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Measurable residual disease (MRD) status in chronic lymphocytic leukemia (CLL), assessed on and after treatment, correlates with increased progression-free and overall survival benefit. More recently, MRD assessment has been included in large clinical trials as a primary outcome and is increasingly used in routine practice as a prognostic tool, a therapeutic goal, and potentially a trigger for early intervention. Modern therapy for CLL delivers prolonged remissions, causing readout of traditional trial outcomes such as progression-free and overall survival to be inherently delayed. This represents a barrier for the rapid incorporation of novel drugs to the overall therapeutic armamentarium. MRD offers a dynamic and robust platform for the assessment of treatment efficacy in CLL, complementing traditional outcome measures and accelerating access to novel drugs. Here, we provide a comprehensive review of recent major clinical trials of CLL therapy, focusing on small-molecule inhibitors and monoclonal antibody combinations that have recently emerged as the standard frontline and relapse treatment options. We explore the assessment and reporting of MRD (including novel techniques) and the challenges of standardization and provide a comprehensive review of the relevance and adequacy of MRD as a clinical trial endpoint. We further discuss the impact that MRD data have on clinical decision-making and how it can influence a patient’s experience. Finally, we evaluate how upcoming trial design and clinical practice are evolving in the face of MRD-driven outcomes.

Abstract: Tisagenlecleucel is approved for adults with relapsed/refractory (r/r) follicular lymphoma (FL) in the third- or later-line setting. The primary analysis (median follow-up, 17 months) of the phase 2 ELARA trial reported high response rates and excellent safety profile in patients with extensively pretreated r/r FL. Here, we report longer-term efficacy, safety, pharmacokinetic, and exploratory biomarker analyses after median follow-up of 29 months (interquartile range, 22.2-37.7). As of 29 March 2022, 97 patients with r/r FL (grades 1-3A) received tisagenlecleucel infusion (0.6 × 108-6 × 108 chimeric antigen receptor-positive viable T cells). Bridging chemotherapy was allowed. Baseline clinical factors, tumor microenvironment, blood soluble factors, and circulating blood cells were correlated with clinical response. Cellular kinetics were assessed by quantitative polymerase chain reaction. Median progression-free survival (PFS), duration of response (DOR), and overall survival (OS) were not reached. Estimated 24-month PFS, DOR, and OS rates in all patients were 57.4% (95% confidence interval [CI], 46.2-67), 66.4% (95% CI, 54.3-76), and 87.7% (95% CI, 78.3-93.2), respectively. Complete response rate and overall response rate were 68.1% (95% CI, 57.7-77.3) and 86.2% (95% CI, 77.5-92.4), respectively. No new safety signals or treatment-related deaths were reported. Low levels of tumor-infiltrating LAG3+CD3+ exhausted T cells and higher baseline levels of naïve CD8+ T cells were associated with improved outcomes. Tisagenlecleucel continued to demonstrate highly durable efficacy and a favorable safety profile in this extended follow-up of 29 months in patients with r/r FL enrolled in ELARA. This trial was registered at www.clinicaltrials.gov as #NCT03568461., (© 2024 American Society of Hematology. Published by Elsevier Inc. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Background: The combination of ibrutinib and venetoclax has been shown to improve outcomes in patients with chronic lymphocytic leukemia (CLL) as compared with chemoimmunotherapy. Whether ibrutinib-venetoclax and personalization of treatment duration according to measurable residual disease (MRD) is more effective than fludarabine-cyclophosphamide-rituximab (FCR) is unclear., Methods: In this phase 3, multicenter, randomized, controlled, open-label platform trial involving patients with untreated CLL, we compared ibrutinib-venetoclax and ibrutinib monotherapy with FCR. In the ibrutinib-venetoclax group, after 2 months of ibrutinib, venetoclax was added for up to 6 years of therapy. The duration of ibrutinib-venetoclax therapy was defined by MRD assessed in peripheral blood and bone marrow and was double the time taken to achieve undetectable MRD. The primary end point was progression-free survival in the ibrutinib-venetoclax group as compared with the FCR group, results that are reported here. Key secondary end points were overall survival, response, MRD, and safety., Results: A total of 523 patients were randomly assigned to the ibrutinib-venetoclax group or the FCR group. At a median of 43.7 months, disease progression or death had occurred in 12 patients in the ibrutinib-venetoclax group and 75 patients in the FCR group (hazard ratio, 0.13; 95% confidence interval [CI], 0.07 to 0.24; P<0.001). Death occurred in 9 patients in the ibrutinib-venetoclax group and 25 patients in the FCR group (hazard ratio, 0.31; 95% CI, 0.15 to 0.67). At 3 years, 58.0% of the patients in the ibrutinib-venetoclax group had stopped therapy owing to undetectable MRD. After 5 years of ibrutinib-venetoclax therapy, 65.9% of the patients had undetectable MRD in the bone marrow and 92.7% had undetectable MRD in the peripheral blood. The risk of infection was similar in the ibrutinib-venetoclax group and the FCR group. The percentage of patients with cardiac serious adverse events was higher in the ibrutinib-venetoclax group than in the FCR group (10.7% vs. 0.4%)., Conclusions: MRD-directed ibrutinib-venetoclax improved progression-free survival as compared with FCR, and results for overall survival also favored ibrutinib-venetoclax. (Funded by Cancer Research UK and others; FLAIR ISRCTN Registry number, ISRCTN01844152; EudraCT number, 2013-001944-76.)., (Copyright © 2023 Massachusetts Medical Society.)

Background: The approval of Bruton tyrosine kinase (BTK) inhibitors in patients with previously untreated chronic lymphocytic leukaemia (CLL) was based on trials which compared ibrutinib with alkylating agents in patients considered unfit for fludarabine, cyclophosphamide, and rituximab, the most effective chemoimmunotherapy in CLL. We aimed to assess whether ibrutinib and rituximab is superior to fludarabine, cyclophosphamide, and rituximab in terms of progression-free survival., Methods: This study is an interim analysis of FLAIR, which is an open-label, randomised, controlled, phase 3 trial in patients with previously untreated CLL done at 101 UK National Health Service hospitals. Eligible patients were between 18 and 75 years of age with a WHO performance status of 2 or less and disease status requiring treatment according to International Workshop on CLL criteria. Patients with greater than 20% of their CLL cells having the chromosome 17p deletion were excluded. Patients were randomly assigned (1:1) by means of minimisation (Binet stage, age, sex, and centre) with a random element in a web-based system to ibrutinib and rituximab (ibrutinib administered orally at 420 mg/day for up to 6 years; rituximab administered intravenously at 375 mg/m 2 on day 1 of cycle 1 and at 500 mg/m 2 on day 1 of cycles 2-6 of a 28-day cycle) or fludarabine, cyclophosphamide, and rituximab (fludarabine 24 mg/m 2 per day orally on day 1-5, cyclophosphamide 150 mg/m 2 per day orally on days 1-5; rituximab as above for up to 6 cycles). The primary endpoint was progression-free survival, analysed by intention to treat. Safety analysis was per protocol. This study is registered with ISRCTN, ISRCTN01844152, and EudraCT, 2013-001944-76, and recruiting is complete., Findings: Between Sept 19, 2014, and July 19, 2018, of 1924 patients assessed for eligibility, 771 were randomly assigned with median age 62 years (IQR 56-67), 565 (73%) were male, 206 (27%) were female and 507 (66%) had a WHO performance status of 0. 385 patients were assigned to fludarabine, cyclophosphamide, and rituximab and 386 patients to ibrutinib and rituximab. After a median follow-up of 53 months (IQR 41-61) and at prespecified interim analysis, median progression-free survival was not reached (NR) with ibrutinib and rituximab and was 67 months (95% CI 63-NR) with fludarabine, cyclophosphamide, and rituximab (hazard ratio 0·44 [95% CI 0·32-0·60]; p<0·0001). The most common grade 3 or 4 adverse event was leukopenia (203 [54%] patients in the fludarabine, cyclophosphamide, and rituximab group and 55 [14%] patients in the ibrutinib and rituximab group. Serious adverse events were reported in 205 (53%) of 384 patients receiving ibrutinib and rituximab compared with 203 (54%) of 378 patients receiving fludarabine, cyclophosphamide, and rituximab. Two deaths in the fludarabine, cyclophosphamide, and rituximab group and three deaths in the ibrutinib and rituximab group were deemed to be probably related to treatment. There were eight sudden unexplained or cardiac deaths in the ibrutinib and rituximab group and two in the fludarabine, cyclophosphamide, and rituximab group., Interpretation: Front line treatment with ibrutinib and rituximab significantly improved progression-free survival compared with fludarabine, cyclophosphamide, and rituximab but did not improve overall survival. A small number of sudden unexplained or cardiac deaths in the ibrutinib and rituximab group were observed largely among patients with existing hypertension or history of cardiac disorder., Funding: Cancer Research UK and Janssen., Competing Interests: Declaration of interests PH reports funding for the study and provision of investigational medicinal products from Janssen and AbbVie; personal consulting fees from Janssen, AbbVie, and AstraZeneca; personal speaker fees from Janssen, AbbVie, AstraZeneca, and BeiGene; institutional support of clinical trials from Janssen, AbbVie, Gilead Sciences, and F Hoffman-La Roche. AP reports unrestricted educational grants to her institution from Janssen, Pharmacyclics, and AbbVie. ABl reports speaker fees from Janssen and AbbVie and support for conference attendance from AbbVie. ABr reports personal payment for presentations from Janssen-Cilag and AstraZeneca and personal payment for attending meetings from AbbVie. BK reports personal payment or honoraria for lectures from AbbVie and AstraZeneca and a voluntary unpaid role as CLL Support Associate Trustee. RW reports payment for lectures from AbbVie, AstraZeneca, Janssen, and BeiGene; support for attending meetings from AbbVie and Janssen; and participation on a data safety monitoring board or advisory board for AstraZeneca, Janssen, SecuraBio, and AbbVie. MF reports travel support for conference attendance from AbbVie and remunerated participation on an advisory board for AstraZeneca. GP reports honoraria for delivering educational sessions from Janssen-Cilag and Roche. NM reports payment or honoraria for presentations from Amgen and Kite Gilead; support for attending meetings or travel from Takeda; and participation on a data safety monitoring board or advisory board for Kite Gilead, Amgen, and AbbVie. KC reports personal speakers fees from Roche, Takeda, Kite, Gilead, and Incyte; support for travel and registration for meetings from Roche, Takeda, Kite, and BMS; and participation on a data safety monitoring board or advisory board for Roche, Takeda, Celgene, Atara, Gilead, Kite, Janssen, and Incyte. AS reports receipt of part of her salary from the Oxford Biomedical Research Centre; grants from Janssen and AstraZeneca; honoraria for presentations from Roche, AbbVie, Janssen, BeiGene, and AstraZeneca; and receipt of equipment, materials, drugs, medical writing, gifts, or other services from Illumina, Oxford Nanopore Technology, and Adaptive Biotechnology. FF reports grants from Cancer Research UK and AbbVie; consulting fees from BC Platform; payment or honoraria for presentations from AbbVie, Janssen-Cilag, Acerta, and BeiGene; support for attending meetings or travel from AbbVie; and participation on a data safety monitoring board or advisory board for BeiGene. NE reports personal speaker payments from AstraZeneca and Roche and support for attending meetings and travel from AbbVie. SP reports personal honoraria for presentations from Gilead, AstraZeneca, AbbVie, BeiGene, and Takeda. CPF reports personal consultancy fees from AbbVie, AstraZeneca, Atarabio, BMS, GenMab, Gilead–Kite, Incyte, Lilly, Morphosys, Ono, Roche, and Takeda; payment for educational events from Janssen, Incyte, and Roche; institution research funding from BeiGene; support for attending meetings or travel from Roche; and participation on trial steering committees for GenMab, Morphosys, and Roche. DRH is employed by Roche and holds stock or stock options from Roche. AH reports unrestricted educational grants to her institution from Janssen, Pharmacyclics, and AbbVie and receipt of a speaker fee from AbbVie. JMB reports unrestricted educational grants to her institution from Janssen, Pharmacyclics, and AbbVie. DAC reports unrestricted educational grants to his institution from Janssen, Pharmacyclics, and AbbVie; payment to institution for educational lectures from Janssen; participation on a data safety monitoring board for an academically led investigator-initiated CLL study and personal payment for meeting attendance and report preparation from University Hospital Cologne. SJ reports receipt of unrestricted educational grants to her institution from Janssen, Pharmacyclics and AbbVie. NG reports unrestricted educational grants to her institution from Janssen, Pharmacyclics, and AbbVie and participation on an advisory board for AbbVie. PEMP reports grants from Roche and Gilead; payment or honoraria for presentations from AbbVie, AstraZeneca, BeiGene, Gilead, and Janssen; support for attending meetings or travel from AbbVie; and participation on a data safety monitoring board or advisory board for AbbVie, BeiGene, and Novartis. DA reports receipt of part of his salary from the National Institute for Health and Care Research and Medical Research Council and support to attend meetings from CSL Behring. AR reports grants to his institution from AbbVie, Janssen, Pharmacyclics, and Roche; consulting fees from BeiGene and Pharmacyclics paid to a company of which AR is a director; payment or honoraria for presentations from AbbVie, Beckman Coulter, BD Biosciences, BeiGene, and Janssen paid to a company of which AR is a director; support for attending meetings or travel from Janssen; participation on a data safety monitoring board or advisory board from AbbVie and Janssen; and receipt of equipment from Beckman Coulter. TM reports payment for lectures and presentations from Janssen, AbbVie, and AstraZeneca; support for attending conferences from Janssen, AbbVie, and AstraZeneca; and participation on advisory boards for Janssen, AbbVie, AstraZeneca, Lilly, BeiGene, and Morphosys. All other authors declare no competing interests., (Copyright © 2023 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.)

Transmission of the SARS-CoV-2 virus and its corresponding disease (COVID-19) has been shown to impose a higher burden on cancer patients than on the general population. Approved vaccines for use include new technology mRNA vaccines such as BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna), and nonreplicating viral vector vaccines such as Ad26.COV2.S (Johnson & Johnson) and AZD1222 (AstraZeneca). Impaired or delayed humoral and diminished T-cell responses are evident in patients with cancer, especially in patients with haematological cancers or those under active chemotherapy. Herein we review the current data on vaccine immunogenicity in cancer patients, including recommendations for current practice and future research., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The ELARA trial indicates tisagenlecleucel (tisa-cel) is an effective anti-CD19 chimeric antigen receptor T-cell therapy for relapsed or refractory follicular lymphoma (r/r FL). As ELARA is a single-arm trial, this study compares tisa-cel outcomes from the ELARA trial with usual care from a real-world cohort. ELARA enrolled 98 patients as of 29 March 2021 (median follow-up: 15 months from enrollment). Usual care data were obtained from ReCORD-FL, a global retrospective study of patients with r/r FL, who met similar eligibility criteria to ELARA. With a data cutoff date of 31 December 2020, 187 patients with ≥2 preceding treatment lines were included in the ReCORD-FL (median follow-up: 57 months from third-line) study. An indirect treatment comparison was performed for 97 patients from the ELARA trial and 143 patients from the ReCORD-FL study with no missing data on baseline factors. The line of therapy for which outcomes were assessed was selected or matched between cohorts using propensity score modeling. After baseline factor adjustment via weighting by odds, complete response rate (CRR; 95% confidence interval) was 69.1% (59.8%-78.3%) for tisa-cel vs. 37.3% (26.4%-48.3%) for usual care; overall response rate was 85.6% (78.7%-92.5%) vs. 63.6% (52.5%-74.7%). Kaplan-Meier probability of being progression/event-free at 12 months was 70.5% (61.4%-79.7%) for tisa-cel vs. 51.9% (40.6%-63.3%) for usual care, with hazard ratio (HR)=0.60 (0.34-0.86); 12-month overall survival was 96.6% (92.9%-100%) vs. 71.7% (61.2%-82.2%), with HR=0.2 (0.02-0.38). In conclusion, tisa-cel was associated with a 1.9-fold higher complete response rate and a 1.4-fold higher rate of being progression or event free at 12 months vs usual care, as well as a death risk reduction of 80%. The findings provide additional evidence on the benefit of tisa-cel in patients with r/r FL after ≥2 treatment lines. This trial was registered at www.clinicaltrials.gov as NCT03568461., (© 2022 by The American Society of Hematology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).)

CD19 CAR-T have emerged as a new standard treatment for relapsed/refractory (r/r) large B-cell lymphoma (LBCL). CAR-T real-world (RW) outcomes published to date suggest significant variability across countries. We provide results of a large national cohort of patients intended to be treated with CAR-T in the UK. Consecutive patients with r/r LBCL approved for CAR-T by the National CAR-T Clinical Panel between December 2018 and November 2020 across all UK CAR-T centres were included. 404/432 patients were approved [292 axicabtagene ciloleucel (axi-cel), 112 tisagenlecleucel (tisa-cel)], 300 (74%) received the cells. 110/300 (38.3%) patients achieved complete remission (CR) at 6 months (m). The overall response rate was 77% (52% CR) for axi-cel, 57% (44% CR) for tisa-cel. The 12-month progression-free survival was 41.8% (axi-cel) and 27.4% (tisa-cel). Median overall survival for the intention-to-treat population was 10.5 m, 16.2 m for infused patients. The incidence of grade ≥3 cytokine release syndrome and neurotoxicity were 7.6%/19.6% for axi-cel and 7.9%/3.9% for tisa-cel. This prospective RW population of CAR-T eligible patients offers important insights into the clinical benefit of CD19 CAR-T in LBCL in daily practice. Our results confirm long-term efficacy in patients receiving treatment similar to the pivotal trials, but highlight the significance of early CAR-T failure., (© 2022 British Society for Haematology and John Wiley & Sons Ltd.)

This study (ReCORD-FL) sought to construct a historical control cohort to augment single-arm trials in relapsed/refractory follicular lymphoma (r/r FL). A retrospective study in 10 centers across North America and Europe was conducted. Adults with grade 1-3A FL were required to be r/r after ≥2 therapy lines including an anti-CD20 and an alkylator. After first becoming r/r, patients were required to initiate ≥1 additional therapy line, which defined the study index date. Endpoints were observed from start of each therapy line (including index line) until death, last follow-up, or December 31, 2020. Endpoints were complete response (CR) rate, overall response rate (ORR), time to next treatment or death (TNT-D), event-free survival (EFS), and overall survival (OS). One hundred eighty-seven patients were identified. Most patients' (80.2%) index therapy occurred in third line (3L) (range, 3L-6L). Median follow-up from FL diagnosis was 9 years (range, 1-21 years). CR and ORR to the index therapy were 39.0% and 70.6%, respectively. Median (95% confidence interval) EFS from index was 14.6 (11.0-18.0) months; median OS from index was 10.6 years. Outcomes worsened across successive treatment lines and for patients who were double refractory (r/r to both an anti-CD20 monoclonal antibody and an alkylator) or POD24 (progressed ≤24 months after front-line anti-CD20) at index. Findings demonstrate the unmet need of FL patients with multiply relapsed, double refractory, or POD24 disease. Based on robustness of the historical data collected and comparability with a previous study (SCHOLAR-5), ReCORD-FL presents a valuable source of control data for comparative studies in r/r FL., (Copyright © 2022 the Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the European Hematology Association.)

Interactions between chronic lymphocytic leukemia (CLL) cells and T-cell subsets in the lymph node microenvironment are thought to play a central role in disease biology. To study these interactions in a model of the CLL lymph node microenvironment, we characterized T-cell subsets in CLL nurselike cell (NLC) co-cultures. We focused on T-follicular helper (Tfh) cells, which are characterized by CXCR5 expression and localization to B-cell follicles. In co-cultures from 28 different CLL patients, we detected an expansion of Tfh cells based on PD-1, BCL6, and ICOS expression, with increased IL-21 and downmodulated CD40L surface expression. Regulatory T cells (Treg), which promote immune tolerance, also expanded in NLC co-cultures. T-cell receptor (TR) gene repertoire analyses confirmed the clonal expansion of CD4 + T cells, with an enrichment of TR clonotypes commonly expanded also in primary CLL samples. Multicolor confocal microscopy revealed that Tfh, but not Treg co-localize with proliferating CLL cells in CLL lymph node sections. Collectively, these data provide new insight into the cellular and molecular cross-talk between CLL and T-cell subsets, resulting in clonal expansion of T-helper cells and interaction of Tfh cells with proliferating CLL cells which may open new avenues for therapeutic targeting., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Tisagenlecleucel is an autologous anti-CD19 chimeric antigen receptor-T cell therapy with clinically meaningful outcomes demonstrated in patients with relapsed/refractory (r/r) B-cell lymphoma. In a previous pilot study of tisagenlecleucel in r/r follicular lymphoma (FL), 71% of patients achieved a complete response (CR). Here we report the primary, prespecified interim analysis of the ELARA phase 2 multinational trial of tisagenlecleucel in adults with r/r FL after two or more treatment lines or who relapsed after autologous stem cell transplant (no. NCT03568461). The primary endpoint was CR rate (CRR). Secondary endpoints included overall response rate (ORR), duration of response, progression-free survival, overall survival, pharmacokinetics and safety. As of 29 March 2021, 97/98 enrolled patients received tisagenlecleucel (median follow-up, 16.59 months; interquartile range, 13.8-20.21). The primary endpoint was met. In the efficacy set (n = 94), CRR was 69.1% (95% confidence interval, 58.8-78.3) and ORR 86.2% (95% confidence interval, 77.5-92.4). Within 8 weeks of infusion, rates of cytokine release syndrome were 48.5% (grade ≥3, 0%), neurological events 37.1% (grade ≥3, 3%) and immune effector cell-associated neurotoxicity syndrome (ICANS) 4.1% (grade ≥3, 1%) in the safety set (n = 97), with no treatment-related deaths. Tisagenlecleucel is safe and effective in extensively pretreated r/r FL, including in high-risk patients., (© 2021. The Author(s), under exclusive licence to Springer Nature America, Inc.)

The tumor microenvironment (TME) plays an essential role in the development, growth, and survival of the malignant B-cell clone in chronic lymphocytic leukemia (CLL). Within the proliferation niches of lymph nodes, bone marrow, and secondary lymphoid organs, a variety of phenotypically and functionally altered cell types, including T cells, natural killer cells, monocytes/macrophages, endothelial and mesenchymal stroma cells, provide crucial survival signals, along with CLL-cellinduced suppression of antitumor immune responses. The B-cell receptor pathway plays a pivotal role in mediating the interaction between CLL cells and the TME. However, an increasing number of additional components of the multifactorial TME are being discovered. Although the majority of therapeutic strategies employed in CLL hitherto have focused on targeting the leukemic cells, emerging evidence implies that modulation of microenvironmental cells and CLL-TME interactions by novel therapeutic agents significantly affect their clinical efficacy. Thus, improving our understanding of CLL-TME interactions and how they are affected by current therapeutic agents may improve and guide treatment strategies. Identification of novel TME interactions may also pave the road for the development of novel therapeutic strategies targeting the TME. In this review, we summarize current evidence on the effects of therapeutic agents on cells and interactions within the TME. With a growing demand for improved and personalized treatment options in CLL, this review aims at inspiring future exploration of smart drug combination strategies, translational studies, and novel therapeutic targets in clinical trials.

Patient-derived xenograft models of chronic lymphocytic leukemia (CLL) can be created using highly immunodeficient animals, allowing analysis of primary tumor cells in an in vivo setting. However, unlike many other tumors, CLL B lymphocytes do not reproducibly grow in xenografts without manipulation, proliferating only when there is concomitant expansion of T cells. Here we show that in vitro pre-activation of CLL-derived T lymphocytes allows for a reliable and robust system for primary CLL cell growth within a fully autologous system that uses small numbers of cells and does not require pre-conditioning. In this system, growth of normal T and leukemic B cells follows four distinct temporal phases, each with characteristic blood and tissue findings. Phase 1 constitutes a period during which resting CLL B cells predominate, with cells aggregating at perivascular areas most often in the spleen. In Phase 2, T cells expand and provide T-cell help to promote B-cell division and expansion. Growth of CLL B and T cells persists in Phase 3, although some leukemic B cells undergo differentiation to more mature B-lineage cells (plasmablasts and plasma cells). By Phase 4, CLL B cells are for the most part lost with only T cells remaining. The required B-T cell interactions are not dependent on other human hematopoietic cells nor on murine macrophages or follicular dendritic cells, which appear to be relatively excluded from the perivascular lymphoid aggregates. Notably, the growth kinetics and degree of anatomic localization of CLL B and T cells is significantly influenced by intravenous versus intraperitoneal administration. Importantly, B cells delivered intraperitoneally either remain within the peritoneal cavity in a quiescent state, despite the presence of dividing T cells, or migrate to lymphoid tissues where they actively divide; this dichotomy mimics the human condition in that cells in primary lymphoid tissues and the blood are predominately resting, whereas those in secondary lymphoid tissues proliferate. Finally, the utility of this approach is illustrated by documenting the effects of a bispecific antibody reactive with B and T cells. Collectively, this model represents a powerful tool to evaluate CLL biology and novel therapeutics in vivo ., Competing Interests: NC received the DART molecule, the DART control molecule, and financial support to carry out the studies in Figure 8 from Janssen Pharmaceuticals, Inc. The remaining 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 Patten, Ferrer, Chen, Kolitz, Rai, Allen, Barrientos, Ioannou, Ramsay and Chiorazzi.)

Given the immune system's importance for cancer surveillance and treatment, we have investigated how it may be affected by SARS-CoV-2 infection of cancer patients. Across some heterogeneity in tumor type, stage, and treatment, virus-exposed solid cancer patients display a dominant impact of SARS-CoV-2, apparent from the resemblance of their immune signatures to those for COVID-19 + non-cancer patients. This is not the case for hematological malignancies, with virus-exposed patients collectively displaying heterogeneous humoral responses, an exhausted T cell phenotype and a high prevalence of prolonged virus shedding. Furthermore, while recovered solid cancer patients' immunophenotypes resemble those of non-virus-exposed cancer patients, recovered hematological cancer patients display distinct, lingering immunological legacies. Thus, while solid cancer patients, including those with advanced disease, seem no more at risk of SARS-CoV-2-associated immune dysregulation than the general population, hematological cancer patients show complex immunological consequences of SARS-CoV-2 exposure that might usefully inform their care., Competing Interests: Declaration of interests The authors declare no competing interests., (Crown Copyright © 2021. Published by Elsevier Inc. All rights reserved.)

Cancer treatment has been transformed by checkpoint blockade therapies, with the highest anti-tumor activity of anti-programmed death 1 (PD-1) antibody therapy seen in Hodgkin lymphoma. Disappointingly, response rates have been low in the non-Hodgkin lymphomas, with no activity seen in relapsed/refractory chronic lymphocytic leukemia (CLL) with PD-1 blockade. Thus, identifying more powerful combination therapy is required for these patients. Here, we preclinically demonstrate enhanced anti-CLL activity following combinational therapy with anti-PD-1 or anti-PD-1 ligand (PD-L1) and avadomide, a cereblon E3 ligase modulator (CELMoD). Avadomide induced type I and II interferon (IFN) signaling in patient T cells, triggering a feedforward cascade of reinvigorated T-cell responses. Immune modeling assays demonstrated that avadomide stimulated T-cell activation, chemokine expression, motility and lytic synapses with CLL cells, as well as IFN-inducible feedback inhibition through upregulation of PD-L1. Patient-derived xenograft tumors treated with avadomide were converted to CD8+ T cell-inflamed tumor microenvironments that responded to anti-PD-L1/PD-1-based combination therapy. Notably, clinical analyses showed increased PD-L1 expression on T cells, as well as intratumoral expression of chemokine signaling genes in B-cell malignancy patients receiving avadomide-based therapy. These data illustrate the importance of overcoming a low inflammatory T-cell state to successfully sensitize CLL to checkpoint blockade-based combination therapy., (© 2021 by The American Society of Hematology.)

Given advanced age, comorbidities, and immune dysfunction, chronic lymphocytic leukemia (CLL) patients may be at particularly high risk of infection and poor outcomes related to coronavirus disease 2019 (COVID-19). Robust analysis of outcomes for CLL patients, particularly examining effects of baseline characteristics and CLL-directed therapy, is critical to optimally manage CLL patients through this evolving pandemic. CLL patients diagnosed with symptomatic COVID-19 across 43 international centers (n = 198) were included. Hospital admission occurred in 90%. Median age at COVID-19 diagnosis was 70.5 years. Median Cumulative Illness Rating Scale score was 8 (range, 4-32). Thirty-nine percent were treatment naive ("watch and wait"), while 61% had received ≥1 CLL-directed therapy (median, 2; range, 1-8). Ninety patients (45%) were receiving active CLL therapy at COVID-19 diagnosis, most commonly Bruton tyrosine kinase inhibitors (BTKi's; n = 68/90 [76%]). At a median follow-up of 16 days, the overall case fatality rate was 33%, though 25% remain admitted. Watch-and-wait and treated cohorts had similar rates of admission (89% vs 90%), intensive care unit admission (35% vs 36%), intubation (33% vs 25%), and mortality (37% vs 32%). CLL-directed treatment with BTKi's at COVID-19 diagnosis did not impact survival (case fatality rate, 34% vs 35%), though the BTKi was held during the COVID-19 course for most patients. These data suggest that the subgroup of CLL patients admitted with COVID-19, regardless of disease phase or treatment status, are at high risk of death. Future epidemiologic studies are needed to assess severe acute respiratory syndrome coronavirus 2 infection risk, these data should be validated independently, and randomized studies of BTKi's in COVID-19 are needed to provide definitive evidence of benefit.

CD4 + T-follicular helper cells are essential for the survival, proliferation, and differentiation of germinal center B cells and have been implicated in the pathogenesis of follicular lymphoma (FL). To further define the role of these cells in FL, we used multiparameter confocal microscopy to compare the architecture of normal and neoplastic follicles and next generation sequencing to analyze the T-cell receptor repertoire in FL lymph nodes (LN). Multiparameter analysis of LN showed that the proportion of T-follic-ular helper cells (T FH ) in normal and neoplastic follicles is the same and that the previously reported increase in T FH numbers in FL is thus due to an increase in the number and not content of follicles. As in normal germinal centers, T FH were shown to have a close spatial correlation with proliferating B cells in neoplastic follicles, where features of immunological synapse formation were observed. The number of T FH in FL correlate with the rate of B-cell proliferation and T FH co-localized to activation induced cytidine deaminase expressing proliferating B cells. T-cell receptor repertoire analysis of FL LN revealed that follicular areas are significantly more clonal when compared to the rest of the LN. These novel findings show that neoplastic follicles and germinal centers share important structural features and provide further evidence that T FH may play a role in driving B-cell proliferation and genomic evolution in T FH Our results also suggest that targeting this interaction would be an attractive therapeutic option., (Copyright© 2020 Ferrata Storti Foundation.)

Purpose: The treatment of chronic lymphocytic leukemia (CLL) has been revolutionized by targeted therapies that either inhibit proliferation (ibrutinib) or reactivate apoptosis (venetoclax). Both significantly improve survival in CLL and replace chemoimmunotherapy for many patients. However, individually, they rarely lead to eradication of measurable residual disease (MRD) and usually are taken indefinitely or until progression. We present the CLARITY trial that combined ibrutinib with venetoclax to eradicate detectable CLL with the intention of stopping therapy., Patients and Methods: CLARITY is a phase II trial that combined ibrutinib with venetoclax in patients with relapsed or refractory CLL. The primary end point was eradication of MRD after 12 months of combined therapy. Key secondary end points were response by International Workshop on CLL criteria, safety, and progression-free and overall survival., Results: In 53 patients after 12 months of ibrutinib plus venetoclax, MRD negativity (fewer than one CLL cell in 10,000 leukocytes) was achieved in the blood of 28 (53%) and the marrow of 19 (36%). Forty-seven patients (89%) responded, and 27 (51%) achieved a complete remission. After a median follow-up of 21.1 months, one patient progressed, and all patients were alive. A single case of biochemical tumor lysis syndrome was observed. Other adverse effects were mild and/or manageable and most commonly were neutropenia or GI events., Conclusion: The combination of ibrutinib plus venetoclax was well tolerated in patients with relapsed or refractory CLL. There was a high rate of MRD eradication that led to the cessation of therapy in some patients. The progression-free and overall survival rates are encouraging for relapsed and refractory CLL.

Venetoclax is a BCL2 inhibitor with activity in relapsed/refractory (R/R) chronic lymphocytic leukaemia (CLL). We conducted a multi-centre retrospective analysis of 105 R/R CLL patients who received venetoclax pre-National Health Service commissioning. The median age was 67 years and median prior lines was 3 (range: 1-15). 48% had TP53 disruption. At ≥2 lines, 60% received a Bruton Tyrosine Kinase inhibitor (BTKi) and no prior phosphoinositide 3-kinase inhibitor (Pi3Ki), 25% received a Pi3Ki and no prior BTKi, and 10% received both. Patients discontinued B cell receptor inhibitor (BCRi) because of toxicity in 44% and progression in 54%. Tumour lysis syndrome risk was low, intermediate or high in 27%, 25%, and 48% respectively. Overall response was 88% (30% complete response [CR]). The overall response rate was 85% (CR 23%) in BTKi-exposed patients, 92% (CR 38%) in Pi3Ki-exposed patients and 80% (CR 20%) in both (P = 0·59). With a median follow-up of 15·6 months, 1-year progression-free survival was 65·0% and 1-year overall survival was 75·1%. Dose reduction or temporary interruption did not result in an inferior progression-free or discontinuation-free survival. Risk of progression or death after stopping a prior BCRi for progression was double compared to those stopping for other reasons (predominantly toxicity) (Hazard Ratio 2·01 P = 0·05). Venetoclax is active and well tolerated in R/R CLL post ≥1 BCRi. Reason(s) for stopping BCRi influences venetoclax outcomes., (© 2019 British Society for Haematology and John Wiley & Sons Ltd.)

B-cell receptor activation, occurring within lymph nodes, plays a key role in the pathogenesis of chronic lymphocytic leukemia and is linked to prognosis. As well as activation of downstream signaling, receptor ligation triggers internalization, transit to acidified endosomes and degradation of ligand-receptor complexes. Herein, we investigated the relationship between these two processes in normal and leukemic B cells. We found that leukemic B cells, particularly anergic cases lacking the capacity to initiate downstream signaling, internalize and accumulate ligand in acidified endosomes more efficiently than normal B cells. Furthermore, ligation of either surface CD79B, a B-cell receptor component required for downstream signaling, or surface Immunoglobulin M (IgM) by cognate agonistic antibody, showed that the two molecules internalize independently of each other in leukemic but not normal B cells. Since association with surface CD79B is required for surface retention of IgM, this suggests that uncoupling of B-cell receptor internalization from signaling may be due to the dissociation of these two molecules in leukemic cells. A comparison of lymph node with peripheral blood cells from chronic lymphocytic leukemia patients showed that, despite recent B-cell receptor activation, lymph node B cells expressed higher levels of surface IgM. This surprising finding suggests that the B-cell receptors of lymph node- and peripheral blood-derived leukemic cells might be functionally distinct. Finally, long-term therapy with the Bruton's tyrosine kinase inhibitors ibrutinib or acalabrutinib resulted in a switch to an anergic pattern of B-cell receptor function with reduced signaling capacity, surface IgM expression and more efficient internalization., (Copyright© 2018 Ferrata Storti Foundation.)