A UGT1A1 Genotype-Directed Study of Belinostat Pharmacokinetics and Toxicity

Background: High-grade neuroendocrine carcinomas (HGNEC) are cancers that develop in different parts of the body, including the digestive tract, genitals, neck, and head. One drug (belinostat), combined with 2 other drugs (etoposide and cisplatin), is approved to treat HGNEC. But some people may have a gene variant that affects how quickly their body gets rid of the drug; these people may do better with different dosages of belinostat. Objective: To test higher or lower doses of belinostat based on gene variants in people with HGNEC. Eligibility: People aged 18 years and older with HGNEC. Design: Participants will be screened. They will have a physical exam with blood tests. Some blood will be used for genetic testing. They will have imaging scans and a test of their heart function. Samples of tumor tissue may be collected. All 3 study drugs (belinostat, etoposide, cisplatin) are given through a tube attached to a needle inserted into a vein. Treatment will be given in 21-day cycles. For cycles 1 through 6: Participants will come to the clinic for the first 4 days. They will be given all 3 drugs. Imaging scans and other tests will be repeated. Each visit will last 4 to 8 hours. After cycle 6: Participants may continue treatment with belinostat alone. They will come to the clinic for the first 3 days of each cycle. They may continue treatment for up to 5 years if the drug is helping them. Participants will have a follow-up visit 30 days after their last dose of belinostat. Then they will receive follow-up visits by phone or email every 3 to 6 months.