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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.

Chimeric antigen receptor T (CART) cells are engineered with an artificial receptor which redirects T cells to recognize cancer cells expressing a particular surface antigen. CART cell therapy has been astonishingly successful at eradicating certain B cell malignancies, but relapse is common, and efficacy is lacking in many cancers. Gene editing of CART cells is being investigated to enhance efficacy and safety and to develop off-the-shelf products. Currently, genome engineering tools used to modify CART cells include zinc finger nucleases, transposons, TALENs, and CRISPR-Cas9. CRISPR-Cas9 uses a trans-activating (tracrRNA): CRISPR RNA (crRNA) duplex to trigger imprecise DNA repair through targeted double stranded breaks, causing indels and often resulting in loss of protein function. Gene-edited CART cells have entered the clinic to provide an allogeneic cell source (TALEN TCRα knockout), safer treatment (CRISPR-Cas9 GM-CSF knockout), and resistance to exhaustion (CRISPR-Cas9 PD-1 knockout). CRISPR-Cas9 PD-1 knockout (PD-1k/o) CART cells were well-tolerated in a first-in-human clinical trial. However, clinically tested CRISPR-Cas9-edited CART cells showed only modest loss of function (~25%) of PD-1 upon infusion. Additionally, off-target editing has been observed in the clinic and remains a concern. We hypothesized that using next-generation CRISPR-Cas12a systems will result in enhanced editing efficiency and precision. CRISPR-Cas12a has a smaller protein component than CRISPR-Cas9, uses a single crRNA without a tracrRNA for simplified delivery and leaves staggered 5' overhangs. These properties, along with lower intrinsic off-target activity than Cas9, render Cas12a a powerful gene editing tool. First, we compared the knockout efficiency of Cas9 and Cas12a in three therapeutically relevant genetic targets in T cells by delivering ribonucleoprotein complexes containing the crRNA and Cas protein of interest. We showed that Cas12a more effectively knocked out CD3, GM-CSF, and PD-1 expression compared to Cas9 (Figure 1A), demonstrating the potential of Cas12a in further genetically editing T cell therapies. We then used electroporation with Cas9 and Cas12a to generate PD-1k/o in lentivirally transduced CD19-targeted CART (CART19) cells with the aim of making exhaustion-resistant CART19 cells through CRISPR gene editing. CART19 and PD-1k/o CART19 cells were repeatedly stimulated with CD19+ NALM6 target cells for one week, and exhaustion marker expression was measured over time with flow cytometry. The expression of CTLA4, TIM3, and LAG3 were similar between CART19 groups, but PD-1 expression was lower in Cas9 PD-1k/o CART19 cells and almost completely eradicated in Cas12a PD-1k/o CART19 cells compared to wildtype or mock shocked CART19 cells (Figure 1B). We then compared the functionality of wildtype, mock shocked, and Cas9 or Cas12a PD-1k/o CART19 cells in vitro to ensure that neither the electroporation process nor PD-1 knockout impaired CART19 cell antitumor activity. Over a range of effector-to-target ratios and with repeated stimulation with target cells, cytotoxicity was comparable across all CART19 cell groups (Figure 1C). All CART19 cell groups demonstrated robust proliferation in response to both nonspecific and antigen-specific stimulation and over one week of repeated antigen stimulation with NALM6 target cells (Figure 1D). We also confirmed that all CART19 cell groups demonstrated strong degranulation and cytokine production in response to nonspecific and antigen-specific stimulation, regardless of electroporation or PD-1 knockout (Figure 1E). In summary, our data demonstrate that Cas12a can be used as a gene editing tool to efficiently knock out therapeutically relevant genes in CART19 cell therapy. Additionally, Cas12a demonstrated improved knockout efficiency over Cas9 in three different genomic targets. PD-1 knockout via Cas9 or Cas12a reduced PD-1 expression on the CART19 cell surface, and PD-1 expression was almost completely ablated with Cas12a gene editing. Electroporation and PD-1 knockout did not impact the effector functions of the CART19 cells, including cytotoxicity, degranulation, cytokine secretion, or proliferation. In vivo studies assessing the antitumor efficacy and CART19 cell persistence are ongoing. Overall, Cas12a is a promising, efficient method of gene knockout to enhance the safety and efficacy of CART cells. Disclosures Sakemura: Humanigen: Patents & Royalties. Cox:Humanigen: Patents & Royalties. 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; Mettaforge: Patents & Royalties; Lentigen: Research Funding.

Background: Isatuximab (SAR650984) is an IgG1k monoclonal antibody that binds with high affinity to CD38 expressed on plasma cells in AL amyloidosis. It has been shown to be efficacious and well tolerated in relapsed and refractory multiple myeloma as a single agent and in combination. Here we report on the preliminary results of a prospective multi-center, phase II study of isatuximab in previously treated patients with AL amyloidosis (NCT03499808). Methods: Eligibility included age ≥ 18 years, relapsed or refractory systemic AL amyloidosis, ≥ 1 prior line of therapy, measurable disease (defined as a positive monoclonal serum immunofixation electrophoresis (IFE) or urine IFE, a serum free light chain ratio outside of the normal range (0.25-1.65), and a difference in the involved versus the uninvolved serum free light chain of ≥ 4.5 mg/dL), at least one organ involved, not refractory to daratumumab, ECOG performance status 0-2, creatinine clearance ≥25 mL/min as measured by 24-hour urine collection or as estimated by Cockcroft and Gault formula, and NT-proBNP ≤8500 pg/mL. Patients received isatuximab intravenously 20 mg/kg weekly during the first 28 day cycle and every other week during cycles 2 through 24 for a maximum of 24 cycles. The primary objective was hematologic response with secondary objectives of organ response, safety, progression free survival, and overall survival. Results: At data cut-off (July 24, 2020), 43 patients were registered from March 2018 to September 2019 at 14 institutions. Thirty six patients were eligible with 35 patients receiving at least one dose of isatuximab. Of the eligible patients, the median age was 70 (range 40-81). Prior therapies included proteasome inhibitors in 32 patients (89%), high dose therapy followed by autologous stem cell transplant in 17 patients (47%), immunomodulatory therapy in 9 patients (25%), and anti-CD38 monoclonal antibody therapy in 2 patients (6%). Single organ system involvement was seen in 19 patients (53%), ≥ 2 organ systems in 17 patients (47%), 16 patients (44%) had renal involvement, and 24 (67%) had cardiac involvement. For those with cardiac involvement, 7 patients (29%) had cardiac biomarker stage II and 9 patients (38%) had stage III disease using the Revised Mayo Staging (Kumar S et al., J Clin Oncol, 2012). A total of 17 patients remain on therapy. The median duration on treatment for eligible patients is currently 11.8 months (current range, 0.3-22.1). Of the 19 patients who discontinued treatment, the most common reasons included adverse events in 5 patients (26%), disease progression in 4 patients (21%), sub-optimal response in 2 patients (11%), and concerns related to COVID-19 in 2 patients (11%). The current median follow up is 16.3 months. The most common drug-related AEs were infusion related reactions in 18 patients (50%) with the majority (16/18) being grade I or II, anemia in 9 patients (25%) with the majority (8/9) being grade I, and lymphopenia in 8 patients (22%). Patient characteristics and preliminary safety data were previously presented at the International Symposium on Amyloidosis. The overall hematologic response rate was 77%. Hematological complete response (CR) was observed in 1 of 35 evaluable (completing at least 1 dose) patients (3%), very-good-partial response (VGPR) in 19 patients (54%), and partial response (PR) in 7 patients (20%). Conclusions: Isatuximab demonstrates encouraging efficacy in previously treated patients with AL amyloidosis. The administration of isatuximab in these patients is associated with a good safety profile similar to other monoclonal antibodies against CD38. The data will be updated at the meeting. Disclosures Sanchorawala: Prothena: Research Funding; Caelum: Research Funding; Oncopeptide: Research Funding; Janssen: Research Funding; Regeneron: Other: advisory board; Caleum: Other: advisory board; Proclara: Other: advisory board; Abbvie: Other: advisory board; UpToDate: Patents & Royalties; Takeda: Research Funding; Celgene: Research Funding. Kapoor:Sanofi: Consultancy, Research Funding; Celgene: Honoraria; Cellectar: Consultancy; Janssen: Research Funding; Amgen: Research Funding; GlaxoSmithKline: Research Funding; Takeda: Honoraria, Research Funding. Neparidze:GlaxoSmithKline: Research Funding; Janssen: Research Funding; Sanofi: Membership on an entity's Board of Directors or advisory committees, Other: Advisory board; Eidos Therapeutics: Membership on an entity's Board of Directors or advisory committees, Other: Diagnostic committee member . Sarosiek:Spectrum: Research Funding. Durie:Amgen, Celgene, Johnson & Johnson, and Takeda: Consultancy. Usmani:Incyte: Research Funding; Takeda: Consultancy, Honoraria, Other: Speaking Fees, Research Funding; Sanofi: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Other: Speaking Fees, Research Funding; SkylineDX: Consultancy, Research Funding; Merck: Consultancy, Research Funding; Array Biopharma: Research Funding; Pharmacyclics: Research Funding; Celgene: Other; Seattle Genetics: Consultancy, Research Funding; GSK: Consultancy, Research Funding; BMS, Celgene: Consultancy, Honoraria, Other: Speaking Fees, Research Funding; Amgen: Consultancy, Honoraria, Other: Speaking Fees, Research Funding; Abbvie: Consultancy. Orlowski:Laboratory research funding from BioTheryX, and clinical research funding from CARsgen Therapeutics, Celgene, Exelixis, Janssen Biotech, Sanofi-Aventis, Takeda Pharmaceuticals North America, Inc.: Research Funding; STATinMED Research: Consultancy; Founder of Asylia Therapeutics, Inc., with associated patents and an equity interest, though this technology does not bear on the current submission.: Current equity holder in private company, Patents & Royalties; Sanofi-Aventis, Servier, Takeda Pharmaceuticals North America, Inc.: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen, Inc., AstraZeneca, BMS, Celgene, EcoR1 Capital LLC, Forma Therapeutics, Genzyme, GSK Biologicals, Ionis Pharmaceuticals, Inc., Janssen Biotech, Juno Therapeutics, Kite Pharma, Legend Biotech USA, Molecular Partners, Regeneron Pharmaceuticals, Inc.,: Honoraria, Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: Isatuximab is FDA approved for relapsed refractory myeloma in combination with pomalidomide and dexamethasone. Isatuximab is not FDA approved for AL amyloidosis.

333 Background: Hepatitis B is a cause of hepatocellular carcinoma (HCC) globally, irrespective of viral loads. Interestingly, this process is not necessarily mediated through cirrhosis and may in fact involve oncogenic processes. Prior studies have suggested specific oncogenic gene expression pathways affected by viral regulatory proteins. Thus, identifying these genes and associated pathways could highlight predictive factors for HCC transformation, and has implications in early diagnosis and treatment. Methods: We employed our Search, Tag, Analyze, Resource (STARGEO) platform to conduct a meta-analysis of public data from NCBI's Gene Expression Omnibus. We performed meta-analysis consisting of 155 tumor samples compared against 185 adjacent non-tumor samples. We present the results from the meta-analysis in Ingenuity Pathway Analysis. Results:Our analysis revealed LXR/RXR activation, LPS-IL-1 mediation inhibition of RXR, and FXR/RXR activation as top canonical pathways amongst others. Top upstream regulators identified included the Ras family gene RABL6. The role of RABL6 in oncogenesis is beginning to unfold but its specific role in HBV-related HCC remains undefined. Our causal analysis suggests RABL6 mediates pathogenesis of HBV-related HCC through promotion of genes related to cell division, epigenetic regulation, and Akt signaling. Additionally, HOXA10 was a top upstream regulator and was strongly upregulated in our analysis. While described in other cancer, HOXA10 has not been well documented in HBV-related HCC and our causal analysis suggests it mediates pathogenesis through downregulation of tumor suppressors and its protective effect from oxidative stress. Conclusions: This meta-analysis describes possible role of viral regulatory proteins such as RABL6 and HOXA10 in the pathogenesis of HBV -related HCC. Further prospective studies are needed to confirm our findings.

PURPOSE To evaluate the effects of daratumumab, lenalidomide, and dexamethasone (D-Rd) versus lenalidomide and dexamethasone (Rd) on patient-reported outcomes (PROs) in the phase III MAIA study. PATIENTS AND METHODS PROs were assessed on the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30-item and the EuroQol 5-dimensional descriptive system at baseline and every 3 months during treatment. By mixed-effects model, changes from baseline are presented as least squares means with 95% CIs. RESULTS A total of 737 transplant-ineligible (TIE) patients with newly diagnosed multiple myeloma were randomly assigned to D-Rd (n = 368) or Rd (n = 369). Compliance with PRO assessments was high at baseline (> 90%) through month 12 (> 78%) for both groups. European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30-item global health status scores improved from baseline in both groups and were consistently greater with D-Rd at all time points. A global health status benefit was achieved with D-Rd, regardless of age (< 75 and ≥ 75 years), baseline Eastern Cooperative Oncology Group (ECOG) performance status score, or depth of response. D-Rd treatment resulted in significantly greater reduction in pain scores as early as cycle 3 ( P = .0007 v Rd); the magnitude of change was sustained through cycle 12. Reductions in pain with D-Rd were clinically meaningful in patients regardless of age, ECOG status, or depth of response. Similarly, PRO improvements were observed with D-Rd and Rd on the EuroQol 5-dimensional descriptive system visual analog scale score. CONCLUSION D-Rd compared with Rd was associated with faster and sustained clinically meaningful improvements in PROs, including pain, in transplant-ineligible patients with newly diagnosed multiple myeloma regardless of age, baseline ECOG status, or depth of treatment response.

Objective In this study, we aimed to determine the cause of death (COD) after the diagnosis of neuroendocrine tumors (NET). Methods We used the Surveillance, Epidemiology and End Results (SEER) Program to review patients diagnosed with NET during 2000 to 2016. Patients were followed until death, and different CODs were determined. Results Of 94,399 patients with NETs, 40.9% died during the study period. During the first year of diagnosis, most deaths were from NETs (73%), followed by other cancers (11.2%) and cardiac diseases (4.6%). After more than 10 years, NET deaths decreased to 24.3%, whereas other cancers and cardiac disease became more common. Neuroendocrine tumors were responsible for 42.8%, 63.4%, and 81.2% of deaths in grade I, grade II, and grade III, respectively. For grade I localized NET, other cancers (22.2%) were the most common COD followed by NET (19.7%), whereas in grade 2 localized NET, NET was COD in 31.1% of cases followed by other cancers (22.4%). In metastatic disease, NET was the most common COD regardless of grade. Conclusions For low-grade localized NET, deaths were mostly secondary to non-NET causes. In contrast, NET is responsible for most of deaths in metastatic NET regardless of grade.

Abstract Pancreatic neuroendocrine tumors (PNETs) are the second most common neoplasm of the pancreas after ductal adenocarcinoma. The clinical behavior of PNETs is very difficult to predict, especially for well-differentiated PNETs. Several classification systems have been developed to differentiate benign from malignant PNETs. The current 5th edition WHO (2019) updated the grading system of PNETs which is now entirely based on proliferative rate (either mitotic count or Ki-67 index). In this article, we systemically reviewed the evolution of the histologic classification and grading systems for well-differentiated PNETs. Meanwhile, we also report a comprehensive summary of immunohistochemical and molecular prognostic factors for PNETs patients, including CK19, KIT, PD-L1/PD-L1, UCH-L1 and CNPY2. We believe that more reliable grading systems and prognostic markers are emerging and will change the landscape of treatment for well-differentiated PNETs.

Abstract BACKGROUND Chimeric antigen receptor T cell (CART) therapy has revolutionized the treatment landscape for hematological malignancies, its efficacy remains limited in solid tumors. EGFRvIII is a truncated version of the wild type EGFR in which deletion of exons 2–7 of the extracellular domain leads the variant (EGFRvIII) that is strongly antigenic and is mostly expressed on tumor cells. EGFR amplification (tEGFR) almost uniformly precedes the presence of EGFRvIII on tumor cells. The heterogeneity of surface receptor expression and immunosuppressive stromal microenvironment underscore the need to develop CART strategies to target multiple tumor antigens simultaneously. METHODS we generated tEGFR/EGFRvIII directed CAR construct by cloning a clinically relevant tEGFR and EGFRvIII specific scFv into a second generation CAR construct (41BB stimulated) in a third generation lentivirus backbone. This was used to transfect 293T cells and the generated lentivirus particles were used to transduce T cells and generate EGFRvIII/tEGFR CART cells. GBM primary patient derived cell lines were used in these experiments. These cells were passaged and maintained in patient derived xenograft models. RESULTS EGFRvIII/tEGFR directed CART cells exhibited potent antitumor activity against EGFRvIII/tEGFR + GBM cell lines: with 100% killing at 1.25:1, 2.5:1, 5:1 and 10:1 E:T ratio on multiple PDX cell lines with EGFRvIII expression and EGFR over-expression (greater than five copies of EGFR gene) at 24 hours of incubation. Conclusion: We demonstrate that targeting EGFRvIII and over-expressed EGFR with CART cells is feasible, efficacious and represents a promising therapeutic strategy to target GMB. Data from in vivo and combinatorial CART experiments will be reported at the meeting.

Introduction: In 2017, a two-dose recombinant zoster vaccine (RZV) containing glycoprotein E (gE) and a novel adjuvant was approved to prevent herpes zoster and its complications in adults ≥50 years of age in the US. There are limited data on the immunogenicity and safety of RZV in patients with chronic lymphocytic leukemia (CLL). Methods: Between 8/15/2018 and 11/4/2019, RZV-naïve patients with CLL and monoclonal B-cell lymphocytosis (MBL) seen at Mayo Clinic, Rochester, MN were enrolled in this IRB-approved study. All participants received two doses of vaccine, at 0 and 2 months after enrollment. Cell-mediated immunity was measured by dual-color interferon γ (IFN- γ) and interleukin 2 (IL-2) FLUOROSpot in peripheral blood mononuclear cells (PBMC) after depletion of ≥50% leukemic B cells. Results were reported in spot forming cells (SFC)/106 PBMC in wells stimulated with gE overlapping peptides or varicella zoster virus (VZV) inactivated cell lysate. Response rate was defined as the proportion of participants who achieved a ≥2-fold increase in IFN- γ or IL-2 SFC/106 PBMC one month after the second dose of vaccine compared with pre-vaccination baseline levels. We also determined the geometric mean fold rise (GMFR) and geometric mean count (GMC) of SFC /106 PBMC at baseline and 90 days after the first dose of vaccine. Two cohorts were enrolled: Cohort 1 consisted of individuals with previously untreated MBL and CLL; and Cohort 2 consisted of CLL participants who were on Bruton tyrosine kinase inhibitor (BTKi) therapy. We compared the response data to historic age-and sex-matched healthy controls who received RZV. Chi-square or Fisher's exact tests measured differences in response rates and Kruskall-Wallis tested for differences in continuous variables. Among CLL participants, multivariable regression analysis was used to investigate the association between day 90 SFC and prior BTKi treatment, accounting for age at RZV, age at CLL diagnosis, sex, and day 0 SFC. Results: Sixty-one participants were enrolled. Paired samples were available for 41 participants (22 in Cohort 1 and 19 [18 ibrutinib and 1 acalabrutinib] in Cohort 2), and 68 age- and sex-matched healthy controls. Baseline characteristics of MBL/CLL participants are shown in Table 1. Compared to healthy controls, participants with MBL/CLL had a significantly lower IFN-γ VZV-specific response rate (41% vs. 63%, p=0.03) and IFN-γ gE-specific response (56% vs. 96%, p&lt;0.001); although there were no differences in IL-2 response rates to VZV (51% vs 68%, p=0.09) or gE (95% vs. 100%, p=0.14, Table 2). There were differences in GMFR between participants with MBL/CLL and controls that reached statistical significance for IFN-γ and IL-2 gE-specific responses and borderline significance for IFN-γ VZV-specific responses (Table 2). VZV-specific response rates did not significantly differ between individuals with untreated MBL/CLL and those receiving BTKi (52% vs. 28%, p=0.12 for IFN- γ; (62% vs. 39%, p=0.15 for IL-2), nor did IL-2 gE-specific responses (96% vs. 95%, p=1.0). However, untreated MBL/CLL participants had significantly higher IFN- γ gE-specific response rate compared to BTKi-treated individuals (73% vs. 37%, p=0.02, Table 2). IFN- γ and IL-2 VZV- and gE-specific SFC GMC was significantly higher at Day 90 compared to Day 0 in all vaccinees, although the magnitude of response was significantly lower in MBL/CLL participants compared to healthy controls (Table 3). Among participants with MBL/CLL, age at diagnosis, age at receipt of RZV, and sex did not predict response to vaccination after accounting for prevaccination values. No serious adverse events were noted among MBL/CLL participants while on this study. Additional analyses including determination of humoral immunogenicity and long-term follow up to ascertain risk of herpes zoster infection are ongoing at this time. Conclusion: RZV was associated with lower cell mediated immunogenicity in MBL/CLL participants compared to healthy older adults. Among individuals with CLL, BTKi treatment was associated with decreased cell mediated immunogenicity of the vaccine. Given the inferior response rates, an additional dose of RZV may be considered to boost responses and should be studied in this patient population. Disclosures Johnson: GSK: Research Funding. Ding:Abbvie: Research Funding; Astra Zeneca: Research Funding; DTRM: Research Funding; 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; 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. Kenderian:Humanigen: Consultancy, Patents & Royalties, Research Funding; Torque: Consultancy; Novartis: Patents & Royalties, Research Funding; Kite: Research Funding; Gilead: Research Funding; Juno: Research Funding; BMS: Research Funding; Tolero: Research Funding; Mettaforge: Patents & Royalties; Lentigen: Research Funding; MorphoSys: Research Funding; Sunesis: Research Funding. Wang:Novartis: Research Funding; Incyte: Research Funding; Innocare: Research Funding. Kay:Juno Theraputics: 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; 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; Agios Pharma: Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees; Sunesis: Research Funding; Abbvie: Research Funding; MEI Pharma: Research Funding; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta Pharma: Research Funding; 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. Levin:GSK: Research Funding. Kennedy:ICW Ventures: Research Funding. Weinberg:GSK: Research Funding. Parikh:GlaxoSmithKline: Honoraria; AstraZeneca: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; TG Therapeutics: Research Funding; Merck: Research Funding; AbbVie: Honoraria, Research Funding; MorphoSys: Research Funding; Verastem Oncology: Honoraria; Pharmacyclics: Honoraria, Research Funding; Genentech: Honoraria; Ascentage Pharma: Research Funding.

Background: Clinical factors including previous history of AF, heart failure, hypertension, valvular heart disease, increased age and male gender increase the risk of AF in CLL patients (Shanafelt, Leukemia and Lymphoma 2017). Treatment with Bruton tyrosine kinase inhibitors (BTKi) such as ibrutinib has also been associated with an increased risk of AF in CLL. We evaluated the role of artificial intelligence electrocardiography (AI-ECG) in predicting ibrutinib-induced AF (and, for reference, AF unrelated to ibrutinib) in patients with CLL. Methods: We identified two cohorts of CLL patients using the Mayo Clinic CLL Database. Cohort 1 included patients evaluated within 12 months of CLL diagnosis who did not ever receive ibrutinib. Cohort 2 included patients who were treated with ibrutinib. The electrocardiographic signature of AF in sinus rhythm was detected by an AI-ECG algorithm previously developed using a convolutional neural network (Attia, Lancet 2019). The baseline AI-ECG AF score (positive defined as &gt;0.10 on a scale of 0-1 which offers best balance between sensitivity and specificity per Attia et al.) was computed based on ECGs obtained within 10 years prior to CLL diagnosis (Cohort 1) or 10 years prior to initiation of ibrutinib therapy (Cohort 2). Patients with AF at baseline, missing data, or with ECGs previously used to train the AI algorithm were excluded. Reverse Kaplan Meier diagrams were plotted for both cohorts grouped by AI-ECG positivity. Cox proportional hazards were fitted to assess the predictive ability of AI-ECG in both cohorts. Results: After screening 2,739 patients and applying exclusion criteria (126 patients had baseline AF) a total of 1,149 patients with median 4 (interquartile range [IQR] 2-9) baseline ECGs were included in the analysis (Figure 1A). Cohort 1 included 951 patients with a median follow up of 3.0 (IQR 0.6-7.0) years and positive baseline AI-ECG in 546 (57%) patients. Cohort 2 included 198 patients with a median follow up of 1.6 (IQR 0.7-3.2) years and positive baseline AI-ECG in 91 (46%) patients. In Cohort 1, the median age was 67 years (IQR 58-72), 681 (72%) of patients were men, 68% had low/intermediate risk CLL-International Prognostic Index (IPI), and 32% had high/very high-risk CLL-IPI. In Cohort 2, the median age was 69 years (IQR 62-75), 139 (70%) of patients were men, 13% had low/intermediate risk CLL-IPI, and 87% had high/very high-risk CLL-IPI. AF occurred during follow up in 164 patients (17%) in Cohort 1 and 46 patients (23%) in Cohort 2. In both Cohorts 1 and 2, a positive baseline AI-ECG significantly increased the incidence of AF during follow up (log rank &lt;0.001) (Figure 1B and C). Hazard ratios (for positive vs. negative AI-ECG) were 33.9 (95% confidence interval [CI] 15.0-76.6) for Cohort 1 and 14.8 (95% CI 5.3-41.3) for Cohort 2. Conclusion: The addition of AI to a standard 12-lead ECG obtained during normal sinus rhythm - an inexpensive and ubiquitous test - predicts the occurrence of future AF in patients with CLL. This holds true irrespective of BTKi -based therapy and has important implications for the management of CLL patients. Disclosures Ding: Merck: Membership on an entity's Board of Directors or advisory committees, Research Funding; DTRM: Research Funding; Astra Zeneca: Research Funding; Abbvie: 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. Kenderian:BMS: Research Funding; Gilead: Research Funding; Novartis: Patents & Royalties, Research Funding; Mettaforge: Patents & Royalties; Juno: Research Funding; MorphoSys: Research Funding; Lentigen: Research Funding; Sunesis: Research Funding; Tolero: Research Funding; Kite: Research Funding; Humanigen: Consultancy, Patents & Royalties, Research Funding; Torque: Consultancy. Wang:Novartis: Research Funding; Innocare: Research Funding; Incyte: Research Funding. Kay:Juno Theraputics: 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; 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; Agios Pharma: Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees; Sunesis: Research Funding; Abbvie: Research Funding; MEI Pharma: Research Funding; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta Pharma: Research Funding; 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. Kapoor:Cellectar: Consultancy; Janssen: Research Funding; Sanofi: Consultancy, Research Funding; Amgen: Research Funding; Takeda: Honoraria, Research Funding; Celgene: Honoraria; GlaxoSmithKline: Research Funding. Parikh:MorphoSys: Research Funding; Janssen: Honoraria, Research Funding; AstraZeneca: Honoraria, Research Funding; Merck: Research Funding; AbbVie: Honoraria, Research Funding; Ascentage Pharma: Research Funding; Genentech: Honoraria; Verastem Oncology: Honoraria; GlaxoSmithKline: Honoraria; TG Therapeutics: Research Funding; Pharmacyclics: Honoraria, Research Funding.