The purpose of this study is to test an experimental approach called cell therapy for neuroblastoma or retinoblastoma. This study will take a patient's own white blood cells (T cells) and change them to turn against the cancer. These cells are an experimental treatment and have not been approved by the FDA. CAR T cells have been used to treat other cancers, but GPC2 CAR T cells have not been administered to human patients prior to this clinical trial.

If they choose to participate in this study, active participation will last approximately 12 months. Participants will also be asked to sign consent to a separate long term follow-up protocol to monitor their health for up to 15 years after their last GPC2 CAR T treatment.

This study will assess the safety and effectiveness of GPC2 CAR T cells. Overall, approximately 45 subjects will be enrolled on this study.

This study involves taking a study drug called ALRN-6924. ALRN-6924 is an investigational cancer treatment that activates p53, which suppresses the growth of tumors by blocking proteins in the cell called MDM2 and MDMX that inhibit p53 from doing its job. The overall goals of this study are to evaluate the side effects and benefits of ALRN-6924 in patients with relapsed or treatment refractory solid tumor or brain tumor, and to determine the best dose of ALRN-6924 for children and adolescents. This study will also look at how the body breaks down ALRN-6924 by measuring the amount of ALRN-6924 in the blood over time after a dose.

This study aims to explore a new type of magnetic resonance imaging (MRI) called Chemical Exchange Saturation Transfer (CEST) in children aged 6-18 years with brain tumors. An MRI is a machine that takes detailed pictures of the brain. The CEST MRI used in this study is still being tested and has not been approved by the FDA yet. The study wants to find out if this new type of MRI can help doctors evaluate brain tumors. CEST MRI creates images using water molecules and protons in the brain. Early research shows that CEST could be helpful in understanding brain tumor changes.

This study will enroll 5 participants.

This study focuses on a new type of magnetic resonance imaging (MRI) called Magnetic Resonance Elastography (MRE) for children aged 6-18 years, both with and without brain tumors. An MRI is a machine that creates detailed pictures of the brain. MRE combines MRI with gentle vibrations from a pillow-like device to study how soft tissues, like the brain, respond to these vibrations. Although MRE is used clinically to assess liver stiffness, it is not yet FDA-approved for brain imaging. This study aims to see if MRE could help doctors with diagnosing and managing brain tumors in children. The procedure does not involve any injections, including sedatives or contrast agents.

The study will enroll 30 participants.

This study is for children ages 6-18 years, both with and without brain tumors. The goal is to see if the two new types of magnetic resonance imaging (MRI) scans can help doctors diagnose brain tumors in children. An MRI is a machine that takes detailed pictures of the brain. The new types of MRI images in this study are still being tested and not yet approved by the FDA for finding brain tumors. Sodium MRI creates images of sodium distribution in the brain and is helpful for studying different brain conditions. CEST MRI creates images using water molecules and protons in the brain. Both methods are safe and do not require any injections, including sedatives or contrast agents.