• Histologically confirmed diagnosis of RMS (except pleomorphic RMS)

• Written informed consent from the patient and/or the parent/legal guardian

• Phase 1b Dose Finding - IRIVA Inclusion

• Entered in to the FaR-RMS study at diagnosis

• Very High Risk disease

• Age \>12 months and ≤25 years

• No prior treatment for RMS other than surgery

• Medically fit to receive treatment

• Adequate hepatic function:

∙ Total bilirubin ≤ 1.5 times upper limit of normal (ULN) for age, unless the patient is known to have Gilbert's syndrome

‣ ALT or AST \< 2.5 X ULN for age

• Absolute neutrophil count ≥1.0x 109/L

• Platelets ≥ 80 x 109/L

• Adequate renal function: estimated or measured creatinine clearance ≥60 ml/min/1.73 m2

⁃ Documented negative pregnancy test for female patients of childbearing potential

⁃ Patient agrees to use contraception during therapy and for 12 months after last trial treatment (females) or 6 months after last trial treatment (males), where patient is sexually active

⁃ Written informed consent from the patient and/or the parent/legal guardian