Primary Objectives~To determine the safety and tolerability of fulvestrant, palbociclib and erdafitinib in patients with ER+/HER2-/FGFR-amplified MBC.~Secondary Objectives~To determine the anti-tumor effect of fulvestrant, palbociclib and erdafitinib in patients with ER+/HER2-/FGFR-amplified MBC.~Pharmacokinetic assessments of erdafitinib~Correlative Objectives~To determine the therapeutic predictive role of FGFR1-4, CCND1-2, CDK4 and CDK6 amplifications, and RB1 and ESR1 mutations on clinical outcome~To determine if the FGFR1 amplification levels is an early surrogate of response~To determine if the cfDNA results at disease progression show new genomic alterations potentially associated with resistance to CDK4/6 and FGFR inhibition~To determine pharmacodynamic biomarkers of FGFR inhibition
This is an open-label, multi-institution, phase Ib trial that evaluates the safety and tolerability and preliminary anti-tumor activity of fulvestrant, palbociclib and erdafitinib in patients with ER+/HER2-/FGFR-amplified metastatic breast cancer.