Dose-Escalation Study of Pixantrone Monotherapy in Pediatric Patients With Relapsed or Refractory Cancer

Inclusion Criteria: 1. Patient and/or guardian have signed an Informed Consent Form and Assent approved by the Institutional Review Board or Institutional Ethics Committee, as appropriate and necessary, on a per-age basis 2. Age 6 months to 21 years old (initial qualifying diagnosis must have been made at or before the age of 18 and the patient must be under the care of a pediatric hematologist/oncologist) 3. Patient received a diagnosis of lymphoma or any non-hematologic malignancy (except central nervous system \[CNS\] tumors) for which the patient is considered relapsed or refractory. (NOTE: CNS metastases are allowable in patients who are deemed not at risk for progression during the first 30 days, who are neurologically stable, and, if on corticosteroids, have been on a stable corticosteroid dose for at least 2 weeks.) Patients who have \>1 malignancy ongoing during screening are not eligible 4. Patient must have one or more of the following treatment statuses: * Has failed at least 2 prior lines of chemotherapy * Has no curative chemotherapy treatment option available * Is not considered a candidate for available chemotherapy treatment options 5. In dose-escalation accrual, patients may have un-measurable disease (such as bone marrow/bone involvement or diffuse tumors) 6. In dose-escalation accrual, patients may have un-measurable disease in cases where the standard of care would indicate the need for adjuvant chemotherapy after definitive surgery or radiation, but for whom no standard chemotherapy options are available 7. In expansion cohort accrual, patients must have disease that is evaluable or measurable for response and progression per standard criteria for their diagnosis (Refer to the Appendices: RECIST 1.1 Criteria for Evaluation of Solid Tumors, Including Neuroblastoma, Appendix 18.4\], Evaluation of Neuroblastoma \[Appendix 18.6\], and the Lymphoma Staging and Disease Response Criteria \[Appendix 18.5\]) 8. Karnofsky-Lansky performance status (as per age of patient) ≥50 (Appendix 18.1) 9. Patient must have one or more of the following cardiac function measurements by echocardiogram: * Left ventricular ejection fraction (LVEF) ≥55% * Left ventricular shortening fraction (LVSF) ≥27% 10. Hemoglobin ≥8 g/dL (can be post-transfusion) 11. Platelet count ≥75 × 109/L 12. Absolute neutrophil count (ANC) ≥0.75 × 109/L 13. Serum direct/conjugated bilirubin ≤1.5 × upper limit of normal (ULN); patients with clinically diagnosed Gilbert's syndrome and total bilirubin ≤5 × ULN may be enrolled 14. Aspartate aminotransferase (AST; also called serum glutamic-oxaloacetic transaminase \[SGOT\]) and alanine aminotransferase (ALT; also called serum glutamic-pyruvic transaminase \[SGPT\]) ≤2.5 × ULN, or ≤5 × ULN if elevation is due to hepatic involvement by tumor 15. Serum creatinine ≤2 × ULN 16. Patients must meet the following criteria with respect to prior cancer therapy, radiotherapy, and stem cell transplants: 1. Myelosuppressive chemotherapy: At least 3 weeks must have elapsed since the completion of myelosuppressive chemotherapy (4 weeks if prior nitrosourea) and resolution of all nonhematologic toxicities to ≤grade 1. 2. Biologic (anti-neoplastic agent): * Oral tyrosine kinase inhibitors or other similar agents. At least 7 days must have elapsed since the completion of therapy with a biologic agent and all non-hematologic toxicities must have resolved to ≤grade 1 prior to enrollment * Anti-IGFR-1R and other monoclonal antibodies: the shorter of 3 half-lives or 6 weeks must have elapsed since previous monoclonal antibody therapy and resolution of all non-hematologic toxicities to ≤grade 1 prior to enrollment 3. Myeloid Growth Factor: Must not have received within 1 week prior to entry into this study (2 weeks in the case of PEG-filgrastim) 4. Radiotherapy: At least 4 weeks must have elapsed and all non-hematologic toxicities must have resolved to ≤grade 1 prior to enrollment. Previously radiated lesions cannot be used to assess response unless those sites are the sites of disease progression 5. Stem cell transplant (SCT): For autologous SCT, ≥3 months must have elapsed. For allogeneic SCT, ≥6 months must have elapsed and there must be no evidence of active graft versus host disease 17. All acute toxicities related to prior treatment recovered to grade ≤1 , except alopecia and hematologic parameters specified in the inclusion criteria 18. Willingness and ability to comply with the visit schedule and assessments required by the study protocol, including effective birth control (Section 5.4) for sexually active patients Exclusion Criteria: 1. Investigator-predicted life expectancy of less than two months 2. Investigator-predicted inability to tolerate pixantrone monotherapy treatment adverse effects for less than two months 3. Prior anthracycline treatment with a cumulative dose exceeding 450 mg/m2 (calculated based on doxorubicin equivalents) 4. Active National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) ≥grade 3 infection, or a lower grade infection deemed resistant or refractory to available antimicrobial agents, or infection requiring ongoing antibiotic treatment 5. Major surgery ≤7 days and/or with incomplete/inadequate wound healing prior to start of study treatment 6. Known acute or chronic hepatitis B or hepatitis C virus infection 7. Known seropositivity for human immunodeficiency virus (HIV) 8. Any experimental/investigational therapy ≤28 days prior to start of study treatment 9. Myocardial infarction within the past 6 months 10. New York Heart Association class II, III or IV heart failure 11. Any contraindication, known allergy, or hypersensitivity to any investigational drug(s) 12. Pregnant or lactating 13. Planned radiotherapy or surgical procedures for the qualifying malignancy 14. Any psychological, familial, sociological, or geographical condition potentially hampering compliance with the study procedures or follow-up schedules 15. Other severe and/or uncontrolled medical disease that could compromise participation in the study, or any medical or psychiatric condition that, in the opinion of the investigator, would make study drug administration hazardous or obscure the interpretation of data