Dual therapy with fulvestrant and the irreversible HER2 kinase inhibitor neratinib reversed treatment-acquired hormone resistance in metastatic estrogen receptor (ER)–positive breast cancer cells.
Elaine Mardis, PhD, a spokesperson for the American Association of Cancer Research, hailed the research by Utthara Nayar, PhD, and colleagues as “groundbreaking and unexpected” during a briefing held in advance of the annual meeting of the American Association for Cancer Research. The lab experiments were part of a whole-exome sequencing study of metastatic ER-positive tumor biopsies from 168 patients, 12 of whom had acquired the HER2 mutations, said Dr. Nayar of the Dana-Farber Cancer Institute, Boston.
The findings have prompted a phase 2 trial of the combination, which is now recruiting patients, Dr. Nayar said. The 5-year study seeks 152 women with inoperable locally advanced or metastatic ER-positive breast cancer with a confirmed HER2-positive mutation. Patients will be randomized to the combination of neratinib and fulvestrant or to neratinib alone. The primary outcome is progression-free survival.
“We also hope to be able to develop upfront combinations to preempt the resistance and lead to more durable responses,” Dr. Nayar said.