Large Granular Lymphocyte Leukemia Patients Research Articles

Abstract 3201: Preclinical development of a novel Romidepsin nanoparticle for the treatment of T-Cell lymphoid malignancies

Abstract The histone deacetylase inhibitors (HDACi) have long been regarded as an important class of drugs for treating T-cell lymphoid malignancies (TCL). Romidepsin (Romi), a bicyclic peptide, was approved for patients with relapsed or refractory cutaneous (CTCL) and peripheral T-cell lymphomas (PTCL). Unfortunately, the approval of Romi for relapsed/refractory PTCL was withdrawn due to a negative Phase 4 post-marketing requirement. Given its potent activity against Class I HDACs, Romi is considered one of the most effective HDAC inhibitors studied and used in patients with TCL. Herein, we report on a first-in-class nanoparticle of Romi (NanoRomi) with a superior safety and efficacy profile compared to the free drug in preclinical models of PTCL and large granular lymphocyte leukemia (LGLL). We developed a first-in-class NanoRomi using our proprietary amphiphilic di-block copolymer-based nanochemistry platform. NanoRomi was characterized in cell viability, flow cytometry, and western blotting (WB) assays to determine the concentration-effect relationships with regard to the induction of apoptosis and histone acetylation in cell lines representative of TCL and LGLL, as well as primary LGLL patient PBMC samples. In addition, we performed extensive in vivo modeling using murine xenografts of CTCL, including repeated dose toxicity, biodistribution, efficacy, and survival studies. Cytotoxicity assays demonstrated superior/comparable activity of NanoRomi (IC50: 1.1-2.3 nM) compared to free Romi (IC50: 4.8-10.6 nM) across all PTCL and LGLL cell lines studied, while in primary LGLL samples, NanoRomi exhibited superior cytotoxicity (2-fold) compared to Romi. WB analysis showed that NanoRomi induced apoptosis and increased acetylation of histone H3 and H4 in a time and concentration-dependent manner in cell lines representing CTCL, ALK+-ALCL, and LGLL. Repeat dose toxicity studies in CTCL xenografts confirmed that the overall tolerability of NanoRomi was substantially better than Romi. Tracking studies with a fluorescent dye (DiO) in the NanoRomi demonstrated preferential localization of NanoRomi in tumors of mice compared to the normal organs after 6 hours of drug administration. NanoRomi exhibited superior efficacy in the murine CTCL xenograft models, including a significant improvement in overall survival compared to Romi. Collectively, these data show that NanoRomi exhibits markedly superior pharmacokinetics, tolerability, and efficacy in models of TCL. We anticipate that the improved activity and tolerability of NanoRomi relate to the altered pharmacologic profile and superior bioavailability of the drug, which optimizes the effects of the drug for its influence on epigenetic biology. This unique platform offers the prospect of improving the tolerability and efficacy of epigenetic treatment strategies in these challenging diseases. Citation Format: Ipsita Pal, Anuradha Illendula, Andrea Joyner, Tess M. Deddens, Deepthi P. Damera, Todd E. Fox, Marya E. Dunlap-Brown, Kallesh D. Jayappa, Thomas P. Loughran, David J. Feith, Owen A. O'Connor. Preclinical development of a novel Romidepsin nanoparticle for the treatment of T-Cell lymphoid malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3201.

Epidemiological Insights into Large Granular Lymphocyte Leukemia: A Nationwide SEER Database Study

Background: Large granular lymphocytic (LGL) leukemia is a rare hematological malignancy that arises from cytotoxic T lymphocytes (T-LGL) or natural killer (NK) cells. LGL leukemia accounts for 2% to 5% of chronic lymphoproliferative disorders in the United States of America. LGL leukemia can either present as an indolent type or an aggressive type. Most patients remain asymptomatic and often have associated autoimmune diseases, such as rheumatoid arthritis and hematologic dyscrasias. We analyzed the demographic characteristics of LGL leukemia patients and investigated the influence of social determinants on their survival. Methods: We performed a retrospective cohort study of the Surveillance, Epidemiology, and End Results (SEER) database for patients diagnosed with LGL leukemia between years 2000 and 2020. Patient demographics, year of diagnosis, and timeline of treatment were analyzed by descriptive statistics. Cox proportional hazards regression analysis was performed to identify the factors influencing the survival of these patients. Results: A total of 2589 patients were diagnosed with LGL leukemia. Median age of diagnosis was 67 years. 59.4% were aged more than 65 years of age at the time of diagnosis, 52.7% were males, 81.5% were Caucasians, 64% had an annual income of more than $65,000, and 84.2% lived in metropolitan areas. 91.8% were diagnosed in the past decade after 2010. It is worth noting that 64.5% of the patients received treatment more than six months after diagnosis of LGL leukemia. 81.5% of patients were Caucasians, 9.6% were African Americans, 5.3% were Asians/Pacific Islanders, followed by 2% Hispanics and 1.5% American Indians. At the time of the last follow-up, 65.5% of patients were alive, with an overall median survival of forty months. 70% of patients had LGL leukemia as the only primary malignancy. Age less than 65 years had better outcomes than the older age group (HR 0.32). Female gender was protective (HR 0.69). Poor outcomes were seen in patients with an annual income of less than $65,000 (HR 1.21). The year of diagnosis and residence had no significant effect on survival. Marriage improved the outcomes of patients (HR 0.78) (Table 1). Patients receiving treatment within six months of diagnosis had higher mortality (HR 1.43) than the rest of the population. Caucasians comprised majority of the patient population and had better prognoses (HR 0.11) than Asians/Pacific Islanders (HR 0.49), Hispanics (HR 0.82), and African Americans (HR 0.97) (Figure 1). Conclusion: We present a population-based analysis and the determinants of survival in patients with LGL leukemia, a rare malignancy. The number of cases has increased in the past decade. Significant patient factors influencing survival in LGL leukemia patients include younger age at diagnosis, female gender, marriage and higher annual income.

Incidence, Clinical Features, and Outcomes of Large Granular Lymphocyte Leukemia

Introduction: - Large Granular Lymphocyte (LGL) leukemia is a rare and diverse hematologic disorder characterized by the clonal proliferation of large granular lymphocytes in the peripheral blood and bone marrow. Despite its rarity, population-based studies on LGL leukemia remain limited. This study aims to comprehensively analyze clinical characteristics and outcomes among patients with LGL leukemia. Methods: - We utilized the Surveillance, Epidemiology, and End Results (SEER) database 17 registry to identify patients diagnosed with large granular lymphocytic leukemia between 2000-2020. Data analysis was conducted using SEER*Stat version 8.4.1.2 and STATA. Univariate survival analysis was done using a Kaplan Meir plot with a log-rank test, and the Cox proportion hazard regression model was used for multivariate survival analysis. Results: - We identified a total of 2,589 LGL leukemia cases during the study period. The calculated incidence of LGL leukemia was 0.14 cases per 1,000,000 individuals (range: 0.14 - 0.15). Male patients exhibited a higher incidence rate ratio of 1.19 (95% CI: 1.11 - 1.27, p < 0.01) than females. However, females tended to be diagnosed younger than males (67 vs. 68, p < 0.01). Most cases were observed in the White population (83%) compared to other racial groups. The median age at diagnosis was 67 years (ranging from 7 to 85 years). Patients aged above 70 years showed the highest incidence of LGL leukemia (0.80) in contrast to those aged 45-54 years (0.30) and 55-64 years (0.63). Notably, there was a significant increasing trend in LGL leukemia incidence, with an incidence rate ratio of 13.50 (95% CI: 10.5-17.6, p < 0.001) in the period 2015-2019 compared to 2000-2004. Approximately 32.7% of patients received chemotherapy; the median time from diagnosis to treatment was one month. The survival rates at 12, 36, and 60 months for LGL leukemia patients were 88.9%, 76.5%, and 66.5%, respectively, with a median follow-up of 40 months. Multivariate analysis revealed that females had a more favorable survival outcome than males (HR: 0.78, 95% CI: - 0.64 - 0.97, p: 0.02). Moreover, patients who underwent chemotherapy exhibited better survival than those who did not (HR: 0.72, 95% CI: 0.56 - 0.93, p: 0.01). Elderly patients above 60 years of age had poorer survival rates (HR: 3.1, 95% CI: 2.34 - 4.01, p < 0.01), and no significant difference in outcomes was observed based on the timing of chemotherapy initiation from the time of diagnosis. Conclusion: - This study represents the most extensive and most recent population-based investigation of LGL leukemia. The findings highlight the potential benefits of chemotherapy in improving survival and indicate better outcomes in female patients. Further research is warranted to validate these promising results and gain deeper insights into the management and prognosis of LGL leukemia.

DR-01, a Non-Fucosylated Anti-CD94 Antibody, Depletes Leukemic Cells in Ex Vivo and In Vivo Models of Large Granular Lymphocyte Leukemia

Large granular lymphocyte leukemia (LGLL) is a rare leukemia more frequently occurring in the elderly population with three major subtypes: T-LGLL, chronic lymphoproliferative disorder of NK cells (CLPD-NK) and aggressive NK cell leukemia (ANKL). Over 50% of patients develop complications including severe neutropenia, thrombocytopenia and anemia, thus predisposing patients to opportunistic infections. In addition, treatments are limited to standard immunosuppressive therapy such as methotrexate, cyclosporine or cyclophosphamide, with complete response rates of only 50% or less for each agent. Thus, novel and effective therapies for LGLL patients are critically needed. Dren Bio is developing DR-01, a non-ligand blocking, non-fucosylated monoclonal antibody targeting CD94. CD94 is a type II transmembrane receptor identified on mature, cytotoxic lymphocytes such as healthy NK and terminally differentiated CD8 T cells. In the context of disease, CD94 is known to be upregulated on LGLL cells. DR-01 functions through depletion of target cells via antibody-mediated cellular cytotoxicity (ADCC) by means of fratricide, a method in which the same cell type induces ADCC on each other. Through characterization of DR-01 using various ELISA and cell-based assays, DR-01 was determined to bind with nanomolar affinity to CD16a (EC50: 0.04µg/mL) and to CD94 on healthy human donor NK cells, cynomolgus monkey NK cells and LGLL cells (EC50: 0.5-1nM). DR-01 induces potent, dose-dependent depletion of CD94+ cells in ex vivo ADCC assays (IC50: 1ng/mL) of peripheral blood mononuclear cells (PBMCs) from healthy and diseased individuals. Furthermore, DR-01 has been shown to be well tolerated in a 4-week dose-range finding and Good Laboratory Practice (GLP) study in cynomolgus monkeys from 5-100mg/kg on a weekly dosing regimen. A 12-color flow cytometry panel was applied to a cohort of patient LGLL PBMCs to profile CD94 expression and other cytotoxic markers associated with the disease, including CD16, CD57 and functional binding partners of CD94 such as NKG2A and NKG2C. CD94 was identified on 97% (37/38) of patient samples screened, ranging from 400 to 725,000 receptors per cell. All patient leukemic cells expressed variable levels of CD16 and CD57. NKG2A and NKG2C were present in over 5% of total leukemic cells in 37% (14/38) and 21% (8/38) of patient samples, respectively. In addition, DR-01 was able to deplete LGL leukemic cells with high potency and in a dose-dependent manner in a functional ADCC assay (IC50:1-10ng/mL). The mechanism of fratricide was demonstrated through degranulation of the leukemic population via expression of CD107a. Cytokine profiling results are pending. To demonstrate in vivo efficacy of DR-01 in a disease model of LGLL, humanized NSG-Tg(hIL-15) mice engrafted with patient LGLL splenocytes were utilized. Optimal splenocyte engraftment (5-20% human CD45+ cells in blood) was achieved within 3 weeks post-inoculation with 10 million PBMCs per pre-sublethally irradiated mouse. The engrafted leukemic population partially preserved the CD94 expression profile from the patient leukemic cells and was successfully depleted (>90%) in blood, bone marrow, spleen and liver 1-week post-treatment with a single dose of DR-01 at 5mg/kg. Overall, DR-01 is a non-fucosylated anti-CD94 antibody with high affinity and potent leukemic cell depleting ability ex vivo and in vivo. The favorable toxicity profile of DR-01 in cynomolgus monkeys precede clinical studies in LGLL patients. Additional profiling and evaluation of DR-01 in LGLL patient samples ex vivo as part of a pre-phase I study is ongoing. A phase I/II trial has been initiated to assess the safety and efficacy of DR-01 in previously treated LGLL patients.

Presence of Activating STAT3 Mutations in the CD8+ T Cells of Rheumatoid Arthritis Patients

Rheumatoid Arthritis (RA) is a systemic autoimmune disorder afflicting around 1% of the global population. It is treated with a variety of immunosuppressants typically progressing from first line therapies such as low dose methotrexate (MTX) or other disease modifying anti-rheumatic drugs (DMARDs) to second line treatments such as tumor necrosis factor (TNF) inhibitors or other biologics designed to target pro-inflammatory cytokines. Several factors are used to anticipate and measure disease severity including Disease Activity Measures (DAM) and positivity of rheumatoid factor (RF), antibodies to cyclic citrullinated protein (CCP), C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR). Presence of anti-CCP antibody is the most specific of these markers of RA, and its presence may be associated with more severe disease. Large granular lymphocyte (LGL) leukemia is a rare hematologic malignancy characterized by clonal proliferation of natural killer or CD8+ T cells, somatic activating mutations in the signaling transducer and activator of transcription 3 (STAT3) gene, and clinical features including neutropenia and anemia. Interestingly, LGL leukemia is strongly associated with RA, with as high as 36% of patients exhibiting concomitant RA. There is significant overlap between the diseases. Both RA alone and in combination with LGL leukemia exhibit cytotoxic T cell expansions, HLA-DR4 enrichment, female bias, and RA-associated autoantibodies. The dominant molecular hallmark of LGL leukemia is somatic activating STAT3 mutation. Most patients exhibit increased activation of STAT3 through phosphorylation, and 50% or more patients have a mutation in STAT3, the most common being missense mutations, Y640F and D661Y. Of note, LGL leukemia patients with one or more STAT3 mutations are more likely to suffer from concomitant RA. Based on these observations, we hypothesized that STAT3 mutations would be enriched in RA patients compared to the general population and that the presence of mutations may correlate with specific clinical characteristics of RA. In this study, blood samples and demographic data were simultaneously collected from 96 RA patients at the UVA Rheumatology Clinic. CD8+ cells were isolated from blood samples and DNA was extracted and analyzed via droplet digital PCR to detect Y640F, D661Y, and S614R_G618R STAT3 mutations. Figure A shows that roughly 3% (3/96) of the RA samples had a STAT3 mutation in greater than 5% of the DNA analyzed. Additionally, an even larger proportion of RA patients had either Y640F or D661Y mutations at a rate of between 1:100 and 1:1000 cells (10/96 Y640F, 14/96 D661Y). These samples were classified as mutated for the purposes of statistical analysis. Of the 9 healthy control samples analyzed, only one exhibited a mutation of this size (1/9 Y640F, 0/9 D661Y). Correlation with clinical parameters showed similar disease manifestations between WT and STAT3 mutant samples. However, CCP differed between mutational types, with the Y640F group exhibiting higher positivity than the D661Y group (Figure B). Taken together, the increased presence of STAT3 activating mutations in CD8+ cells isolated from RA blood samples as well as the difference in CCP positivity between D661Y and Y640F mutational groups merits further investigation of these pathways in RA. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

LGL leukemia patients exhibit substantial protective humoral responses following SARS-CoV-2 vaccination.

Large granular lymphocyte leukemia is a rare chronic lymphoproliferative disorder of cytotoxic cells. Other hematological malignancies such as CLL and multiple myeloma have been associated with poor vaccination response and markedly increased severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) mortality rates, specifically in patients who have undergone immunosuppressive therapy. Given the immunosuppressive therapies often used to treat the disease, large granular lymphocytic (LGL) patients may be especially vulnerable to SARS‐CoV‐2 infection. A questionnaire was sent to all patients in the LGL Leukemia Registry at the University of Virginia (UVA) to obtain information on vaccination status, type of vaccine received, side effects of vaccination, patient treatment status before, during, and after vaccination, antibody testing, history of coronavirus disease 2019 (COVID‐19) infection, and presence or absence of booster vaccination. Antibody testing of 27 patients who had quantitative SARS‐CoV‐2 Spike Protein IgG levels determined by University of Virginia medical laboratories via the Abbott Architect SARS‐CoV‐2 IgG II assay were collected. The assay was scored as reactive at a threshold of ≥50.0 AU/mL or nonreactive with a threshold of <50.0 AU/mL. LGL patients without treatment as well as patients who held treatment prior to their vaccination have a robust humoral response to SARS‐CoV‐2 vaccines. Patients who did not hold their immunosuppressive treatments have signifigantly diminished vaccine response compared to those who held their immunosuppressive treatment. Our findings support a dual strategy of pausing immunotherapy during the vaccination window and administration of the SARS‐CoV‐2 booster to all LGL leukemia patients to maximize protective antibodies.

Cytokines in the Pathogenesis of Large Granular Lymphocytic Leukemia

Large granular lymphocytic leukemia (LGLL) is a lymphoproliferative disorder of older adults characterized by the clonal expansion of cytotoxic T/natural killer cells due to constitutive pro-survival signaling. In recent years, it has become clear that cytokines and their receptors are aberrantly expressed in LGLL cells. The exact initiation process of LGLL is unknown, although several cytokine-driven mechanisms have emerged. Elevated levels of several cytokines, including interleukin-15 (IL-15) and platelet-derived growth factor (PDGF), have been described in LGLL patients. Evidence from humans and animal models has shown that cytokines may also contribute to the co-occurrence of a wide range of autoimmune diseases seen in patients with LGLL. The goal of this review is to provide a comprehensive analysis of the link between cytokines and pro-survival signaling in LGLL and to discuss the various strategies and research approaches that are being utilized to study this link. This review will also highlight the importance of cytokine-targeted therapeutics in the treatment of LGLL.

Isolated anemia in patients with large granular lymphocytic leukemia (LGLL)

Patients with large granular lymphocytic leukemia (LGLL) frequently present with neutropenia. When present, anemia is usually accompanied by neutropenia and/or thrombocytopenia and isolated anemia is uncommon. We evaluated a cohort of 244 LGLL patients spanning 15 years and herein report the clinicopathologic features of 34 (14%) with isolated anemia. The patients with isolated anemia showed a significantly male predominance (p = 0.001), a lower level of hemoglobulin (p < 0.0001) and higher MCV (p = 0.017) and were less likely to have rheumatoid arthritis (p = 0.023) compared to the remaining 210 patients. Of the 34 LGLL patients with isolated anemia, 13 (38%) presented with pure red cell aplasia (PRCA), markedly decreased reticulocyte count and erythroid precursors, and more transfusion-dependence when compared to non-PRCA patients. There was no other significant clinicopathologic difference between PRCA and non-PRCA patients. 32 patients were followed for a median duration of 51 months (6–199). 24 patients were treated (11/11 PRCA and 13/21 non-PRCA patients, p < 0.02). The overall response rate to first-line therapy was 83% [8/11 (72.7%) for PRCA, 12/13 (92.3%) for non-PRCA], including 14 showing complete response and 6 showing partial response with a median response duration of 48 months (12–129). Half of non-PRCA patients who were observed experienced progressive anemia. During follow-up, no patients developed neutropenia; however, 5/27 (18.5%) patients developed thrombocytopenia. No significant difference in overall survival was noted between PRCA and non-PRCA patients. In summary, this study demonstrates the unique features of LGLL with isolated anemia and underscores the importance of recognizing LGLL as a potential cause of isolated anemia, which may benefit from disease-specific treatment. LGLL patients with PRCA were more likely to require treatment but demonstrated similar clinicopathologic features, therapeutic responses, and overall survival compared to isolated anemia without PRCA, suggesting PRCA and non-PRCA of T-LGLL belong to a common disease spectrum.

Manifestation of Large Granular Lymphocyte Leukemia in Pediatric and Young Adult Population Is Distinct from Older Adult Cohorts

Introduction: Large Granular Lymphocyte (LGL) leukemia is a rare lymphoproliferative disorder usually manifested in elderly individuals, with mean age of onset at 65. However, LGL leukemia cases in pediatric and young adult (age <30) populations are occasionally observed. Severity of disease, response to routine LGL treatments (methotrexate, cyclophosphamide, cyclosporine), and molecular profiling of this cohort is largely unknown, with only a few case reports describing the occurrence. Here we present the first comprehensive analysis of pediatric and young adult LGL leukemia patients, where we compare demographic and hematologic parameters, frequency of STAT3 mutations, whole exome and transcriptomic profile, and treatment responses to the older adult (age >50) cohort.Methods: We retrospectively collected clinical data from 23 young adult (age <30), 105 adult (age 30-50), and 89 older adult (age >50) LGL leukemia patients. All participants signed informed consent to provide biospecimens and clinical records to the LGL Leukemia Registry. Whole exome (PBMC and saliva) and RNA sequencing (PBMC) was conducted on 115 patients. Sanger sequencing was utilized to determine STAT3 mutational status in the remaining 102 patients.Results: STAT3 is the most frequently mutated gene in LGL leukemia, and the mutation is associated with lower absolute neutrophil counts (ANC). We observed no differences in the frequency of STAT3 somatic mutations in young adult, adult, and older adult LGL leukemia (p=0.143). However, we detected a significant positive linear relationship between age of the patient and ANC values (p=0.002) for STAT3 mutant patients (Figure 1A). STAT3 wild-type (WT) patients did not display this relationship (p=0.756). No age associated trends were detected for hemoglobin values, although we detected decreasing red blood cell (RBC) values with increasing age for both STAT3 mutated and WT patients (p= 0.031, 0.010, respectively). No difference in sex (male vs female) balance was found within the young adult cohort (p=0.190). As rheumatoid arthritis (RA) is observed in ~30% of LGL leukemia patients, we asked if this prevalence also holds in the younger cohort. RA was observed in similar proportion in all young, adult, and older adult groups (p=1).To compare the severity of disease manifestation between the age groups, we first asked how many patients ever initiated LGL-related treatments in each age group. We found that patients under 50 are more likely to be on LGL related treatments compared to patients over the age of 50 (p=0.016) (Figure 1B). Next, we examined length of survival between age groups. Despite increased initiation of LGL related treatments, no statistically significant difference in overall survival (OS) was observed between patients under 50 and patients over the age of 50 (p=0.33) (Figure 1C). Therefore, we asked if the treatment response in younger patients is better compared to older patients. We observed no statistically significant differences in the routine LGL treatment responses between patients under 50 and patients over the age of 50 (p=0.732).Interestingly, epigenetic and chromatin modifier mutations are equally common in patients 50 years old and under relative to older adult patients (p= 0.271) (Figure 1D). Transcriptomic analysis of the PBMC data revealed enrichment of TNFα signaling in patients older than 50, while IFNα and IFNγ signaling was enriched in patients 50 years old and younger.Conclusions: We report the clinical and molecular analysis of LGL leukemia in pediatric/young adult and adult patients compared to the older adult patients that comprise the majority of LGL cases. We show that while STAT3 mutation frequency is similar across all age groups, younger patients with STAT3 mutation show lower ANC values compared to older patients. Importantly, we show that younger patients exhibit a more severe disease, as indicated by increased initiation of LGL treatment. However, overall survival in younger groups compared to older patients is not impacted. Finally, we show that younger patients display similar proportions of epigenetic and chromatin modifying mutations that are a prominent feature of older patients, and feature enrichment of IFNα and IFNγ signaling distinct from older patients. [Display omitted] DisclosuresFeith: Kymera Therapeutics: Membership on an entity's Board of Directors or advisory committees. Loughran: Dren Bio: Membership on an entity's Board of Directors or advisory committees; Keystone Nano: Membership on an entity's Board of Directors or advisory committees; Bioniz Therapeutics: Membership on an entity's Board of Directors or advisory committees; Kymera Therapeutics: Membership on an entity's Board of Directors or advisory committees.

Neutropenia and Large Granular Lymphocyte Leukemia: From Pathogenesis to Therapeutic Options.

Large granular lymphocyte leukemia (LGLL) is a rare lymphoproliferative disorder characterized by the clonal expansion of cytotoxic T-LGL or NK cells. Chronic isolated neutropenia represents the clinical hallmark of the disease, being present in up to 80% of cases. New advances were made in the biological characterization of neutropenia in these patients, in particular STAT3 mutations and a discrete immunophenotype are now recognized as relevant features. Nevertheless, the etiology of LGLL-related neutropenia is not completely elucidated and several mechanisms, including humoral abnormalities, bone marrow infiltration/substitution and cell-mediated cytotoxicity might cooperate to its pathogenesis. As a consequence of the multifactorial nature of LGLL-related neutropenia, a targeted therapeutic approach for neutropenic patients has not been developed yet; moreover, specific guidelines based on prospective trials are still lacking, thus making the treatment of this disorder a complex and challenging task. Immunosuppressive therapy represents the current, although poorly effective, therapeutic strategy. The recent identification of a STAT3-mediated miR-146b down-regulation in neutropenic T-LGLL patients emphasized the pathogenetic role of STAT3 activation in neutropenia development. Accordingly, JAK/STAT3 axis inhibition and miR-146b restoration might represent tempting strategies and should be prospectively evaluated for the treatment of neutropenic LGLL patients.

Therapeutic Efficacy of Mcl-1 Antagonism in Large Granular Lymphocyte Leukemia

Introduction: Large granular lymphocyte (LGL) leukemia is a spectrum of rare clonal lymphoproliferative disorders, all of which involve expansion of large granular lymphocytes. Immunosuppressive regimens using methotrexate or cyclophosphamide are utilized as front-line treatments in LGL leukemia but are not curative nor are they effective in all patients. The aggressive LGL variants have no effective treatment and are refractory to conventional chemotherapy. The lack of effective and targeted therapies results from an incomplete picture of survival mechanisms that contribute to the pathogenesis of leukemic LGLs.We have previously reported that STAT3 is constitutively active in LGL leukemia cells and up to 40% of patients harbor activating mutations in STAT3 within the leukemic clone. We have also reported that the pro-survival Bcl-2-family protein Mcl-1 is upregulated in LGL leukemia patients. Additionally, we have identified MCL1 as a transcriptional target of STAT3 in leukemic LGLs. Recently, novel small molecule inhibitors of Mcl-1 have been identified including marinopyrrole A (maritoclax) and its derivative KS18. These inhibitors effectively induced apoptosis in Mcl-1-dependent cells and suppressed the growth of Mcl-1-dependent hematologic cancer xenografts in nude mice without apparent toxicity. Thus, this study further investigates the role of Mcl-1 in LGL leukemia and the potential therapeutic application of the Mcl-1 antagonists maritoclax and KS18.Results: Knockdown of Mcl-1 in human-derived LGL leukemia cell lines (TL1 and NKL) resulted in decreased cell viability by MTS assay and increased apoptosis by flow cytometry in Mcl-1 siRNA versus scramble siRNA-transfected cells (NKL and TL-1 cells: p < 0.001). Treatment with maritoclax or KS18 decreased cell proliferation and increased apoptosis in NKL, TL1 and RNK16 (rat-derived LGL leukemia cell line) cells (Maritoclax, EC50: 2.45, 1.43 and 1.23 μM respectively) (KS18, EC50: 1.30, 0.60 and 0.31 μM respectively). Ex vivo treatment with maritoclax and KS18 induced selective apoptosis in PBMCs from LGL leukemia patients (NK-LGL, n = 6; T-LGL, n = 12) but not normal donor PBMCs (n = 4) (Maritoclax and KS18, p < 0.0001). Importantly, there was no significant difference in treatment efficacy in patient cells with wild-type STAT3 (n = 9) versus mutant STAT3 (Y640F, n = 5; D661Y, n = 3). We then proceeded to mechanistic studies of Mcl-1 antagonism. Both maritoclax and KS18 induced selective and dose-dependent Mcl-1 degradation by western blot in NKL, TL1, RNK16 and PBMCs from LGL leukemia patients. We further delineated that this effect was proteasome dependent as it is reversible by pre-treatment with MG132, a proteasome inhibitor.Preclinical in vivo studies were then conducted in Fisher F344 rats that were transplanted with primary leukemic LGL cells and monitored for signs of leukemia through serial CBC and body weight measurements. Leukemic rats developed progressive anemia, thrombocytopenia and leukocytosis and significant weight loss. Rats were treated with vehicle or KS18 (2.5 or 5.0 mg/kg i.p. daily) upon detection of leukemic features. In non-leukemic KS18-treated rats, there were no observed toxicities and there was no difference in survival or weight gain versus vehicle-treated non-leukemic rats. However, leukemic KS18-treated rats exhibited findings consistent with tumor lysis syndrome, including sudden death associated with severely increased serum LDH and increased apoptosis in heart and spleen tissues. At necropsy, leuk/KS18 rats exhibited significantly decreased infiltration and elevated apoptosis of leukemic cells in heart and spleen tissues. Conversely, in leuk/veh rats, spleen tissue lacked normal histologic structure with red pulp replaced almost completely by leukemia cells. Ex vivo KS18 treatment also decreased the viability of PBMC and spleen cells from leukemic animals (p < 0.0001). These data indicate that Mcl-1 is a promising therapeutic target as evidenced by potent therapeutic efficacy of KS18 in LGL cell lines and primary patient material and in an aggressive rat model of LGL leukemia. Further studies are required in order to optimize drug dose, timing and concentrations of KS18 in order to prevent potential tumor lysis syndrome and optimize therapeutic benefit. DisclosuresGru:Seattle Genetics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees.

TCR γδ Large Granular Lymphocyte Leukemia (LGLL) Displays Features between CD8+ and CD4+ TCR αβ LGLL

BackgroundT-large granular lymphocyte leukemia (T-LGLL) is a rare and heterogeneous lymphoproliferative disorder characterized by the chronic proliferation of clonal Large Granular Lymphocytes (LGLs) with cytotoxic activity. Usually, leukemic cells of this T-cell neoplasia express the αβ T-cell receptor (TCR); only a small subset of cases expresses the γδ TCR denoting the TCRγδ-LGLL. Currently, among the different LGL diseases, TCRγδ-LGLL remains less studied and several clinical and laboratory data already described in TCRαβ-LGLL have not yet been explored in TCRγδ-LGLL. In particular, data are still missing about STAT3 and STAT5b mutations, frequently observed in TCRαβ-LGLL, and about T-LGL clonotypes discovered to be private to TCRαβ-LGLL as compared to healthy controls.AimsThis work was aimed to perform the analysis on: STAT3 and STAT5b mutations, LGL immunophenotype, TCRγ clonotype repertoire and clinical presentations in a group of TCRγδ-LGLL patients. The objective was to reveal common and different features of this rare kind of LGLL with the more frequent TCRαβ-LGLL.MethodsThe cohort of study included 11 patients affected by TCRγδ-LGLL. Sanger sequencing was used for mutational analysis on hot-spot regions of the 2 genes more frequently mutated in LGL disorders, STAT3 and STAT5b . Immunophenotype of LGL clone was defined by flow cytometry analysis. CDR3 repertoire and frequency distribution of TCR gamma gene rearrangements were obtained by Next-Generation Sequencing (NGS).ResultsTCRγδ-LGLL showed a higher occurrence of STAT mutations (82%) as compared to TCRαβ-LGLL (43%). In detail, 9 out of 11 TCRγδ LGLL patients were characterized by STAT3 or STAT5b mutations in a mutually exclusive pattern. Being characterized by both STAT3 and STAT5b mutations, TCRγδ LGLL resembles both CD8+ TCRαβ-LGLL and CD4+ TCRαβ-LGLL, the first being mostly associated to STAT3 mutations and the latter to STAT5b . Similarly, TCRγδ-LGLL showed the same relationship observed between immunophenotype and kind of mutation in TCRαβ-LGLL: TCRγδ-LGLL patients with CD56- LGL immunophenotype were characterized by STAT3 mutations (as in CD8+ TCRαβ-LGLL), while TCRγδ-LGLL patients with CD56+ LGL immunophenotype by STAT5b mutations (as in CD4+ TCRαβ-LGLL). Anyway, in TCRγδ-LGLL no correlation was found between mutations and clinical course as observed in CD8+ TCRαβ-LGLL patients carrying STAT mutations, rather, we observed that patients with γδLGLs positive for Vδ2 showed frequently indolent course, while Vδ1 was associated to a more symptomatic disease (4 out of 5 symptomatic patients were Vδ1+). By NGS we obtained the TCR gamma repertoire of each patient and we revealed that all patients were clonal with the exception of 2 showing a polyclonal pattern. The 2 polyclonal cases were the only 2 patients without STAT mutations. Among the remaining STAT3 mutated patients (n=4), 3 were polyclonal and one biclonal, while STAT5b mutated patients (n=5) were more frequently monoclonal (4/5 monoclonal and 1/5 biclonal). Considering the CDR3 repertoire of the immunodominant clones, as observed in TCRαβ-LGLL, common clonotype sequences were present with low frequency in almost all TCRγδ-LGLL patients. Interestingly, 2 different CDR3 sequences were found shared in different patients at frequency >10% of the total rearrangements. In terms of clonal rearrangements, Vγ3-Jγ1/2, Vγ9-JγP and Vγ8-Jγ1/2 were the combination usages most frequently detected, showing a limited combinatorial diversity of TCR genes similarly to CD4+ and differently from CD8+ TCRαβ-LGLL, this last having larger variability. Analysis about the clonotype repertoire in a 2 years-follow up showed that patients maintain their clonal pattern along the time.ConclusionsOur results highlight common and different characteristics of TCRγδ-LGLL as compared to TCRαβ-LGLL. The data suggest that TCRγδ-LGLL can be considered the intersection of the 2 types of TCRαβ-LGLL, sharing CD8+ or CD4+ T-LGLL mutational and phenotype features. Similarly to TCRαβ-LGLL, also TCRγδ disease showed a decreased diversity of TCR repertoire, with common TCR sequences shared among patients and with limited number of Vγ-Jγ combinations. A distinctive feature of TCRγδ-LGLL is that STAT mutations do not correlate with a symptomatic clinical behavior, rather, Vδ1 expression appears to be indicative for symptomatic disease. DisclosuresGalimberti:Bristol-Myers Squibb: Speakers Bureau; Novartis: Speakers Bureau; Incyte: Speakers Bureau; Pfizer: Speakers Bureau.

STAT3 activation in large granular lymphocyte leukemia is associated with cytokine signaling and DNA hypermethylation

Large granular lymphocyte leukemia (LGLL) is characterized by somatic gain-of-function STAT3 mutations. However, the functional effects of STAT3 mutations on primary LGLL cells have not been studied in detail. In this study, we show that CD8+ T cells isolated from STAT3 mutated LGLL patients have high protein levels of epigenetic regulators, such as DNMT1, and are characterized by global hypermethylation. Correspondingly, treatment of healthy CD8+ T cells with IL-6, IL-15, and/or MCP-1 cytokines resulted in STAT3 activation, increased DNMT1, EZH2, c-MYC, l-MYC, MAX, and NFκB levels, increased DNA methylation, and increased oxidative stress. Similar results were discovered in KAI3 NK cells overexpressing gain-of-function STAT3Y640F and STAT3G618R mutants compared to KAI3 NK cells overexpressing STAT3WT. Our results also confirm that STAT3 forms a direct complex with DNMT1, EZH2, and HDAC1. In STAT3 mutated LGLL cells, DNA methyltransferase (DNMT) inhibitor azacitidine abrogated the activation of STAT3 via restored SHP1 expression. In conclusion, STAT3 mutations cause DNA hypermethylation resulting in sensitivity to DNMT inhibitors, which could be considered as a novel treatment option for LGLL patients with resistance to standard treatments.

Large granular lymphocytic leukemia - A retrospective study of 319 cases.

Large granular lymphocytic leukemia (LGLL) is a rare hematological malignancy that arises from cytotoxic T lymphocytes (T-LGLL) in 85% of cases and natural killer (NK) cells in the rest. A significant knowledge gap exists regarding the pathogenesis, treatment choices, and prognostic factors of LGLL. We report a cohort of 319 consecutive LGLL patients who presented to our cancer center between 2001 and 2020. A total of 295 patients with T-LGLL and 24 with chronic NK-cell lymphoproliferative disorder (CLPD-NK) were identified. The median age was 65 years (range, 17-90 years). Eighty-three patients (26.0%) had autoimmune diseases. A total of 119 patients (37.3%) had coexisting malignancies, 66 (20.7%) had solid tumors, and 59 (18.5%) had hematological malignancies. Most coexisting malignancies were diagnosed before the diagnosis of LGLL. Treatment was needed for 57% of patients. Methotrexate (MTX), cyclophosphamide (Cy), and cyclosporine A (CSA) were most used and had similar response rates between 61.5%-74.4%. Cy produced more complete responses (32.3%) compared to MTX and CSA (15.7% and 23.1%, respectively). Thrombocytopenia, splenomegaly, and female gender (after controlling for autoimmune diseases) were associated with decreased response rates to MTX, CSA, or Cy. Autoimmune diseases were associated with increased response rates. Thrombocytopenia was an independent risk factor for worse survival.

Large Granular Lymphocytic Leukemia with Coexisting Malignancies

Introduction: Large granular lymphocytic leukemia (LGLL) is a rare, indolent malignancy arising from cytotoxic T cells (~85%) or NK cells (~15%). The coexistence of LGLL with MDS, B cell neoplasms and plasma cell dyscrasias have been reported in case reports and two retrospective studies (Gayal et al 2018, Viny et al 2008). However, those studies were limited by sample size and a small number of coexisting malignancies. To our knowledge, there is no systematic study on coexisting solid tumors with LGLL in the literature. In present study, we systemically analyzed the coexisting malignancies (CMs) including solid tumors and hematological malignancies (liquid tumors) in our LGLL patients (pts). We compared the clinical features, immunophenotype, treatment responses and estimated outcomes of CM-associated LGLL and non-CM associated LGLL pts. Methods: Total 303 consecutive LGLL pts evaluated at Moffitt Cancer Center (MCC) between 2001 and 2017 were included in the study. Pts who did not meet the WHO diagnostic criteria of peripheral blood (PB) LGL count ≧ 2.0 k/μL but presented with persistent LGL clonal populations along with characteristic immunophenotype, matching clinical features and bone marrow involvement with clonal LGL population were considered to have LGLL. Results: Among the total 303 LGLL patients, 123 (40.6%) had at least 1 CM. The maximum number of coexisting malignancies were 3. 114 pts (37.6%) had invasive cancers (excluding non-melanomatous skin cancer), 83 (27.1%) had solid tumors and 60 (19.8%) had liquid tumors. The most frequent invasive solid tumors in our LGLL patients were: prostate cancer, breast cancer, lung cancer, colorectal cancer, and melanoma. The most frequent liquid tumors were: B-cell lymphoma, T-cell lymphoma, CLL/SLL, CML and MM (Table 1). The number of patients with CM diagnosed before, at the same time and after LGLL diagnosis were 103, 7, and 28, respectively. Table 2 compared the clinical features of LGLL pts with CM to those without CM separated into liquid and solid tumors. Compared to pts without CM, LGLL patients with liquid tumors were older, less likely to have B symptoms (49.2% vs 73.6%, respectively), less likely to be neutropenic (32.1% vs 53.4%), less likely to be pRBC transfusion dependent (7.3% vs 24.5%), and less likely to require treatment (33.3% vs 61.1%). LGLL pts with solid tumors compared to those without CM were older, more likely to be Caucasians, more likely to have NK-cell LGLL (13.3% vs 6.1%), and less likely to have B symptoms (59.5% vs 73.6%). NGS testing was performed in 25 patients. Activating STAT3 mutations were detected in 9/21 patients without CM and 1/4 patients with CM (p=0.63 by Fisher's exact test). None of tested pts demonstrated STAT5B mutation. An extensive 10-color flow cytometry panel was employed after year 2015 in 34 pts. The immunophenotype was similar between CM-associated T-LGLLs and non-CM associated T-LGLLs except that CM-associated T-LGLL pts were more likely to be CD56+ (6/11 vs 3/23, p=0.03 by Fish's exact test). CM-associated LGLLs and non-CM associated LGLLs had comparable response rates to treatments (Table 3). The median follow-up time for all patient population was 4.8 years. Pts with CM had worse overall survival (OS) (Figure 1). The survival difference was significant after adjusting for age, gender and race (data not shown). Conclusions: In the present study of 303 consecutive LGLL pts, 40.6% had CM, including 27.4% with solid tumors and 19.8% with liquid tumors. CM-associated LGLLs had similar clinical and pathologic features and treatment responses as non-CM associated LGLLs, except that LGLL pts with CM were less likely to be symptomatic and less likely required treatment. Earlier detection of LGLL in pts with liquid tumors may have contributed to those differences. Interestingly, T-cell LGLLs with CM were more likely to be CD56 positive and LGLLs associated with solid tumors were more likely to be derived from NK-cell lineage. The high incidence of CMs in LGLL can be explained by the following hypotheses: 1) CM provided an initial antigenic stimulus and contributed to the pathogenesis of LGLL or alternatively, 2) host immunosuppression due to clonal LGLL proliferation promoted development of CM. The findings in this study that a majority of CMs manifested prior to LGLL diagnosis favor the first hypothesis. Our results provide additional insights into the pathogenesis of LGLL. Disclosures Komrokji: BMS: Honoraria, Speakers Bureau; Agios: Speakers Bureau; Novartis: Honoraria; Acceleron: Honoraria; Incyte: Honoraria; Abbvie: Honoraria; Geron: Honoraria; Jazz: Honoraria, Speakers Bureau. Sokol:EUSA Pharma: Consultancy, Honoraria, Speakers Bureau; Kyowa/Kirin Inc.: Membership on an entity's Board of Directors or advisory committees; Kymera Therapeutics: Membership on an entity's Board of Directors or advisory committees.

Thalidomide Plus Prednisone and Methotrexate for Symptomatic Large Granular Lymphocyte Leukemia: A Prospective, Single-Center, Pilot Study

Background: Large granular lymphocyte leukemia (LGLL) is one type of chronic lymphocytic proliferative disorders, which commonly manifests as infiltration of large granular lymphocytes in both peripheral blood and bone marrow. LGLL now includes two entities with similar clinical course, treatment strategy and outcomes: T-cell large granular lymphocytic leukemia and chronic lymphoproliferative disorder of NK cells. The standard therapy for LGLL is still elusive. Here, we presented the efficacy and safety of combinatorial oral immunoregulatory regimen thalidomide, prednisone, and methotrexate (TPM regimen) in a prospective phase 2 clinical trial. Methods: We designed this phase 2 investigator-initiated clinical trial (NCT04453345) to evaluate the clinical response and safety of the combination of thalidomide, prednisone, and methotrexate in symptomatic treatment naïve LGLL patients. The TPM regimen includes thalidomide 50-100mg per night, prednisone 0.5-1.0mg/kg qod and methotrexate 10mg/m2 per week. This regimen will be administrated for up to 12 months until disease progression or intolerable. Then, thalidomide maintenance will continue for another year or until intolerance. Meanwhile, we set Cyclosporin A (CsA) alone or plus steroids as control. Treatment dosage for CsA was 3-5mg/Kg/day with or without steroids (prednisone) 0.5-1 mg/Kg/day. The primary endpoint of this study was the complete response rate. Results: From Aug 2013, to Jan 2020, twenty-eight patients were enrolled in this study. The median follow-up time was 26 months (range: 7-96). Twenty-five patients (89%) achieved hematologic and symptomatic response. Among them, 21 patients (75%) achieved complete response (CR) and four patients achieved partial response. The median time to best clinical response was 6 months (2-18). The 3-years progression-free-survival (PFS) rate was 90%, and 3-years overall survival (OS) rate was 92%. The median PFS time was not reached in TPM group. The curative effect was better for TPM treatment group, both for overall response (OR) (TPM 89% (25/28) vs CsA 49% (49/99), P=0.000) and CR (TPM 75% (21/28) vs CsA 20% (20/99), P=0.000). Adverse events were uncommon, two patients had grade 1-2 nausea and one had grade 3 nausea. Two patients had grade 1-2 constipation and one patient experienced grade 1-2 peripheral neuritis. Conclusion: The efficacy of this TPM regimen is higher than the history reports with limited adverse events. The multiple-center clinical trial has been initiated to validate this conclusion. Disclosures No relevant conflicts of interest to declare.

Analysis of Genomic Landscape of Large Granular Lymphocyte Leukemia Reveals Etiologic Insights

Introduction: Large Granular Lymphocyte (LGL) leukemia is a rare lymphoproliferative disorder characterized by clonal expansion of either CD3+ cytotoxic T cells expressing T cell receptor (TCR) alpha beta or CD3- natural killer (NK) cells. A less frequent CD3+ T cell subtype expresses TCR gamma delta (GD). Here, we present the molecular landscape of known LGL types (T, NK, GD) from analysis of the largest patient cohort assembled to date. An integrative analysis of genomic datasets from all LGL subtypes is necessary to more precisely define the shared and unique etiology of this rare disorder. Methods: We collected paired saliva and PBMC samples and related clinical information from 116 LGL leukemia patients after informed consent. The assembled cohort consisted of 93 T-LGL, 11 NK-LGL, and 12 GD T-LGL patients. Genomic analyses were performed on the leukemic (PBMC) and germline (saliva) samples after whole exome sequencing (WES) and transcriptome sequencing (RNAseq, PBMC only). Results: Somatic mutations were detected in the previously described potential drivers STAT3 (n=56), TNFAIP3 (n=9), and PIK3R1 (n=4). We also identified somatic mutations in CDH8 (n=3) and CCL22 (n=4), which we postulate as putative drivers based on mutational clustering. CDH8 was mutated in all three LGL subtypes, but CCL22 somatic mutations were only observed in NK-LGL patients. We observed that STAT3 and CCL22 together account for 64% (7/11) of NK-LGL cases. STAT3 is the most recurrently mutated gene in LGL leukemia, yet concurrent molecular and clinical features are incompletely defined. Interestingly, patients with STAT3 mutations have a higher mutational burden (P=0.0006) compared to those with wild-type (WT) STAT3. This effect is independent of the age of the patient, which correlates with the mutational burden (R=0.26, P=0.0039) and agrees with the finding that the dominant mutational signatures in this cohort exhibit clock-like properties. We also observed that patients with STAT3 mutations are enriched (P=0.0273) for additional mutations in chromatin modifier enzymes such as KMT2D, TET2, DNMT3A, and SETD1B (Figure 1). We found that ~10% of the samples exhibit broad somatic copy-number aberrations, and a patient with somatic mutations in STAT3 and KMT2D displayed high-level microsatellite instability. STAT3 mutations were also significantly associated with increased expression of genes involved in apoptosis, complement activation, and interferon cytokine signaling compared to STAT3 WT (FDR &amp;lt; 0.05). Early-onset LGL patients with age 51 years or less (n=28), as defined by the bottom quartile of the cohort, displayed no differential enrichment of the somatic driver genes. Interestingly, the age of the patient was significantly associated with absolute neutrophil counts (ANC) (P = 0.0068), with younger patients exhibiting lower neutrophil counts, even after adjusting for the presence of STAT3 mutation, as it is associated with lower ANC. As neutropenia is a hallmark feature of LGL leukemia and often a trigger for initiating therapy, the association of young age with lower neutrophil counts and lower somatic mutational burden suggests other mechanisms may be involved. Focusing on the germline variants, we found that 17 of the patients (14.6%) had at least one pathogenic or likely pathogenic germline variant with known oncogenic association as annotated using CharGer. 5 patients had pathogenic mutations in known tumor suppressors including FANCC (n=1), BRCA1 (n=1), PALB2 (n=1), MUTYH (n=1), and SDHA (n=1), while 1 patient had pathogenic mutations in ALK, a known oncogene. Conclusions: We report on the genomic analyses done on whole exome and RNA-seq data from the largest cohort assembled for LGL leukemia to date. We show that the presence of STAT3 mutation is significantly associated with an increase in mutation burden and additional somatic mutations in chromatin modifiers, hinting at potential pathogenic mechanisms within STAT3 mutated patients. By combining LGL subtypes in our analysis, we were able to identify CDH8 as a putative driver that is present in T, NK, and GD subtypes. Additionally, we report CCL22 mutations specific to NK-LGL leukemia, however did not detect any subtype specific mutations in GD T-LGL. We found that about 15% of the patients carry at least one pathogenic germline variant with known oncogenic associations. These findings highlight emerging etiologic insights into this rare disorder. Disclosures Feith: Kymera Therapeutics: Membership on an entity's Board of Directors or advisory committees. Loughran:Keystone Nano: Membership on an entity's Board of Directors or advisory committees; Bioniz Therapeutics: Membership on an entity's Board of Directors or advisory committees; Kymera Therapeutics: Membership on an entity's Board of Directors or advisory committees; Dren Bio: Membership on an entity's Board of Directors or advisory committees.

Insights Into Genetic Landscape of Large Granular Lymphocyte Leukemia.

Large granular lymphocyte leukemia (LGLL) is a chronic proliferation of clonal cytotoxic lymphocytes, usually presenting with cytopenias and yet lacking a specific therapy. The disease is heterogeneous, including different subsets of patients distinguished by LGL immunophenotype (CD8+ Tαβ, CD4+ Tαβ, Tγδ, NK) and the clinical course of the disease (indolent/symptomatic/aggressive). Even if the etiology of LGLL remains elusive, evidence is accumulating on the genetic landscape driving and/or sustaining chronic LGL proliferations. The most common gain-of-function mutations identified in LGLL patients are on STAT3 and STAT5b genes, which have been recently recognized as clonal markers and were included in the 2017 WHO classification of the disease. A significant correlation between STAT3 mutations and symptomatic disease has been highlighted. At variance, STAT5b mutations could have a different clinical impact based on the immunophenotype of the mutated clone. In fact, they are regarded as the signature of an aggressive clinical course with a poor prognosis in CD8+ T-LGLL and aggressive NK cell leukemia, while they are devoid of negative prognostic significance in CD4+ T-LGLL and Tγδ LGLL. Knowing the specific distribution of STAT mutations helps identify the discrete mechanisms sustaining LGL proliferations in the corresponding disease subsets. Some patients equipped with wild type STAT genes are characterized by less frequent mutations in different genes, suggesting that other pathogenetic mechanisms are likely to be involved. In this review, we discuss how the LGLL mutational pattern allows a more precise and detailed tumor stratification, suggesting new parameters for better management of the disease and hopefully paving the way for a targeted clinical approach.

Coexistence of B-Cell Dyscrasia with Large Granular Lymphocytic Leukemia

Large granular lymphocytic leukemia (LGLL) is an indolent disease and often associated with autoimmune disorders such as rheumatoid arthritis. The association of humoral immune disorders resulting from abnormal B cell activity, may affect original LGLL pathogenesis, clinical presentation and management through modifying disease presentation, progression and/ or resistance to standard care. Coexistence of T cell LGL leukemia with B cell abnormalities has previously been identified in the literature although described in sporadic case reports. However, no large case series or cohorts have been collected so far to study the frequency of the B-cell dyscrasia (BCD) associated with LGLL and describe clinical/ hematological findings in patients with this co-association. Here, we conducted a retrospective review of patients diagnosed with LGL leukemia at The Cleveland Clinic Foundation to search for any associated BCDs. We then classified our population into 2 groups: LGLL with BCD vs. LGLL without BCD, and comprehensively compared them for baseline, clinical and molecular characteristics. A total of 244 T-LGL patients were collected and studied. All cases were uniformly diagnosed with LGLL if 3 out of 4 following criteria were fulfilled, including: 1) LGL count &gt;500/µL in blood for more than 6 months; 2) presence of abnormal CTLs expressing CD3, CD8 and CD57 by flow cytometry; 3) preferential usage of a TCR Vβ family by flow cytometry; 4) TCR gene rearrangement by PCR. Molecular studies including targeted deep sequencing for STAT3mutations were performed. Bone marrow biopsy results were reviewed to exclude other conditions. Endpoints of the study were death or lost to follow up. In our cohort, we found a frequent manifestation of humoral immune system abnormalities. We identified coexisting BCD in 45% (109/ 244) of LGLL patients, of whom 28 (11.2%) had monoclonal gammopathy of unknown significance (MGUS), and 13 (5.2%) had chronic lymphocytic leukemia (CLL/SLL). Six LGLL patients had multiple myeloma (2.4%). Moreover, polyclonal hypergammaglobulinemia (n=28, 11.2%) or hypogammaglobulinemia (n=14, 5.6%) was reported in 42 LGLL-patients (16.8%). The frequency of other disorders of B-cell origin was also examined. The total incidence of B-cell abnormalities in our LGLL cohort was 45%. Indeed an heterogeneous appearance of other B-cell disorders was observed including mantle cell lymphoma (n=2), DLBCL (n=6), marginal zone lymphoma (n=3), Waldenstrom's macroglobulinemia (n=1), Burkitt's lymphoma (n=1), indolent lymphoma (n=1), Hodgkin's lymphoma (n=1), non-Hodgkin's lymphoma (n=3), neck lymphoma (n=1), and smoldering myeloma (n=2). Patient with LGLL-BCD were older as compared to the ones without (median age: 62 vs. 63 years; ≥60 years: 57% vs. 69%, respectively), although the difference was not statistically significant (P=0.07). Gender was equally distributed (male: 54%, n=132; female: 46%, n=112) in patients who developed BCD. Conventional cytogenetics showed that patients without BCD were more often associated with abnormal cytogenetics (24%, n=9) as compared to LGLL-BCD (9%, n=5). Interestingly, BCD was found in 55 men and 54 women in whom only 6 patients had NK-LGLL while the remaining (n=103 patients) had T-LGLL suggesting a higher association with LGLL of T- rather than of NK-cell origin. Leukopenia was observed in 25/109 patients, with average absolute lymphocytes of 4.18 k/µL and LGL count of 2333 k/µL. Blood count showed: neutropenia in 44, anemia in 65, and thrombocytopenia in 29 out of 109 LGLL patients with BCD. TCR rearrangements were seen in 74 while somatic STAT3 mutations were observed in 37 LGLL patients while more enriched (44%, n=52) in LGLL without BCD. The association of other autoimmune conditions e.g., rheumatoid arthritis, was not different between the two groups (15% vs. 16% in LGLL with BCD vs. without; P=0.8). In sum, our investigation shows that BCD were frequent in LGLL and coexisted in 45% of the patients, commonly in the form of MGUS, and/ or hypergamaglobulinemia. Perhaps, the co-association of B-cell pathology with LGLL suggests that the two diseases either share pathogenetic driving mechanisms to enhance both B cells and T cells clones or that immunological dysfunction in setting of B cell dyscrasia could trigger/potentiate LGL expansion and/or transformation in this context. Disclosures No relevant conflicts of interest to declare.

Large Granular Lymphocytic Leukemia Coexists with Clonal Hematopoiesis of Indeterminate Potential

Large granular lymphocytic leukemia (LGL) is a lymphoproliferative cytotoxic T cell (CTL) that typically presents in elderly population. The spectrum of the disease ranges from semi-reactive oligoclonal to clonal CTL expansion, and from silent to a chronic leukemia with para-neoplastic manifestation. However the description of the disease still preceded the new genetic landscape mapping techniques. In lieu of this, we analyzed the genetic landscape of LGL using a set of 33 genes. Interestingly, not only did the deeper analysis help with a better understanding of the complex CTL proliferative processes but indicated a suspected association with conditions such as clonal hematopoiesis of indeterminate potential (CHIP). Association of LGL with age related CH has been described in the past by us and others. Our results indicate that LGL is often associated with the presence of myeloid mutations, generally consistent with the most common typical CHIP mutations (DNMT3A, TET2, ASXL1). We then analyzed a set of 13 patients with coexistent MDS/LGL. This observation raises the question that LGL is, at least in some cases, a tumor surveillance response. All LGL patients were diagnosed using a stringent single center diagnostic criteria and at the time of diagnosis, were also checked for other conditions including MDS to prevent any risks of overlooked diagnoses. A previously well described diagnostic standard of &gt;3/5 positive criteria was used; (i) presence of large granular lymphocytes (&gt;500/μL, by differential counts from complete blood count) for &gt;6 months; (ii) abnormal cytotoxic T lymphocytes expressing CD2, CD56 and CD57 and lacking CD28; (iii) preferential usage of a TCR Vβ family by flow cytometry; and (iv) TCR gene rearrangement by PCR; (v) bone marrow infiltration with LGL is another diagnostic criterion but a designated marrow biopsy is often not performed in clear LGL which are otherwise asymptomatic. Coexistent presence of MDS and LGL was confirmed in 13/240 (5%) of the patients. These patients displayed typical features of MDS including abnormal cytogenetics (8/13), dysmorphia of myeloid cells in the bone marrow (13/13), ringed sideroblasts (1/13) and the presence of highly clonal somatic myeloid mutations (8/13) with an average VAF of 28+3%. When compared to LGL only, the MDS/LGL series had 15% vs. 39% (P=0.014) STAT3/5b mutations. We detected the presence of mutant myeloid clones in 25% (41/161) of the patients with pure LGL with an average VAF of 35+ 2%. Suspecting that these mutations may be present early in MDS and CHIP, we compared the mutational spectrum of LGL against MDS (n=835) and CHIP. Indeed, an overlap between the typical CHIP mutations was noted with LGL; in addition the clonal burden in CHIP was observed to be lower, 13% vs. 33% in LGL indicating a more advanced myeloid disease in LGL. This could be due to overlapping demographics or through a common pathophysiologic link. Spliceosomal mutations, cohesion complex, PRC2 and RAS mutations were overrepresented in MDS and CHIP in comparison to LGL. Our results indicate that LGL is often associated with myeloid mutations that are also typical in CHIP. Though, age-related changes or other mutagenic stressors, including inflammatory changes could be contributing factors to both LGL and CHIP outgrowth, conversely LGL may evolve as a consequence of a tumor surveillance response to myeloid neoplasms or CHIP. While the coexistence of MDS and LGL has been described in the past, and our analysis corroborates this, we observed that LGL may also coexist with CHIP in some patients. The implication of this would be beneficial to our understanding of, not only, the individual diseases but could also impact care in CHIP survivorship. Disclosures Nazha: MEI: Other: Data monitoring Committee; Novartis: Speakers Bureau; Jazz Pharmacutical: Research Funding; Incyte: Speakers Bureau; Tolero, Karyopharma: Honoraria; Daiichi Sankyo: Consultancy; Abbvie: Consultancy. Saunthararajah:EpiDestiny: Consultancy, Equity Ownership, Patents &amp; Royalties; Novo Nordisk: Consultancy. Sekeres:Celgene: Membership on an entity's Board of Directors or advisory committees; Millenium: Membership on an entity's Board of Directors or advisory committees; Syros: Membership on an entity's Board of Directors or advisory committees. Maciejewski:Novartis: Consultancy; Alexion: Consultancy.