KRAS and breast cancer: In summary, we described the efficacy of MSU42011 in preclinical models of HER2-positive breast cancer and A/J lung cancer with an activating Kras mutation, its ability to increase anti-tumor immune cell populations in both animal models, and the ability of this novel RXR agonist to further decrease tumor burden when combined with anti-PD1 and anti-PDL1 antibodies.