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

Inclusion Criteria:

1. Participant must have a pathologic/histologic confirmed newlydiagnosed/relapsed/recurrent solid tumor or lymphoma without bone marrowinvolvement.

2. Participant must be a candidate to receive myelosuppressive chemotherapy, with afebrile neutropenia rate of at least 20% as outlined in the National ComprehensiveCancer Network (NCCN) guidelines.

3. Participant has adequate hematological, renal, and hepatic function.

4. Participant must have an echocardiogram (ECHO) or multigated acquisition (MUGA)within 14 days of Screening if receiving a cardiotoxic therapy and have a cardiacejection fraction of >50%.

5. Participant must have a lumbar puncture, if clinically indicated, to rule outcentral nervous system (CNS) involvement within 14 days of study entry.

6. Participant has a Karnofsky performance level ≥50% for patients ≥16 years of age ora Lansky performance level ≥50 for children <16 years of age.

Exclusion Criteria:

1. Participant has an uncontrollable infection, has an underlying medical condition,and/or another serious illness that would impair the ability of the participant toreceive protocol-specified treatment.

2. Participant has had previous exposure to filgrastim (within 7 days), pegfilgrastim (within 14 days), or other granulocyte colony stimulating factor (G-CSF) products inclinical development within 2 weeks prior to the administration of study drug (eflapegrastim)

3. Participant requires concurrent radiation therapy specifically in Cycle 1.

4. Participant has had prior bone marrow or hematopoietic stem cell transplant and/orhas concurrent bone marrow involvement in their malignancy, including leukemia.

5. Participant has had spinal radiation therapy within 30 days prior to studyenrollment.

6. Participant has used any investigational drugs, biologics or devices within 30 daysprior to study treatment or plans to use any of these during the study.

7. Participant has a known sensitivity or previous reactions to any of the G-CSFproducts.

8. Participant with active CNS disease.

9. Participant has not recovered from previous treatment adverse events to ≤Grade 1.