Since adding the CTLA-4 inhibitor ipilimumab has already shown anti-tumor activity in PD-1-refractory patients with metastatic MCC [7], combined ICB according to the ongoing CheckMate-358 study (NCT02488759) seems to be a promising treatment option for avelumab-refractory patients. The gene discussed is CTLA4; the disease is Merkel cell skin cancer.