Trametinib (Trm) cardiotoxicity typically manifests as reversible contractile dysfunction in affected cancer patients.(15, 16) To determine whether rodents provide a suitable model for studying this adverse effect, we gavaged female mice with trametinib 3 mg/kg(1) or vehicle daily for 14 days (Figure 1A) leading to complete abrogation of ERK1/2 phosphorylation in heart lysates (Figure 1B). Here, MAPK3 is linked to cancer.