A Study of Alectinib in RET-rearranged Non-small Cell Lung Cancer or RET-mutated Thyroid Cancer

This is a Phase I/II research study, which means that researchers are testing different doses of the drug alectinib in participants with cancer to evaluate its safety, determine a safe dosage range, and identify side effects. The FDA (the U.S. Food and Drug Administration) has approved alectinib as a treatment option for NSCLC, but at a different dosage. There are two parts to this study, Phase 1 and Phase 2. In Phase 1, patients with ALK or RET rearranged NSCLC will receive different doses of alectinib to determine the highest dose that can be administered without severe or unmanageable side effects. This is called the maximum tolerated dose and will be the recommended dose for the next part of the study, Phase 2. A Phase I clinical trial tests the safety of an investigational drug and also tries to define the appropriate dose of the investigational drug to use for further studies. "Investigational" means that the drug is being studied. During Phase 2, participants with RET rearranged NSCLC or thyroid cancer will be given the maximum tolerated dose. During both Phase 1 and Phase 2, the investigators will determine the effect alectinib has on the body, and the effect alectinib has on cancer. Alectinib belongs to a class of drugs known as tyrosine kinase inhibitors, which stop tyrosine kinases from working. Tyrosine kinases are enzymes that are responsible for activating many proteins in the body's cells. The ALK and RET kinases play an important role in the survival and growth of tumor cells and in the ability of tumor cells to spread to different parts of the body. In laboratory studies and in patients, alectinib has been shown to block the ALK and RET kinases. By blocking these kinases and stopping them from working, it is hoped that alectinib may prevent the survival of tumor cells in addition to stopping their growth and ability to spread. The purpose of this research study is to learn about the effects of the study drug alectinib, and to find the best dose for treating ALK-positive or RET-positive cancers.