This study investigates the effects of an investigational medication combined with two other treatments, irinotecan hydrochloride and temozolomide, in patients with solid tumors or lymphoma that have returned or are not responding to treatment. Solid tumors are abnormal masses of tissue that usually do not contain cysts or liquid areas, and lymphoma is a type of cancer that begins in the immune system cells. The study aims to find the highest dose of the investigational medication that can be given safely and to understand its side effects and how it moves through the body in children with these types of cancer.

Participants will receive the investigational medication as an intravenous infusion on specific days of a 28-day cycle and a 21-day cycle. Irinotecan hydrochloride will also be given as an intravenous infusion, while temozolomide will be taken orally. The study will monitor for any toxicities, which are harmful effects of the drugs, and will collect information on how the investigational medication is processed by the body.

• Who can participate: Children with recurrent or refractory solid tumors, including CNS tumors and lymphoma, are eligible if they have measurable or evaluable disease and have recovered from prior treatments. They must not have received prior exposure to the investigational medication.
• Study details: Participants will receive the investigational medication intravenously along with irinotecan hydrochloride, and take temozolomide orally. A placebo is not used in this study.