GPR84 antagonist 2 (compound 33) is a potent, selective, and orally active GPR84 antagonist (IC50=8.95 nM). GPR84 antagonist 2 shows improved potency in the calcium mobilization assay and the ability to inhibit the chemotaxis of neutrophils and macrophages upon GPR84 activation. GPR84 antagonist 2 has the potential for the research of ulcerative colitis.