Cilengitide (EMD 121974) is the α_vβ₃ and α_vβ₅ integrin receptor antagonist. In cell adhesion studies assessing the human melanoma M21 or UCLA-P3 human lung carcinoma cell lines, Cilengitide inhibits integrin-mediated binding to vitronectin with IC₅₀s of 0.4 and 0.4 μM. In vitro treatment of Cilengitide, at a concentration greater than 1 µM, shows concentration- and time-dependent cytotoxic effects. However, lower doses of Cilengitide monotherapy (0.1 and 0.5 µM) does not elicit the effective death of the both U87MG and U251MG cells. Significant cytotoxic effects are observed in the U87MG cells with the addition of 1 µM Cilengitide in combination with Belotecan monotherapy at concentration of 6.25 nM. Higher concentrations of Cilengitide (5 and 25 µM) does not significantly increase cell death in the U87MG and U251MG compare to a lower concentration of Cilengitide (1 µM).