A phase I, first-in-human study reveals for the first time, an investigational drug that is effective and safe for patients with cancers caused by an alteration in the receptor tyrosine kinase known as RET. The drug appears to be promising as a potential therapy for RET-driven cancers, such as medullary and papillary thyroid, non-small cell lung, colorectal and bile duct cancers, which have been historically difficult to treat.