MDM2 degrader activates wild-type p53 in Merkel cell carcinoma
This study explores the efficacy of MDM2 degraders, KTX-049 and KT-253, in treating Merkel cell carcinoma (MCC), an aggressive skin cancer. MCC tumors often exhibit clonal integration of Merkel cell polyomavirus, with virus-positive (MCCP) and virus-negative tumors showing distinct molecular profiles. MDM2, a key target of the ST-MYCL-Tip60 complex in MCCP, inhibits p53-mediated tumor suppression. Our results demonstrate that KTX-049 is over 100 times more potent than the MDM2 inhibitor DS-3032 in MCC cell lines with wild-type p53, effectively degrading MDM2 and activating a p53 response. Mathematical modeling suggests that KTX-049 disrupts the p53-MDM2 feedback loop, enhancing its potency. In vivo, KT-253 showed significant tumor growth inhibition in patient-derived xenograft models. However, observed resistance was linked to TP53 mutations. These findings highlight the potential of MDM2 degraders as a therapeutic strategy for MCC tumors with wild-type p53 and underscore the need for further investigation into resistance mechanisms and combination therapies.