Description_x000D_ Biochem/physiol Actions_x000D_ BIO 1211 is a selective, tight-binding α4β1 (VLA-4, very late antigen-4; koff = 1.4 x 10-4/s, KD = 70 pM) integrin antagonist (VCAM-Ig Jurkat surface binding IC50 = 1 nM; integrin-mediated cell adhesion IC50 = 4 nM/α4β1, 2 μM/α4β7, >100 μM/α1β1, α5β1, α6β1, αLβ2, αIIBβ3) based on the Leu-Asp-Val (LDV) sequence from the alternatively spliced connecting segment-1 (CS-1) of fibronectin (aa 1980-1983). In addition to probing α4β1-mediated cellular responses, BIO 1211 is also widely used in animal disease models in vivo, including MS (5-10 mg/kg; murine EAE) and asthma (1-10 mg/kg via intranasal or nebulizer to mice, rats, sheep; 3 mg/sheep iv.).