• 6 months ≤age≤18 years, no gender limitation;

• The Karnofsky (≥16 years old) or Lansky (\< 16 years old) physical status score is at least 50;

• The expected survival time is not less than 12 weeks;

• Heart function: A) Cardiac COLOR ultrasound detection LVEF≥ 50%; B) EKG suggests no myocardial ischemia;C) No history of arrhythmia requiring drug intervention before enrollment;

• Patients who meet the clinical diagnostic criteria and are diagnosed with pediatric rhabdomyosarcoma;

• Patients who have progressed, relapsed or refractory after first-line treatment (failed to achieve complete or partial response after recent treatment);

• Measurable lesions (according to RECIST 1.1 standards, CT scan length of tumor lesions ≥10mm, CT scan short diameter of lymph node lesions ≥15mm, measurable lesions have not received radiotherapy, freezing and other local treatments);

• The patient must fully recover from the acute toxic effects of all previous anticancer chemotherapy: A) Myelosuppressive chemotherapy: at least 21 days after the last myelosuppressive chemotherapy (42 days if nitrosourea was used previously);B) Experimental drug or anticancer therapy other than chemotherapy: not available within the first 28 days of planned initiation of AI or VIT. Complete recovery from clinically significant toxicity of the therapy must be determined;C) Hematopoietic growth factor: at least 14 days after the last administration of long-acting growth factor or 3 days after the last administration of short-acting growth factor;D) Immunotherapy: at least 42 days after completion of any type of immunotherapy (except steroids), such as immune checkpoint inhibitors and tumor vaccines; E) X-ray therapy (XRT) : at least 14 days after local palliative XRT (small mouth); For other substantial bone marrow (BM) irradiation, it must be completed for at least 42 days; F) Stem cell infusion without total body irradiation (TBI) : there is no evidence of active graft-versus-host disease and the transplant or stem cell infusion must be completed at least 56 days after the infusion;

• Laboratory tests during screening should meet the following conditions: A) Absolute value of neutrophils (ANC) ≥1.5×109/L (if bone marrow invasion, ANC≥1.0×109/L); B) Platelet count (PLT) ≥75×109/L (PLT≥50×109/L for bone marrow invasion); C) Bilirubin (sum of combined + uncombined) ≤ 2.5× upper limit of normal value (ULN) (corresponding to age), patients with confirmed Gilbert's syndrome can be included in the group according to the investigator's judgment; D) Estimated glomerular filtration rate ≥30 mL/min/1.73 m2 or serum creatinine (Cr) ≤ 1.5ULN (calculated according to the standard Cockcroft-Gault formula); E) Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.5×ULN (5 times ULN if liver metastasis is present)

⁃ Able to comply with outpatient treatment, laboratory monitoring and necessary clinical visits during the study period;

⁃ The parent/guardian of the child or adolescent subject is capable of understanding, agreeing to, and signing the study Informed consent (ICF) and the applicable child consent form prior to initiating any program-related procedures; Subject is capable of expressing consent with parental/guardian consent (if applicable).