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Limited data are available on breakthrough COVID-19 in patients with hematologic malignancy (HM) after anti–severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination. Adult patients with HM, ≥1 dose of anti-SARS-CoV-2 vaccine, and breakthrough COVID-19 between January 2021 and March 2022 were analyzed. A total of 1548 cases were included, mainly lymphoid malignancies (1181 cases, 76%). After viral sequencing in 753 cases (49%), the Omicron variant was prevalent (517, 68.7%). Most of the patients received ≤2 vaccine doses before COVID-19 (1419, 91%), mostly mRNA-based (1377, 89%). Overall, 906 patients (59%) received COVID-19-specific treatment. After 30-day follow-up from COVID-19 diagnosis, 143 patients (9%) died. The mortality rate in patients with the Omicron variant was 7.9%, comparable to other variants, with a significantly lower 30-day mortality rate than in the prevaccine era (31%). In the univariable analysis, older age (P < .001), active HM (P < .001), and severe and critical COVID-19 (P = .007 and P < .001, respectively) were associated with mortality. Conversely, patients receiving monoclonal antibodies, even for severe or critical COVID-19, had a lower mortality rate (P < .001). In the multivariable model, older age, active disease, critical COVID-19, and 2-3 comorbidities were correlated with a higher mortality, whereas monoclonal antibody administration, alone (P < .001) or combined with antivirals (P = .009), was protective. Although mortality is significantly lower than in the prevaccination era, breakthrough COVID-19 in HM is still associated with considerable mortality. Death rate was lower in patients who received monoclonal antibodies, alone or in combination with antivirals., EPICOVIDEHA has received funds from Optics COMMIT (COVID-19 Unmet Medical Needs and Associated Research Extension) COVID-19 RFP program by GILEAD Science, United States (Project 2020-8223).

ETNK1 kinase is responsible for the phosphorylation of ethanolamine to phosphoethanolamine (P-Et) (Kennedy, 1956, J Biol Chem). Recurrent somatic mutations occurring on ETNK1 were identified in about 13% of patients affected by atypical chronic myeloid leukemia (aCML), in 3-14% of chronic myelomonocytic leukemia (CMML), and in 20% of systemic mastocytosis (SM) patients with eosinophilia (Gambacorti-Passerini, 2015, Blood; Lasho, 2015, Blood Cancer J). ETNK1 mutations, encoding for H243Y, N244S/T/K, and G245V/A amino acid substitutions, cluster in a very narrow region of the ETNK1 catalytic domain and cause an impairment of ETNK1 enzymatic activity leading to a significant decrease in the intracellular concentration of P-Et (Gambacorti-Passerini, 2015, Blood). Despite this evidence, however, their oncogenic role remained largely unexplained. Here, we investigated the specific role of these mutations by using cellular CRISPR/Cas9 and ETNK1 overexpression models as well as aCML patients' samples. We showed that mutated ETNK1 causes a significant increase in mitochondrial activity (1.87 fold increase compared to WT; p=0.0002) and in ROS production (2.05 fold increase compared to WT; p Disclosures Rea: Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees. Gambacorti-Passerini:Bristol-Myers Squibb: Consultancy; Pfizer: Honoraria, Research Funding.

Recurrent somatic mutations in ETNK1 (Ethanolamine-Kinase-1) were identified in several myeloid malignancies and are responsible for a reduced enzymatic activity. Here, we demonstrate in primary leukemic cells and in cell lines that mutated ETNK1 causes a significant increase in mitochondrial activity, ROS production, and Histone H2AX phosphorylation, ultimately driving the increased accumulation of new mutations. We also show that phosphoethanolamine, the metabolic product of ETNK1, negatively controls mitochondrial activity through a direct competition with succinate at mitochondrial complex II. Hence, reduced intracellular phosphoethanolamine causes mitochondria hyperactivation, ROS production, and DNA damage. Treatment with phosphoethanolamine is able to counteract complex II hyperactivation and to restore a normal phenotype., ETNK1 mutations are recurrent in leukemia but how they contribute to oncogenesis is still unclear. Here, the authors show that ETNK1 mutations increase mitochondrial activity, ROS and H2AX levels and that these effects can be rescued upon phosphoethanolamine supplementation.