CTLA4 and gastrointestinal stromal tumor: A clinical study using IM in combination with the CTLA-4 inhibitor Ipilimumab in 10 patients with advanced GISTs showed that 9 patients (8 with mutations in KIT exon 11 and 1 with a mutation in KIT exon 13) all progressed, but in 1 case of WT GIST, the tumor shrank by 68% (37).