HER-2 T798I

These findings were consistent with those reported for SUMMIT hormone receptor-positive (HR+) HER2-mutant mBC cohorts, in which patients treated with N or N + fulvestrant (N+F) experienced promising clinical responses but shorter DOR. Although limited by small numbers, addition of T to N in patients with HER2-mutant mTNBC, despite deepening and prolonging response, did not appear to preclude eventual emergence of either on-pathway (ERBB3) or off-pathway (KRAS, TP53) mutations. In contrast to observations in N+F+T-treated patients with HR+, HER2-mutant disease, no additional HER2 alterations were detected upon progression in N+T-treated patients with mTNBC in this small dataset. Future investigations may evaluate clinical utility of sequencing therapies targeted to mutations acquired in response to N-based therapy in patients with HER2-mutant mTNBC.

HER2 mutations drive the growth of a subset of breast cancers and are targeted with HER2 tyrosine kinase inhibitors (TKI) such as neratinib...Cells expressing double HER2 mutations exhibited resistance to most HER2 TKIs but retained sensitivity to mobocertinib and poziotinib...Double-mutant cells showed enhanced MEK/ERK signaling, which was blocked by combined inhibition of HER2 and MEK. Together, these findings reveal the driver function of secondary HER2 mutations in resistance to HER2 inhibition and provide a potential treatment strategy to overcome acquired resistance to HER2 TKIs in HER2-mutant breast cancer.

Introduction: The irreversible pan-HER inhibitor NER showed modest single agent activity for HER2mut MBC in Part I of MutHER trial. NER, or N+F, is active for HER2mut MBC with good tolerability. Adding trastuzumab at PD induced further response, supporting dual HER2 blockade for HER2mut MBC.

P2, N=150, Recruiting, Spectrum Pharmaceuticals, Inc | Not yet recruiting --> Recruiting