Clinical trial (study) comparing the efficacy and safety of mifamurtide versus standard treatment containing sorafenib in pediatric and young adult patients with high-risk osteosarcoma

Prior treatment

• Arterial or venous thrombotic or embolic events, such as stroke (including transient ischemic attacks), deep vein thrombosis, or pulmonary embolism, within the last 6 months before the first study drug administration.
• Any bleeding or hemorrhagic event ≥ CTCAE v5 grade 3 within 4 weeks before the first study drug administration.
• Diagnosis of other malignancies prior to study enrollment.
• Prior treatment with mifamurtide.
• Concomitant treatment with other drugs that may interact with mifamurtide or sorafenib or other cytotoxic agents.
• Persistent toxicity related to prior therapy precludes treatment with mifamurtide or sorafenib.
• Requirement or likely need for corticosteroids at doses >10 mg prednisolone (or equivalent) daily or other immunosuppressive medications.

Other illness

• Failure to meet any of the inclusion criteria.
• Active hepatitis B or C infection or chronic hepatitis B or C infection requiring antiviral therapy.
• Hypersensitivity to the study drug or any of its components (including mifamurtide and sorafenib).

Lab values

• Other acute or persistent disorders, behaviors, or abnormal laboratory test results that may increase the risks associated with participation in this clinical trial or with the study drug, or that may affect the interpretation of the study results, or that, in the opinion of the investigator, disqualify the patient from participating in the study.
• Significant cardiac conduction abnormalities, including known familial long QT syndrome or a screening corrected QT interval (QTc) >480 ms.
• Symptoms of congestive heart failure or left ventricular ejection fraction <50%.

Other

• Planning to become pregnant, being pregnant, or breastfeeding.
• Uncontrolled blood pressure (blood pressure values ​​not maintained within the recommended range (≥140/90 mmHg) despite treatment).

• Age ≥ 5 years and ≤ 30 years at the time of study enrollment.
• Recovery from adverse effects of prior surgery and/or radiotherapy.
• Consent to use effective contraception throughout the study period and for at least 1 year after discontinuation of study treatment in patients at pubertal and sexual maturity.
• Osteosarcoma confirmed by histopathological examination based on previously performed tests.
• Providing written, informed consent to participate in the study (including treatment with mifamurtide and sorafenib) in accordance with current legal regulations.
• Patient classified as high-risk.
• Life expectancy of at least 12 weeks from the date of signing the informed consent.
• Patient deemed fit to receive systemic treatment.
• Patient deemed able to swallow tablets.
• Disease in complete remission or stable disease according to WHO criteria prior to randomization.
• Completed surgery (major surgery ≥ 2 weeks) and radiotherapy (≥ 4 weeks) prior to IMP administration.