This study has several parts and involves taking a study drug called alpelisib. Some participants enrolled into Stage 2 will receive a placebo for the first part of the study (24 weeks) and will then receive the study drug. The purpose of this study is to find out if the study drug is safe and effective (can help) people with a confirmed diagnosis of lymphatic malformation (LyM) and a documented mutation in the PIK3CA gene

This study involves taking a study drug called venetoclax with or without standard of care chemotherapy. The overall goal of this study is to see if adding venetoclax to standard chemotherapy leads to improved survival for children and young adults with relapsed acute myeloid leukemia (AML). The study may last up to 9 years and will enroll male and female patients from the ages of 29 days to 21 years of age.

Children (less than 10 years of age) are eligible if they have been diagnosed with either a medulloblastoma tumor or CNS embryonal tumors of the brain or spinal cord. The standard approach to the treatment of these brain tumors in young children may include surgery, radiation therapy to the brain and spinal cord and chemotherapy. Radiation therapy is the use of high energy x-rays to kill cancer cells. Chemotherapy means treatment with cancer killing drugs. This research study will compare two different treatment regimens to see which is better for treating children with this type of brain cancer.

The purpose of this study is to see if a new investigational topical (applied to the skin) formulation of sirolimus, PTX-022 (the study drug), is safe and effective in treating participants with microcystic Lymphatic Malformations.