Phase I Azacitidine will be administered intravenously from d-2 to d1, starting from dose level 1. Based on the BOIN design described above, if no DLT is identified in level 1, the dose will be escalated stepwise to levels 2, 3, and then 4.~Subjects will receive intravenous azacitidine combined with CHOP regimen every 3 weeks as below:~Level 1 - Azacitidine 50mg/m2 D-2, -1, 1 Level 2 - Azacitidine 75mg/m2 D-2, -1, 1 Level 3 - Azacitidine 100mg/m2 D-2, -1, 1 Level 4 - Azacitidine 125mg/m2 D-2, -1, 1~Azacitidine at each level will be combined with the corresponding CHOP regimen as follows:~Cyclophosphamide 750mg/m2 d1~Doxorubicin 50 mg/m2 d1~Vincristine 1.4 mg/m2 (Max: 2 mg) d1~Prednisolone 100mg PO d1-5~Phase II~Azacitidine determined dose daily for D-2, -1, 1, Cyclophosphamide 750mg/m2 d1, Doxorubicin 50 mg/m2 d1, Vincristine 1.4 mg/m2 (Max: 2 mg) d1, Prednisolone 100mg PO d1-5 (6 cycles in total)~Use prophylactic trimethoprim-sulfamethoxazole 1T from the day of study drug administration to 21 days after the last dose of study treatment~Administer Peg-GCSF on study d2.~After Cycle 2, the study treatment can be administered if the ANC has been restored to ≥1,500/μL and platelets to ≥75,000/μL, and non-hematological toxicities that occurred in the previous cycle, except alopecia, have resolved to Grade 1 or less on d1 of each cycle.~If these hematological and non-hematological toxicities are not resolved, the clinical trial can be delayed for up to 21 days.~Consolidation therapy~After completing the planned first-line therapy in the clinical trial, the following consolidation therapy should be performed, regardless of the azacitidine dose level.~Azacitidine 75mg/m2 d1-5 (every 4 weeks, total 12 cycles)
Induction treatment (every 3 weeks, total 6 cycles)~Azacitidine D-2, -1, 1 (level 1: 50mg/m2, level 2: 75mg/m2, level 3: 100mg/m2, level 4: 125mg/m2)~Cyclophosphamide 750mg/m2 d1~Doxorubicin 50 mg/m2 d1~Vincristine 1.4 mg/m2 (Max: 2 mg) d1~Prednisolone 100mg PO d1-5 Maintenance treatment (every 4 weeks, total 12 cycles)~Azacitidine 75mg/m2 d1-5