Hsp90 inhibitors are also effective at inhibiting EML4-ALK-driven tumourigenesis in vivo in the mouse [22,23], and the treatment of three ALK+ NSCLC patients with the Hsp90 inhibitor, IPI-504, resulted in a partial response in two of the patients and stable disease in the other [25]. The gene discussed is EML4; the disease is non-small cell lung carcinoma.