Venetoclax Therapy in a Heavily Treated Cohort of Patients with Relapsed or Refractory Acute Myeloid Leukemia: Update of the Pethema Registry Experience

Abstract Introduction The prognosis of patients with relapsed or refractory acute myeloid leukemia (RR-AML) is very poor, and treatment options are very limited. The exciting results of venetoclax (VEN) in untreated AML have led to its off-label use in RR-AML. However, evidence in RR-AML is still scarce and the available data are mostly from retrospective and single-center studies. The aim of our study was to analyze the effectiveness of VEN use in patients with RR-AML reported to the PETHEMA AML epidemiological registry. Initial results were presented previously (Labrador J, et al. ASH 2020). Here, we report an updated analysis. Methods We conducted a retrospective, multicenter, observational study of a cohort of patients with AML-RR who were treated with venetoclax in the hospitals of the PETHEMA group. We evaluated efficacy, CR/CRi rate and overall survival (OS). We performed a descriptive analysis. Overall survival (OS) was calculated using the Kaplan-Meier method. Results Fifty-one patients were included, 33 men and 18 women, with a median age of 68 years (25-82). The main characteristics of the included patients are shown in Table 1. With a median follow-up of 167 days, 10/51 patients (19%) continued to receive VEN at the time of analyses. Patients received a median of 2 cycles (0-8). VEN was administered with azacitidine (AZA) in 59%, with decitabine (DEC) in 29% and with low-dose cytarabine (LDAC) in 12% of patients, respectively. The CR/CRi and partial response (PR) rates were 12.4% and 10.4%, respectively. The CR/RCi and overall response (ORR, CR/CRi+PR) was higher in patients receiving VEN+AZA (17.9% and 32.1%) than in those receiving DEC + VEN (6.7% and 13.3%) or LDAC + VEN (0%). The presence of NPM1 or CEBPA variants were the only two variables associated with increased CR/CRi with VEN in RR-AML. Median OS was 104 days (95% CI: 56 - 151) (Figure 1A), 120 days in combination with AZA, 104 days with DEC, and 69 days with LDAC; p=0.875. Treatment response (Figure 1B) and ECOG 0 were the only variables that influenced OS in a multivariate model adjusted for age and sex (Table 2). VEN-resistant patients who received subsequent salvage therapy had superior median OS (98 vs. 5 days, p=0.004).Twenty-eight percent of patients required discontinuation of VEN due to toxicity. Sixty-one percent of patients required admission, mainly due to infections (45%), 10% due to bleeding and other causes in 12%. One case of tumor lysis syndrome was described. Conclusions Our real-life series depicts a marginal probability of CR/CRi and poor OS after venetoclax-based salvage. Patients treated with this regimen had very poor-risk features, and were heavily pre-treated, which could explain in part the observed poor outcomes. Although follow-up is still short, the small proportion of responders did not reach the median OS. Further studies will help to identify those patients potentially benefiting from venetoclax-based salvage regimens. Figure 1 Figure 1. Disclosures Belén Vidriales: Roche: Consultancy; Novartis: Speakers Bureau; Astellas: Consultancy, Speakers Bureau; Jazz: Consultancy, Speakers Bureau. Pérez-Encinas: Janssen: Consultancy. Tormo: Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Montesinos: Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Glycomimetics: Consultancy; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Karyopharm: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Incyte: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Forma Therapeutics: Consultancy; Sanofi: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Teva: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Stemline/Menarini: Consultancy; Tolero Pharmaceutical: Consultancy; Agios: Consultancy; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Astellas Pharma, Inc.: Consultancy, Honoraria, Other: Advisory board, Research Funding, Speakers Bureau. OffLabel Disclosure: Venetoclax for Patients with Relapsed or Refractory Acute Myeloid Leukemia

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