4-IBP is a selective σ1 agonist with a high level of affinity for the σ1 receptor (Ki = 1.7 nM) and a moderate affinity for the σ2 receptor (Ki = 25.2 nM) . IC50 value: 1.7 nM (Ki) Target: σ1 in vitro: 4-IBP is a σ1 receptor agonist, decreases the migration of human cancer cells, including glioblastoma cells. 4-IBP is used to investigate whether targeting theσ1 receptor could modify in vitro the migration rates of human cancer cells and increase the sensitivity of metastasizing human A549 NSCLC cells and infiltrating human glioblastoma cells to cytotoxic insults of either proapoptotic or proautophagic drugs.[1] in vivo: 4-IBP increases the antitumor effects of temozolomide and irinotecan in immunodeficient mice that were orthotopically grafted with invasive cancer cells.[1]