A total of 56 adult AML patients with a median age of 66.5 (range 34–83) years were included in this analysis. Table 1 provides information about morphology, AML-type and genetics including risk stratification.

48.2% (n = 27) presented with de novo AML, 51.8% (n = 29) with secondary AML (sAML) including one patient with treatment association (Table 1). The median time of myelodysplastic syndrome (MDS) diagnosis to sAML development was 11.7 (1.7 – 156.4) months (data not shown).

Eastern Cooperative Oncology Group (ECOG) performance status rated 31 patients (55.3%) as 0–1 and 25 patients (44.6%) as 2–3, respectively.

Cytogenetic risk profiling was performed for 55 of 56 patients (98.2%) and resulted in favorable, intermediate and adverse risk in 0 (0%), 34 (60.7%) and 21 (37.5%), respectively. Data for molecular aberrations were available in 54 of 56 (96.4%) AML patients. Risk stratification according to the current ELN criteria 2017 showed a distribution in favorable, intermediate and adverse risk in 5 (8.9%), 17 (30.3%) and 32 (57.1%) of patients, respectively (Table 1). Further characteristics of those patients who received alloHSCT (39.3%, n = 22) are summarized in Table S1.

Treatment intentions are illustrated in the CONSORT diagram (Fig. 1) and detailed information is provided in Table 2.

CONSORT diagram: detailed overview about different treatment cohorts and disease settings. 1One pt received HMA-VEN as first-line treatment with intention to alloHSCT. 2Including 2 pts with AML relapse after second alloHSCT. 33 pts received VEN twice in relapse after alloHSCT without response (excluded from analysis). VEN Venetoclax, pt(s) patient(s), HMA hypo-methylating agent, alloHSCT allogeneic hematopoietic stem cell transplantation

For first-line therapy, VEN was applied in 18 AML patients, 23 patients received VEN as subsequent therapy (r/r AML without prior alloHSCT). A third subgroup was treated with VEN due to disease relapse following alloHSCT (n = 15). Of note, 7 patients were successfully transitioned to alloHSCT after VEN treatment (demographics and survival are reported in Table S1 and Figure S1, C, respectively). Notably, one patient received VEN/HMA as first-line treatment before subsequent alloHSCT. Since all other VEN/HMA first-line patients (n = 17) were treated within a palliative setting, the only patient underwent alloHSCT was not included in survival analysis for first-line VEN treatment group.

The majority of patients received VEN in combination with an HMA agent backbone, including 22 (39.3%) decitabine and 28 (50%) AZA (Table 2).

Median time of VEN treatment was 3.4 (0.6 – 22.1) months with a median application of 3 (1–18) treatment cycles (28 days). The overall mean drug dosage was 149 (20.9–362.5) mg. In 85.7% of all patients, concurrent azole medication was applied (posaconazole 47.9%, fluconazole 22.9% and isavuconazole 18.7%). Interruption of treatment was necessary in 16 patients (28.6%) being the majority due to grade 4 neutropenia (93.7%) and one patient due to severe nausea and emesis (6.2%).

22 of 38 patients (57.9%) were refractory to any treatment line prior to VEN. In median, one CR (range 0–4) with a median of 1.5 (range 0–8) therapy lines could be achieved prior to initiation of VEN treatment. Information on prior or subsequent treatment regimens to VEN is indicated in Table 2. Importantly, except for 3 patients receiving alloHSCT, no response to further treatment approaches after VEN could be achieved.

Subgroup analyses with respect to treatment intention showed a median OS starting at VEN treatment initiation of 13.3 (2.2–20.5) months, 5.0 (0.8–24.3) months, 4.0 (1.5–22.1) months for first-line treatment, subsequent line treatment and post-alloHSCT, respectively (Fig. 2A, B). Median follow-up was 11.5 (6.1 – 22.3) months since diagnosis of AML. Of note, survival rates for patients who received VEN prior to alloHSCT were calculated separately with a median OS of 11.5 (10.4–22.3) months (Figure S1, C).

Kaplan–Meier estimates for OS and PFS were measured from starting VEN treatment in indicated groups (A and B, respectively), OS and PFS since VEN initiation in patients who achieved CRc (C and D, respectively). OS overall survival, alloHSCT allogeneic hematopoietic stem cell transplantation, PFS progression-free survival, CRc composite complete remission (CR + CRi + CRp), VEN Venetoclax

Patients who achieved CRc on VEN treatment had a median OS of 20.8 (2.5–24.3) months and PFS of 20.5 (2.6 – 24.3) months, respectively (Fig. 2C, D).

For the whole cohort, OS starting at AML diagnosis was 18.7 (2.8 – 125.3) months and not reached in patients who received CRc (2-year OS: 63%) (Figure S1 A, B). RFS for the whole cohort was 10.2 (2.2 – 24.3) months (Figure S1, D).

An ORR of 51.8% was achieved for the whole population (data not shown). In detail, ORR of 61.1% was seen when VEN was applied as first-line treatment, 52.2% for subsequent line treatment and 42.8% at relapse post-alloHSCT (Fig. 3). Median time to first response for patients achieving CRc was 2.7 (1.4 – 16.2) months. Differences in ORR were also seen when comparing distinct genetic subgroups. Patients with cytogenetically intermediate-risk features showed an ORR of 57.5% whereas only 42.8% in high-risk patients (Fig. 3B). Presence of FLT3-ITD was associated with an ORR of 12.5%, in contrast 71.4% in NPM1 and / or IDH1,2 mutated AML, respectively (Fig. 3B). In multivariable analysis, NPM1 mutation retained independent favorable prognostic significance with regard to achieving CRc (HR 19.14, 95% CI 2.303 – 436.2, p < 0.05).

Bone marrow response rates for treatment cohorts (A) and distinct genetic subgroups (B). alloHSCT allogeneic hematopoietic stem cell transplantation; ORR overall response rate, PD progressive disease, SD stable disease, PR partial remission, CRc composite complete remission (CR + CRi + CRp), n.a. not assessed

With respect to genetic subgroups, no difference in survival since VEN initiation was seen for cytogenetic (intermediate vs. high risk) and ELN risk groups (favorable + intermediate vs. high-risk) (Fig. 4A, B): 6.4 (2.2–24.3) months for intermediate vs. 4.9 (1.1–20.8) months for high-risk cytogenetics (p = 0.598) and 6.4 (1.1–22.2) months vs. 5.0 (2.2–24.3) months for ELN high-risk vs. favorable + intermediate, respectively (p = 0.565).

Kaplan–Meier estimates for survival time were measured from starting VEN treatment for intermediate vs. high-risk cytogenetics (A), ELN 2017 risk groups (B), according to FLT3-ITD (C) and NPM1 or IDH1/2 mutational status (D). VEN venetoclax, ELN European leukemia net

Analysis of distinct molecular subgroups revealed that patients harboring FLT3-ITD mutation (14.3%, n = 8) had a significantly reduced median OS of 3.4 (1.9 – 4.9) months compared to 10.4 (0.8 – 24.3) months for those without an activating FLT3-ITD mutation (HR 4.45, 95% CI 0.89–22.12, p = 0.0002).

In contrast, comparing survival of patients with NPM1, IDH1, or IDH2 mutations without co-occurring FLT3-ITD mutations with the remaining cohort, an increased sensitivity to VEN-based therapy has been demonstrated: 11.2 (5 – 24.3) months versus 5.0 (0.8–22.1), respectively (HR 0.53, 95% CI 0.23 – 1.21, p = 0.131) (Fig. 4D).

Furthermore, assessment of blood count and transfusion (in-)dependence was performed. As demonstrated in Table 3, median count for platelets was 12 × 109/l (12–317) and 42.5 × 109/l (12–280) on days 0 and 100 of treatment, respectively. Transfusion dependence for platelets was decreasing from 62.9% to 47.2% and for red blood cells (RBC) from 75.9% to 55.5% during the first 100 days of treatment. Median neutrophil count was 0.39 × 109/l (range 0.1–12.5) and 0.2 × 109/l (range 0.1–3.8) at days 0 and 100 of treatment, respectively. On day 60, 17 of 49 patients (36%) showed an increase of the neutrophil count compared to baseline value.

The median of the mean VEN dosage of the whole cohort was 149 mg/d (20.9 – 362.5) with a median treatment duration of 105 (18 – 674) days (Table 2).

To uncover a potential impact of VEN dosing on survival or response rates, patients with a mean daily dose of VEN ≤ 100 mg (n = 22) were compared to those with > 100 mg (n = 34). Kaplan–Meier analysis demonstrates a median survival of 6.4 (1.5–17.7) months and 8.1 (1.1–24.3) months for patients having received a mean daily dose of ≤ 100 mg and > 100 mg, respectively (p = 0.357) (Fig. 5A). Doses of > 100 mg showed an increased ORR (55.9%) compared with patients receiving ≤ 100 mg mean dosage (45.5%). Progressive disease while on VEN treatment was noted in 22.3% and 8.9% comparing the cohorts of ≤ 100 mg and > 100 mg, respectively (Fig. 5B).

Kaplan–Meier estimates for survival time since start of VEN treatment according to mean dosage of VEN (A). Bone marrow response rates according to mean dosage of VEN (B). CRc composite complete remission (CR + CRi + CRp), PR partial remission, SD stable disease, PD progressive disease, n.a. not assessed, VEN venetoclax

Most frequent grade 3 and 4 side effects were hematologic with neutropenia, thrombocytopenia, and anemia (44.6%, 14.5%, 12%, respectively) (Fig. 6). Grade 3 renal insufficiency occurred in 3 patients (5.3%) including two cases of tumor lysis syndrome. One patient suffered from severe retinal bleeding, another patient from dysesthesia und body aches. Common adverse events are summarized in Fig. 6. Non-relapse mortality rate was 8.9% (5/56 patients) and early deaths till day 30 since treatment start occurred in 3.5% (2/56 patients).

Assessment of VEN toxicities according to CTC classification. VEN venetoclax, CTC common toxicity criteria