MK-0812 is a potent and selective CCR2 antagonist, which was developed by Merck. This drug has entered clinical trials for both rheumatoid arthritis and multiple sclerosis. However, the rheumatoid arthritis trial was terminated because of lack of favorable outcomes when MK-0812 failed to show any early clinical improvement. The outcome of the multiple sclerosis trial of MK-0812 also had negative outcomes.