This study is for kids and young adults with a brain cancer called low-grade glioma. It will test if a drug called vinblastine helps another drug called selumetinib work better. Selumetinib works by stopping cancer cells from growing, and vinblastine helps stop these cells from dividing. The study has two parts: one part tests the best dose of vinblastine, and the other compares selumetinib alone to both drugs together. The study includes regular MRIs to check how well the treatment is working. This will last for up to 27 cycles, with each cycle lasting 28 days. After treatment, the patients will have check-ups every few months for up to 5 years.

• Time Commitment: The treatment lasts up to 2.5 years, with follow-ups for 5 years.
• Participation Requirements: You must be between 2-25 years old and have progressive or recurrent low-grade glioma.
• Potential Risks: The study will examine the side effects of the treatment.