We tested the effect of MSI-1436 (Supplemental Figure 1A; supplemental material available online with this article; https://doi.org/10.1172/jci.insight.158199DS1), an allosteric inhibitor of PTP1B for which efficacy and specificity has been demonstrated in animal models of HER2+ breast cancer (19). This evidence concerns the gene PTPN1 and breast cancer.