This phase I trial evaluates the side effects and best dose of selinexor and venetoclax in combination with chemotherapy in treating patients with acute myeloid leukemia or acute leukemia of ambiguous linage that has come back (relapsed) or does not respond to treatment. Venetoclax may stop the growth of cancer cells by blocking Bcl-2, a protein needed for cancer cell survival. Selinexor may stop the growth of cancer cells by blocking CRM1, which help the body's immune system to find and kill cancer cells. Chemotherapy drugs, such as fludarabine and cytarabine, work in different ways to stop the growth of cancer cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Colony-stimulating factors, such as granulocyte colony-stimulating factor, may increase the production of blood cells and may help the immune system recover from the side effects of chemotherapy. Giving venetoclax and selinexor with chemotherapy may help control the disease in patients with acute myeloid leukemia or acute leukemia of ambiguous lineage.

Severe Aplastic Anemia (SAA) is a rare condition in which the body stops producing enough new
blood cells. SAA can be cured with immune suppressive therapy or a bone marrow transplant.
Regular treatment for patients with aplastic anemia who have a matched sibling (brother or
sister), or family donor is a bone marrow transplant. Patients without a matched family donor
normally are treated with immune suppressive therapy (IST). Match unrelated donor (URD) bone
marrow transplant (BMT) is used as a secondary treatment in patients who did not get better
with IST, had their disease come back, or a new worse disease replaced it (like leukemia).

This trial will compare time from randomization to failure of treatment or death from any
cause of IST versus URD BMT when used as initial therapy to treat SAA.

The trial will also assess whether health-related quality of life and early markers of
fertility differ between those randomized to URD BMT or IST, as well as assess the presence
of marrow failure-related genes and presence of gene mutations associated with MDS or
leukemia and the change in gene signatures after treatment in both study arms.

This study treatment does not include any investigational drugs. The medicines and procedures
in this study are standard for treatment of SAA.

This is a global, multicenter Phase 1/3 study to evaluate the efficacy and safety of
selinexor plus ruxolitinib in JAK inhibitor (JAKi) treatment-nave myelofibrosis (MF)
participants. The study will be conducted in two phases: Phase 1 (open-label) and Phase 3
(double-blind). Phase 1 (enrollment completed) was an open-label evaluation of the safety and
recommended dose (RD) of selinexor in combination with ruxolitinib and included a dose
escalation using a standard 3+3 design (Phase 1a) and a dose expansion part (Phase 1b). In
Phase 3, JAKi treatment-nave MF participants are enrolled in 2:1 ratio to receive the
combination therapy of selinexor + ruxolitinib or the combination of placebo + ruxolitinib.