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Competing Interests: Thomas Chatzikonstantinou received honoraria from AbbVie. Lydia Scarfò received honoraria from AbbVie, AstraZeneca, BeiGene, Lilly, Janssen, Octapharma. Gloria Iacoboni received honoraria and travel support from Novartis, Kite/Gilead, Bristol‐Myers Squibb, Abbvie, Autolus, Miltenyi, and AstraZeneca. Rosa Collado received support for attending meetings from Janssen‐Cilag and S.A. Sara Galimberti received honoraria support for attending meetings from AbbVie, AstraZeneca, Jazz, Novartis, and Incyte, honoraria from Roche, Celgene, Pfizer, and Janssen, and support for attending meetings from Jazz, AstraZeneca, and Roche. Romain Guieze received honoraria, consulting fees, and support for attending meetings from AbbVie, Beigene, Roche, Janssen, and AstraZeneca. Eleftheria Hatzimichael received honoraria from AbbVie, Janssen‐Cilag, AstraZeneca, and Roche. Yair Herishanu received honoraria from Janssen, AbbVie, Roche, AstraZeneca, Medion, and Lilly. José‐Ángel Hernández‐Rivas received honoraria as a consultant from Janssen, AbbVie, AstraZeneca, Lilly, and BeiGene and support for attending meetings from Janssen, AbbVie, AstraZeneca, and BeiGene. Ozren Jaksic received honoraria from Johnson and Johnson, AstraZeneca, and Lilly, honoraria from Johnson and Johnson, AbbVie, AstraZeneca, and Lilly, and support for attending meetings from Johnson and Johnson, and AbbVie. Kamel Laribi received consulting fees from AbbVie, AstraZeneca, Janssen, Beigene, Takeda, and Novartis. Maya Koren‐Michowitz received honoraria from Novartis, Pfizer, and Gad Medical LTD. and support for attending meetings from Novartis. Arnon P. Kater received advisory board fees and research money from Janssen, AbbVie, BMS, AstraZeneca, and Roche/Genentech, and support for attending meetings from Janssen and AbbVie. Ioannis Kotsianidis received honoraria and consulting fees from AbbVie and Janssen. Ivana Milosevic received honoraria from AbbVie, Roche, Sandoz, AstraZeneca, and Janssen, and support for attending meetings from AbbVie, Roche, and Takeda. Almudena Navarro‐Bailón received honoraria, advisory board fees, and support for attending meetings from AbbVie, AstraZeneca, Takeda, Janssen, and Beigene. Jacopo Olivieri received honoraria from AbbVie, AstraZeneca, and Janssen. Gianluigi Reda received consulting fees from AbbVie, AstraZeneca, Janssen, and Beigene, and is currently employed by AstraZeneca. Gian M. Rigolin received honoraria for participation in speaker's bureau from AbbVie, Astra Zeneca, Beigene, and Janssen, and support for attending meetings from Janssen. Mattia Schipani received honoraria and support for attending meetings from AstraZeneca, AbbVie, and Janssen‐Cilag and owns shares of stock in AbbVie, AstraZeneca, Merck, Eli Lilly, Sanofi, Johnson and Johnson, Pfizer, Gilead, and GSK. Tereza Shokralla and Stephan Stilgenbauer reports research funding from, consultancy or advisory role for, honoraria from, speakers' bureau participation for, and travel support from AbbVie, Amgen, AstraZeneca, BeiGene, Bristol Myers Squibb, Celgene, Gilead, GlaxoSmithKline, Hoffmann‐La Roche, Incyte, Infinity, Janssen, Novartis, and Sunesis. Eric Tse received support for attending meetings from Takeda. Theodoros Vassilakopoulos received honoraria from Takeda, Roche, Genesis Pharma, Merck, Novartis, Gilead, Sandoz, AstraZeneca, Integris, and Servier, and support for attending meetings from Takeda, Roche, Genesis Pharma, Merck, Pfizer, and Winmedica. Candida Vitale received honoraria from AbbVie, consulting fees from AstraZeneca, and support for attending meetings from AstraZeneca, Takeda, and Janssen. Renata Walewska received honoraria from AbbVie, AstraZeneca, and Beigene, support for attending meetings from Janssen, AbbVie, and AstraZeneca, and advisory board fees from AbbVie, AstraZeneca, Janssen, Beigene, and SecuraBio. Lucrecia Yañez received honoraria from AbbVie, AstraZeneca, Novartis, Gilead, Janssen, Jazz, MSD, and Pfizer, support for attending meetings from AbbVie, AstraZeneca, Gilead, Janssen, and Pfizer, and advisory board fees from AbbVie, AstraZeneca, Jazz, Janssen, Beigene, and Celgene. Francesc Bosch received consulting fees, honoraria, and payment for expert testimony from AbbVie, Genentech, Novartis, Takeda, Janssen, Roche, Mundipharma, Celgene/BMS, AstraZeneca, Lilly, Beigene, Gilead and TG Therapeutics, Advantage Allogene, Lava Therapeutics, and Enterome. Stephen Mulligan received advisory board fees from AbbVie, AstraZeneca, Janssen, Roche, and BeiGene. Maria Angelopoulou received consulting fees from AbbVie, Takeda, Janssen, Roche, Genesis, Gilead, and Amgen and honoraria from AbbVie, Takeda, Roche, Genesis, Gilead, and Novartis. Fatih Demirkan received support for attending meetings from Janssen and AbbVie. Tomas Papajík received honoraria and advisory board fees from AbbVie, Janssen‐Cilag, and AstraZeneca, and support for attending meetings from AstraZeneca. Marta Coscia received honoraria, advisory board fees, and support for attending meetings from AbbVie, AstraZeneca, and Janssen. Constantine Tam received honoraria from AbbVie, Beigene, Janssen, and LOXO. Antonio Cuneo received honoraria, advisory board fees, and support for attending meetings from AbbVie, AstraZeneca, Beigene, Janssen, and Lilly. Gianluca Gaidano received honoraria from Abbvie, AstraZeneca, BeiGene, Hikma, Incyte, Janssen, and Lilly. Niki Stavroyianni received honoraria from Janssen, AbbVie, AstraZeneca, and Lilly, and support for attending meetings from Janssen and AstraZeneca. Lukas Smolej received consulting fees, honoraria, and support for attending meetings from AbbVie, AstraZeneca, and Janssen and advisory board fees from AbbVie and AstraZeneca. Martin Spacek received honoraria and consulting and advisory board fees, and support for attending meetings from AbbVie, AstraZeneca, and Janssen. Michael Doubek received research support and honoraria from AbbVie, AstraZeneca, and Janssen. Eugene Nikitin received honoraria from AbbVie. Kostas Stamatopoulos received research support from AbbVie, AstraZeneca, Janssen, Novartis, and Roche; honoraria from AbbVie, AstraZeneca, Bristol Myers Squibb, Lilly, and Janssen. Paolo Ghia received research support from AbbVie, AstraZeneca, BMS, Janssen and honoraria from AbbVie, AstraZeneca, BeiGene, BMS, Galapagos, Genmab, Janssen, Loxo Oncology @Lilly, MSD, Roche, and is an Editor of HemaSphere. Georgios Karakatsoulis, Eva Minga, Dimitra Chamou, Jana Kotaskova, Christos Demosthenous, Elisa Albi, Miguel Alcoceba, Salem Al‐Shemari, Thérèse Aurran‐Schleinitz, Francesca Bacchiarri, Sofia Chatzileontiadou, Zadie Davis, Marcos Daniel de Deus Santos, Maria Dimou, Elena Dmitrieva, David Donaldson, Gimena Dos Santos, Barbara Dreta, Maria Efstathopoulou, Shaimaa El‐Ashwah, Alicia Enrico, Andrzej Frygier, Andrea Galitzia, Eva Gimeno, Valerio Guarente, Sean Harrop, Elżbieta Kalicińska, Volkan Karakus, Bonnie Kho, Maria Kislova, Εliana Konstantinou, Zuzana Kubova, Jorge Labrador, Deepesh Lad, Luca Laurenti, Thomas Longval, Alberto Lopez‐Garcia, Juan Marquet, Stanislava Maslejova, Carlota Mayor‐Bastida, Biljana Mihaljevic, Fatima Miras, Riccardo Moia, Marta Morawska, Uttam K. Nath, Irina Panovska‐Stavridis, Maria Papaioannou, Cheyenne Pierie, Anna Puiggros, Rosa Ruchlemer, Annett Schiwitza, Yandong Shen, Tereza Shokralla, Martin Simkovic, Svetlana Smirnova, Dina S. A. Soliman, Tamar Tadmor, Kristina Tomic, Andrea Visentin, George Vrachiolias, Vojin Vukovic, Zhenshu Xu, Munci Yagci, Mohamed Yassin, Jana Zuchnicka, David Oscier, Alessandro Gozzetti, Panagiotis Panagiotidis, Blanca Espinet, Paolo Sportoletti, Gerassimos A. Pangalis, Viola M. Popov, Bella Biderman, Roberta Murru, Rainer Claus, Livio Trentin, Darko Antic, Olga B. Kalashnikova, Mark Catherwood, Sarka Pospisilova, and Anastasia Chatzidimitriou have no conflict of interest to disclose.

Background: Patients with chronic lymphocytic leukemia (CLL) have a higher risk of developing other malignancies (OMs) compared to the general population. However, the impact of CLL-related risk factors and CLL-directed treatment is still unclear and represents the focus of this work., Methods: We conducted a retrospective international multicenter study to assess the incidence of OMs and detect potential risk factors in 19,705 patients with CLL, small lymphocytic lymphoma, or high-count CLL-like monoclonal B-cell lymphocytosis, diagnosed between 2000 and 2016. Data collection took place between October 2020 and March 2022., Findings: In 129,254 years of follow-up after CLL diagnosis, 3513 OMs were diagnosed (27.2 OMs/1000 person-years). The most common hematological OMs were Richter transformation, myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Non-melanoma skin (NMSC) and prostate cancers were the most common solid tumors (STs).The only predictor for MDS and AML development was treatment with fludarabine and cyclophosphamide with/without rituximab (FC ± R) (OR = 3.7; 95% CI = 2.79-4.91; p < 0.001). STs were more frequent in males and patients with unmutated immunoglobulin heavy variable genes (OR = 1.77; 95% CI = 1.49-2.11; p < 0.001/OR = 1.89; 95% CI = 1.6-2.24; p < 0.001).CLL-directed treatment was associated with non-melanoma skin and prostate cancers (OR = 1.8; 95% CI = 1.36-2.41; p < 0.001/OR = 2.11; 95% CI = 1.12-3.97; p = 0.021). In contrast, breast cancers were more frequent in untreated patients (OR = 0.17; 95% CI = 0.08-0.33; p < 0.001).Patients with CLL and an OM had inferior overall survival (OS) than those without. AML and MDS conferred the worst OS (p < 0.001)., Interpretation: OMs in CLL impact on OS. Treatment for CLL increased the risk for AML/MDS, prostate cancer, and NMSC. FCR was associated with increased risk for AML/MDS., Funding: AbbVie, and EU/EFPIAInnovative Medicines Initiative Joint Undertaking HARMONY grant n° 116026., Competing Interests: TC received honoraria from AbbVie. LS received consulting fees from AbbVie, BeiGene, AstraZeneca, Lilly, and Janssen, honoraria from Janssen and Octapharma, support for attending meetings from BeiGene and Janssen and advisory board fees from Merck. SMu received advisory board fees from AbbVie, AstraZeneca, Janssen, Roche and BeiGene. JAHR received honoraria as a consultant from Janssen, AbbVie, AstraZeneca, Lilly, and BeiGene and support for attending meetings from Janssen, AbbVie, AstraZeneca, and BeiGene. LI received honoraria from AbbVie, Roche, and Janssen-Cilag. APK received advisory board fees and research money from Janssen, AbbVie, BMS, AstraZeneca, Roche/Genentech, support for attending meetings from Janssen and AbbVie. M-DL received travel expenses from Janssen and AbbVie. GMR received honoraria for participation to speaker's bureau from AbbVie, Astra Zeneca, Beigene, and Janssen, and support for attending meetings from Janssen. JVT received consulting fees from AbbVie, AstraZeneca, BeiGene, and Janssen, honoraria for scientific talks from AbbVie, AstraZeneca, BeiGene, Janssen, Lilly, and Roche, travel support from AbbVie, AstraZeneca, BeiGene, Janssen, Roche, and Lilly, and advisory boards fees for AbbVie, Amgen, AstraZeneca, BeiGene. GI received honoraria from Novartis, BMS, Sandoz, AstraZeneca, Janssen, Kite/Gilead, and Miltenyi, support for attending meetings from Kite/Gilead, AstraZeneca, and AbbVie and advisory board fees from Kite/Gilead, Novartis, BMS, and Autolus. FBi received support for attending meetings from AbbVie. RCo received support for attending meetings from Janssen-Cilag and S.A. SG received honoraria support for attending meetings from AbbVie, AstraZeneca, Jazz, Novartis, and Incyte, honoraria from Roche, Celgene, Pfizer, and Janssen, and support for attending meetings from Jazz, AstraZeneca, and Roche. RGS received support for attending meetings from AbbVie and S.L.U. RG received honoraria, consulting fees, and support for attending meetings from AbbVie, Beigene, Roche, Janssen, AstraZeneca. YH received honoraria from Janssen, AbbVie, Roche, AstraZeneca, Medion, and Lilly. OJ received honoraria from Johnson and Johnson, AstraZeneca, and Lilly, honoraria from Johnson and Johnson, AbbVie, AstraZeneca, and Lilly, and support for attending meetings from Johnson and Johnson, and AbbVie. LK received consulting fees from AbbVie, AstraZeneca, Janssen, Beigene, Takeda, and Novartis. MKM received honoraria from Novartis, Pfizer, and Gad Medical LTD and support for attending meetings from Novartis. IKo received honoraria and consulting fees from AbbVie and Janssen. IM received honoraria from AbbVie, Roche, Sandoz, AstraZeneca, and Janssen, and support for attending meetings from AbbVie, Roche, and Takeda. ANB received honoraria, advisory board fees and support for attending meetings from AbbVie, AstraZeneca, Takeda, Janssen, and Beigene. JO received honoraria from AbbVie, AstraZeneca, and Janssen. GR received consulting fees from AbbVie, AstraZeneca, Janssen, and Beigene, and is currently employed by AstraZeneca. TP received honoraria and advisory board fees from AbbVie, Janssen-Cilag, and AstraZeneca and support for attending meeting from AstraZeneca. MS received honoraria and support for attending meeting from AstraZeneca, AbbVie, and Janssen-Cilag and owns shares of stock in AbbVie, AstraZeneca, Merck, Eli Lilly, Sanofi, Johnson and Johnson, Pfizer, Gilead, and GSK. MSp received honoraria and consulting and advisory board fees, and support for attending meeting from AbbVie, AstraZeneca, and Janssen. ET received support for attending meetings from Takeda. TV received honoraria from Takeda, Roche, Genesis Pharma, Merck, Novartis, Gilead, Sandoz, AstraZeneca, Integris, and Servier and support for attending meetings from Takeda, Roche, Genesis Pharma, Merck, Pfizer, and Winmedica. CV received honoraria from AbbVie, consulting fees from AstraZeneca and support for attending meeting from AstraZeneca, Takeda, and Janssen. RW received honoraria from AbbVie, AstraZeneca, and Beigene, support for attending meetings from Janssen, AbbVie, and AstraZeneca and advisory board fees from AbbVie, AstraZeneca, Janssen, Beigene, and SecuraBio. EWS received honoraria from AbbVie, Roche, and Janssen-Cilag and support for attending meetings from AbbVie. LY received honoraria from AbbVie, AstraZeneca, Novartis, Gilead, Janssen, Jazz, MSD, and Pfizer, support for attending meetings from AbbVie, AstraZeneca, Gilead, Janssen, and Pfizer, and advisory board fees from AbbVie, AstraZeneca, Jazz, Janssen, Beigene, and Celgene. MAn received consulting fees from AbbVie, Takeda, Janssen, Roche, Genesis, Gilead, and Amgen and honoraria from AbbVie, Takeda, Roche, Genesis, Gilead, and Novartis. MC received honoraria, advisory board fees, and support for attending meetings from AbbVie, AstraZeneca, and Janssen. ACu received honoraria, advisory board fees, and support for attending meetings from AbbVie, AstraZeneca, Beigene, Janssen, and Lilly. FD support for attending meetings from Janssen and AbbVie. GG received honoraria, and advisory board fees from AbbVie, AstraZeneca, Beigene, Janssen and advisory board fees from Lilly. EN received honoraria from AbbVie. LSm received consulting fees, honoraria and support for attending meetings from AbbVie, AstraZeneca, and Janssen and advisory board fees from AbbVie and AstraZeneca. NS received honoraria from Janssen, AbbVie, AstraZeneca, and Lilly, and support for attending meetings from Janssen and AstraZeneca. CT received honoraria from AbbVie, Beigene, Janssen, and LOXO. FB received consulting fees, honoraria and payment for expert testimony from AbbVie, Genentech, Novartis, Takeda, Janssen, Roche, Mundipharma, Celgene/BMS, AstraZeneca, Lilly, Beigene, Gilead and TG Therapeutics, Advantage Allogene, Lava Therapeutics, and Enterome. MDo received honoraria and advisory board fees from AbbVie, AstraZeneca and Janssen, advisory board fees from Swixx, and support for attending meetings from Janssen. PG received honoraria and consulting fees from AbbVie, AstraZeneca, BMS, Janssen, Lilly/Loxo Oncology, MSD, and Roche; grant support from AbbVie, AstraZeneca, BMS, Janssen. KS received honoraria from Janssen, AbbVie, Lilly and AstraZeneca, consulting fees and support for attending meetings from Janssen and AstraZeneca. GK, EM, DC, JK, CD, MA, SA, TAS, FBa, MB, ACa, AM, AKM, RC, SC, ACh, ZD, MDi, DD, GDS, BD, ME, SEA, AE, AF, AG, EG, IGGM, AGo, AjG, RGu, SH, EH, SJ, EKa, VK, BK, MK, EK, RJK, JL, DL, IL, TL, ALG, JM, LMR, MMa, SM, CMB, BM, FM, RM, MMo, RMu, UKN, ACO, DO, IPS, MP, ZK, PP, CP, AP, LR, RR, MDDS, AS, YS, MSi, SS, DSAS, TT, KT, AV, GV, VV, ZX, MYa, MY, JZ, DA, BB, MCa, RCl, BE, OBK, LL, GP, PPa, VMP, SP, PS, LT, AC, have no conflict of interest to disclose., (© 2023 Published by Elsevier Ltd.)

In chronic lymphocytic leukaemia (CLL) the efficacy of SARS-CoV-2 vaccination remains unclear as most studies have focused on humoral responses. Here we comprehensively examined humoral and cellular responses to vaccine in CLL patients. Seroconversion was observed in 55.2% of CLL with lower rate and antibody titres in treated patients. T-cell responses were detected in a significant fraction of patients. CD4 + and CD8 + frequencies were significantly increased independent of serology with higher levels of CD4 + cells in patients under a Bruton tyrosine kinase (BTK) or a B-cell lymphoma 2 (BCL-2) inhibitor. Vaccination skewed CD8 + cells towards a highly cytotoxic phenotype, more pronounced in seroconverted patients. A high proportion of patients showed spike-specific CD4 + and CD8 + cells producing interferon gamma (IFNγ) and tumour necrosis factor alpha (TNFα). Patients under a BTK inhibitor showed increased production of IFNγ and TNFα by CD4 + cells. Vaccination induced a Th1 polarization reverting the Th2 CLL T-cell profile in the majority of patients with lower IL-4 production in untreated and BTK-inhibitor-treated patients. Such robust T-cell responses may have contributed to remarkable protection against hospitalization and death in a cohort of 540 patients. Combining T-cell metrics with seroprevalence may yield a more accurate measure of population immunity in CLL, providing consequential insights for public health., (© 2022 The Authors. British Journal of Haematology published by British Society for Haematology and John Wiley & Sons Ltd.)

Recurrent loss-of-function mutations of BCL6 co-repressor (BCOR) gene are found in about 4% of AML patients with normal karyotype and are associated with DNMT3a mutations and poor prognosis. Therefore, new anti-leukemia treatments and mouse models are needed for this combinatorial AML genotype. For this purpose, we first generated a Bcor -/- knockout mouse model characterized by impaired erythroid development (macrocytosis and anemia) and enhanced thrombopoiesis, which are both features of myelodysplasia/myeloproliferative neoplasms. We then created and characterized double Bcor -/- /Dnmt3a -/- knockout mice. Interestingly, these animals developed a fully penetrant acute erythroid leukemia (AEL) characterized by leukocytosis secondary to the expansion of blasts expressing c-Kit+ and the erythroid marker Ter119, macrocytic anemia and progressive reduction of the thrombocytosis associated with loss of Bcor alone. Transcriptomic analysis of double knockout bone marrow progenitors revealed that aberrant erythroid skewing was induced by epigenetic changes affecting specific transcriptional factors (GATA1-2) and cell-cycle regulators (Mdm2, Tp53). These findings prompted us to investigate the efficacy of demethylating agents in AEL, with significant impact on progressive leukemic burden and mice overall survival. Information gained from our model expands the knowledge on the biology of AEL and may help designing new rational treatments for patients suffering from this high-risk leukemia.

Ibrutinib represents extraordinary progress in the treatment of chronic lymphocytic leukemia (CLL). However, treatment-related adverse events limit the benefit of this agent. This observational, multicenter study focused on the incidence, risk factors, and prognostic impact of infections in 494 patients with CLL treated with an ibrutinib-based treatment. Ibrutinib was given to 89 (18%) previously untreated patients (combined with rituximab, 24) and 405 (82%) relapsed/refractory patients. Pneumonia (PN), grade ≥3 non-opportunistic infections (NOI), and opportunistic infections (OI) were recorded in 32% of patients with an overall incidence rate per 100 person-year of 15.3% (PN, 10%; NOI, 3.3%; OI, 2%). Infections were the reason for the permanent discontinuation of ibrutinib in 9% of patients. Patients who experienced pneumonia or a severe infection showed a significantly inferior survival than those who were infection-free ( p < 0.0001). A scoring system based on the three factors associated with a significant and independent impact on infections-PN or severe infection in the year before starting ibrutinib, chronic obstructive pulmonary disease, ≥2 prior treatments-identified patients with a two- to threefold increase in the rate of infections. In conclusion, the results of this study highlight the adverse impact of infectious events on the outcomes of CLL patients treated with ibrutinib.

Key features of chronic lymphocytic leukemia (CLL) are defects in the immune system and the ability of leukemic cells to evade immune defenses and induce immunosuppression, resulting in increased susceptibility to infections and disease progression. Several immune effectors are impaired in CLL, including T and natural killer (NK) cells. The role of T cells in defense against CLL and in CLL progression and immunotherapy has been extensively studied. Less is known about the role of NK cells in this leukemia, and data on NK cell alterations in CLL are contrasting. Besides studies showing that NK cells have intrinsic defects in CLL, there is a large body of evidence indicating that NK cell dysfunctions in CLL mainly depend on the escape mechanisms employed by leukemic cells. In keeping, it has been shown that NK cell functions, including antibody-dependent cellular cytotoxicity (ADCC), can be retained and/or restored after adequate stimulation. Therefore, due to their preserved ADCC function and the reversibility of CLL-related dysfunctions, NK cells are an attractive source for novel immunotherapeutic strategies in this disease, including chimeric antigen receptor (CAR) therapy. Recently, satisfying clinical responses have been obtained in CLL patients using cord blood-derived CAR-NK cells, opening new possibilities for further exploring NK cells in the immunotherapy of CLL. However, notwithstanding the promising results of this clinical trial, more evidence is needed to fully understand whether and in which CLL cases NK cell-based immunotherapy may represent a valid, alternative/additional therapeutic option for this leukemia. In this review, we provide an overview of the current knowledge about phenotypic and functional alterations of NK cells in CLL and the mechanisms by which CLL cells circumvent NK cell-mediated immunosurveillance. Additionally, we discuss the potential relevance of using NK cells in CLL immunotherapy.

NOTCH1 mutations and deregulated signal have been commonly found in chronic lymphocytic leukemia (CLL) patients. Whereas the impact of NOTCH1 mutations on clinical course of CLL has been widely studied, the prognostic role of NOTCH1 activation in CLL remains to be defined. Here, we analyzed the activation of NOTCH1/NOTCH2 (ICN1/ICN2) and the expression of JAGGED1 (JAG1) in 163 CLL patients and evaluated their impact on TTFT (Time To First Treatment) and OS (Overall Survival). NOTCH1 activation (ICN1+) was found in 120/163 (73.6%) patients. Among them, 63 (52.5%) were NOTCH1 mutated (ICN1+/mutated) and 57 (47.5%) were NOTCH1 wild type (ICN1+/WT). ICN1+ patients had a significant reduction of TTFT compared to ICN1-negative (ICN1-). In the absence of NOTCH1 mutations, we found that the ICN1+/WT group had a significantly reduced TTFT compared to ICN1- patients. The analysis of IGHV mutational status showed that the distribution of the mutated/unmutated IGHV pattern was similar in ICN1+/WT and ICN1- patients. Additionally, TTFT was significantly reduced in ICN1+/ICN2+ and ICN1+/JAG1+ patients compared to ICN1-/ICN2- and ICN1-/JAG1- groups. Our data revealed for the first time that NOTCH1 activation is a negative prognosticator in CLL and is not correlated to NOTCH1 and IGHV mutational status. Activation of NOTCH2 and JAGGED1 expression might also influence clinical outcomes in this group, indicating the need for further dedicated studies. The evaluation of different NOTCH network components might represent a new approach to refine CLL risk stratification., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Baldoni, Del Papa, De Falco, Dorillo, Sorrentino, Rompietti, Adamo, Nogarotto, Cecchini, Mondani, Silva Barcelos, Moretti, Mameli, Fabi, Sorcini, Stella, Giancola, Guardalupi, Ulbar, Plebani, Guarente, Rosati, Di Nicola, Marchioni, Di Ianni and Sportoletti.)

Chronic lymphocytic leukemia (CLL) shows constitutive phosphatidylinositol 3-kinase (PI3K) activation resulting from aberrant regulation of the B-cell receptor (BCR) signaling. PI3K inhibitors have been evaluated in CLL therapy, bringing a new treatment opportunity for patients with this disease. Despite the proven therapeutic efficacy, the use of approved PI3K inhibitors is limited by severe immune-mediated toxicities and given the availability of other more tolerable agents. This article reviews the relevance of PI3K signaling and pharmacologic inhibition in CLL. Data on efficacy and toxicity of PI3K inhibitors are also presented, as well as strategies for overcoming barriers for their clinical use in CLL treatment.