Combining Neratinib with CDK4/6, mTOR, and MEK Inhibitors in Models of HER2-positive Cancer

Purpose: Neratinib is an irreversible, pan-HER tyrosine kinase inhibitor that is FDA approved for HER2-overexpressing/amplified (HER2(+)) breast cancer. In this preclinical study, we explored the efficacy of neratinib in combination with inhibitors of downstream signaling in HER2(+) cancers in vitro and in vivo. Experimental Design: Cell viability, colony formation assays, and Western blotting were used to determine the effect of neratinib in vitro. In vivo efficacy was assessed with patient-derived xenografts (PDX): two breast, two colorectal, and one esophageal cancer (with HER2 mutations). Four PDXs were derived from patients who received previous HER2-targeted therapy. Proteomics were assessed through reverse phase protein arrays and network-level adaptive responses were assessed through Target Score algorithm. Results: In HER2(+) breast cancer cells, neratinib was synergistic with multiple agents, including mTOR inhibitors ever-olimus and sapanisertib, MEK inhibitor trametinib, CDK4/6 inhibitor palbociclib, and PI3Ka inhibitor alpelisib. We tested efficacy of neratinib with everolimus, trametinib, or palbociclib in five HER2 (+) PDXs. Neratinib combined with everolimus or trametinib led to a 100% increase in median event-free survival ( EFS; tumor doubling time) in 25% (1/4) and 60% (3/5) of models, respectively, while neratinib with palbociclib increased EFS in all five models. Network analysis of adaptive responses demonstrated upregulation of EGFR and HER2 signaling in response to CDK4/6, mTOR, and MEK inhibition, possibly providing an explanation for the observed synergies with neratinib. Conclusions: Taken together, our results provide strong preclinical evidence for combining neratinib with CDK4/6, mTOR, and MEK inhibitors for the treatment of HER2(+) cancer.

Automated summary

In this preclinical study, neratinib showed synergistic effects with multiple agents in HER2(+) breast cancer cells, and combination with CDK4/6, mTOR, and MEK inhibitors demonstrated significant efficacy in patient-derived xenograft models. These findings provide strong preclinical evidence for the combination therapy of neratinib with CDK4/6, mTOR, and MEK inhibitors for HER2(+) cancer treatment.