This clinical trial is testing two medicines, *trametinib* and *azacitidine*, in kids with a type of blood cancer called juvenile myelomonocytic leukemia (JMML). JMML affects the blood and bone marrow. The trial is divided into two parts based on risk level. Lower-risk patients will receive trametinib and azacitidine, while higher-risk patients will receive these plus two more drugs, fludarabine and cytarabine.

**Key Points:**

• **Duration:** The treatment lasts up to a year (12 courses) for lower-risk and about two months (2 courses) for higher-risk patients.
• **Eligibility:** Must be 1 month to 21 years old, meet specific health criteria, and no prior leukemia treatments, except some allowed medicines.
• **Risks:** Cannot join if there's a known allergy to study drugs or certain other health issues, like infections or existing syndromes.

Before starting, doctors will check kidney, liver, heart, and reproductive health to ensure safety. Patients and families should discuss with doctors to understand the benefits and risks involved in participating.