Drugs known as EGFR inhibitors—such as erlotinib (Tarceva), gefitinib (Iressa), and afatinib (Gilotrif)—are very effective in treating non-small cell lung cancer (NSCLC) with mutations in the EGFR gene. However, patients eventually develop drug resistance, usually caused by new EGFR mutations. T790M is the most common EGFR drug resistance mutation. CO-1686 is a novel drug that inhibits EGFR with the T790M mutation, as well as other mutant EGFR. A small study showed that eight of nine patients who had the T790M resistance mutation experienced more than 10% tumor shrinkage when treated with CO-1686. And, a new formulation of CO-1686 has been found to produce higher, more consistent, well-tolerated drug concentrations in patients.