This study was a single-arm, open study. After the screening period, arsenic-resistant APL patients were treated with interferon α-2b, arsenic and venetoclax. The efficacy (ORR) and safety were evaluated.

Eligible APL patients with arsenic-resistant relapse will enter the run-in period, and the subjects in the run-in phase will be treated with arsenic combined with venetoclax. After the run-in period, the patients were treated with interferon α-2b, arsenic trioxide for injection and venetoclax until the outcome of CR/PR/PD/ death/withdrawal/loss to follow-up occurred. Tumor assessments were performed every 4 to 6 weeks (as determined by the investigator) during trial treatment. Those who achieved CR/PR/PD/ withdrawal were then returned to standard treatment (treatment regimen was determined by the clinician), and those who completed the combination treatment period of the trial entered the survival follow-up period.

Inclusion Criteria:

• 1. Must sign an informed consent form (ICF) indicating that he or she understands the purpose of, and procedures required for, the study and is willing to participate in the study.
• 2. Age 18-70 years old (including boundary value);
• 3. The presence of promyelocytic leukemia-retinoic acid receptor alpha (PML-RARα) confirmed by morphological features, cytogenetic analysis, and real-time quantitative polymerase chain reaction (qPCR);
• 4. Arsenic relapse resistant patients: patients who had relapsed (including molecular relapse) after remission with ATO in the previous treatment, and could not be relieved after standard treatment;
• 5. Eastern Cooperative Oncology Group (ECOG) performance status score 0-2;
• 6. The expected survival time is more than 3 months.

Exclusion Criteria:

• 1. Allergy or contraindication to any study drug involved in the protocol;
• 2. Physical examination, electrocardiogram, laboratory examination, vital signs and test related abnormalities are clinically significant (subject to clinician's judgment);
• 3. Other serious conditions that may limit the patient's participation in the trial, such as severe liver or kidney disease; "Patients with advanced infection, uncontrolled diabetes mellitus, severe cardiac dysfunction (e.g., clinically significant prolongation of the QT interval, potentially fatal torsades de pointes) or a history of angina or major heart disease, autoimmune diseases (as judged by the clinician);"
• 4. Pregnant or lactating women;
• 5. Epilepsy and central nervous system dysfunction;
• 6. Active hepatitis B, active hepatitis A, HIV positive;
• 7. Participate in other clinical trials at the same time
• 8. Any condition for which, in the opinion of the investigator, participation would not be in the best interest of the participant (eg, compromise the well-being) or that could prevent, limit, or confound the protocol-specified assessments.