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7500 Background: Increased selectivity of the Bruton tyrosine kinase inhibitor (BTKi) acalabrutinib (Aca) vs ibrutinib (Ib) may improve tolerability. We conducted an open-label, randomized, noninferiority, phase 3 trial to compare Aca vs Ib in patients (pts) with chronic lymphocytic leukemia (CLL). Methods: Previously treated CLL pts with del(17p) or del(11q) by central lab were randomized to receive oral Aca 100 mg BID or Ib 420 mg QD (stratified by del(17p) status, ECOG PS [2 vs ≤1], and number of prior therapies [1–3 vs ≥4]) until progression or unacceptable toxicity. Primary endpoint was progression-free survival (PFS) as assessed by IRC; secondary endpoints of all grade atrial fibrillation (AF), grade ≥3 infection, Richter transformation, and overall survival (OS) were assessed in hierarchical order. Results: 533 pts (Aca, n=268; Ib, n=265) were randomized (median age 66 y; median 2 prior therapies; del(17p) 45.2%; del(11q) 64.2%). At a median follow-up of 40.9 mo (range 0.0–59.1), Aca was noninferior to Ib with a median PFS of 38.4 mo in both arms (HR 1.00; 95% CI 0.79–1.27). Aca was statistically superior to Ib in all-grade AF incidence (9.4% vs 16.0%; P=0.023). Among the other secondary endpoints, incidences of grade ≥3 infection (Aca: 30.8%, Ib: 30.0%) and Richter transformation (Aca: 3.8%, Ib: 4.9%) were comparable between arms. Median OS was not reached in either arm (HR 0.82 [95% CI 0.59–1.15]), with 63 (23.5%) deaths in the Aca arm and 73 (27.5%) in the Ib arm. Among any-grade AEs in ≥20% of pts in either arm, Aca was associated with a lower incidence of hypertension (9.4%, 23.2%), arthralgia (15.8%, 22.8%), and diarrhea (34.6%, 46.0%) but a higher incidence of headache (34.6%, 20.2%) and cough (28.9%, 21.3%). AEs led to treatment discontinuation in 14.7% of Aca- vs 21.3% of Ib-treated pts. Among any-grade events of clinical interest, cardiac, hypertension, and bleeding events were less frequent with Aca (Table). Conclusions: In this first head-to-head trial of BTKis in CLL, Aca demonstrated non-inferior PFS with less cardiotoxicity and fewer discontinuations due to AEs vs Ib. Clinical trial information: NCT02477696. [Table: see text]

Abstract The utility of the chronic lymphocytic leukemia-international prognostic index (CLL-IPI) in predicting outcomes of individuals with Rai 0 stage CLL and monoclonal B-cell lymphocytosis (MBL) is unclear. We identified 969 individuals (415 MBL and 554 Rai 0 CLL; median age, 64 years; 65% men) seen at Mayo Clinic between 1 January 2001 and 1 October 2018, and ascertained time to first therapy (TTFT) and overall survival (OS). After a median follow up of 7 years, the risk of disease progression needing therapy was 2.9%/y for MBL (median, not reached) and 5%/y for Rai 0 CLL (median, 10.4 years). Among patients with low, intermediate, and high/very high-risk CLL-IPI risk groups, the estimated 5-year risk of TTFT was 13.5%, 30%, and 58%, respectively, P< .0001 (c-statistic = 0.69); and the estimated 5-year OS was 96.3%, 91.5%, and 76%, respectively, P< .0001 (c-statistic = 0.65). In a multivariable analysis of absolute B-cell count with individual factors of the CLL-IPI, the absolute B-cell count was associated with shorter TTFT (hazard ratio [HR] for each 10 × 109/L increase: 1.31; P< .0001) and shorter OS (HR: 1.1; P = .02). The OS of the entire cohort was similar to that of the age- and sex-matched general population of Minnesota (P = .17), although Rai 0 CLL patients with high and very high-risk CLL-IPI score had significantly shorter OS (P= .01 and P= .0001, respectively). The results of this study demonstrate the ability of CLL-IPI to predict time from diagnosis to first treatment (an end point not affected by therapy) in a large cohort of patients whose only manifestation of disease is a circulating clonal lymphocyte population.

Abstract Background: There is little prospective, longitudinal data on the health outcomes of low count MBL in the U.S. adult population. We screened for MBL in asymptomatic adults with normal blood counts using highly sensitive flow-cytometry in a clinic-based cohort of participants from the Mayo Clinic Biobank and explored the relationship between MBL and risk of hospitalization with infection. Methods: The Mayo Clinic Biobank is a large scale biorepository of 50,000 adults (age>18) seen in primary care-based clinics. All consented participants completed a health history questionnaire and provided blood samples. For the present study, we focused on the study participants from Olmsted County, Minnesota, 40 years of age or older who had stored PBMC. We used these PBMC to screen for MBL using an 8 color (CD38, CD45, Kappa, Lambda, CD19, CD23, CD5 and CD20) flow cytometry assay validated to consistently detect clonal B-cell events to the 0.005% level (1/20,000 events). The sensitivity of this approach of collecting 500,000 events from isolated PBMC is 2-3-fold higher than collecting 500,000 events from whole blood due to the increased concentration of lymphocytes in these samples. Infections associated with hospitalization were considered serious or life-threatening infections. Every hospitalization at both Mayo Clinic and Olmsted Medical Center hospitals in Olmsted County, MN following the sample collection was reviewed to document hospitalization with infection. Data on hospitalization with infection was abstracted from clinical records using our previously published approach (Moriera, Leukemia 27:136). This approach allows medical record validation and review of detailed clinical and treatment information related to infection. For this analysis, follow-up began at date of sample collection and ended at the earliest of death, migration from Olmsted County, or 12/31/2016. The individual abstracting information on hospitalization for infection was blinded to the results of MBL screening. Chi-square tests were used to assess associations between MBL status and demographic characteristics. Cox regression models were used to determine association with risk of hospitalization with infection accounting for the competing risk of death using Fine Gray models. Results : We screened for MBL in 1045 Olmsted County residents age 40 and older. Of these, 984 (94%) had interpretable results. 119 of these 984 (12%) had a clonal B-cell population detected including 106 (11%) with CLL phenotype (CD5, CD19, CD20 [dim], CD23, kappa or lambda light chain restriction [dim]).This analysis focused on the 106 individuals with CLL-like MBL clones (mean age 69 years, 55% male) and the 865 individuals with normal immunophenotype (mean age 61 years, 40% male). The presence of CLL phenotype MBL was strongly associated with age. MBL was detected in 3% of patients age 40-49 years, 7% of those 50-59, 10% of those 60-69, 20% of those 70-79, and 27% of those age 80+ (p<0.001). MBL was also more common among men (women 8%; men 14%; p=0.003). After a median follow-up of 7 years from biobank enrollment, 76 of the 971 participants were hospitalized with infection in Olmsted County at least once. The estimated cumulative incidence of infections at 7 years was 19% for LC MBL and 9% for those without MBL (Figure). The most frequent site of infections for which these individuals were first hospitalized were pneumonia (14 individuals; 18%), cellulitis (20 individuals; 26%), urinary tract infection (21 individuals; 26%), and blood stream infection (6 individuals; 8%). An association between LC MBL and hospitalization with infection was observed with the unadjusted HR for hospitalization with infection among the 106 Olmsted County residents with LC MBL relative to the 865 Olmsted County residents with normal immunophenotype is 2.41 (95%CI: 1.39-4.19; p=0.002). After adjusting for age and sex, the HR is 1.65 (95% CI: 0.95-2.88; p=0.08). Conclusions: We report one of the first studies to systematically explore the relationship between LC MBL and the risk of serious infection. It appears that individuals with LC MBL may be at increased risk for serious infection. If this observation is confirmed, it would suggest that 5-10% of adults over age 40 (6-12 million U.S. adults) have a largely unstudied condition with potentially serious health implications. Figure 1 Figure 1. Disclosures Shanafelt: Hospira: Research Funding; AbbVie: Research Funding; Celgene: Research Funding; Pharmacyclics: Research Funding; Jannsen: Research Funding; GlaxoSmithKline: Research Funding; Genentech: Research Funding. Kay: Gilead: Research Funding; Agios: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Research Funding; Tolero Corporation: Research Funding. Parikh: Pharmacyclics: Research Funding; AstraZeneca: Honoraria; Pharmacyclics: Honoraria.

Abstract Background The two major types of cold autoimmune hemolytic anemias are cold agglutinin disease (CAD) and paroxysmal cold hemoglobinuria (PCH). In CAD, the cold agglutinin is usually IgM with anti-I specificity. In PCH, the Donath-Landsteiner (DL) antibody is a cold reacting IgG with anti-P specificity. In this study, we describe the clinical and serological characteristics of patients with autoimmune hemolytic anemia positive for both cold agglutinin and DL antibodies. Methods On review of our immunohematology reference laboratory database, we identified patients over a 16-year period (January 2000- March 2016) with the following: i) age ≥18 years, ii) hemoglobin (Hb) <12g/dL, iii) positive direct antiglobulin test (DAT) with hemolysis (increased lactate dehydrogenase/low serum haptoglobin/ elevated indirect bilirubin), and iv) tested for both CAD and DL antibodies. We classified the patients into 3 cohorts. Cohort 1 included patients positive for both cold agglutinin (titer ≥1:64) and DL antibodies. Cohort 2 consisted of patients with DL antibody but no cold agglutinin (titer <1:64), while Cohort 3 was comprised of patients with cold agglutinin but no DL antibody. We evaluated the clinical response based on the GIMEMA (Gruppo Italiano Malattie EMatologiche dell'Adulto) criteria (Barcellini W, et al . Blood 2014) defined as i) complete (CR): hemoglobin ≥12 g/dL with normalization of at least one previously abnormal hemolytic marker; ii) partial (PR): hemoglobin 10-12 g/dL with hemolysis; or iii) none (NR): if any of the above criteria were not met. Results Seven patients had cold autoimmune hemolytic anemia with concomitant cold agglutinin and DL antibodies (Cohort 1). The clinical and serological characteristics are described in table 1. The median age at diagnosis was 68 years (range: 59-78) and the median hemoglobin at onset was 10.3 g/dL (range: 8.2-10.6). Six had red cell agglutination in the blood smear. Two patients had a recent history of infection (1 with Mycoplasma pneumoniae and 1 with upper respiratory tract infection). The median follow-up was 4.8 months (range: 1.0-166.4). Five patients received steroid/other immunosuppressants and two were managed conservatively. The clinical response to treatment was CR in 28.6% patients, PR in 42.9%, and NR in 14.3%. In comparison, Cohort 2 had a 20% CR, 20% PR and 40% NR, while Cohort 3 had a 50% CR, 25% PR and 25% NR, respectively. Conclusion Our study is the first series describing patients with cold autoimmune hemolytic anemia with concomitant cold agglutinin and DL antibodies. In terms of clinical response, patients with negative DL antibodies and cold agglutinin titers >1:64 had better response (50% CR, Cohort 3) to immunosuppressants compared to patients with positive DL antibody (20-30% CR, Cohorts 1 and 2). Large scale studies may be warranted to determine the treatment strategies among patients with concomitant DL and high cold agglutinin titers. Disclosures Kay: Agios: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Research Funding; Tolero Corporation: Research Funding; Gilead: Research Funding. Winters: Fresenius Kabi USA: Consultancy; Eliaz Therapeutics Inc: Membership on an entity's Board of Directors or advisory committees; Sanofi Inc: Other: Moderated opinion leader's forum; Wiley Blackwell: Employment; Regional Health Inc: Consultancy; Mayo Clinic: Employment; Grifols International SA: Consultancy.

AbstractNon‐steroidal anti‐inflammatory drugs (NSAIDs) and statin drugs may protect against the development of non‐Hodgkin lymphoma (NHL), but data are limited, particularly for NHL subtypes. Furthermore, some in vitro, animal and epidemiologic data suggest there may be a synergistic effect of these two agents, but there has been no test of this hypothesis in NHL. We evaluated the self‐reported use of NSAIDs and statins in a clinic‐based study of 1703 NHL patients and 2199 frequency‐matched controls. Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for potential confounding variables. We observed an inverse association of regular use of low‐dose aspirin with risk of NHL (OR = 0.82; 95% CI 0.70‐0.96) that was stronger with longer duration of use (P < .01). There were no associations for use of regular or extra‐strength aspirin, ibuprofen, other NSAIDs, statins or other cholesterol‐lowering drugs with NHL risk, while an inverse association with COX‐2 inhibitors was equivocal. There was also no interaction of low‐dose aspirin and statins on NHL risk. Inverse associations of similar magnitude to all NHL were observed for regular use of low‐dose aspirin with diffuse large B‐cell, follicular, marginal zone and all other lymphomas, although not all associations were statistically significant. In conclusion, low‐dose aspirin but not regular/extra strength aspirin, other NSAIDs or statin use was associated with lower risk of NHL. Beyond the potential for the primary prevention of NHL, these data also point to a role of anti‐platelet or other effects of low‐dose aspirin in lymphomagenesis that warrant follow‐up.

Introduction: Richter transformation (RT) refers to transformation of chronic lymphocytic leukemia (CLL) to diffuse large B-cell lymphoma (DLBCL) or other aggressive lymphomas. The incidence, clinical characteristics, and outcomes of RT with CNS involvement remain undefined. Methods: Biopsy-confirmed RT diagnosed from 4/1993 to 4/2018 was identified from the Mayo Clinic CLL database. RT cases with CNS involvement were further reviewed, with clinical characteristics, treatment and follow-up data abstracted. Overall survival (OS) was defined as time from CNS involvement to death from any cause and analyzed using the Kaplan-Meier method. Results: Among 204 CLL patients with biopsy-proven RT, 15 patients had documented CNS involvement by imaging (parenchymal n=11, ocular n=1, parenchymal and ocular n=1, leptomeningeal n=1, cranial and spinal nerve roots n=1). Biopsy confirmation of CNS involvement was available in 11 patients. Of these 15 patients, 10 had CNS involvement at initial RT diagnosis, and 5 patients developed CNS involvement at RT progression, with a median time from RT diagnosis to CNS involvement of 14.9 months (range 2.8-41.1). Prior to RT, 11 patients (73.3%) received no treatment for CLL, 3 (53.4%) received chemoimmunotherapy (CIT) only (1-3 lines), and 1 patient (6.7%) received CIT (1 line) and ibrutinib. CLL FISH results were available in 9 patients, with del(17p) in 2, trisomy 12 in 2, del(13q) in 3, and normal results in 2. One patient had TP53 mutation (FISH result unavailable). IgHV mutation status was known in 3 patients and 1 was unmutated. The median time to RT was 4.4 years (range 0-11.4). The median age at RT diagnosis was 70 years (range 59-78), and 9 (60%) were male. The histology of RT was DLBCL in all 15 patients (diagnosed by CNS biopsy in 8 and other biopsies in 7), with GCB subtype in 6 and non-GCB subtype in 3. MYC rearrangement was detected in 4 of 6 patients tested, and 2 of those also had BCL-2 rearrangement (MYC/BCL-2 double hit). Of the 10 patients with CNS involvement at initial RT diagnosis, 4 had isolated CNS involvement (confirmed by brain biopsy [n=2] or vitreous biopsy [n=2]). All 4 patients were treated with high dose (HD) methotrexate (MTX) based regimen, and 3 patients achieved complete remission (CR) and underwent autologous stem cell transplant with continued CR, while 1 patient achieved partial remission and received whole brain radiotherapy (WBRT) at disease progression. Six patients had both systemic and CNS involvement (confirmed by brain biopsy [n=2] or CSF examination [n=2] in 4; the other 2 were diagnosed by imaging). All 6 patients received CNS directed therapy (HD MTX [n=5] or WBRT [n=1]) as well as systemic therapy (R-CHOP [n=5] or HyperCVAD [n=1]), with varied short duration of disease control (Figure 1A). Of the 5 patients who developed CNS involvement at RT progression (after 1-2 lines of therapy including first-line R-CHOP), 2 had isolated CNS involvement (1 was confirmed by CSF examination and the other was by imaging only). Both were treated with HD MTX based regimen, and 1 achieved a durable remission of 2 years but eventually had CNS relapse, while the other had no response and received WBRT with limited benefit. Three patients had both systemic and CNS involvement (2 were confirmed by CSF examination and the other was by imaging only), and all 3 patients were treated with HD MTX based regimen but all had CNS disease progression within 3 months (Figure 1A). The OS after CNS involvement for all 15 RT patients was 9.4 months (95% CI 2.3-19.1). Patients with CNS involvement at initial RT diagnosis had numerically longer OS compared to patients who developed CNS involvement at RT progression (median OS 13.0 vs 4.1 months, P = 0.137; Figure 1B). Patients with isolated CNS involvement had better OS compared to patients with both CNS and systemic involvement (median OS 32.0 vs 5.3 months, P = 0.009; Figure 1C). Three of the 4 patients who only had isolated CNS involvement at the time of RT diagnosis have ongoing long term remission and survival (Figure 1A). Conclusions: In this large series of RT, approximately 1 in 14 patients had CNS involvement. Patients with isolated CNS involvement appeared to have favorable long term outcome; however, RT patients with both systemic and CNS involvement had extremely poor survival. The incidence, molecular characteristics, and optimal management of RT with CNS involvement in the novel agent era warrant future multicenter studies. Disclosures Wang: Incyte: Research Funding; Innocare: Research Funding; Novartis: Research Funding. Parikh:GlaxoSmithKline: Honoraria; Pharmacyclics: Honoraria, Research Funding; AstraZeneca: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; MorphoSys: Research Funding; TG Therapeutics: Research Funding; Merck: Research Funding; AbbVie: Honoraria, Research Funding; Ascentage Pharma: Research Funding; Genentech: Honoraria; Verastem Oncology: Honoraria. Kay:Tolero Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol Meyer Squib: Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta Pharma: Research Funding; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Research Funding; MEI Pharma: Research Funding; Sunesis: Research Funding; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees; Agios Pharma: Membership on an entity's Board of Directors or advisory committees; Cytomx: Membership on an entity's Board of Directors or advisory committees; Morpho-sys: Membership on an entity's Board of Directors or advisory committees; Rigel: Membership on an entity's Board of Directors or advisory committees; Oncotracker: Membership on an entity's Board of Directors or advisory committees; Dava Oncology: Membership on an entity's Board of Directors or advisory committees; Juno Theraputics: Membership on an entity's Board of Directors or advisory committees. Witzig:AbbVie: Consultancy; MorphSys: Consultancy; Immune Design: Research Funding; Karyopharm Therapeutics: Research Funding; Incyte: Consultancy; Spectrum: Consultancy; Celgene: Consultancy, Research Funding; Acerta: Research Funding. Nowakowski:MorphoSys: Consultancy, Research Funding; Roche: Consultancy, Research Funding; Celgene/BMS: Consultancy, Research Funding; Kite: Consultancy; Denovo: Consultancy; Kymera: Consultancy; Ryvu: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other; Curis: Consultancy; Seattle Genetics: Consultancy; Nanostrings: Research Funding. Ansell:Trillium: Research Funding; AI Therapeutics: Research Funding; Affimed: Research Funding; Regeneron: Research Funding; Takeda: Research Funding; ADC Therapeutics: Research Funding; Seattle Genetics: Research Funding; Bristol Myers Squibb: Research Funding. Kenderian:MorphoSys: Research Funding; Sunesis: Research Funding; Tolero: Research Funding; BMS: Research Funding; Juno: Research Funding; Gilead: Research Funding; Kite: Research Funding; Novartis: Patents & Royalties, Research Funding; Torque: Consultancy; Humanigen: Consultancy, Patents & Royalties, Research Funding; Lentigen: Research Funding; Mettaforge: Patents & Royalties. Ding:DTRM: Research Funding; Merck: Membership on an entity's Board of Directors or advisory committees, Research Funding; Beigene: Membership on an entity's Board of Directors or advisory committees; alexion: Membership on an entity's Board of Directors or advisory committees; MEI Pharma: Membership on an entity's Board of Directors or advisory committees; Octapharma: Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Research Funding; Abbvie: Research Funding.

Introduction: Richter's syndrome (RS) represents transformation of chronic lymphocytic leukemia (CLL) into a highly aggressive lymphoma with dismal prognosis. Transcriptomic alterations have been described in CLL but most studies focused on peripheral blood samples with minimal data on RS-involved tissue. Moreover, transcriptomic features of RS have not been well defined in the era of CLL novel therapies. In this study we investigated transcriptomic profiles of CLL/RS-involved nodal tissue using samples from a clinical trial cohort of refractory CLL and RS patients treated with Pembrolizumab (NCT02332980). Methods: Nodal samples from 9 RS and 4 CLL patients in MC1485 trial cohort were reviewed and classified as previously published (Ding et al, Blood 2017). All samples were collected prior to Pembrolizumab treatment. Targeted gene expression profiling of 789 immune-related genes were performed on FFPE nodal samples using Nanostring nCounter® Analysis System (NanoString Technologies, Seattle, WA). Differential expression analysis was performed using NanoStringDiff. Genes with 2 fold-change in expression with a false-discovery rate less than 5% were considered differentially expressed. Results: The details for the therapy history of this cohort were illustrated in Figure 1a. All patients exposed to prior ibrutinib before the tissue biopsy had developed clinical progression while receiving ibrutinib. Unsupervised hierarchical clustering using the 300 most variable genes in expression revealed two clusters: C1 and C2 (Figure 1b). C1 included 4 RS and 3 CLL treated with prior chemotherapy without prior ibrutinib, and 1 RS treated with prior ibrutinib. C2 included 1 CLL and 3 RS received prior ibrutinib, and 1 RS treated with chemotherapy. The segregation of gene expression profiles in samples was largely driven by recent exposure to ibrutinib. In C1 cluster (majority had no prior ibrutinb), RS and CLL samples were clearly separated into two subgroups (Figure 1b). In C2 cluster, CLL 8 treated with ibrutinib showed more similarity in gene expression to RS, than to other CLL samples treated with chemotherapy. In comparison of C2 to C1, we identified 71 differentially expressed genes, of which 34 genes were downregulated and 37 were upregulated in C2. Among the upregulated genes in C2 (majority had prior ibrutinib) are known immune modulating genes including LILRA6, FCGR3A, IL-10, CD163, CD14, IL-2RB (figure 1c). Downregulated genes in C2 are involved in B cell activation including CD40LG, CD22, CD79A, MS4A1 (CD20), and LTB, reflecting the expected biological effect of ibrutinib in reducing B cell activation. Among the 9 RS samples, we compared gene profiles between the two groups of RS with or without prior ibrutinib therapy. 38 downregulated genes and 10 upregulated genes were found in the 4 RS treated with ibrutinib in comparison with 5 RS treated with chemotherapy. The top upregulated genes in the ibrutinib-exposed group included PTHLH, S100A8, IGSF3, TERT, and PRKCB, while the downregulated genes in these samples included MS4A1, LTB and CD38 (figure 1d). In order to delineate the differences of RS vs CLL, we compared gene expression profiles between 5 RS samples and 3 CLL samples that were treated with only chemotherapy. RS samples showed significant upregulation of 129 genes and downregulation of 7 genes. Among the most significantly upregulated genes are multiple genes involved in monocyte and myeloid lineage regulation including TNFSF13, S100A9, FCN1, LGALS2, CD14, FCGR2A, SERPINA1, and LILRB3. Conclusion: Our study indicates that ibrutinib-resistant, RS-involved tissues are characterized by downregulation of genes in B cell activation, but with PRKCB and TERT upregulation. Furthermore, RS-involved nodal tissues display the increased expression of genes involved in myeloid/monocytic regulation in comparison with CLL-involved nodal tissues. These findings implicate that differential therapies for RS and CLL patients need to be adopted based on their prior therapy and gene expression signatures. Studies using large sample size will be needed to verify this hypothesis. Figure Disclosures Zhao: Merck: Current Employment. Blumenschein:Merck: Current Employment. Yearley:Merck: Current Employment. Wang:Novartis: Research Funding; Incyte: Research Funding; Innocare: Research Funding. Parikh:Verastem Oncology: Honoraria; GlaxoSmithKline: Honoraria; Pharmacyclics: Honoraria, Research Funding; MorphoSys: Research Funding; Ascentage Pharma: Research Funding; Genentech: Honoraria; AbbVie: Honoraria, Research Funding; Merck: Research Funding; TG Therapeutics: Research Funding; AstraZeneca: Honoraria, Research Funding; Janssen: Honoraria, Research Funding. Kenderian:Sunesis: Research Funding; MorphoSys: Research Funding; Humanigen: Consultancy, Patents & Royalties, Research Funding; Gilead: Research Funding; BMS: Research Funding; Tolero: Research Funding; Lentigen: Research Funding; Juno: Research Funding; Mettaforge: Patents & Royalties; Torque: Consultancy; Kite: Research Funding; Novartis: Patents & Royalties, Research Funding. Kay:Astra Zeneca: Membership on an entity's Board of Directors or advisory committees; Acerta Pharma: Research Funding; Juno Theraputics: Membership on an entity's Board of Directors or advisory committees; Dava Oncology: Membership on an entity's Board of Directors or advisory committees; Oncotracker: Membership on an entity's Board of Directors or advisory committees; Sunesis: Research Funding; MEI Pharma: Research Funding; Agios Pharma: Membership on an entity's Board of Directors or advisory committees; Bristol Meyer Squib: Membership on an entity's Board of Directors or advisory committees, Research Funding; Tolero Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Research Funding; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Rigel: Membership on an entity's Board of Directors or advisory committees; Morpho-sys: Membership on an entity's Board of Directors or advisory committees; Cytomx: Membership on an entity's Board of Directors or advisory committees. Braggio:DASA: Consultancy; Bayer: Other: Stock Owner; Acerta Pharma: Research Funding. Ding:DTRM: Research Funding; Astra Zeneca: Research Funding; Abbvie: Research Funding; Merck: Membership on an entity's Board of Directors or advisory committees, Research Funding; Octapharma: Membership on an entity's Board of Directors or advisory committees; MEI Pharma: Membership on an entity's Board of Directors or advisory committees; alexion: Membership on an entity's Board of Directors or advisory committees; Beigene: Membership on an entity's Board of Directors or advisory committees.

Background MBL is a precursor to chronic lymphocytic leukemia (CLL) and is subclassified into low-count (LC) MBL (absolute B-cell count&lt;0.5x109/L) and high-count (HC) MBL (absolute B-cell count between 0.5 and 5x109/L). We previously reported that a polygenic risk score (PRS) based on a weighted average of 41 CLL-susceptibility variants was associated with risk of both MBL and CLL among a cohort of individuals from CLL families. Here we evaluate this PRS in an independent cohort of MBL and CLL individuals of European ancestry (EA), all of whom were ascertained agnostic to CLL family-history status. We also evaluate the PRS by MBL subtype (LC/HC), and in African American (AA) CLL cases and controls. Methods We genotyped 535 EA MBLs (139 HC-MBL, 396 LC-MBLs), 735 CLLs (640 EA, 95 AA), and 2,866 controls (2,631 EA, 235 AA) from the Mayo Clinic CLL Resource, Duke University, and Weill Cornell Medical College. We computed the CLL-PRS for each individual and used logistic regression to estimate odds ratios (OR) and 95% confidence intervals, adjusting for age and sex. To assess discriminatory accuracy, we computed the c-statistic. Among EA individuals, we calculated a trend test among LC-MBL, HC-MBL, and CLL risk using the P-value for heterogeneity from a polytomous logistic regression analysis. Moreover, we plotted a boxplot for the PRS among controls, LC-MBL, HC-MBL, and EA CLL, as well as for AA CLL cases and controls, and tested the statistical difference using the Kruskal Wallis test and Mann-Whitney test, respectively. Results We found a significant association of PRS with overall MBL risk (OR=1.87, P=1.1x10-28) with good discrimination (c-statistic=0.72). Significant associations were also found for LC-MBL (OR=1.75, P=7.5x10-19, c-statistic=0.72), HC-MBL (OR=2.22, P=1.4x10-17, c-statistic=0.74), and CLL of EA (OR=2.60, P=1.2x10-62, c-statistic=0.78), with a significant difference among these cohorts (Figure 1.A) and a significant positive trend across these cohorts (Pheterogeneity=8.4x10-6). Although we observed a 33% increased risk of CLL in AA (c-statistic=0.57), the PRS was borderline significant (P=0.07, Figure 1.B). Conclusion The CLL-PRS is a strong prediction-tool for risk of CLL and MBL among individuals of EA. Future studies are needed to improve the PRS for AAs including performing GWAS of AA in order to identify CLL-susceptibility SNPs that are more representative within known CLL loci and to discover novel CLL loci that are unique for AAs. Disclosures Parikh: GlaxoSmithKline: Honoraria; Janssen: Honoraria, Research Funding; Ascentage Pharma: Research Funding; AbbVie: Honoraria, Research Funding; Merck: Research Funding; TG Therapeutics: Research Funding; Genentech: Honoraria; Pharmacyclics: Honoraria, Research Funding; MorphoSys: Research Funding; AstraZeneca: Honoraria, Research Funding; Verastem Oncology: Honoraria. Braggio:DASA: Consultancy; Bayer: Other: Stock Owner; Acerta Pharma: Research Funding. Brander:Genentech: Consultancy, Honoraria, Other, Research Funding; Juno/Celgene/BMS: Other, Research Funding; MEI Pharma: Other, Research Funding; Ascentage: Other, Research Funding; ArQule: Consultancy, Other, Research Funding; NCCN: Other; Teva: Consultancy, Honoraria; Tolero: Research Funding; AstraZeneca: Consultancy, Honoraria, Other, Research Funding; Pharmacyclics LLC, an AbbVie Company: Consultancy, Honoraria, Other, Research Funding; Pfizer: Consultancy, Other; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; Novartis: Consultancy, Other; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; Tolero: Research Funding; Teva: Consultancy, Honoraria; DTRM: Other, Research Funding; BeiGene: Other, Research Funding; Novartis: Consultancy, Other; NCCN: Other; Verastem: Consultancy, Honoraria, Other, Research Funding. Cerhan:NanoString: Research Funding; BMS/Celgene: Research Funding. Kay:Astra Zeneca: Membership on an entity's Board of Directors or advisory committees; Agios Pharma: Membership on an entity's Board of Directors or advisory committees; Sunesis: Research Funding; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta Pharma: Research Funding; Juno Theraputics: Membership on an entity's Board of Directors or advisory committees; Morpho-sys: Membership on an entity's Board of Directors or advisory committees; Rigel: Membership on an entity's Board of Directors or advisory committees; Cytomx: Membership on an entity's Board of Directors or advisory committees; Tolero Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol Meyer Squib: Membership on an entity's Board of Directors or advisory committees, Research Funding; MEI Pharma: Research Funding; Abbvie: Research Funding; Oncotracker: Membership on an entity's Board of Directors or advisory committees; Dava Oncology: Membership on an entity's Board of Directors or advisory committees. Furman:Acerta: Consultancy; AstraZeneca: Consultancy, Research Funding; Beigene: Consultancy; Abbvie: Consultancy; Pharmacyclics: Consultancy; Sunesis: Consultancy; TG Therapeutics: Consultancy, Research Funding; Verastem: Consultancy; Incyte: Consultancy; Genentech: Consultancy; Janssen: Consultancy, Speakers Bureau; Loxo Oncology: Consultancy; Oncotarget: Consultancy. Shanafelt:Mayo Clinic: Patents & Royalties: and other intellectual property; Genentech, Pharmacyclics LLC, an AbbVie Company, AbbVie, GlaxoSmithKline, and Merck: Research Funding.