This study is a prospective, single-center, single-arm exploratory clinical study, aiming to complete the preliminary clinical observation of 12 children with relapsed/refractory acute myeloid leukemia treated with JK500 cell injection to evaluate the safety of clinical infusion and the initial efficacy of JK500 cell injection in the treatment of children with relapsed/refractory acute myeloid leukemia.

The Main components of JK500 cell injection are regenerative natural killer (NK) cells derived from human embryonic stem cells and 0.9% sodium chloride solution.

Inclusion Criteria:

1. Age ≤18, male or female;
2. Patients diagnosed as acute myeloid leukemia (AML) according to the revised World Health Organization (WHO) criteria in 2016;
3. Patients who failed to achieve CR after two standard-dose induction therapy or had recurrence within six months after CR;
4. The subject or the guardian of the subject must fully understand the purpose, nature, method and possible adverse reactions of the test, agree the subject as the subject, and sign the informed consent.

Exclusion Criteria:

1. Acute promyelocytic leukemia, chronic myelocytic leukemia, acute mixed-cell leukemia or known central nervous system leukemia;

2. AML associated with congenital syndromes such as Down syndrome, Fanconi's anemia, Bloom's syndrome, Koch's syndrome, or congenital aplastic anemia;

3. The subjects have active virus infection, and during the screening period, the serum virology test is performed, and the human immunodeficiency virus (HIV) antibody is positive, hepatitis B surface antigen or E antigen is positive, hepatitis C antibody is positive, or treponema pallidum antibody is positive;

4. Presence of active systemic infection; Participated in a drug trial within the past 4 weeks;

5. Patients who suffered from a clinically significant disease within 28 days before receiving the study product or underwent a major surgical operation within 28 days before receiving the study product, or are expected to need major surgery during the trial;

6. children with liver and kidney dysfunction, including:

   1. Serum creatinine >2× upper limit of normal reference value;
   2. Serum total bilirubin > 2× upper limit of normal reference value;
   3. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) > 2× upper limit of normal reference values

7. Children who have used live attenuated vaccine 4 weeks before administration or plan to use live attenuated vaccine within 6 months after administration;

8. Have any other conditions that may cause the subject to be unable to complete the study or present a significant risk to the subject in the opinion of the Investigator.