These data compare favorably with erlotinib, which has previously demonstrated a low nanomolar IC50 in vitro.21 In addition to EGFR inhibition, WSD-0922 has specificity for Ephrin receptors, HER4, and Src Family Kinase (SFK) members (Table 1), targets that have been associated with EGFR tyrosine kinase inhibitor resistance22,23 and thus could augment the clinical effectiveness of the drug in GBM. Here, EGFR is linked to glioblastoma.