Efficacy and Safety of Venetoclax Plus Azacitidine for Patients With Treatment-Naive High-Risk Myelodysplastic Syndromes

• Venetoclax (14 days) + azacitidine regimen was well tolerated in patients with treatment-naive HR MDS, with no unexpected safety findings

• The regimen produced complete remission in 29.9% of patients, marrow complete remission in 50.5%, and 26-month median overall survival

Patients with higher-risk myelodysplastic syndromes (HR MDS) have a median survival of ~1.5 years with azacitidine, and hematopoietic stem cell transplantation is their only curative option. Therefore, improved therapies are needed. This phase 1b study investigated safety and efficacy of venetoclax, a selective BCL-2 inhibitor, at the recommended phase 2 dose (RP2D: 400 mg for 14 days/28-day cycle), in combination with azacitidine (75 mg/m2 for 7 days/28-day cycle) for treatment-naive HR MDS (NCT02942290). Safety was the primary outcome, and complete remission (CR) rate was the primary efficacy outcome. Secondary outcomes included rates of modified overall response (mOR), hematologic improvement (HI), overall survival (OS), and time to next treatment (TTNT). As of May 2023, 107 patients received venetoclax and azacitidine combination at the RP2D. Best response of CR or marrow CR was observed in 29.9% and 50.5% of patients (mOR, 80.4%). Median OS was 26.0 months, with 1-year and 2-year survival estimates of 71.2% and 51.3%, respectively. Of 59 patients who were red blood cell and/or platelet transfusion-dependent at baseline, 24 (40.7%) became transfusion-independent on study, including 11 (18.6%) who also achieved CR. Fifty-one (49.0%) of 104 evaluable patients achieved HI. Median TTNT excluding transplantation was 13.4 months. Adverse events reflected known safety profiles for venetoclax and azacitidine, including constipation (53.3%), nausea (49.5%), neutropenia (48.6%), thrombocytopenia (44.9%), febrile neutropenia (42.1%), and diarrhea (41.1%). Overall, venetoclax plus azacitidine at the RP2D was well tolerated and had favorable outcomes. A phase 3 study (NCT04401748) is ongoing to confirm survival benefit of this combination.