ribociclib and erdafitinib

Using an ORF kinome screen in MCF-7 cells treated with the CDK4/6 inhibitor ribociclib plus fulvestrant, we identified FGFR1 as a mechanism of drug resistance. FGFR1-amplified/ER+ breast cancer cells and MCF-7 cells transduced with FGFR1 were resistant to fulvestrant ± ribociclib or palbociclib. This resistance was abrogated by treatment with the FGFR tyrosine kinase inhibitor (TKI) lucitanib. Addition of the FGFR TKI erdafitinib to palbociclib/fulvestrant induced complete responses of FGFR1-amplified/ER+ patient-derived-xenografts. Next generation sequencing of circulating tumor DNA (ctDNA) in 34 patients after progression on CDK4/6 inhibitors identified FGFR1/2 amplification or activating mutations in 14/34 (41%) post-progression specimens. Finally, ctDNA from patients enrolled in MONALEESA-2, the registration trial of ribociclib, showed that patients with FGFR1 amplification exhibited a shorter progression-free survival compared to patients with wild type FGFR1. Thus, we propose breast cancers with FGFR pathway alterations should be considered for trials using combinations of ER, CDK4/6 and FGFR antagonists.

Topics: Aminopyridines; Animals; Antineoplastic Agents, Hormonal; Antineoplastic Combined Chemotherapy Protocols; Breast Neoplasms; Circulating Tumor DNA; Cyclin D1; Cyclin-Dependent Kinase 4; Cyclin-Dependent Kinase 6; Drug Resistance, Neoplasm; Female; Fulvestrant; High-Throughput Nucleotide Sequencing; Humans; MCF-7 Cells; Mice; Mutation; Naphthalenes; Piperazines; Progression-Free Survival; Proportional Hazards Models; Protein Kinase Inhibitors; Purines; Pyrazoles; Pyridines; Quinolines; Quinoxalines; Receptor, Fibroblast Growth Factor, Type 1; Receptor, Fibroblast Growth Factor, Type 2; Receptors, Estrogen; Signal Transduction; Xenograft Model Antitumor Assays