Erlotinib is the typical first treatment for patients with lung cancers that have the EGFR mutation. The cancer usually shrinks at first, but after awhile, it begins to grow again. The purpose of this study is to find the best dose of the combination of an investigational drug called SNX-5422 and erlotinib in patients whose lung cancers have started to grow on erlotinib treatment alone. The hope is that giving both drugs together will stop tumors from growing.
SNX-5422 works against cancer by blocking a protein that cancer cells need called HSP90. Laboratory studies have shown that combining SNX-5422 and erlotinib can shrink lung tumors that initially responded to erlotinib but are now growing. SNX-5422 has been assessed alone in patients, but this is the first study to combine SNX-5422 and erlotinib in patients. Both drugs are taken orally (by mouth).