STA-9090 is a novel, small-molecule inhibitor of Hsp90. Unlike earlier generations of Hsp90 inhibitors, STA-9090 has been shown to be a potent inducer of apoptosis in a variety of cell lines and has anti-tumor activity in multiple types of human xenografts. As was seen with other Hsp90 inhibitors, STA-9090 also induces apoptosis in a number of SCLC cell lines.