GSK-1904529A, also known as GSK 4529, is an IGF-1R Inhibitor, is is a promising candidate for therapeutic use in IGF-IR–dependent tumors. GSK1904529A selectively inhibits IGF-IR and IR with IC50s of 27 and 25 nmol/L, respectively. GSK1904529A blocks receptor autophosphorylation and downstream signaling, leading to cell cycle arrest. It inhibits the proliferation of cell lines derived from solid and hematologic malignancies, with multiple myeloma and Ewing's sarcoma cell lines being most sensitive. Oral administration of GSK1904529A decreases the growth of human tumor xenografts in mice, consistent with a reduction of IGF-IR phosphorylation in tumors. Despite the potent inhibitory activity of GSK1904529A on IR in vitro and in vivo , minimal effects on blood glucose levels are observed in animals at doses that show significant antitumor activity. (source: Clin Cancer Res May 1, 2009 15; 3058 )