A Study to Evaluate the Safety and Pharmacokinetics of Eflapegrastim in Pediatric Participants With Solid Tumors or Lymphomas and Treated With Myelosuppressive Chemotherapy

This study is testing a medication called eflapegrastim, which helps the body produce more white blood cells after chemotherapy, in children with solid tumors or lymphomas. This type of drug (called a G-CSF) can reduce the risk of serious infections during cancer treatment. **You may be eligible if...** - Your child has a confirmed solid tumor or lymphoma (not involving the bone marrow) - Your child is scheduled to receive chemotherapy that carries a high risk of causing low white blood cell counts (febrile neutropenia rate of at least 20%) - Your child's blood counts, kidney, and liver function are adequate - Your child is able to perform basic daily activities (performance score ≥50%) **You may NOT be eligible if...** - Your child has an uncontrolled infection or serious medical condition - Your child has recently received other white blood cell stimulating drugs (filgrastim within 7 days, pegfilgrastim within 14 days) - Your child needs radiation therapy at the same time as chemotherapy in the first cycle - Your child has had a bone marrow transplant or has leukemia - Your child has had spinal radiation within the past 30 days Talk to your doctor to see if this trial is right for you.