Study of Hsp90 Inhibitor, STA-9090 for Relapsed or Refractory Small Cell Lung Cancer

Small cell lung cancer (SCLC) is a chemotherapy and radiotherapy sensitive tumor, but with very high rates of relapse and metastasis, resulting in a very poor outcome. Among limited-stage patients, the relapse rate is at least 80% and among extensive-stage patients, the relapse rate is 95-98%. The impetus to develop more effective therapies against novel targets in SCLC is therefore high. Hsp-90 inhibitors are a new class of drugs with important anti-malignant potential in a variety of tumor types because of the reliance of multiple oncoproteins on Hsp90 function. Although small cell neuroendocrine tumors generally carry many mutated oncoproteins, without clearly defined clients for Hsp90 mediating inhibitor effects in these cells, a recent study demonstrated that Hsp90 inhibition causes massive apoptosis by activating the intrinsic apoptotic pathway in a number of SCLC cell lines. SCLC is a particularly attractive target for apoptosis inducing drugs because of high growth rates and evidence of molecular alterations affecting apoptotic mechanisms. 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. Based on the anti-tumor potential seen pre-clinically with Hsp90 inhibition, the potent effects of STA-9090 seen pre-clinically as compared with other inhibitors in the same class, as well as early data suggesting safety and tolerability of this drug in the Phase I setting, we propose to study the single-agent activity of STA-9090 in a Phase II trial of patients with relapsed or refractory small cell lung cancer.