A pro-drug strategy to identify orally efficacious VLA-4 antagonists is described. Potential pro-drugs were evaluated for their physical chemical characteristics and in vitro properties, including solubility, stability, permeability and plasma stability. Based on this characterization, promising compounds were identified for in vivo pharmacokinetic evaluation. These studies resulted in the identification of a pro-drug that exhibited desirable blood levels in PK studies in several different species.