selective oral inhibitor of FGFR1-3 approved for the treatment of adults with relapsed or refractory MLN FGFR1. Efficacy and safety data for 41 patients with MLN FGFR1 in the ongoing FIGHT-203 study of pemigatinib were previously reported. Median daily pemigatinib dose was 9.5 mg; treatment-emergent adverse events led to dose interruptions in 66% of patients. Rates of complete response (CR) among the 38 patients evaluable for clinical response and rates of complete cytogenetic response (CCyR) for the 40 patients evaluable for cytogenetic response were 74% and 70%, respectively. CR and CCyR occurred in >80% of patients with chronic phase disease and in >50% of patients with blast phase disease. Here we present an analysis of centralized fluorescence in situ hybridization (FISH) evaluation of bone marrow (BM) cells and serial characterization of levels of FGFR1 fusion transcripts in this same cohort.
Methods: FIGHT-203 (NCT03011372) is an ongoing open-label, multicenter, phase 2 study evaluating pemigatinib in patients ≥18 years old with MLN FGFR1 and ≥1 prior therapy. The starting dose was pemigatinib 13.5 mg daily (2 weeks on, 1 week off). Following protocol amendments, patients without prior therapy were eligible to enroll, and the dosing regimen was changed to a continuous schedule. Patients were censored for cytogenetic and molecular follow-up at the time of transplantation. CCyR was defined as 0 metaphases positive for the respective reciprocal translocation in ≥20 evaluated BM metaphases on local and/or central karyotyping or 0 cells (or not exceeding the lower level of detection of the probe) with the FGFR1 rearrangement in ≥200 BM cells on local and/or central break-apart FISH assays (central FISH prioritized). As part of the translational research plan, fusion partner genes were identified with next-generation sequencing (NGS; FusionPlex, Archer, Boulder, CO, USA) and targeted PCR profiling of RNA extracted from whole blood; droplet digital PCR (ddPCR) assays were developed to monitor the frequencies of specific FGFR1 fusion transcripts in RNA extracted from whole blood samples (estimated limit of detection, 0.05 copies/μL).
Results: As of June 30, 2021, 39 of 41 enrolled and treated patients were evaluable for translational analyses. Among the 39 patients with whole blood samples, FGFR1 fusion partner genes identified on translational testing were ZMYM2 (n=17), BCR (n=11), FGFR1OP (n=4), TPR (n=3), TRIM24 (n=2), and C14orf93, CCDC6, CNTRL and ETV6 (n=1 each). Two of 39 patients had 2 fusions detected ( ZMYM2 and BCR, n=1; ZMYM2 and TPR, n=1). C14orf93, CCDC6 and ETV6 have not been previously identified as FGFR1 fusion partner genes. Central FISH assessment of BM cells confirmed FGFR1-aberrantcells were reduced to undetectable levels in responding patients but rebounded in some patients during periods of treatment interruption (Figure A). Serial ddPCR of whole blood samples demonstrated marked reductions in FGFR1 fusion transcripts for the 34 patients with ≥3 measures while on treatment (Figure B). Among patients with CR, 81.0% had a >2-log reduction and 47.6% had a >3-log reduction in detectable FGFR1 fusion transcripts. Smaller reductions in FGFR1 fusion transcripts were observed in patients with stable disease. Changes in FGFR1 fusion transcripts correlated with FGFR1 FISH results (Pearson coefficient = 0.81) and reflected changes in treatment intensity.
Conclusion:Several new FGFR1 fusion partner genes, including C14orf93, CCDC6, and ETV6 were identified with NGS and PCR profiling. Pemigatinib treatment resulted in marked decreases in the percentages of cells with the FGFR1 rearrangement on FISH, as well as 2-3 log reductions in FGFR1 fusion transcripts in patients with MLN FGFR1. Further investigations are ongoing to determine the relationship between pemigatinib dose intensity and the depth and durability of molecular response.
Disclosures
Reiter:AOP Orphan Pharmaceuticals: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Blueprint Medicines Corporation: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte Corporation: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Kiladjian:Incyte Corporation: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; AOP Orphan Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; AbbVie, AOP Health, Bristol-Myers Squibb, GlaxoSmithKline, Incyte, Novartis, Pharmaessentia.: Consultancy. Patel:Cogent Biosciences: Consultancy, Membership on an entity's Board of Directors or advisory committees; Blueprint Medicines Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS/Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees. Shomali:Blueprint Medicines Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Rambaldi:Abbvie: Honoraria. Verstovsek:Roche: Research Funding; Protagonist Therapeutics: Research Funding; PharmaEssentia: Research Funding; Promedior: Research Funding; Ital Pharma: Research Funding; AstraZeneca: Research Funding; Blueprint Medicines Corporation: Research Funding; NS Pharma: Research Funding; Novartis: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Constellation Pharmaceuticals: Consultancy; Pragmatist: Consultancy; Sierra Oncology: Consultancy, Research Funding; CTI BioPharma Corp.: Research Funding; Genentech: Research Funding; Gilead: Research Funding; Incyte Corporation: Consultancy, Research Funding. Oh:Abbvie: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Cogent: Membership on an entity's Board of Directors or advisory committees; Constellation/Morphosys: Membership on an entity's Board of Directors or advisory committees; CTI Biopharma: Membership on an entity's Board of Directors or advisory committees; Geron: Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Membership on an entity's Board of Directors or advisory committees; Morphic: Membership on an entity's Board of Directors or advisory committees; Protagonist: Membership on an entity's Board of Directors or advisory committees; Sierra Oncology/GSK: Membership on an entity's Board of Directors or advisory committees. Usuki:Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; SymBio: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Yauklt: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Nippon Shinyaku: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Ohara: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Ono: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Otsuka: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sando: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sumitomo-Dainippon: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Kyowa-Kirin: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; MSD: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Mundi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Chugai: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Daichi Sankyo: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Eisai: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte Corporation: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Aperis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Alnylam Japan: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Alxion: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Harrison:BMS: Honoraria, Speakers Bureau; Morphosys: Honoraria, Speakers Bureau; Abbvie: Honoraria, Speakers Bureau; Galecto: Honoraria, Speakers Bureau; AOP: Honoraria, Speakers Bureau; GSK: Honoraria, Speakers Bureau; CTI: Honoraria, Speakers Bureau; Novartis: Honoraria, Research Funding, Speakers Bureau. Ritchie:Bristol Myers Squibb: Consultancy, Research Funding; Celgene: Other: Travel Support, Speakers Bureau; Novartis: Consultancy, Other: Travel Support, Research Funding, Speakers Bureau; Astellas Pharma, Jazz Pharmaceuticals, NS Pharma: Research Funding; Ariad: Speakers Bureau; Celgene, Incyte Corporation, Novartis: Consultancy; Pfizer: Consultancy, Other: travel, Research Funding. Akard:Sanofi: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Beigene: Consultancy, Honoraria; Astellas: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Incyte Corporation: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Hernandez Boluda:Pfizer, BMS, Incyte, and Novartis: Membership on an entity's Board of Directors or advisory committees. Huguet:Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Clinign: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Servier: Consultancy, Membership on an entity's Board of Directors or advisory committees. Oliveira:Incyte Corporation: Current Employment, Current equity holder in publicly-traded company. Zhen:Incyte Corporation: Current Employment, Current equity holder in publicly-traded company. George:Celgene/BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Blueprint Medicines Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees; ARUP Laboratories: Current Employment; Cogent Biosciences: Consultancy, Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees. Colucci:Incyte Corporation: Current Employment, Current equity holder in publicly-traded company. Gilmartin:Incyte Corporation: Current Employment, Current equity holder in publicly-traded company. Gotlib:Abbvie, Blueprint Medicines Corporation, BMS, Cogent Biosciences, Incyte Corporation, and Protagonist Therapeutics: Research Funding. Vannucchi:Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Incyte: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Blueprint: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Imago BioSciences, Inc., a subsidiary of Merck & Co., Inc., Rahway, NJ, USA: Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AOP: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; GSK: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.
