Enasidenib in IDH2-Mutated Malignant Sinonasal and Skull Base Tumors

Background: Cancers of the nasal cavity or skull base are rare. They often are not diagnosed until they are at an advanced stage, and they often spread to other parts of the body. These cancers may have mutations in a gene called IDH2. Researchers want to find out if a drug (enasidenib) that targets the IDH2 mutation can help people with these cancers. Objective: To test enasidenib in people with cancers of the nasal cavity or skull base. Eligibility: People aged 18 years and older with rare cancers of the nasal cavity or the base of the skull. Their cancer must have an IDH2 gene mutation, and it must have recurred locally or spread to other parts of the body. These cancers can include sinonasal undifferentiated carcinoma; olfactory neuroblastoma; sinonasal large-cell neuroendocrine carcinoma; poorly differentiated sinonasal adenocarcinoma; or chondrosarcoma. Design: Participants will be screened. They will have a physical exam with blood and urine tests and tests of their heart function. They will have imaging scans of their brain, skull base, neck, chest, abdomen, and pelvis. A sample of tumor tissue will be collected. Enasidenib is a tablet taken by mouth with a glass of water. Participants will take the drug once a day, every day, in 28-day cycles. They will not have resting periods between cycles. Participants will visit the clinic on the first day of each cycle to receive the tablets they will need to take at home until the beginning of the next cycle. They will keep a diary to record the time of each dose they take. Participants may remain in the study as long as the drug is helping them....