CLM3, a pyrazolopyrimidine derivative, is a multiple tyrosine kinase inhibitor. CLM3 shows antiproliferative and proapoptotic activity on endothelial and cancer cells, synergistically enhanced by SN38. These effects are mainly due to its inhibition of phosphorylation of VEGFR-2 , EGFR and RET tyrosine kinases and their related signaling pathways.