Inclusion Criteria:
* 1\. Signed informed consent and compliance with study procedures;
* 2\. Male or female participants aged ≥18 years at the time of consent;
* 3\. Diagnosis of relapsed or refractory acute myeloid leukemia (R/R AML) according to the 2016 World Health Organization (WHO) classification;
* 4\. ECOG PS 0-2;
* 5\. Life expectancy ≥3 months;
* 6\. Adequate bone marrow reserve and organ function as defined below:
1. Bone marrow reserve: Peripheral WBC \< 25 × 10⁹/L (leukocyte-reducing agents are allowed, with a washout period of at least 5 half-lives prior to study drug administration);
2. Coagulation: International normalized ratio (INR) ≤ 2;
3. Hepatic function: Total bilirubin (TBIL) ≤ 1.5 × ULN; ALT and AST ≤ 2.5 × ULN. In cases of hepatic involvement: ALT or AST ≤ 5 × ULN, and TBIL ≤ 3 × ULN;
4. Renal function: Creatinine clearance ≥60 mL/min (Cockcroft-Gault), or serum creatinine ≤1.5 × ULN;
5. Cardiac function: Left ventricular ejection fraction (LVEF) ≥50%; QTcF ≤450 ms for males, ≤470 ms for females.
* 7\. Female participants of childbearing potential and fertile male participants with partners of childbearing potential must use medically approved contraception during treatment and for 6 months after the final dose.
Exclusion Criteria:
* 1\. Known hypersensitivity to WBC100 capsules or any of their excipients;
* 2\. Diagnosis of acute promyelocytic leukemia (APL);
* 3\. Diagnosis of mixed phenotype acute leukemia, chronic myeloid leukemia in blast crisis, or AML transformed from myelodysplastic syndromes (MDS) or myeloproliferative neoplasms (MPN);
* 4\. Subjects with relapse after allogeneic HSCT, grade ≥ 2 acute GVHD, extensive chronic GVHD requiring immunosuppressive therapy, or autologous HSCT within the past 90 days;
* 5\. Subjects who have undergone major surgery, have active ulcers, or have unhealed wounds within 28 days prior to the first dose;
* 6\. Received other investigational drugs or treatments within 28 days prior to the first administration, or are still within the safety follow-up period of another clinical trial;
* 7\. Subjects with a history of severe cardiovascular or cerebrovascular conditions, including but not limited to:
1. Significant arrhythmias or conduction disorders (e.g., ventricular arrhythmias, Grade II-III AV block);
2. Thromboembolic events requiring anticoagulation or presence of vena cava filter;
3. NYHA Class III-IV heart failure;
4. Poorly controlled hypertension (SBP ≥140 mmHg or DBP ≥90 mmHg despite treatment).
* 8\. Evidence of severe or uncontrolled systemic diseases, such as refractory effusions, poorly controlled diabetes, or significant disorders of the psychiatric, neurological, cardiovascular, respiratory, endocrine, gastrointestinal, hepatic, or renal systems;
* 9\. History or presence of immunodeficiency, autoimmune disease requiring systemic immunosuppressants, or organ transplantation;
* 10\. Congestive heart failure, aortic dissection, stroke (excluding lacunar infarct), unstable angina, myocardial infarction, bypass surgery, or pulmonary embolism within 180 days prior to first dosing;
* 11\. Known risk factors for QT prolongation, including congenital long QT syndrome or drug-induced arrhythmia history;
* 12\. Positive for syphilis antibodies, HIV, active HBV infection (HBsAg+ or HBcAb+ with HBV DNA ≥1000 IU/mL), or active HCV infection (HCV Ab+ with detectable HCV RNA);
* 13\. Active infection requiring systemic treatment, including uncontrolled bacterial, viral, or fungal infections;
* 14\. Gastrointestinal conditions preventing oral drug intake or absorption, such as severe vomiting, chronic diarrhea, intestinal stoma, malabsorption, or inability to swallow;
* 15\. Use of strong CYP450 inhibitors/inducers that cannot be stopped ≥7 days before dosing;
* 16\. Receipt of monoclonal antibodies, ADCs, radiotherapy within 28 days (14 days for localized radiotherapy), cytotoxic chemotherapy, targeted small molecules within 14 days or 5 half-lives, or CAR-T therapy within 100 days;
* 17\. Receipt of any live or attenuated vaccines (e.g., influenza, varicella) within 28 days;
* 18\. History of other malignancies within 2 years, except adequately treated basal cell carcinoma, carcinoma in situ of cervix or breast, or squamous cell carcinoma of the skin;
* 19\. History of psychiatric or neurological disorders that may interfere with protocol compliance;
* 20\. Inability to tolerate venous blood draws;
* 21\. Pregnant or breastfeeding women, or women with positive serum hCG during screening;
* 22\. Any condition deemed by the investigator to make the subject unsuitable for study participation.
