CTLA4 and pachyonychia congenita: Preliminary results from a phase II study investigating the combination of the CTLA-4 inhibitor ipilimumab with the PD-1 inhibitor nivolumab showed a 25% response rate in men whose PC had progressed after second-generation hormonal therapy, and a 10% response rate in men whose PC had progressed after hormonal therapy and chemotherapy [4].