Clinical Characteristics and Outcomes of AML Patients Treated with Frontline CPX 351 or HMA/Venetoclax: A Single Institution's Experience

Introduction: Treatment options for newly diagnosed patients (pts) with acute myeloid leukemia (AML) have historically been limited. The combination of a hypomethylating agent and venetoclax (HMA/Ven) has emerged as standard of care treatment for elderly and/or unfit pts with newly diagnosed AML. Liposomal cytarabine/daunorubicin (CPX-351) has also become standard of care therapy for pts with AML with myelodysplasia related changes or therapy-related AML. Despite being an intensive regimen, CPX-351 may have a more favorable toxicity profile compared to other intensive regimens. As a result, CPX-351 may be offered to older fit pts who may not have been candidates for traditional induction regimens. As the landscape for frontline treatment options evolves, there are now overlapping pt populations who may be eligible for either frontline treatment option. A retrospective study that included clinical trial pts demonstrated similar response rates in pts treated with HMA/Ven and CPX-351 (Asghari Blood 2019). Similarly, a study of secondary AML pts receiving HMA/Ven and CPX-351 showed no difference in remission rate or survival (Salhotra Am J Hematol 2021). There remains a shortage of data describing clinical characteristics of pts selected for and treated with standard-of-care HMA/Ven and CPX-351. We present a study on our center's experience.

Methods: The purpose of this study was to evaluate the clinical characteristics and outcomes of adult pts with newly diagnosed AML who were treated with either CPX-351 or HMA/Ven as initial therapy. Consecutive pts treated with either of these two induction therapies between August 2017 and June 2021 were evaluated retrospectively. Pts were eligible for response evaluation if they received at least 3 doses of CPX-351 or 28 days (1 cycle) of venetoclax ("response cohort"). All pts treated with CPX-351 or HMA/Ven were included in survival analysis ("survival cohort"). Response assessment is based on ELN-2017 criteria. Pt characteristics were described and compared using Fisher's Exact tests. Kaplan-Meier methods were used to summarize overall survival, and log-rank tests were used for the comparison of frontline therapies. Cox proportional-hazards regression estimated hazard ratio (HR), 95% confidence interval (CI), and interactions between frontline therapy and age at induction start.

Results: A total of 79 pts were identified receiving frontline HMA/Ven or CPX-351; 61 pts (77%) were evaluable for response. Of the response cohort, 21 (34%) were treated with CPX-351 and 40 (66%) with HMA/Ven; pt characteristics are described in Table 1. CPX-351 pts were younger at start of induction (P<0.001); many pts in both treatment groups had unfavorable ELN risk scores at diagnosis (CPX 43%, HMA/Ven 41%; P>0.99). 33% and 23% of the HMA/Ven cohort achieved CR and CRi respectively; in the CPX-351 cohort 57% and 5% achieved CR and CRi respectively. A greater fraction of CPX-351 pts proceeded to allogeneic stem cell transplant than HMA/Ven pts (67% vs 23%; P<0.001). No differences were detected in achievement of MRD negativity by flow cytometry (P=0.51) or molecular profile (P=0.52).

Median follow-up for all pts was 18.9 months; 42 deaths occurred. Differences in survival between the frontline therapies were not detected in the survival cohort (HR, 1.31; 95% CI, 0.67 to 2.57; P=0.43) nor the response cohort (HR, 0.97; 95% CI, 0.45 to 2.09; P=0.93); these results were unaffected by adjustments for age at induction, ELN risk score, and transplant status.

8 pts who initially received CPX-351 and had refractory disease later went on to receive HMA/Ven reinduction; 2 achieved CRi, 2 MLFS, 3 Refractory and 1 Death in Aplasia. 1 pt who initially received HMA/Ven with refractory disease went on to receive CPX-351. This pt was refractory to CPX-351.

Conclusion: HMA/Ven and CPX-351 are effective frontline treatment options with similar response rates and survival outcomes in newly diagnosed adults with AML. Pts treated with CPX-351 were younger and more likely to proceed with allogeneic transplantation, in line with standard practice. Though there was heterogeneity in pt populations, age did not appear to affect outcomes. As the landscape for standard-of-care upfront treatment for AML continues to evolve, further studies are warranted to determine optimal therapy selection and sequencing.

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