Purpose:

To evaluate efficacy and safety of venetoclax + azacitidine among treatment-naïve patients with FLT3-mutant acute myeloid leukemia.

Patients and Methods:

Data were pooled from patients enrolled in a phase III study (NCT02993523) that compared patients treated with venetoclax + azacitidine or placebo + azacitidine and a prior phase Ib study (NCT02203773) where patients were treated with venetoclax + azacitidine. Enrolled patients were ineligible for intensive therapy due to age ≥75 years and/or comorbidities. Patients on venetoclax + azacitidine received venetoclax 400 mg orally (days 1–28) and azacitidine (75 mg/m2; days 1–7/28-day cycle). FLT3 mutation was analyzed centrally on pretreatment bone marrow aspirates.

Results:

In the biomarker evaluable population, FLT3 mutation was detected in 42 (15%) and 22 (19%) patients in the venetoclax + azacitidine and azacitidine groups. Composite complete remission [CRc; complete remission (CR) + CR with incomplete hematologic recovery (CRi)] rates (venetoclax + azacitidine/azacitidine) for FLT3-mutant patients were 67%/36%, median duration of remission (DoR) was 17.3/5.0 months, and median OS was 12.5/8.6 months. The CRc rates among FLT3 wild-type patients were 67%/25%, median DoR 18.4/13.4 months, and median OS 14.7/10.1 months. In patients treated with venetoclax + azacitidine, CRc in patients with FLT3-ITD and FLT3-TKD was 63% and 77% and median OS was 9.9 and 19.2 months, and in comutated FLT3-ITD + NPM1 patients, CRc was 70%, median DoR was not reached, and median OS was 9.1 months. There were no unexpected toxicities in the venetoclax + azacitidine group.

Conclusions:

When treated with venetoclax + azacitidine, patients with FLT3 mutations and FLT3 wild-type had similar outcomes. Future analyses in larger patient populations may further define the impact of venetoclax + azacitidine in patients harboring FLT3-ITD.

See related commentary by Perl and Vyas, p. 2719

This article is featured in Highlights of This Issue, p. 2717

Translational Relevance

The fms-like tyrosine kinase 3 (FLT3) gene is mutated in approximately 20% of patients with acute myeloid leukemia (AML) ≥70 years and correlates with high leukemic burden and increased risk of relapse. The results of the phase III VIALE-A trial showed that patients treated with venetoclax and azacitidine had higher remission rates and more prolonged overall survival (OS) as compared with patients treated with azacitidine alone. Herein, we further evaluated the efficacy and safety of the combination and reported that the remission rates and OS among patients with or without FLT3 mutation were similar, suggesting that venetoclax and azacitidine may be used for treatment-naïve AML patients who are ineligible for intensive chemotherapy regimens irrespective of FLT3 mutations. Although high remission rates were observed among patients exhibiting both FLT3-ITD and TKD mutations, the impact on OS warrants confirmation in larger datasets.

Acute myeloid leukemia (AML) is a highly heterogeneous disease with genomic abnormalities, including NPM1, TP53, FLT3, and IDH1/2, that are predictors of treatment outcomes (1). The fms-like tyrosine kinase 3 (FLT3) gene is mutated in approximately 20% of patients with acute myeloid leukemia (AML) ≥70 years (2). Both FLT3-internal tandem duplication (ITD) and FLT3-tyrosine kinase domain (TKD) mutations are associated with AML proliferation and potentially targetable with small molecule inhibitors (3, 4). The presence of FLT3-ITD mutation correlates with a high leukemic burden with increased risk of relapse and is recognized to be a driver mutation in patients with AML (5). In particular, high (>0.5) mutant-to-wild-type (WT) allelic ratios (AR) in the FLT3-ITD gene are associated with inferior prognosis (6, 7). In patients with a normal cytogenetic profile, AML with NPM1 mutation has a favorable prognosis, but in coexistence with FLT3-ITD, the risk level of AML depends on the AR of FLT3-ITD (8). NPM1 mutation with low AR of FLT3-ITD is considered as a favorable-risk group, but when combined with high AR, it is classified as an intermediate-risk group (9). Despite a low or high AR of FLT3-ITD, patients with a comutation of FLT3-ITD and NPM1 belong to the intermediate-risk category according to the recent National Comprehensive Cancer Network (NCCN) guidelines (10). Overall, there is limited evidence on the prognostic implications of FLT3 and NPM1 mutations among older patients.

For treatment-naïve AML patients with FLT3 mutation, the current standard treatment entails induction with intensive chemotherapy in physically fit or younger patients and in combination with the FLT3 inhibitor, midostaurin (11). Other FLT3-inhibitors have induced modest single-agent responses with short-lived remissions among patients with relapsed/refractory disease, while combination trials with intensive chemotherapy in first-line fit patients are ongoing (12–14). Currently, there is no approved targeted therapy option for treatment-naïve patients with AML harboring a FLT3 mutation ineligible for intensive therapy. Preliminary results from a phase III randomized trial (NCT02752035) failed to show a survival benefit with the addition of gilteritinib to azacitidine in patients with FLT3-mutant AML ineligible for intensive chemotherapy (15).

Overexpression of BCL-2 is a predictor of poor response to chemotherapy and can lead to therapeutic resistance in AML (16). Mutations in FLT3 lead to subsequent constitutive activation of FLT3 kinase and its downstream proliferative signaling pathways, including the Ras/MAPK kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway and PI3K/Akt pathway (17). FLT3-ITD is also known to activate the STAT5 pathway (18). STAT5 induces its target genes such as cyclin D1, c-myc, and the antiapoptotic gene p21, which are essential for cell growth (19–21), and also increased BCL-XL and MCL1 protein expression (22). Azacitidine can induce expression of the BH3-only sensitizing/neutralizing NOXA and PUMA proteins, which inhibit MCL-1 and BCL-XL, increasing the dependence of the malignant cell on BCL-2. Combining venetoclax with azacitidine has been shown to induce apoptosis in malignant myeloid cells (23) and to be synergistic to overcome antiapoptotic signals downstream of an activated FLT3 pathway (24, 25). Figure 1 represents a simplified schematic of the mechanism of venetoclax and azacitidine action in the downstream FLT3 signaling pathway.

Figure 1.

Venetoclax and azacitidine work synergistically to overcome antiapoptotic signals downstream of an activated FLT3 pathway.

Figure 1.

Venetoclax and azacitidine work synergistically to overcome antiapoptotic signals downstream of an activated FLT3 pathway.

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In a prior phase Ib study, treatment with venetoclax and a hypomethylating agent (azacitidine or decitabine) demonstrated a 72% composite complete remission rate [CRc defined by complete remission (CR) plus CR with incomplete count recovery (CRi)] among patients with FLT3 mutation with a median duration of remission (DoR) of 11.0 [6.5–not evaluable (NE)] months. These results were further validated by the phase III VIALE-A study where patients with FLT3 mutation, when treated with venetoclax and azacitidine, had significantly higher CRc rates (72.4% vs. 36.4%) and longer median overall survival (OS; 13.6 months vs. 8.6 months) as compared with azacitidine alone (26, 27). Herein, we further detail the efficacy and safety of venetoclax and azacitidine among treatment-naïve AML patients with comorbidities and/or age ≥75 years, ineligible for intensive treatment and harboring a FLT3 mutation.

Patients and treatment

Data were pooled from patients enrolled in an ongoing randomized phase III VIALE-A study (NCT02993523) comparing patients treated with venetoclax combined with azacitidine or placebo with azacitidine and a prior phase Ib study (NCT02203773) where a subset of patients was treated with venetoclax and azacitidine. Patients enrolled were ≥18 years with a confirmed diagnosis of AML by the World Health Organization criteria. Both studies required that the patients be ineligible for standard induction chemotherapy either due to age ≥75 years or due to the presence of comorbidities. Patients were excluded if they had white blood cell (WBC) count >25 × 109/L. Additional eligibility criteria have been previously published (26, 28). This analysis included patients treated with venetoclax at 400 mg orally on days 1 to 28 and azacitidine at 75 mg/m2 intravenously or subcutaneously on days 1 to 7 every 28-day cycle. Patients treated with azacitidine alone received the same standard dose of azacitidine as above.

Both study protocols and related documents were approved by the applicable regional review boards or ethics committees and were conducted in accordance with the International Conference on Harmonization, Good Clinical Practice guidelines, and the Declaration of Helsinki. All patients provided written informed consent.

Assessment of outcomes

Disease responses were evaluated per modified International Working Group (IWG) response criteria for AML and as previously described (26, 29, 30). Efficacy was assessed as CRc (CR + CRi), DoR among responders, and OS. CR was defined as absolute neutrophil count >103/μL, platelets >105/μL, and red cell transfusion independence for at least 56 days between the first and last day of treatment, and bone marrow with <5% blasts. CRi was defined as all criteria for CR, except for neutropenia ≤103/μL or thrombocytopenia ≤105/μL. Duration of CRc was defined as the number of days from the date of first response (CR or CRi) per the modified IWG criteria for AML to the earliest evidence of confirmed morphologic relapse, confirmed progressive disease, or death due to disease progression. OS was defined as the time from randomization to the date of death from any cause. Response assessments were performed at screening, end of cycle 1, and every three cycles thereafter. Adverse events were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events Version 4.0 (31).

Assessment of molecular data

Deoxyribose nucleic acid (DNA) was isolated from bone marrow (BM) aspirates collected from patients prior to the first dose of the study drug and analyzed centrally. For the VIALE-A study, Leukostrat CDx FLT3 mutation assay panel (Invivoscribe) was used to detect FLT3-ITD or FLT3-TKD. The next-generation sequencing (NGS) MyAML gene assay (Invivoscribe) was used to detect NPM1 comutation and was also used to detect FLT3-ITD or FLT3-TKD in 22 patients with insufficient material for the Leukostrat CDx FLT3 assay. For the phase Ib study, FLT3 and NPM1 mutations were detected by the MyAML gene assay. The Leukostrat CDx is a polymerase chain reaction (PCR) based assay designed to detect ITD and TKD mutation in D835 and I836 in the FLT3 gene, whereas MyAML is a next-generation targeted sequencing assay capable of detecting variants in the entire coding region of the FLT3 gene. Given these differences, the FLT3 mutations as determined by MyAML were limited to those recognizable by the Leukostrat CDx assay (FLT3-ITD or TKD in D835 or I836 with a variant allelic frequency ≥ 2.5%, which corresponds with a mutant to wild-type signal ratio ≥0.05). Concordance between the two methodologies was assessed. Patients with positive test results for FLT3 were counted as mutation “detected”; patients with a negative test result were counted as mutation “not detected,” and patients without a result either due to an inconclusive test or missing specimen were counted as missing or indeterminate.

Statistical analysis

Demographics were summarized by descriptive statistics. Remission rates were summarized in counts and proportions, and CIs were estimated using the exact binomial method. OS and DoR were evaluated by the Kaplan–Meier methodology. The hazard ratios (HR) and 95% confidence interval (CI) between treatment groups were estimated using the Cox proportional hazards model.

Concordance between Leukostrat CDx and MyAML assays for FLT3 mutation was evaluated using positive percent agreement and negative percent agreement instead of sensitivity and specificity as both assays have the potential for false-negative tests.

Data sharing statement

This clinical trial data can be requested by any qualified researchers who engage in rigorous, independent scientific research and will be provided following the review and approval of a research proposal and Statistical Analysis Plan (SAP) and execution of a Data Sharing Agreement (DSA). Data requests can be submitted at any time, and the data will be accessible for 12 months, with possible extensions considered. For more information on the process or to submit a request, visit the following link: https://www.abbvie.com/our-science/clinical-trials/clinical-trials-data-and-information-sharing/data-and-information-sharing-with-qualified-researchers.html.

Patient disposition and baseline characteristics

The data cut-off dates were January 4, 2020, for the phase III VIALE-A study, and July 19, 2019, for the phase Ib study. In the pooled analysis, there were 353 patients in the venetoclax and azacitidine group (VIALE-A, n = 286; phase Ib, n = 67) and 145 patients in the azacitidine group.

In the biomarker evaluable population (venetoclax and azacitidine group, n = 280; azacitidine group, n = 117), FLT3 mutations were detected (venetoclax and azacitidine group vs. azacitidine group) in 15% (42/280) versus 19% (22/117), and 85% (238/280) versus 81% (95/117) were FLT3 WT, respectively. The study design and overview of the molecular categorization of patients are shown in Fig. 2 and Supplementary Table S1. The key demographic and clinical characteristics are shown in Table 1. In FLT3-mutated patients, higher rates of poor-risk cytogenetics (14.3% vs. 4.5%) and secondary AML (21.4% vs. 13.6%) were observed in the venetoclax and azacitidine versus azacitidine group, respectively.

Figure 2.

Study design and molecular classification. *One patient in the venetoclax and azacitidine group and one patient in the azacitidine group had both FLT3-ITD and TKD mutation; One patient in the venetoclax and azacitidine group was indeterminate for NPM1 comutation status.

Figure 2.

Study design and molecular classification. *One patient in the venetoclax and azacitidine group and one patient in the azacitidine group had both FLT3-ITD and TKD mutation; One patient in the venetoclax and azacitidine group was indeterminate for NPM1 comutation status.

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Table 1.

Baseline characteristics of patients.

Venetoclax + AzacitidineAzacitidine
FLT3 mutatedFLT3 wild typeFLT3 mutatedFLT3 wild type
(n = 42)a(n = 238)(n = 22)(n = 95)
Age, median (range) 75.0 (49.0–91.0) 77.0 (53.0–90.0) 75.0 (65.0–85.0) 76.0 (60.0–90.0) 
Age category - n (%) 
 <65 3 (7.1) 7 (2.9) 4 (4.2) 
 65–<75 17 (40.5) 75 (31.5) 9 (40.9) 30 (31.6) 
 ≥75 22 (52.4) 156 (65.5) 13 (59.1) 61 (64.2) 
Gender - n (%) 
 Female 18 (42.9) 97 (40.8) 6 (27.3) 39 (41.1) 
 Male 24 (57.1) 141 (59.2) 16 (72.7) 56 (58.9) 
ECOG performance status - n (%) 
 0–1 17 (40.5) 148 (62.2) 11 (50.0) 59 (62.1) 
 2–3 25 (59.5) 90 (37.8) 11 (50.0) 36 (37.9) 
Cytogenetics - n (%) 
 Intermediate 36 (85.7) 141 (59.2) 21 (95.5) 48 (50.5) 
 Poor 6 (14.3) 97 (40.8) 1 (4.5) 47 (49.5) 
Bone marrow blast count - n (%) 
 <30% 7 (16.7) 76 (31.9) 3 (13.6) 28 (29.5) 
 ≥30%–<50% 4 (9.5) 59 (24.8) 4 (18.2) 23 (24.2) 
 ≥50% 31 (73.8) 103 (43.3) 15 (68.2) 44 (46.3) 
Type of AML - n (%) 
De novo AML 33 (78.6) 175 (73.5) 19 (86.4) 67 (70.5) 
 Secondary AML 9 (21.4) 63 (26.5) 3 (13.6) 28 (29.5) 
AML-MRC - n (%) 8 (19.0) 81 (34.0) 7 (31.8) 36 (37.9) 
RBC or platelet transfusion within 8 weeks prior to the first dose of study drug or randomization - n (%) 24 (57.1) 132 (55.5) 17 (77.3) 53 (55.8) 
FLT3-ITD AR - n (%) 
 <0.5 21 (70.0) — 8 (61.5) — 
 ≥0.5 9 (30.0) — 5 (38.5) — 
Molecular mutations     
 IDH1 or IDH2b 10 (23.8) 64 (27.6) 2 (10.0) 22 (23.4) 
 NPM1c 15 (35.7) 30 (12.6) 8 (36.4) 11 (11.6) 
Venetoclax + AzacitidineAzacitidine
FLT3 mutatedFLT3 wild typeFLT3 mutatedFLT3 wild type
(n = 42)a(n = 238)(n = 22)(n = 95)
Age, median (range) 75.0 (49.0–91.0) 77.0 (53.0–90.0) 75.0 (65.0–85.0) 76.0 (60.0–90.0) 
Age category - n (%) 
 <65 3 (7.1) 7 (2.9) 4 (4.2) 
 65–<75 17 (40.5) 75 (31.5) 9 (40.9) 30 (31.6) 
 ≥75 22 (52.4) 156 (65.5) 13 (59.1) 61 (64.2) 
Gender - n (%) 
 Female 18 (42.9) 97 (40.8) 6 (27.3) 39 (41.1) 
 Male 24 (57.1) 141 (59.2) 16 (72.7) 56 (58.9) 
ECOG performance status - n (%) 
 0–1 17 (40.5) 148 (62.2) 11 (50.0) 59 (62.1) 
 2–3 25 (59.5) 90 (37.8) 11 (50.0) 36 (37.9) 
Cytogenetics - n (%) 
 Intermediate 36 (85.7) 141 (59.2) 21 (95.5) 48 (50.5) 
 Poor 6 (14.3) 97 (40.8) 1 (4.5) 47 (49.5) 
Bone marrow blast count - n (%) 
 <30% 7 (16.7) 76 (31.9) 3 (13.6) 28 (29.5) 
 ≥30%–<50% 4 (9.5) 59 (24.8) 4 (18.2) 23 (24.2) 
 ≥50% 31 (73.8) 103 (43.3) 15 (68.2) 44 (46.3) 
Type of AML - n (%) 
De novo AML 33 (78.6) 175 (73.5) 19 (86.4) 67 (70.5) 
 Secondary AML 9 (21.4) 63 (26.5) 3 (13.6) 28 (29.5) 
AML-MRC - n (%) 8 (19.0) 81 (34.0) 7 (31.8) 36 (37.9) 
RBC or platelet transfusion within 8 weeks prior to the first dose of study drug or randomization - n (%) 24 (57.1) 132 (55.5) 17 (77.3) 53 (55.8) 
FLT3-ITD AR - n (%) 
 <0.5 21 (70.0) — 8 (61.5) — 
 ≥0.5 9 (30.0) — 5 (38.5) — 
Molecular mutations     
 IDH1 or IDH2b 10 (23.8) 64 (27.6) 2 (10.0) 22 (23.4) 
 NPM1c 15 (35.7) 30 (12.6) 8 (36.4) 11 (11.6) 

Abbreviations: AML-MRC, AML with myelodysplasia-related changes; ECOG, Eastern Cooperative Oncology Group.

aFLT3 was detected by CDx assay in 40 patients and by MyAML assay in 2 patients. FLT3-ITD was detected by CDx assay in 28 patients and by MyAML assay in 2 patients.

bIDH1 or IDH2 was detected by CDx assay.

cNPM1 was detected by MyAML assay.

Agreement between the methods of assessing FLT3 mutation

The concordance study of 293 specimens from VIALE-A with results from both assays demonstrated 100% positive percent agreement and 90% negative percent agreement for FLT3 detected by CDx and MyAML assays (Supplementary Table S2). Twenty-four results were discordant between the two assays, of which seven were discordant as MyAML identified a FLT3 mutation type that was not applicable to the FLT3 CDx assay, 16 were detected by MyAML assay below the level of detection for the FLT3 CDx assay, and for one, the reason for discordance was unknown. The 51 patients positive by CDx and the 13 patients positive by MyAML with a FLT3 mutation type detectable by the CDx assay were included as FLT3 mutation detected (ITD or TKD).

Remission rates

Among patients with FLT3 mutation (venetoclax and azacitidine group vs. azacitidine group), the median number of treatment cycles delivered was 7.0 (range: 1.0–31.0) versus 5.0 (1.0–21.0). The CRc rates were higher in the venetoclax and azacitidine group as compared to the azacitidine group [67% (n = 28) vs. 36% (n = 8)], the median time to first response of CR or CRi was 1.2 (95% CI, 0.8–7.7) versus 2.8 (1.0–11.2) months, and the median DoR was 17.3 (95% CI, 10.1–NE) versus 5.0 (1.0–15.9) months. In patients with FLT3 WT (venetoclax and azacitidine group vs. azacitidine group), the CRc rates were 67% (n = 159) versus 25% (n = 24); the median time to first response for CR or CRi was 1.3 (range: 0.7–9.9) versus 2.9 (1.0–13.2) months, and the median DoR was 18.4 (95% CI: 15.1–NE) versus 13.4 (6.7–15.6) months (Fig. 3).

Figure 3.

A, Remission rates in patients with FLT3 mutations and FLT3 wild type by treatment groups. B, Remission rates in patients with FLT3-ITD and FLT3-TKD in the venetoclax and azacitidine group. C, Remission rates in patients with FLT3-ITD+NPM1-mutated versus FLT3-ITD+NPM1 wild type in the venetoclax and azacitidine group. D, Duration of remission among responders with FLT3-ITD+NPM1 mutation versus FLT3-ITD+ NPM1 wild type.

Figure 3.

A, Remission rates in patients with FLT3 mutations and FLT3 wild type by treatment groups. B, Remission rates in patients with FLT3-ITD and FLT3-TKD in the venetoclax and azacitidine group. C, Remission rates in patients with FLT3-ITD+NPM1-mutated versus FLT3-ITD+NPM1 wild type in the venetoclax and azacitidine group. D, Duration of remission among responders with FLT3-ITD+NPM1 mutation versus FLT3-ITD+ NPM1 wild type.

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In patients treated with venetoclax and azacitidine combination, high remission rates were observed in FLT3-ITD and FLT3-TKD subgroups. In patients with FLT3-ITD, the CRc rate was 63% (n = 19); median time to first response for CR or CRi was 1.2 (range: 0.8–4.8) months, and the median DoR was 17.3 (95% CI: 4.6–NE) months. In patients with FLT3-TKD, the CRc rate was 77% (n = 10); median time to first response to CR or CRi was 1.2 (range: 1.0–7.7) months, and the median DoR was 15.9 (95% CI: 2.8–NE) months.

In patients who had a comutation of FLT3-ITD and NPM1, the treatment with venetoclax and azacitidine resulted in a CRc rate of 70% (n = 7). The median time to first response for CR or CRi was 1.2 (range: 1.0–1.9) months. The median DoR was not reached (95% CI: 4.6–NE) and the estimated 12-month in-remission rate was 66.7% (95% CI: 19.5%–90.4%). The patients with FLT3-ITD and NPM1 WT, when treated with venetoclax and azacitidine, attained a CRc rate of 58% (n = 11). The median time to first response for CR or CRi was 1.0 (range: 0.8–4.8) months, and the median DoR was 10.1 (95% CI: 1.8–NE) months.

The remission rates by FLT3-ITD ARs are summarized in Table 2. In addition, the comparisons of remission rates by treatment groups are shown in the Supplementary Table S3 and should be interpreted with caution due to the small number of patients that warrant further investigation. The remission rates and DoR among patients who achieved CR plus CR with a partial hematologic response (CRh) with venetoclax and azacitidine are shown in Supplementary Table S4.

Table 2.

Remission rates among patients treated with venetoclax and azacitidine combination.

FLT3 mutatedFLT3-ITDFLT3-ITD AR < 0.5FLT3-ITD AR ≥ 0.5FLT3-TKDFLT3 wild typeFLT3-ITD and NPM1FLT3-ITD and NMP1 wild type
(n = 42)(n = 30)(n = 21)(n = 9)(n = 13)(n = 238)(n = 10)(n = 19)
CR rate, n (%) 16 (38.1) 9 (30.0) 8 (38.1) 1 (11.1) 7 (53.8) 96 (40.3) 3 (30.0) 6 (31.6) 
CR + CRi, n (%) 28 (66.7) 19 (63.3) 14 (66.7) 5 (55.6) 10 (76.9) 159 (66.8) 7 (70.0) 11 (57.9) 
Duration of CR + CRi (months), median (95% CI) 17.3 (10.1–NE) 17.3 (4.6–NE) 21.0 (3.0–NE) NR (7.4–NE) 15.9 (2.8–NE) 18.4 (15.1–NE) NR (4.6–NE) 10.1 (1.8–NE) 
Time to the 1st response, (months), median (range) 1.2 (0.8–7.7) 1.2 (0.8–4.8) 1.2 (0.9–4.6) 1.2 (0.8–4.8) 1.2 (1.0–7.7) 1.3 (0.7–9.9) 1.2 (1.0–1.9) 1.0 (0.8–4.8) 
CR + CRi by initiation of C-2, n (%) 21 (50.0) 16 (53.3) 12 (57.1) 4 (44.4) 6 (46.2) 97 (40.8) 6 (60.0) 9 (47.4) 
Post-baseline transfusion independence ratea, n (%) 25 (59.5) 17 (56.7) 11 (52.4) 6 (66.7) 8 (61.5) 135 (56.7) 7 (70.0) 9 (47.4) 
FLT3 mutatedFLT3-ITDFLT3-ITD AR < 0.5FLT3-ITD AR ≥ 0.5FLT3-TKDFLT3 wild typeFLT3-ITD and NPM1FLT3-ITD and NMP1 wild type
(n = 42)(n = 30)(n = 21)(n = 9)(n = 13)(n = 238)(n = 10)(n = 19)
CR rate, n (%) 16 (38.1) 9 (30.0) 8 (38.1) 1 (11.1) 7 (53.8) 96 (40.3) 3 (30.0) 6 (31.6) 
CR + CRi, n (%) 28 (66.7) 19 (63.3) 14 (66.7) 5 (55.6) 10 (76.9) 159 (66.8) 7 (70.0) 11 (57.9) 
Duration of CR + CRi (months), median (95% CI) 17.3 (10.1–NE) 17.3 (4.6–NE) 21.0 (3.0–NE) NR (7.4–NE) 15.9 (2.8–NE) 18.4 (15.1–NE) NR (4.6–NE) 10.1 (1.8–NE) 
Time to the 1st response, (months), median (range) 1.2 (0.8–7.7) 1.2 (0.8–4.8) 1.2 (0.9–4.6) 1.2 (0.8–4.8) 1.2 (1.0–7.7) 1.3 (0.7–9.9) 1.2 (1.0–1.9) 1.0 (0.8–4.8) 
CR + CRi by initiation of C-2, n (%) 21 (50.0) 16 (53.3) 12 (57.1) 4 (44.4) 6 (46.2) 97 (40.8) 6 (60.0) 9 (47.4) 
Post-baseline transfusion independence ratea, n (%) 25 (59.5) 17 (56.7) 11 (52.4) 6 (66.7) 8 (61.5) 135 (56.7) 7 (70.0) 9 (47.4) 

Note: CR was defined as absolute neutrophil count >103/μL, platelets >105/μL, red cell transfusion independence (TI) for at least 8 weeks, and bone marrow with <5% blasts; CRi is defined as all criteria for CR, except for neutropenia ≤103/μL or thrombocytopenia ≤105/μL.

Abbreviations: AR, allelic ratio; CR, complete remission; CRi, CR+ incomplete hematologic recovery; NE, not evaluable; NR, not reached.

aPost-baseline transfusion independence is defined as a period of at least 56 days with no red blood cell or platelet transfusion during the evaluation period.

Overall survival

The median OS in patients with FLT3 mutation was 12.5 (95% CI: 7.3–19.2) versus 8.6 (95% CI: 5.9–14.7) months, HR: 0.63 (95% CI: 0.35–1.13) in the venetoclax and azacitidine group versus azacitidine group, respectively (Fig. 4A). In patients with FLT3 WT (Fig. 4B), the median OS was 14.7 (95% CI: 11.3–19.4) months versus 10.1 (95% CI: 6.8–12.7) months, HR: 0.61 (95% CI: 0.46–0.81) in the venetoclax and azacitidine group versus azacitidine group, respectively.

Figure 4.

Kaplan–Meier curves for OS. A, Patients with FLT3 mutation by treatment groups. B, Patients with FLT3 mutation or FLT3 wild type in the venetoclax and azacitidine group. C, Patients with FLT3-ITD and FLT3-TKD in the venetoclax and azacitidine group. D, Patients with FLT3-ITD+NPM1 mutation versus FLT3-ITD+ NPM1 wild type in the venetoclax and azacitidine group.

Figure 4.

Kaplan–Meier curves for OS. A, Patients with FLT3 mutation by treatment groups. B, Patients with FLT3 mutation or FLT3 wild type in the venetoclax and azacitidine group. C, Patients with FLT3-ITD and FLT3-TKD in the venetoclax and azacitidine group. D, Patients with FLT3-ITD+NPM1 mutation versus FLT3-ITD+ NPM1 wild type in the venetoclax and azacitidine group.

Close modal

In patients treated with venetoclax and azacitidine, the median OS was longer in patients with FLT3-TKD as compared with those with FLT3-ITD. In patients with FLT3-TKD, the median OS was 19.2 (95% CI: 1.8– NE) months as compared with 9.9 (95% CI: 5.3–17.6) months in patients with FLT3-ITD (Fig. 4C).

Patients with a comutation of FLT3-ITD and NPM1 had a median OS of 9.1 (95% CI: 1.3–NE) months when treated with venetoclax and azacitidine, and the patients with FLT3-ITD and NPM1 WT had a median OS of 10.6 (95% CI: 2.8–17.2) months (Fig. 4D).

The median OS of patients with FLT3-ITD, FLT3-TKD, FLT3-ITD + NPM1 mutated, and FLT3-ITD + NPM1 WT compared by treatment groups are presented in Supplementary Fig. S1.

Safety

Predominant ≥3 grade hematologic adverse events in patients with versus without FLT3 mutations when treated with venetoclax and azacitidine (≥20% in either group) were febrile neutropenia (38% vs. 42%), thrombocytopenia (38% vs. 35%), neutropenia (33% vs. 33%), and anemia (31% vs. 24%). Common nonhematologic adverse event was pneumonia (21% vs. 24%; Supplementary Table S5). The most common serious adverse events (≥10% in either group) were febrile neutropenia (31% vs. 29%) and pneumonia (14% vs. 20%).

In the venetoclax and azacitidine group, there were 4 (10%) early deaths within 30 days of administration of the study drug in patients with an FLT3 mutation and 16 (7%) deaths in patients who were FLT3 WT. Nine (21%) and 18 (8%) patients in the FLT3 mutated and FLT3 WT in the venetoclax and azacitidine group used hydroxyurea during treatment. Tumor lysis syndrome was reported in one patient from each group; 1 (2.4%) versus 1 (0.4%).

Posttreatment systemic therapy was utilized by 10 (24%) patients with FLT3 mutation after receiving venetoclax and azacitidine as compared to 7 (32%) patients after treatment with azacitidine (Supplementary Table S6).

For older patients with AML who are ineligible for intensive chemotherapy, treatment with venetoclax and azacitidine is now recommended as the new standard of care by the NCCN clinical practice guidelines for AML regardless of mutation status (10). Historically, there have been limited treatment options for patients with AML who are ≥75 years, irrespective of FLT3 mutation, and ineligible for intensive chemotherapy. Among such patients, treatment with the combination of venetoclax and azacitidine led to a 31% higher remission rate and a 37% reduction in the risk of death than treatment with azacitidine alone. The remission rates among patients irrespective of FLT3 mutations were similar when treated with venetoclax and azacitidine, suggesting that the combination maybe be used as an initial treatment option for ineligible treatment-naïve patients with AML either with or without FLT3 mutations.

Although high remission rates were observed among patients exhibiting both FLT3-ITD and TKD mutations, the survival benefit was prominent in patients with FLT3-TKD only. Preclinical studies have found that FLT3-ITD mutations may reduce BCL-2 dependence in AML cells by enhancing the expression of BCL-XL and MCL-1 (32, 33). FLT3-ITD clones may expand or emerge at relapse after venetoclax-based therapy (22). Combining FLT3 inhibitors such as midostaurin, quizartinib, or gilteritinib with venetoclax has been reported to potently and synergistically induce apoptosis in FLT3-ITD AML cell lines (22, 24) and suppress MCL1 overexpression (34, 35). Hence, there is a strong rationale to support clinical investigation of FLT3 inhibitors in combination with venetoclax to treat patients with FLT3-ITD mutated AML, while the benefits of the combination in the FLT3-TKD population warrant further evaluation.

The safety and tolerability of the venetoclax and azacitidine combination among patients with FLT3 mutation were similar to patients with wild-type FLT3 mutation status. The toxicities were predominantly hematologic with the rate of febrile neutropenia being higher in the venetoclax and azacitidine group as compared to the azacitidine group, consistent with the safety data of the overall trial population (26, 28). The toxicities were effectively managed by the standard of care.

A key limitation of this study is the small patient numbers in several of the subgroup analyses, and the comparison and interpretation of the results warrant caution. In addition, the frequency of FLT3 mutations seen in this patient population (15%) is lower than the overall rate of FLT3 mutations (30%) in AML, and as such, the outcomes may not be applicable to the highly proliferative mutant FLT3-driven AML seen in younger adults. Per protocol, the study excluded patients with WBC >25 × 109/L, but hydroxyurea or leukapheresis were permitted to meet this criterion. This exclusion criterion may have resulted in the enrollment of fewer patients who had FLT3-ITD with high ARs. Future analyses in large datasets are required to establish further the efficacy of the combination in these subgroups.

While the data show the efficacy of venetoclax and azacitidine combination among patients with FLT3-mutated AML, other studies are exploring the use of triplet combinations with venetoclax, a hypomethylating agent (azacitidine, decitabine) or low-dose cytarabine, and a targeted FLT3 inhibitor such as with quizartinib (NCT03661307) or gilteritinib (NCT04140487). The preliminary analysis of a phase II trial (NCT03404193) has reported that triplet therapy with FLT3 inhibitor, venetoclax, and decitabine was safe and effective in treating treatment-naïve older patients with FLT3 mutation, with manageable cytopenias (14). If successful, these venetoclax-containing combination therapies may further improve response rates and survival outcomes among patients with FLT3-mutated AML.

In conclusion, the current data demonstrated promising efficacy of venetoclax and azacitidine in FLT3-mutated subgroups. Future analyses in larger patient populations are warranted to further define the risk/benefit of this combination among patients with FLT3 mutations and establish the efficacy of combining this therapy with targeted inhibitors of FLT3.

M. Konopleva reports other support from AbbVie during the conduct of the study as well as grants from AbbVie, Sanofi, Rafael Pharmaceutical, AstraZeneca, Ascentage, Agios, Ablynx, Calithera, Cellectis, Eli Lilly, and Immunomet; other support from Genentech, Janssen, and Reata Pharmaceutical; and grants and other support from F. Hoffman La-Roche, Stemline Therapeutics, and Forty Seven outside the submitted work. M.J. Thirman reports grants from AbbVie during the conduct of the study as well as grants from Merck, Syndax, and TG Therapeutics and personal fees from AbbVie, Adaptive Biotechnologies, AstraZeneca, Celgene, Pharmacyclics, and Genentech outside the submitted work. K.W. Pratz reports grants and personal fees from AbbVie and Astellas during the conduct of the study as well as grants from Millennium and Agios and personal fees from BMS/Celgene, Jazz Pharmaceuticals, Novartis, and Boston Biomedical outside the submitted work. J.S. Garcia reports other support from AbbVie during the conduct of the study as well as personal fees from AbbVie; nonfinancial support and other support from Genentech; and other support from Prelude, AstraZeneca, and Pfizer outside the submitted work. C. Recher reports grants, personal fees, and nonfinancial support from AbbVie during the conduct of the study as well as grants and personal fees from Astellas; grants, personal fees, and nonfinancial support from BMS, Daiichi-Sankyo, Amgen, Jazz Pharmaceuticals, Novartis, and Roche; nonfinancial support from Gilead and Sanofi; personal fees from Janssen, Otsuka, Takeda, and Macrogenics; and grants from Agios and MaatPharma outside the submitted work. V. Pullarkat reports personal fees from AbbVie and Genentech outside the submitted work. H.M. Kantarjian reports research grants from AbbVie, Amgen, Ascentage, BMS, Daiichi-Sankyo, Immunogen, Jazz, Novartis, and Pfizer and speakers bureau honoraria from AbbVie, Amgen, Aptitude Health, Ascentage, Astellas Health, AstraZeneca, Ipsen Pharmaceuticals, KAHRMedical Ltd, NOVA Research, Novartis, Pfizer, Precision Biosciences, and Taiho Pharmaceutical Canada. C.D. DiNardo reports personal fees from Astellas, AbbVie/Genentech, GSK, Novartis, Takeda, Kura, and Genmab; grants and personal fees from Agios/Servier, Celgene/BMS, ImmuneOnc and Foghorn; and nonfinancial support from Notable Labs outside the submitted work. M. Dail reports other support from Genentech/Roche during the conduct of the study as well as other support from Genentech/Roche outside the submitted work; in addition, M. Dail is an employee of Genentech/Roche. Y. Duan reports other support from AbbVie during the conduct of the study as well as other support from AbbVie outside the submitted work. B. Chyla reports other support from AbbVie during the conduct of the study as well as other support from AbbVie outside the submitted work. J. Potluri is an employee of AbbVie. C.L. Miller is an employee of AbbVie. A.H. Wei reports grants, personal fees, and other support from Astellas, AbbVie, Genentech, Amgen, AstraZeneca, Celgene/BMS, Novartis, Servier, and Syndax; grants from Astex; and personal fees and other support from Janssen, MacroGenics, Pfizer, and Gilead outside the submitted work; in addition, A.H. Wei has a patent for venetoclax with royalties paid.

M. Konopleva: Investigation, methodology, writing–review and editing. M.J. Thirman: Supervision, writing–review and editing. K.W. Pratz: Supervision, writing–review and editing. J.S. Garcia: Investigation, writing–review and editing. C. Recher: Supervision, writing–review and editing. V. Pullarkat: Supervision, writing–review and editing. H.M. Kantarjian: Supervision, writing–review and editing. C.D. DiNardo: Supervision, writing–review and editing. M. Dail: Methodology, writing–review and editing. Y. Duan: Data curation, writing–review and editing. B. Chyla: Data curation, methodology, writing–review and editing. J. Potluri: Conceptualization, supervision, methodology, writing–review and editing. C.L. Miller: Resources, writing–review and editing. A.H. Wei: Supervision, writing–review and editing.

The authors wish to thank the patients and their families, the study coordinators, and the support staff. The authors would also like to acknowledge all investigators of studies M14–358 and M15–656.

Medical writing support was provided by Dalia Majumdar, an employee of AbbVie.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

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Supplementary data