Eltanexor Plus Inqovi

Background: Myelodysplastic syndromes (MDS) are diseases that affect the bone marrow. They can inhibit the blood formation process and reduce blood cell counts. High-risk MDS can lead to leukemia. People with high-risk MDS have a low survival rate. Better treatments are needed. Objective: To test a study drug (KPT-8602), combined with another drug (Inqovi), in people with MDS. Eligibility: Adults aged 18 years and older with high-risk MDS that did not respond to treatment. Design: Participants will be screened. They will have a physical exam. They will have blood and urine tests and tests of their heart function. They may have a bone marrow biopsy: Their hip will be numbed; then a needle will be inserted to draw out a sample of soft tissue from inside the bone. They will answer questions about their quality of life. Genetic tests may be performed. KPT-8602 and Inqovi are both tablets taken by mouth. Participants will take these drugs at home on a 28-day cycle. They will take Inqovi once a day on days 1 to 5. They will take KPT-8602 on a schedule assigned by the researcher. Participants will be given a drug diary to record each dose. Participants will visit the clinic for an exam at least once in each cycle. Some tests, including the bone marrow biopsy, may be repeated. Participant will continue treatment for at least 6 cycles. If their disease improves, they may continue taking the drugs after 6 cycles. Participants will have follow-up visits at the clinic for about 8 years.