A series of 18 new imidazo [2, 1-b] thiazole derivatives was synthesized. Their in vitro antiproliferative activities against A375P human melanoma cell line and NCI-60 cell line panel were tested. Compounds 15, 16, 18, 22, 26–28, and 31 showed superior potency against A375P to sorafenib. In addition, compounds 26 and 27 showed selectivity toward melanoma cell lines than for other cancer types. Both compounds exerted sub-micromolar ...