Discovery of a potent, orally bioavailable pyrimidine VLA-4 antagonist effective in a sheep asthma model.

A series of N-(pyrimidin-4-yl)-phenylalanine VLA-4 antagonists is described. Optimization of substituents at the 2 and 5 positions of the pyrimidine ring gave 14, a very potent VLA-4 inhibitor which is orally active in a sheep asthma model.