However, the Adnectin showed a lack of required efficacy in phase 2 clinical trials treating recurrent glioblastoma [48], which was suspected to be caused by a lack of clinical effect from inhibiting VEGFR2 (vascular endothelial growth factor receptor-2) activity (possibly related to broader failures in treatment through the VEGF pathway [49] or from issues with pharmacokinetics of the small Adnectin scaffold). This evidence concerns the gene KDR and glioblastoma.