Outcomes of Therapy with Venetoclax Combined with Hypomethylating Agents in Favorable-Risk Acute Myeloid Leukemia (AML)

Introduction:

Venetoclax (VEN) in combination with a hypomethylating agents (HMA) is associated with a high rate of composite remission (complete remission [CR] and complete remission with incomplete recovery [CRi]) among older and unfit patients with untreated AML. However, data regarding the activity of VEN-HMA in those patients with favorable-risk AML is limited, particularly in those with core-binding factor (CBF) alterations. Although more frequent among younger patients, favorable-risk alterations are also observed among older patients, often unfit for intensive regimens. Even among the subset of older patients (>60 years) with favorable-risk AML eligible for intensive regimens, long-term outcomes are poorer in comparison to younger patients.

Methods:

We retrospectively analyzed outcomes of 46 patients with favorable-risk AML who underwent therapy with VEN-HMA between 2016-2020 at 4 academic cancer centers in US. Favorable-risk AML was defined by the presence of either CBF [t(8;21) and inv(16) or t(16;16)], NPM1 mutation in the absence of FLT-3 ITD mutations; or bi-allelic CEBPA mutations.

Results:

Forty-six patients with favorable risk AML were treated with HMA-VEN, including 26 (57%) with newly diagnosed (ND) and 20 (43%) with relapsed/refractory (R/R) AML (Table1). Ten (22%) patients had CBF, 21 (46%) had NPM1 mutations (NPM1m), and 13 (28%) had bi-allelic CEBPA mutations (CEBPAm). The median age was 70 years, and 54% were females. Patients with R/R AML were younger than ND patients (56 vs. 72 yrs, p=0.003). Twenty (44%) patients had secondary or therapy-related AML, including half of ND patients. The median lines of prior therapy were 2(1-4) in patients with R/R AML, including 6 (30%) who had failed prior allogeneic HCT. Eleven (24%) patients had received HMA prior to HMA-VEN therapy, including 1 patient in the ND cohort for prior MDS. Eleven (24%) patients received azacitidine in combination with VEN, while the rest (76%) of patients received decitabine, including 14 patients who received 10-day decitabine during the first cycle.

The CR/CRi rate among the whole cohort was 80%, including 52% CR and 28% CRi. There was no statistically significant difference in CR/CRi rate between ND and R/R patients (88% vs. 70%, P =0.15). However, patients with history of prior HMA exposure had lower response rate compared to HMA-naïve patients (55% vs. 88%, p= 0.025). No difference in response was observed based on the favorable genetic alteration subgroups (80% in CBF vs. 86% in NPM1m vs. 77% in CEBPAm, p=0.44). Furthermore, no difference in response was observed according to patient age (p= 0.83), AML types (de novo vs. secondary; p= 0.47), prior transplant (p=1.00), or the type and schedule of HMA (P=0.66). Among the responders who had MRD assessment done (n= 26), 22 (85%) achieved MRD negativity by multicolor flow cytometry. Post response, 13 (35%) patients underwent allogeneic transplant consolidation. The median overall survival (OS) for the whole cohort was 18 months (12.5-NA). Median leukemia-free survival (LFS) was 13.2 months (7-20.2) for all responders, 11.2 months (1.7-NA) for ND responders, and 14.0 months (1-NA) for RR responders (p=0.986). The 30- and 60-day mortality for the whole cohort was 0% and 9%, respectively.

Conclusion:

In patients with favorable-risk AML, VEN-HMA combination is associated with a highly promising CR/CRi rate, with durable responses. The majority of responders achieved MRD negativity. Patients with prior use of HMA had lower response rate with VEN-HMA, nonetheless, over half of these patients responded despite most being treated in the R/R setting.