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Background The CLL international prognostic index (CLL-IPI) is a validated staging system for newly diagnosed CLL patients that combines age, clinical stage, serum Beta-2 microglobulin, TP53, and IGHV mutation status into a single score and stratifies CLL patients into four prognostic risk groups with a c-statistic=0.72. Next-generation sequencing identified ~60 putative driver genes recurrently mutated in CLL, and genome-wide association studies (GWAS) identified 41 single nucleotide polymorphisms (SNPs) associated with CLL risk. We previously showed that a polygenic risk score (PRS) of the weighted average of the number of risk alleles among these 41 SNPs is associated with risk of both CLL and MBL. We and others have also shown that the tumor mutational load (TML), i.e., the total number of somatically mutated driver genes, is associated with time to first treatment (TTT). Herein, we examine whether TML and PRS add prognostic value beyond CLL-IPI for disease progression in a cohort of CLL and high-count MBLs. Methods We used the Mayo Clinic CLL resource to identify newly diagnosed (<2 years) previously untreated CLL and high-count MBL patients based on the 2008 International Workshop CLL (IWCLL) criteria . We extracted DNA from CD5+/CD19+ clonal B-cells and sequenced the coding regions of 59 recurrently mutated CLL driver genes using a custom SureSelect panel and Illumina HiSeq 4000. The median coverage depth per sample was 2737X. Somatic mutations were called using MuTect2 in tumor-only mode. Germline variants were eliminated based on minor allele frequencies >0.01%, and by those identified in 1000 Genomes Project, ExAC and/or ESP6500 databases, unless present in known mutation hotspots or COSMIC. After filtering high/moderate impact mutations, we calculated the TML. Peripheral blood DNA was genotyped on Illumina Omni Express array; after extensive quality control metrics, we calculated the germline PRS as the weighted average of the number of risk alleles among the CLL susceptibility SNPs. Cox regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI) to test for associations with TTT. We analyzed the low/intermediate risk groups and the high/very high risk groups in stratified analyses and tested for interactions between CLL-IPI and TML or PRS. Survival curves are displayed using the Kaplan-Meier method using P-values from the log-rank test; the PRS is displayed by tertile categories. Results Of 166 patients (120 CLL, 46 MBL), 67% were male and the median age at diagnosis was 62 years (range: 28-85). The median follow-up was 5.3 years, and 73 were treated for progressive disease as defined by the 2018 IWCLL criteria. Low risk CLL-IPI comprised 51%, intermediate risk 27%, high risk 18%, and very-high risk 4%. The most commonly somatically mutated genes were TP53 (8%), CHD2 (8%), BIRC3 (8%), SF3B1 (7%), and NOTCH1 (7%). We found that 42%, 32%, and 26% of patients had 0, 1, or 2+ genes with somatic mutations, respectively. The median PRS was 8.3 (range: 6.1-11.3) which is consistent with our prior PRS study on CLL/MBL and higher than 7.53 found in 7983 controls from our prior work. When we modeled TML, PRS, sex, CLL/MBL status and CLL-IPI together with the joint effects of CLL-IPI with TML and PRS, both interactions were significant in the model (P=0.008 for TML*CLL-IPI and P=0.014 for PRS*CLL-IPI), with c-statistic=0.81 (CI:0.77-0.85). When we stratified by CLL-IPI, TML was associated with shorter TTT in the low/intermediate risk (N=129, continuous HR=2.36 per TML category, CI: 1.61-3.47, P=1.3x10-5, Figure 1.A), but there was no evidence of an association in the high/very-high risk (N=37, continuous HR=1.12 per TML category, CI: 0.70-1. 78, P=0.64, Figure 1.B), after adjusting for PRS, sex, and CLL/MBL status. However, the PRS was associated with a shorter TTT in the high/very-high risk (continuous HR=1.77 per SD, CI: 1.00-3.12, P=0.048, Figure 1.D), with no evidence of an association in the low/intermediate risk (continuous HR=0.95 per SD, CI: 0.95-1.29, P=0.74, Figure 1.C), after adjusting for TML, sex, and CLL/MBL status. Conclusions In our study, TML was prognostic among the low/intermediate CLL-IPI risk groups while the PRS was prognostic among the high/very-high CLL-IPI risk groups. Sequencing CLL driver genes and genotyping relevant germline SNPs at time of diagnosis may provide incremental value over the CLL-IPI in predicting TTT among patients with CLL/MBL. Disclosures Parikh: MorphoSys: Research Funding; Genentech: Honoraria; AbbVie: Honoraria, Research Funding; AstraZeneca: Honoraria, Research Funding; Pharmacyclics: Honoraria, Research Funding; Janssen: Research Funding; Ascentage Pharma: Research Funding; Acerta Pharma: Research Funding. Ding:Merck: Research Funding; DTRM Biopharma: Research Funding. Cerhan:Celgene: Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; NanoString: Research Funding. Kay:MorphoSys: Other: Data Safety Monitoring Board; Infinity Pharmaceuticals: Other: DSMB; Celgene: Other: Data Safety Monitoring Board; Agios: Other: DSMB.

Treatment with CD19-directed chimeric antigen receptor T cell (CART19) therapy has resulted in unprecedented clinical outcomes and was FDA-approved in acute lymphoblastic leukemia and non-Hodgkin B-cell lymphoma. However, its success in chronic lymphocytic leukemia (CLL) has been modest to date. An increasing body of evidence indicates that impaired CART cell fitness is the predominant mechanism of the relative dysfunction in CLL. The immunosuppressive microenvironment in CLL is well known and in part may be related to the abundance of circulating extracellular vesicles (EVs) bearing immunomodulatory properties. We hypothesized that CLL-derived EVs contribute to CART cell dysfunction. In this study, we aimed to investigate the interaction between circulating EVs isolated from CLL patient plasma (designated as CLL-derived EVs) and CART19 cells. We enumerated and immunophenotyped circulating EVs from platelet free plasma in untreated patients with CLL. We determined their interaction with CART19 cells using second generation, 41BB co-stimulated, lentiviral transduced CART19 cells generated in the laboratory from normal donors (FMC63-41BBζ CART cells). Our findings indicate that CLL-derived EVs impair normal donor CART19 antigen-specific proliferation against the CD19+ mantle cell lymphoma cell line Jeko-1 (Figure 1A). Next, we characterized CLL-derived EVs using nanoscale flow cytometric analysis of surface proteins and compared to healthy controls. Although the total EV particle count was not different between CLL and healthy controls (Figure 1B), there were significantly higher PD-L1+ EVs in patients with CLL (Figure 1C). Based on these results, we sought to assess the physical interaction between CLL-derived EVs and CART cells from normal individuals. When CLL-derived EVs were co-cultured with CART19 and CLL B cells and imaged with super-resolution microscopy, EVs were localized at the T cell-tumor junction (Figure 1D). Furthermore, CLL-derived EVs are captured by T cells as indicated by a significant reduction in the absolute count of EVs when co-cultured with resting T cells (Figure 1E). Having demonstrated that 1) there is an excess of PD-L1+ EVs in patients with CLL (Figure 1C) and 2) CLL-derived EVs physically interact with CART cells (Figures 1D-E), we sought to establish their functional impact on CART19 cells. Here, CART19 cells were stimulated with irradiated CD19+ JeKo-1 cells at a 1:1 ratio in the presence of increasing concentrations of CLL-derived EVs. There was a significant upregulation of inhibitory receptors such as PD-1 and CTLA-4 on the T cells (Figure 1F). This is associated with a reduction in CART effector cytokines (i.e., TNFβ) at higher concentrations of EVs (Figure 1G), suggesting a state of exhaustion in activated CART19 cells in the presence of CLL-derived EVs. This was further supported by transcriptome interrogation of CART19 cells. Here, CART19 cells were stimulated via 24-hour co-culture with the irradiated CD19+ cell line JeKo-1, in the presence of CLL-derived EVs at ratios of 10:1 and 1:1 EV:CART19 and then isolated by magnetic sorting. RNA sequencing of these activated CART19 cells indicated a significant upregulation of AP-1 (FOS-JUN) and YY1 (Figures 1H), known critical pathways in inducing T cell exhaustion. Finally, to confirm the impact of CLL-derived EVs on CART19 functions in vivo, we used our xenograft model for relapsed mantle cell lymphoma. Here, immunocompromised NOD-SCID-ɣ-/- mice were engrafted with the CD19+ luciferase+ cell line JeKo-1 (1x106 cells I.V. via tail vein injection). Engraftment was confirmed through bioluminescent imaging and mice were randomized to treatment with 1) untreated, 2) CART19 cells, or 3) CART19 cells co-cultured ex vivo with CLL-derived EVs for six hours prior to injection. A single low dose of CAR19 (2.5x105) was injected, to induce relapse. Treatment with CART19 cells that were co-cultured ex vivo with CLL-derived EVs resulted in reduced anti-tumor activity compared to treatment with CART19 alone (Figure 1I). Our results indicate that CLL-derived EVs induce significant CART19 cell dysfunction in vitro and in vivo, through a direct interaction with CART cells resulting in a downstream alteration of their exhaustion pathways. These studies illuminate a novel way through which circulating and potentially systemic EVs can lead to CART cell dysfunction in CLL patients. Disclosures Cox: Humanigen: Patents & Royalties. Sakemura:Humanigen: Patents & Royalties. Parikh:Ascentage Pharma: Research Funding; Janssen: Research Funding; AstraZeneca: Honoraria, Research Funding; Genentech: Honoraria; Pharmacyclics: Honoraria, Research Funding; MorphoSys: Research Funding; AbbVie: Honoraria, Research Funding; Acerta Pharma: Research Funding. Kay:Agios: Other: DSMB; Celgene: Other: Data Safety Monitoring Board; Infinity Pharmaceuticals: Other: DSMB; MorphoSys: Other: Data Safety Monitoring Board. Kenderian:Humanigen: Other: Scientific advisory board , Patents & Royalties, Research Funding; Lentigen: Research Funding; Novartis: Patents & Royalties, Research Funding; Tolero: Research Funding; Morphosys: Research Funding; Kite/Gilead: Research Funding.

Despite the success of chimeric antigen receptor T (CART) cell therapy, it is limited by 1) lower rates of durable responses related to inadequate CART cell expansion and trafficking to tumor sites and 2) development of life-threatening complication such as cytokine release syndrome (CRS). Development of a strategy to efficiently and robustly image and track CART cells in the clinic would allow the in vivo characterization of T cell expansion and trafficking to tumor sites as well as the development of strategies to potentially overcome these limitations. The sodium iodide symporter (NIS) is a characterized and sensitive reporter system that has been used for cell imaging in the clinic. We hypothesized that the incorporation of NIS into CART cells would be a sensitive and efficient way to assess CART cell expansion, trafficking, and toxicity. To test our hypothesis, we used two CART cell constructs that are characterized in preclinical models and studied extensively in the clinic: CART19 (41BB costimulated) and BCMA-CART cells (41BB costimulated). First, we generated NIS+CART19 and NIS+BCMA-CART cells through dual transduction of lentiviral vectors (Fig A) and revealed the exclusive 125I uptake by these NIS+CARTs and its inhibition by the NIS inhibitor KClO4in vitro (Fig B). We then analyzed T cell functions of NIS+CART cells. Here, NIS+CART19 or CART19 cells were cultured with the CD19+ acute lymphoblastic leukemia (ALL) cell line NALM6. There was no difference in CART cell cytotoxicity (Fig C), proliferation, or cytokine production (not shown) between NIS+CART19 and CART19. This indicates that the incorporation of NIS into CART cells does not impair their antitumor activity. Next, we evaluated the sensitivity of NIS+CART19 cell detection by TFB-PET in vivo; imaging was performed using an Inveon TFB-PET/CT scanner. Mice received 250 μCi 18F-TFB 45 minutes prior to image acquisition. NIS+CART cells were detectable with TFB-PET when cells were subcutaneously injected at a dose of 1.25x106 cells (Fig D). Having demonstrated that the incorporation of NIS in CART cells provides a sensitive way of their detection by TFB-PET and does not interfere with their effector functions, we tested its efficiency to assess CART cell trafficking in vivo, using multiple myeloma (MM) xenografts. Here, immunocompromised NOD-SCID-ɣ-/- (NSG) mice were engrafted with the BCMA+OPM2 MM cell line (1x106 IV). After engraftment, the tumor burden was assessed by bioluminescence imaging (BLI) and mice were randomized to receive 1) BCMA-CART or 2) NIS+BCMA-CART cells (5x106 IV). Mice were then serially imaged for 1) bioluminescence as a measure of disease burden, and 2) with TFB-PET to assess CART cell expansion and trafficking. As expected, BLI demonstrated that MM predominantly engrafts in bones (Fig E). TFB-PET confirmed trafficking of the NIS+BCMA-CART cells to the bones, corresponding to the areas involved by MM based on BLI (Fig E, right). Both BCMA-CART and NIS+BCMA-CART cells exhibited similarly potent antitumor activity in this model (not shown). Finally, we aimed to explore whether TFB-PET can detect CART massive expansion in vivo and predict the development of CRS. Here, we used an established CRS model in our laboratory. NSG mice were engrafted with patient derived relapsed ALL blasts (5x106 IV). Engraftment was confirmed by peripheral blood sampling. When the leukemic burden is >10 CD19+ cell/µl, mice were treated with either high dose NIS+CART19 cells (5x106 IV) or PBS control. One week after NIS+CART19 cell treatment, mice developed muscle weakness, hunched bodies, and weight loss (Fig F), which correlate with an extreme elevation of cytokines (Sterner et al. Blood 2018). TFB-PET revealed a significant uptake in the bone marrow, spleen, liver, and lungs (Fig G) of the diseased mice but not control mice. Mice were then euthanized, and tissues were harvested. Flow cytometric analysis confirmed an extensive infiltration of CART cells in the liver and spleen. This demonstrates the ability of TFB-PET to detect NIS+CART cell expansion in vivo, correlating with the development of CRS. In summary, our results robustly show that the incorporation of NIS into CART cells provides a sensitive, clinically applicable platform to image CART cells using TFB-PET and to assess their expansion, trafficking to tumor sites, and the development of CRS. These studies illuminate a novel way to noninvasively assess CART cell functions in vivo. Figure Disclosures Sakemura: Humanigen: Patents & Royalties. Suksanpaisan:Imanis: Employment. Cox:Humanigen: Patents & Royalties. Parikh:Janssen: Research Funding; AstraZeneca: Honoraria, Research Funding; Pharmacyclics: Honoraria, Research Funding; MorphoSys: Research Funding; AbbVie: Honoraria, Research Funding; Acerta Pharma: Research Funding; Ascentage Pharma: Research Funding; Genentech: Honoraria. Kay:Agios: Other: DSMB; Infinity Pharmaceuticals: Other: DSMB; Celgene: Other: Data Safety Monitoring Board; MorphoSys: Other: Data Safety Monitoring Board. Peng:Imanis: Equity Ownership. Russell:Imanis: Equity Ownership. Kenderian:Kite/Gilead: Research Funding; Lentigen: Research Funding; Morphosys: Research Funding; Tolero: Research Funding; Humanigen: Other: Scientific advisory board , Patents & Royalties, Research Funding; Novartis: Patents & Royalties, Research Funding.

Overview: B-Chronic lymphocytic leukemia (CLL) is a relatively common B-cell malignancy that has a very heterogeneous clinical course, despite carrying the designation of “chronic,” which is a gross oversimplification. Being able to give some estimate of the rates of disease progression and overall survival (OS) at first diagnosis is, therefore, important in CLL. The ability to accurately predict response to therapy, as well as subsequent duration of response to therapy, is required given the variability of current therapies to induce and sustain treatment responses. The holy grail of prognostics would be to state with accuracy which therapy or types of therapy are best for a given patient. Although there is no complete answer to prognostic counseling, there is a continued development of markers specific to the CLL B cell and/or to its environment, as well as of testing of prognostic models. These models use both traditional and novel prognostic markers that can aid in the dissection of outcome for early-stage CLL in terms of progression risk and time to therapy. This has resulted in significant enhancement of our ability to guide and predict outcome for our patients with CLL.

Abstract Introduction: CLL pts who qualify for participation in clinical trials are often thought of as a highly selected population. Therefore whether safety and efficacy data from these trials can be generalized to all CLL pts treated in the community setting is unknown. Prospective, observational studies can provide significant insight into pt and disease characteristics as well as practice patterns in different clinical settings. Here we report on baseline demographics and clinical characteristics for 1495 pts who participated in the Connect CLL observational study and were followed prospectively. Methods: Connect®CLL is a non study-specific intervention treatment registry which collects data on the management and outcomes of CLL pts in clinical, academic and community practices in the US. Clinical information was prospectively collected for pts treated in community (n=1312), academic (n=155), or government (n=28) centers in the US between March 2010 – Jan 2014. Pts eligible for treatment or on treatment not more than 2 months were eligible for enrollment. Here we report on the baseline demographics and clinical characteristics of a large CLL cohort stratified by AG, LOT and type of treatment center. Results: In total,1,495 pts were accrued with a median age at enrollment of 69 (range 22–99). Pts were Caucasian (92.2%), African American (6.9%), and male (63.7%). Median duration from diagnosis until initial therapy was 3.7 years (range 0-32). Age of enrolled pts was as follows; 527 pts age <65 years (AG1; 35%); 511 age 65–75 (AG2; 34%); and 457 age ≥75 (AG3; 31%) at the time of enrollment. Eight hundred and ninety-four pts (60%) were treated with front-line therapy (LOT1); 259 pts (17%) treated with second-line therapy (LOT2); and 342 pts (23%) treated beyond second-line therapy (LOT≥3). Patient age: Pt age was associated with significant variation in several clinical variables: Charlson comorbidity index (CCI) score ≥3 (AG 1-3 35/46/52%; p<0.0001), ECOG PS = 0 (AG1-3 60, 48, 33%, p<0.0001) and mean creatinine clearance (CrCl) decreased (AG 1-3 101/74/53 mL/min; p<0.0001). Line of therapy: Differences in baseline characteristics were observed between pts enrolled at LOT1 (previously untreated) and LOT2/≥3 (relapsed). Median age of pts accrued at LOT1 was 68 vs. 70 years for pts enrolled at LOT2/≥3 (p=0.007). ECOG PS = 0 was more frequent at LOT1 (50%) vs. LOT2/≥3 (42%) (p=0.0057). CCI ≥3 at LOT1 was 41% vs 48% at LOT2/≥3 (p=0.0072). When adjusted for differences in age, logistic regression also demonstrated significant differences in performance status (PS=0; p=0.02) and CCI (p=0.03) stratified by LOT. Treating institution: Baseline characteristics also differed by type of treating institution. Median age was 63 vs 70 at academic vs non-academic (p<0.0001). Pts treated at academic sites also had lower CCI (CCI≤2; 72.9% vs 54.2%, academic vs non-academic) and higher median CrCl (86.4 vs 71.4) (p=0.0017). In this registry, only 16% of patients under age 75 had CCI <= 2, CrCl >= 70 mL/min, ECOG 0-1; 18% of patients on LOT1 and 12% of pts on LOT=2 would satisfy these criteria. They represent 36% of eligible pts from academic treating institutions and 13% from community/government centers. Only 20% of patients on LOT1 would satisfy enrollment criteria for CLL8 (FCR vs. FC; Hallek; Lancet 2010) CLL 10 (BR vs FCR; NCT00769522). which did not have enrollment restrictions for age. Conclusions:Baseline characteristics of pts with CLL vary by age, LOT, and type of treatment center. In this large prospective observational study, our data confirms that older pts typically have a worse ECOG PS, more medical comorbidities, more advanced disease when initiating therapy and a lower probability of being treated at an academic medical center. Based on inclusion criteria used for entry in either CLL10 or CLL8, fewer than 20% of pts satisfy age, renal clearance, and fitness profile to be considered suitable for aggressive chemoimmunotherapy in the front line setting. This observation supports the notion that current clinical trial data might not always be applicable to the general CLL population seen in the community and argues for designing clinical trials that are more generalizable to the broader pt population. Disclosures Sharman: Gilead: Research Funding; Calistoga: Honoraria; Phamacyclics: Honoraria, Research Funding; Celgene: Consultancy, Research Funding; TG therapeutics: Research Funding; Roche: Research Funding. Mato:Millennium: Speakers Bureau; Celgene: Speakers Bureau; Genentech: Speakers Bureau. Kay:Celgene: Research Funding. Kipps:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Lamanna:Genentech-Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Infinity: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Weiss:Celgene: Consultancy; Phamacyclics: Consultancy; Gilead: Consultancy. Nabhan:Celgene: Honoraria, Research Funding. Flinn:Celgene: Research Funding. Grinblatt:Celgene: Honoraria, Speakers Bureau. Kozloff:Celgene: Consultancy. Farber:Alexion: Equity Ownership, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Speakers Bureau; Janssen/Pharmacyclics: Speakers Bureau; Seattle Genetics: Speakers Bureau; Genentech: Membership on an entity's Board of Directors or advisory committees. Sullivan:Celgene: Employment, Equity Ownership. Street:Celgene: Employment, Equity Ownership. Swern:Celgene: Employment, Equity Ownership. Flowers:TG Therapeutics: Research Funding; Phamacyclics: Research Funding; Acerta: Research Funding; Abbvie: Research Funding; Infinity: Research Funding; Lymphoma Research Foundation: Membership on an entity's Board of Directors or advisory committees; Janssen: Research Funding; Spectrum: Research Funding; Gilead: Research Funding; Genentech: Unpaid consultancy Other; Millennium: Research Funding, Unpaid consultancy, Unpaid consultancy Other; Seattle Genetics: Consultancy; Prescription Solutions: Consultancy; Celgene: Unpaid consultancy Other.

Abstract BACKGROUND: Chronic lymphocytic leukemia (CLL) is a heterogeneous B cell malignancy with patients being categorized into disease subsets based on several key biologic parameters, e.g., mutation status (mutated, M; or unmutated, UM) of the immunoglobulin heavy chain variable region (IGHV), acquired chromosomal abnormalities, and expression of CD38 and CD49d. Furthermore, about one third of CLL patients express stereotyped B cell receptors and/or may acquire high risk common mutations in genes such as NOTCH1 and SF3B1 suggesting ongoing genetic evolution as drivers of disease development. Critical to this concept, those CLL patients with trisomy 12 (T12) defects have a higher incidence of mutations in NOTCH1 and often have a stereotyped receptor. However, T12 patients may have a variable clinical course that appears to be unrelated to these 2 drivers suggesting an additional, possibly non-coding genetic component that may further impact disease progression in these patients. One potentially relevant genetic factor that could influence T12 clinical course is long non-coding RNAs (lncRNAs). LncRNAs are transcripts longer than 200 nucleotides that can affect a number of cellular processes. Importantly, lncRNAs have been implicated in various cancers including malignant hematopoiesis indicating they could be therapeutic targets and/or clinically useful biomarkers. METHODS: To pursue a role for lncRNAs in T12 we used v3.0 Arraystar Human LncRNA Microarrays to assess the global profile of lncRNA expression in CLL with an emphasis on patients with T12. Two cohorts of 6 patients with T12 were selected for comparison: one defined as progressive with a short time to treatment (TTT) (treatment ≤1 year after diagnosis) and one as indolent (no treatment > 5 years after diagnosis). Each cohort included 3 patients with M and 3 with UM IGHV status. RNA from normal CD5+ and CD5- B cells was included as a control. To compensate for the small sample size in each cohort, a significant difference in lncRNA expression between the groups was defined as a fold change (FC) ≥5.0, p-value ≤0.05 and false discovery rate (FDR) ≤ 0.05. RESULTS: An initial global comparison of CD5+/CD5- normal B cells vs all CLL samples found that 609 lncRNAs were differentially expressed using the criteria listed above with 158 lncRNAs having a FC>10. Notable lncRNAs in this group included: LOC541472 (down in CLL and associated with the IL-6 gene), D63785 (up in CLL and associated with TBC1D3C, an oncoprotein), CTC-459I6.1 (up in CLL and associated with RASGRF2) and AC002480.5 (down in CLL and associated with STEAP1B, shown to be overexpressed in prostate cancer). We next evaluated T12 samples and identified 90 candidate lncRNAs that may discriminate between progressive and indolent T12 cases. Within this group were 11 lncRNAs with a FC > 10, 5 of which have no known associated gene. Of those associated with known genes, 3 were ultra-conserved region encoding lncRNAs down-regulated in progressive T12 patients (TTT ≤1 yr) and linked to hephaestin-like protein 1 precursor, pannexin-1, and tubulin beta-3 chain isoform 1. Of potential high relevance we found that the lncRNA LPP-AS1 was down-regulated in progressive T12 patients (TTT ≤1 yr) and known to be associated with the LIM-containing lipoma preferred partner (LPP) gene (p=0.028; FDR=0.03 and FC=18.3). Looking specifically at IGHV M progressive T12 patients (T12M≤1 yr) vs IGHV M indolent T12 patients (T12M>5 yrs), we again found the LPP-AS1 lncRNA was highly down-regulated in T12M≤1 (p=0.00046; FDR=0.006 and FC=34.5) but it was not found to be differentially expressed in the UM T12≤1 yr vs UM T12>5 yr comparison. The LPP gene has been shown to play a role in cell-cell adhesion, motility and signaling, and is often the fusion partner for the mixed lineage leukemia (MLL) gene in secondary acute leukemia. Furthermore, LLP may play a role in breast cancer cell invasion. LPP-AS1 may be participating in IGHV M T12 progression by affecting LPP and thus influencing migration through the lymph node microenvironment. CONCLUSION: While candidate lncRNAs in T12 CLL need to be validated, the LPP-AS1 lncRNA shows promise as a possible marker and potential treatment target for those patients with T12 and M IGHV that may progress rapidly. Further studies are needed to evaluate the impact of lncRNAs on clinical outcome of T12 CLL patients. Disclosures Shanafelt: Hospiria: Research Funding; Pharmacyclics/Jannsen: Research Funding; Cephalon: Research Funding; Celgene: Research Funding; glaxoSmithKline: Research Funding; Genetech: Research Funding; Polyphenon E Int'l: Research Funding. Kay:Celgene: Research Funding.

Abstract Introduction: Monoclonal B cell lymphocytosis (MBL) is an asymptomatic expansion of clonal CD19+/CD5+ B cells with less than 5x109/L cells in the peripheral blood and without other manifestations of chronic lymphocytic leukemia (CLL). Approximately 1% of MBL evolves to CLL requiring therapy per year; thus it is critical to develop more precise tools to identify which MBL will progress to CLL and require treatment. Patients and Methods: In this study, we performed targeted deep sequencing (TDS) on 49 high-count MBL individuals (median B-cell count 3.7x109/L; range 0.8-4.9x109/L) and explored the mutation status of 20 driver genes recurrently mutated in CLL. We analyzed the clonal evolution in 45 of these 49 MBLs by screening 2-4 sequential samples (average time between samples 56 months, range 10-119 months). At last follow-up, 19 cases (39%) had progressed to Rai>0, and 10 cases (20%) required treatment. Tumor and germ line DNAs were isolated from sorted CD5+/CD19+ and CD5-/CD19- cell populations, respectively. Overall, 154 samples from 49 MBL cases (105 tumor and 49 germ line) were screened using semiconductor sequencing technology. The latter genetic information was integrated with relevant clinical and biological parameters, and we evaluated the effect of driver mutations and clonal expansion on time to CLL progression and time to treatment (TTT). Results and Discussion: Our cohort consisted in 17 women and 32 men, with a median age of 66 years (range: 44-80). Five cases presented secondary diseases, including melanoma, lung and bladder cancer. Clinical and biological parameters were collected, including IGHV mutation status (mutated 66%, unmutated 34%), ZAP70 and CD49 expression (25% each). At presentation, 46% of cases had del(13q), 27% trisomy 12, 6% del(11q), and 4% del(17p). Overall, we found somatic non-synonymous mutations in 23 of 49 MBLs (47%) at the initial time point including 22% of cases with more than one mutated driver gene. The average depth of coverage was 730x, thus allowing the identification of small subclonal mutations. Recurrent mutations were found in most of the drivers: CHD2, DDX3X (8% of cases), FBXW7, NOTCH1, SF3B1 (6% each), ATM, BCOR, BIRC3, BRAF, KRAS, MED12, MYD88 and ZMYM3 (4% each). Furthermore, ITPKB, POT1, SAMHD1 and XPO1 were mutated in only one case, whereas no mutations were found in HIST1H1E, RIPK1 and TP53. In 4 individuals, we found two mutations in the same gene (BRAF, DDX3X, KRAS and SAMHD1). Genes that are known to be associated with disease progression in CLL were either mutated with significantly lower incidence (NOTCH1, SF3B1) or not mutated (TP53). Mutations were detected on average 45 months (range 9-73) prior to progression to CLL Rai>0 indicating the early origin of most driver gene mutations in the MBL/CLL continuum. The presence of driver mutations in MBL was associated with shorter TTT (median TTT: present: 96 months vs. not present: not reached, HR: 5.52, 95% CI: 1.2-26.2, P =0.015). Next, we looked at clonal expansion of driver mutations over time (defined as >2-fold change in the allelic frequency of driver mutations between time points). Of 20 MBLs with mutations at baseline who had sequential samples available, 10 cases showed clonal expansion. Seven out of 10 MBLs who required therapy showed clonal expansion, which was detected on average 15 months (range 6-30 month) prior to treatment. Finally, the detection of clonal expansion was significantly associated with reduced TTT (median TTT: clonal expansion: 21 months vs. no clonal expansion: 84 months, HR: 7.79, 95% CI: 1.94-31.3, P <0.001). Conclusion: We have confirmed the existence of recurrent mutations in most CLL putative driver genes at the premalignant MBL stage many years before progression to CLL. Furthermore, the early identification of driver mutations and its clonal expansion predicts a shorter TTT. Of note, clonal evolution under selective pressure has recently been linked to the onset of CLL progression after therapy. In this study, we characterized the clonal dynamics in the pre-malignant stages of the disease and underlined its impact on clinical outcome. Despite the relatively small size of the cohort, these findings suggest that the sequential monitoring of MBL individuals with a simple and reliable technique, such as TDS, will be at least of prognostic use and thus its incorporation in the disease stratification and clinical management should be further tested. Disclosures Fonseca: Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Applied Biosciences: Membership on an entity's Board of Directors or advisory committees; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Millennium: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Binding Site: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Onyx/Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Bayer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding. Kay:Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Research Funding; Tolero Pharma: Research Funding; Genentech: Research Funding; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding; Hospira: Research Funding.

Abstract Introduction: Rituximab (R) improves survival in CLL when added to intensive chemotherapy (such as fludarabine and cyclophosphamide [FCR]), and has been shown to improve progression-free survival when given as maintenance therapy following first- or second-line chemoimmunotherapy. However, early phase 2 studies demonstrated only modest activity of R monotherapy (R mono), particularly at standard dose, and its use as a single agent for pts with CLL has remained controversial. Here we describe the characteristics and outcomes of pts with CLL receiving R mono in a real-world setting. Methods: The Connect CLL registry (NCT01081015), a multicenter, prospective observational cohort study, enrolled 1,494 pts with CLL between 2010-2014 from 179 community, 17 academic, and 3 government sites throughout the USA. Pts were ≥ 18 years and were enrolled ≤ 2 months after initiating any line of therapy (LOT). Pts were treated according to individual physician/patient decision making, and adherence to IWCLL standards cannot be determined. Bone marrow biopsy and CT scans were at the physician's discretion; responses were physician assessed and not centrally reviewed. For this analysis, pts were stratified by first (LOT1) or subsequent LOT (LOT≥2), and by treatment with R mono or other treatments (Tx). Kaplan-Meier methods were used to estimate event-free survival (EFS; event defined as death, progression/relapse, or transformation). A log-rank test was used to evaluate differences in EFS. A multivariate analysis of EFS in LOT1 pts was performed using the Cox regression model. Results: Of the pts enrolled, 105 (11.8%) pts in LOT1 and 81 (13.4%) pts in LOT≥2 received R mono. Of the pts receiving other Tx, 620/784 pts (79%) in LOT1 and 333/524 pts (64%) in LOT≥2 received R in combination. In LOT1, pts receiving R mono were older than pts receiving other Tx (74 vs 67 years; P < 0.0001); in LOT≥2 median ages were comparable (71 vs 70 years). Pts receiving R mono were more likely to have Rai stage 0-1 CLL than pts receiving other Tx, both in LOT1 (63.9% vs 51.8%; P = 0.05) and LOT≥2 (70.4% vs 49.9%; P = 0.005). The proportion of pts receiving R mono vs other Tx with a CCI score of ≥ 4 was similar in LOT1 (25.7% vs 22.8%) and LOT≥2 (32.1% vs 28.4%). Median absolute lymphocyte count at enrollment was lower in pts on R mono vs other Tx in LOT1 (27.7 vs 46.1 x 109/L) but similar in LOT≥2 (35.6 vs 30.2 x 109/L). A lower proportion of pts receiving R mono had FISH/cytogenetics performed at enrollment than pts receiving other Tx in LOT1 (48.6% vs 67.0%; P = 0.0002) and LOT≥2 (30.9% vs 49.6%; P = 0.002). The most common Tx regimens in LOT1 were FCR (25.9%), bendamustine plus R ([BR] 21.0%), R mono (11.8%), fludarabine plus R ([FR] 6.3%), and chlorambucil (4.6%); and in LOT≥2, BR (27.6%), R mono (13.4%), FCR (8.6%), bendamustine (7.4%), FR (4.1%), and ofatumumab (4.0%). The most common reason to initiate treatment in any LOT was bone marrow failure (LOT1, 44.8% vs 39.3%; LOT≥2, 37.0% vs 31.5%; R mono vs other Tx). Duration of therapy was shorter for pts receiving R mono vs other Tx in LOT1 (1.4 vs 4.1 months) and LOT≥2 (1.6 vs 3.3 months). In LOT1, responses were lower in pts on R mono vs other Tx: overall response rate (ORR) was 38.1% vs 64.2% (complete response [CR], 16.2% vs 41.2%; P < 0.0001). In LOT≥2, ORR was 25.9% vs 24.6% for pts on R mono vs other Tx (CR, 9.9% vs 11.5%; P = 0.68). Partial response did not differ significantly between pts receiving R mono vs other Tx in LOT1 and LOT≥2. Pts receiving R mono in LOT1 had inferior median EFS vs other Tx (34 vs 50 months; log-rank P = 0.04); however, after adjusting for factors such as ECOG status and del(17p) status, there was no difference in EFS (HR 0.932; P = 0.79). In pts in LOT≥2, median EFS was similar for R mono and other Tx (15 months for both groups; P = 0.93). Conclusions: Pts receiving R mono as frontline CLL therapy were older than pts receiving other Tx. They also had lower stage disease and lower lymphocyte counts, a shorter duration of treatment, and inferior response rates. Pts receiving R mono in relapsed CLL, more closely approximated pts receiving other Tx in terms of age. Despite the shorter duration of therapy for pts receiving R mono in LOT1 and LOT≥2, both groups had similar ORR and EFS in LOT≥2. These data reinforce the idea that R mono is inadequate as frontline therapy in progressive CLL, and demonstrate the opportunity for improvement in relapsed/refractory disease with novel agents relative to traditional chemoimmunotherapy approaches. Disclosures Sharman: Celgene: Research Funding; Gilead: Research Funding; Pharmacyclics: Research Funding; Acerta: Research Funding; TG Therapeutics: Research Funding; Seattle Genetics: Research Funding. Davids:Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Membership on an entity's Board of Directors or advisory committees, Research Funding; Infinity: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie, Janssen, Gilead: Consultancy; Celgene Corporation: Consultancy. Farber:Seattle Genetics: Research Funding. Grinblatt:Celgene Corporation: Consultancy, Speakers Bureau. Lamanna:Gilead: Research Funding; AbbVie: Research Funding; Genentech: Research Funding; Infinity: Research Funding; Pronai: Research Funding; Celgene Corporation: Research Funding. Mato:TG Therapeutics: Consultancy; Abbvie: Research Funding; Acerta Pharma: Research Funding; Gilead Sciences: Research Funding; ProNAi: Research Funding; TG Therapeutics: Research Funding; Theradex: Research Funding; Pharmacyclics: Consultancy; Gilead Sciences: Consultancy; Abbvie: Consultancy. Nabhan:Astellas: Research Funding; Seattle Genetics: Research Funding; Cardinal Health: Consultancy; Infinity: Consultancy; Abbvie: Consultancy; Genentech: Consultancy, Research Funding; Celgene Corporation: Consultancy, Research Funding. Sullivan:Celgene Corporation: Employment, Equity Ownership. Flick:Celgene Corporation: Employment, Equity Ownership. Kiselev:Celgene Corporation: Employment, Equity Ownership. Bhushan:Celgene Corporation: Employment, Equity Ownership. Swern:Celgene: Employment, Equity Ownership. Flowers:Seattle Genetics: Research Funding; Optum Rx, Seattle Genetics, Genentech/Roche: Consultancy; Celgene Corporation: Consultancy, Honoraria; Spectrum, Janssen, Infinity, AbbVie, Acerta, Pharmacyclics, TG Therapeutics: Research Funding; Millennium: Consultancy, Research Funding; Gilead: Consultancy, Research Funding.