ALBERT

Description: Introduction: Venetoclax (VEN) based therapy has become a standard of care in front line and relapsed-refractory (R/R) CLL based on favorable efficacy and toxicity. Whereas prospective data regarding activity of therapies following ibrutinib (IBR) or idelalisib (IDE) are available in the settings of progression (VEN, non-covalent BTKi) and intolerance (acalabrutinib), how best to manage patients (pts) who discontinue (dc) VEN remains a key unanswered question. With the increased use of VEN in early lines of therapy (LOT; CLL 14, MURANO), the activity of BTK inhibitors (BTKi) and cellular therapies following VEN becomes a critical issue. No prospective study has addressed this question, and currently reported VEN clinical trials have limited information about subsequent treatments. While recent data describe VEN resistance mechanisms (Guieze 2018, Blombery 2019), the impact of VEN resistance on efficacy of post VEN therapies is unknown. To address this gap, we conducted an international study to identify a large cohort of pts who dc VEN and have been subsequently treated. Methods: We conducted an IRB approved multicenter (31 US, EU, South American sites, in partnership with UK CLL Forum and CORE registry), retrospective cohort study of CLL pts who dc VEN for any reason. We examined demographics, dc reasons, responses, survival, adverse events (AEs) and activity of post VEN therapies. Primary endpoints were overall response rate (ORR) and progression free survival (PFS) for the post VEN treatments stratified by treatment type (BTKi, PI3Ki and cellular therapy: CAR-T or alloHSCT). ORR was defined by iwCLL criteria and PFS was defined from VEN dc to disease progression (PD), death, or last follow up for next treatment. Pts were further stratified by BTKi (resistant / intolerant) and PI3Ki exposure prior to VEN. PFS-2 was defined as time from VEN start to tumor progression on IBR or death from any cause. Results: 326 CLL pts who dc VEN in the front line (4%) and R/R settings (96%) were identified. The cohort was 69% male, 87% white, median (med) age 66 (38-91) at VEN start, 27% treated with VEN based combinations (n=88, med 6 cycles anti-CD20 abs). Pre VEN prognostic features: 82% IGHV unmutated (n tested=166), 47% del17p (n=306), 45% TP53 mut (n=217), 39% complex karyotype (n=273), 23% BTK mut (n=79), 18% NOTCH1 mut (n=103), 10% PLCγ2 mut (n=74). Pts received med 3 therapies (0-11) prior to VEN; 40% were BTKi naïve (n=130), 60% were BTKi exposed (196) and 81% were IDE naïve (n=263). Most common reasons for VEN dc were PD (38%), AE (20%), Richter's transformation (RT, 14%), 8% pt preference, and HSCT 5%. Of 326 pts who dc VEN, 188 (58%) were treated with a subsequent LOT, 61 are alive and untreated and 77 died prior to a subsequent LOT. Post VEN sequencing analyses focused on BTKi, PI3Ki and cellular therapy (CAR-T or alloHSCT) activities following VEN dc (Table1). ORR to BTKi was 84% (n=44) vs. 54% (n=30, p

Description: Introduction: Venetoclax (Ven) is approved for relapsed/refractory (R/R) chronic lymphocytic leukemia (CLL) as monotherapy (Ven mono) or in combination (Ven paired) with rituximab based on clinical trials with selected patients (pts) and limited ibrutinib exposure. Whether Ven paired is superior to Ven mono, patterns of care, and outcomes following Ven discontinuation are unknown. Further, better delineation of adverse events (AEs) when Ven is used outside of clinical trials is needed. To address these gaps, we conducted a multicenter, international study in partnership with CLL Collaborative Study of Real World Evidence (CORE) and UK CLL Study Forum examining the clinical experience of 348 Ven treated CLL pts, representing the largest series of Ven treated pts reported to date. Methods: We conducted a retrospective cohort analysis of CLL pts treated with Ven across 24 US and 42 UK academic and community centers. We examined demographics, baseline disease characteristics, dosing, AEs, TLS risk and outcomes, response rates, outcomes (overall survival (OS) and progression free survival (PFS)), and tx sequencing. TLS events were defined by Howard criteria. PFS and OS were estimated by the Kaplan Meier method. Comparisons of outcomes used the Log Rank test. Univariate and multivariate analyses were performed with COX regression. All other comparisons were descriptive. Results: Of these 348 CLL pts, 94% were R/R, median age 67 years (range:37-91), 69% male, 85% white, and 73% Rai stage ≥2. 19% received Ven on clinical trial. 79% had Ven mono; Ven was paired most commonly with anti-CD20 (n=51) and ibrutinib (n=10). Pts received a median of 3 tx (range 0-15) before Ven; 78% received ibrutinib, 29% received PI3Ki, 20% had ≥2 prior kinase inhibitors, and 68% had chemoimmunotherapy. Median time from most recent tx to Ven start was 1.1 months (range 0-62). Pre-Ven prognostic markers included 43% del17p, 34% TP53 mutated, 24% del11q, 38% complex karyotype (≥ 3 abnormalities), and 84% IGHV unmutated (Table 1). TLS risk was low in 38%, intermediate in 34% and high in 28%. During ramp up, TLS was observed in 10% (22 lab, 9 clinical TLS events, 3 missing data). Following dose escalation, 70% achieved a stable Ven dose of 400 mg, 33% required ≥ 1 dose interruption and 27% required ≥ 1 dose reduction. AEs included grade 3 neutropenia 39%, grade 3 thrombocytopenia 29%, infections 25%, grade ≥ 2 diarrhea 7.8%, and neutropenic fever 7.7%. AEs were similar whether treated on or off clinical trial. The ORR to Ven mono, Ven paired was 81% (34% CR), 86% (29% CR). With a median follow-up of 14.2 months, median PFS and OS were not reached (12 month PFS 74%, OS 82%). Figure 1 depicts PFS stratified by Ven mono vs. paired, clinical trial vs. clinical practice, del17p status, and complex karyotype. Pts who discontinued Ven due to AEs had better OS compared with those who discontinued due to progression or Richter Transformation (RT) (Median OS 47 vs. 15.1 vs. 8.6 months, respectively). In multivariate analyses, complex karyotype was the only independent predictor of PFS (HR 2.8, p

Description: Heterozygous mutations in several core members of the spliceosome complex have been reported in Myelodysplastic Syndromes (MDS) and Acute Myeloid Leukemia (AML). In particular high frequency SF3B1 hotspot mutations, a component of the U2 complex involved in the interaction with the branch point (BP) and recognition of the 3' splice sites (ss) during splicing, have been identified in Refractory Anemia with Ringed Sideroblasts (RARS) a subtype of MDS. Using computational analyses of RNAseq from several cancer types including RARS, we identified that SF3B1 hotspot mutations induce aberrant 3'ss selection by recognizing a cryptic AG located between 15 to 24 nucleotides upstream of the canonical AG. Experimental confirmation of these motif features was performed using minigenes in SF3B1 mutant cells. Furthermore, we discovered that SF3B1 mutant utilized a different BP from that used by SF3B1 wild-type providing novel mechanistic insights into changes in function induced by the hotspot mutations. The induction of aberrant splicing can introduce premature termination codons thus targeting mRNA for degradation by Nonsense Mediated Decay (NMD). We predicted that close to 50% of the aberrantly spliced genes would be subject to NMD and showed (using isogenic Nalm-6 cells engineered by AAV homology to express SF3B1K700E or SF3B1K700K) that several of these genes were downregulated at the transcript and protein levels. These downregulated genes/proteins might be involved in the pathogenesis of SF3B1 mutant cancers. Interestingly, pathway analysis of genes differentially expressed or aberrantly spliced in SF3B1 mutant compared to wild-type in RARS samples identified cell differentiation and epigenetics as the primary misregulated pathways. To study the impact of SF3B1 mutations on differentiation, we used the TF-1 differentiation cell model where erythroid differentiation is induced by treatment with erythropoietin (EPO). EPO treatment, as expected, induced erythroid differentiation in TF-1 cells transduced with SF3B1WT, but a block in erythroid differentiation was observed in TF-1 cells transduced with SF3B1K700E (the most common mutation in MDS and chronic lymphocytic leukemia (CLL)). Intriguingly, SF3B1G742D, which is found mutated in CLL but not MDS, did not block differentiation in this myeloid differentiation model, implying that specific SF3B1 mutations and splicing aberrations have important context dependent effects. Pathway analysis comparing SF3B1K700E vs. SF3B1WT or SF3B1G742D identified several genes involved in heme biosynthesis or downstream of GATA1 to be downregulated (such as, AHSP, ALAS2, CCL5, CD36, EPOR, GP1BB, HBB, HBE1, HBG1, PRG2) in SF3B1K700E cells only. This is consistent with the role of SF3B1K700E in RARS. In our analyses, we also identified that ABCB7 is aberrantly spliced and that the aberrant transcript is subject to NMD, causing downregulation of the canonical transcript and protein. ABCB7 is a mitochondrial transporter important in cellular iron metabolism and in heme production; moreover, partial loss of function mutation in ABCB7 has been identified in X-linked sideroblastic anemia and ataxia, demonstrating an iron overload phenotype in cells with defective ABCB7. Interestingly, when ABCB7 was knocked down in TF-1 cells we observed block in differentiation similar to that observed in SF3B1K700E cells suggesting a link between SF3B1 mutation and ABCB7 levels and impaired differentiation. Taken together, these data suggest that SF3B1 mutations induce aberrant splicing and as a consequence downregulation of several genes that contribute to the block in erythroid differentiation, one of the key biological defects observed in MDS. Disclosures Buonamici: H3 Biomedicine: Employment. Darman:H3 Biomedicine: Employment. Perino:H3 Biomedicine: Employment. Agrawal:H3 Biomedicine: Employment. Peng:H3 Biomedicine: Employment. Seiler:H3 Biomedicine: Employment. Feala:H3 Biomedicine: Employment. Bailey:H3 Biomedicine: Employment. Chan:H3 Biomedicine: Employment. Fekkes:H3 Biomedicine: Employment. Keaney:H3 Biomedicine: Employment. Kumar:H3 Biomedicine: Employment. Kunii:H3 Biomedicine: Employment. Lee:H3 Biomedicine: Employment. Mackenzie:Eisai: Employment. Matijevic:Eisai: Employment. Mizui:H3 Biomedicine: Employment. Myint:Eisai: Employment. Park:H3 Biomedicine: Employment. Pazolli:H3 Biomedicine: Employment. Thomas:H3 Biomedicine: Employment. Wang:H3 Biomedicine: Employment. Warmuth:H3 Biomedicine: Employment. Yu:H3 Biomedicine: Employment. Zhu:H3 Biomedicine: Employment. Furman:Acerta Pharma BV: Research Funding; Gilead: Consultancy; Pharmacyclics LLC, an AbbVie Company: Consultancy, Honoraria, Speakers Bureau. Ebert:Celgene: Consultancy; H3 Biomedicine: Consultancy; Genoptix: Consultancy, Patents & Royalties. Smith:H3 Biomedicine: Employment.

Description: Human SLAMF1 (signaling-lymphocytic-activation-molecule-family1, CD150) is a self-ligand adhesion/co-stimulatory molecule wich belongs to a family of 9 receptors. SLAMF1 is also a microbial sensor, as it regulates Gram- bacterial phagosome functions through an ubiquitous cellular autophagic machinery and serves as a receptor for Measles virus. In this work, we investigated expression and function of SLAMF1 in chronic lymphocytic leukemia (CLL) cells. Results indicate that expression of SLAMF1 is lost in a subset of patients with chronic lymphocytic leukemia characterized by an aggressive form of the disease, with shorter time to first treatment (median 2.2 years in SLAMF1- vs 7.6 in SLAMF1+ patients, P=.001) and overall survival (77.5% survival rate at 10 years in SLAMF1- vs 94.7% years in SLAMF1+ patients, P=.036). Consistently, SLAMF1low CLL patients are characterized by clinical or molecular markers of a more aggressive disease. Stable silencing of SLAMF1 in the CLL-like Mec-1 cell line (constitutively SLAMF1+) modulated pathways related to cell migration, cytoskeletal organization and intracellular vesicle formation/recirculation. Decreased expression of CXCR3 and an increased expression of CXCR4, CD38 and CD44 were maintained at the molecular level, likely explaining why SLAMF1- cells show enhanced chemotactic responses to CXCL12. This phenotype was confirmed in primary cells, by comparing a cohorts of SLAMF1high to one of SLAMF1low patients. Gene expression profiling also indicates profound modulation of pathways connected with vesicle formation and recirculation. Consistently, cross-linking of SLAMF1 with an agonisic mAb in primary cells and in the Mec-1 cell line enhanced the generation of autophagic vesicles and their fusion with the lysosomes. Ligation of SLAMF1 with this agonistic monoclonal antibody promoted the autophagic flux, by increasing accumulation of reactive oxygen species (ROS) and inducing phosphorylation of p38, JNK1/2 and bcl-2. The direct consequence was the formation of the autophagy macro-complex containing SLAMF1, the scaffold protein beclin1 and the enzyme Vps34. In agreement with the observation that many drugs used in CLL have autophagy-mediated effects, including fludarabine and the BH3 mimetic ABT-737, SLAMF1-silenced Mec-1 cells or SLAMF1low primary CLL cells were resistant to treatment with both agents. These results indicate that SLAMF1 plays as a critical role in CLL homeostasis. Loss of SLAMF1 expression modulates genetic pathways that regulate chemotaxis and autophagy and that potentially affect drug responses, thus providing a likely explanation for the unfavorable clinical outcome experienced by this patient subset. Restoring SLAMF1 expression in CLL cells would therefore be of therapeutic value for patients with aggressive CLL. Disclosures Gaidano: Morphosys, Roche, Novartis, GlaxoSmith Kline, Amgen, Janssen, Karyopharm: Honoraria, Other: Advisory boards; Celgene: Research Funding.

Description: Extracellular adenosine generated from ATP/ADP through the concerted action of the ectoenzymes CD39 and CD73 elicits potent cytoprotective and immunosuppressive effects mediated by type-1 purinergic receptors. Chronic lymphocytic leukemia (CLL) cells expressing the ectoenzymes CD39 and CD73 can actively produce adenosine, activating an autocrine adenosinergic axis that supports engraftment of leukemic cells in a growth-favorable environment. These effects are mediated by the A2A adenosine receptor, which inhibits chemotaxis and limits spontaneous and drug-induced apoptosis of CLL cells. Following the reported cross-talk between hypoxia and adenosine, we tested the hypothesis of a functional interplay between the adenosinergic axis and hypoxic signals in the CLL microenvironment. Results indicate that culture of CLL cells under hypoxic conditions, such as those observed in lymph nodes from CLL patients, boosts adenosine production, mainly because of the significant increase in the mRNA and protein levels of CD73, the rate-limiting enzyme in adenosine synthesis. CLL also underwent a robust up-regulation of CD26, which functions as an adenosine-deaminase scaffold protein, in keeping with the hypothesis that extracellular nucleotides enter a scavenging pathway, with conversion to inosine and re-uptake by the leukemic cells. Confirmation was obtained using HPLC assays, which showed increased inosine generation under hypoxia. Consistently, expression of membrane nucleoside transporters was also significantly up-regulated. However, hypoxic CLL cells also expressed high levels of the A2A adenosine receptor, which delivered cytoprotective signals and which supported CLL proliferation in response to TLR signaling. Attention was then focused on the stromal and T cell compartments, which are critical to the formation and maintenance of the leukemic niche. Hypoxia enhanced differentiation of circulating monocytes into nurse-like cells, macrophages of the M2 type playing an essential role in nurturing leukemic cells. The enhancement of NLC differentiation under hypoxic conditions relied, at least in part, on the activation of A2A: its engagement by a pharmacological agonist favored NLC generation, with overexpression of indoleamine 2,3-dioxygenase (IDO) and of the M2 macrophage markers CD163 and CD206. Moreover, activation of A2A induced secretion of immunomodulatory cytokines, such as IL-6, IL-10 and CCL18, while pharmacological blockade of A2A under hypoxia prevented NLC differentiation, expansion, expression of immunosuppressive molecules and secretion of cytokines and chemokines. In the T cell compartment, hypoxic cultures were followed by the sharp up-regulation of A2A, without significantly affecting the enzymes that generate adenosine, which were anyway restricted to the regulatory T cell (Treg) compartment. Co-cultures of T lymphocytes and CLL cells under hypoxia resulted in a dramatic decrease of T cell proliferation, partially rescued by A2A receptor antagonists. Furthermore, hypoxic T cells underwent a metabolic switch, with increased expression of nucleoside transporters and enzymes involved in glucose metabolism, suggesting a Warburg effect. This was accompanied by the differentiation of a population of Tr1 cells, characterized by the expression of LAG3 and CD49b and by the secretion of high levels of IL-10 and VEGF. Expression of the PD-1 immuno-inhibitory receptor was enhanced in hypoxic T cells, suggesting that multiple inhibitory mechanisms are activated. We also observed expansion of classical Tregs, defined on the basis of a CD4+/CD25high/CD127low/foxp3+ phenotype. Blockade of the A2A receptor prevented this phenotype, partially restoring T cell proliferation and immune competence. Together, these findings indicate that the adenosinergic and hypoxic axes synergize in shaping the CLL niche, suggesting that pharmacological inhibition of the adenosinergic signals may counteract some of the effects mediated by an hypoxic environment, contributing to disrupt the leukemic niche and to restore the immune system. Disclosures Gaidano: Celgene: Research Funding; MorphoSys; Roche; Novartis; GlaxoSmithKline; Amgen; Janssen; Karyopharm: Honoraria, Other: Advisory boards.

Description: BACKGROUND: Tumor cell survival critically depends on heterotypic communications with non-malignant cells in the microenvironment. Most of these signals converge on the activation of the transcription factor NF-κB that regulates complex cellular functions, including apoptosis, cell survival and proliferation. Even if NF-kB is constitutively active in most malignancies, including chronic lymphocytic leukemia (CLL), and plays a major role in tumorigenesis, there are no currently approved drugs to target it. IT901 has been recently reported as a novel NF-kB inhibitor, showing efficacy in a non-tumor context1. AIM OF THE WORK: The aim of this work is to test the efficacy of IT901 in CLL and in its more aggressive transformation, Richter syndrome (RS), which represents an unmet therapeutic need. The molecular mechanisms of action of IT901 in leukemic cells are studied, alongside its effects on cells belonging to CLL microenvironment. RESULTS: IT901 induces apoptosis in primary leukemic cells in a dose- and time-dependent manner, showing significant efficacy after 24h of treatment. The apoptotic response is independent of the prognostic subgroup. Conversely, IT901 has minimal impact upon normal B cells. Treatment of CLL cells with IT901 interferes with NF-kB transcriptional activity, resulting in a diminished binding of both p50 and p65 to DNA. Moreover, biochemical analyses indicate a diminished expression of these subunits in the nucleus, as well as of the whole NF-kB complex in the cytoplasm. At the molecular level, compromised expression of NF-kB triggers activation of the Caspase-3 apoptotic pathway, with increased expression of pro-apoptotic proteins (e.g., Bim), paralleled by a diminished expression of the anti-apoptotic ones (e.g., XIAP). Concomitantly, a prominent increase in mitochondrial ROS is evident, providing a link between IT901 effects and induction of apoptosis. Recent data reported the involvement of NF-kB as a transcriptional controller of metabolic pathways promoting oxidative phosphorylation in cancer cells. In line with NF-kB constitutive activation in CLL, dynamic measurement of the energetic profile, indicates a reliance on oxidative phosphorylation, with limited glycolytic capacity. After IT901 treatment, there is a dramatic drop in mitochondrial respiration, with compromised ATP production and a net increase in proton leak, suggesting that primary CLL cells are trying to compensate impaired respiration by shifting to glycolysis. This metabolic response is mediated at the transcriptional levels, as IT901 induces a down-modulation of the genes involved in mitochondrial respiration (e.g., ATP5A1) and a concomitant up-modulation of the ones involved in glucose uptake and lactate transport (e.g., GLUT1). The CLL microenvironment is critical for disease progression and for providing protection from drug-induced apoptosis. Therefore it is important to consider the effects of novel drugs also on non-neoplastic bystander elements. Nurse-like cells (NLC) are a population of monocyte-derived activated macrophages that nurtures CLL cells via soluble and cell contact dependent mechanisms. These interactions are known to activate NF-kB signaling in both partners. Consistently, IT901 inhibited nuclear localization of the p65 subunit in NLC and shifted their polarization towards an M1-phenotype. These results are confirmed using a xenograft model. The Mec-1 cell line was injected into NSG mice and left to engraft for 2 weeks before beginning treatment. Animals treated with IT901 are characterized by decreased tumor growth and leukemic cells diffusion compared to controls, as shown by a diminished number of leukemic cells in kidneys, liver and spleen. Finally, IT901 shows promising effects in a small cohort of leukemic cells obtained from RS patients, inducing significant apoptosis by interfering with the expression and nuclear localization of NF-kB. CONCLUSIONS: Altogether, these results indicate that IT901 blocks NF-kB transcriptional activity. This effect is followed by rapid and marked decrease in genes supporting oxidative phosphorylation, causing mitochondrial damage, ROS release and induction of intrinsic apoptosis. Moreover, IT901 interrupts the support that CLL obtains from the microenvironment. Thus, targeting NF-kB by means of IT901 may be effective for CLL, and possibly even RS patients. 1. Y. Shono et al., Cancer Res76, 377 (Jan 15, 2016). Disclosures Furman: Genentech: Consultancy; Janssen: Consultancy; Abbvie: Consultancy, Honoraria; Gilead Sciences: Consultancy; Pharmacyclics: Consultancy, Speakers Bureau.

Description: The co-occurrence of myeloproliferative (MPN) and lymphoproliferative neoplasms (LPN) is rare and many publications have been limited to small case reports. Others have involved a considerable number of patients, but the coexistence remains underreported and inadequately studied. A recent retrospective review reported that a MPN patients have a 2.8-fold higher relative risk of developing LPN. A database developed at Weill Cornell Medicine (WCM) was queried for patients with ≥3 visits between 1998-2018 with a diagnostic code for a MPN and lymphoma or myeloma subtype. Patients identified were verified to ensure that study inclusion criteria were satisfied. Observed co-occurrence was compared to nation-wide reported prevalence. Demographic and clinical details of 24 patients with a MPN and LPN were recorded (Table 1). The ratio of males to females was 1.7. Essential thrombocythemia and polycythemia vera, and chronic lymphocytic leukemia (CLL) were the leading MPN and LPN subtypes, respectively. Patients were assigned to risk or staging categories at diagnosis based on subtype-specific criteria (Table 2). Median values for diagnostic bone marrow biopsy findings in 14 patients were 2% [0-5] for myeloblasts and 80% [15-100] for cellularity. Additionally, 10 patients had evaluated reticulin fibrosis: 5 (50.0%) presented as MF-0, 4 (40.0%) as MF-1, and 1 (10.0%) as MF-2. Progression to myelofibrosis was confirmed by morphology in 1 (4.2%) patient 10.1 years after a polycythemia vera diagnosis and 5.4 years after a diffuse large B-cell lymphoma (DLBCL) diagnosis. Progression to acute myeloid leukemia was confirmed by morphology in 1 (4.2%) patient 2.4 years after a chronic myelomonocytic leukemia diagnosis and 1.2 years after a smoldering myeloma (SM) diagnosis. Interphase fluorescence in situ hybridization (iFISH) detected cytogenetic abnormalities in 5/8 (62.5%) CLL patients: 2/5 (40.0%) and 5/5 (100.0%) patients harbored deletions in trisomy 12 and 13q14, respectively. Immunoglobulin heavy chain variable region gene (IGVH) status was unmutated in 2 (25.0%) patients. One (12.5%) patient was CD38+ and 2/6 (33.0%) patients were ZAP-70+. At diagnosis, all 8 patients presented with early stage disease (Rai stage 0-II). Based on the CLL-specific international prognostic index (IPI), 3/8 (37.5%) and 5/8 (62.5%) presented as low-risk and intermediate-risk, respectively. Of the 6 lymphoma patients: 5 (83.0%) patients presented with Ann Arbor stage-IV disease at diagnosis. Four (66.7%) patients presented as low/intermediate-risk, and 2 (33.3%) presented as high-risk based on disease-specific IPIs. One patient presented with -17p by iFISH. All 4 patients that were evaluated for Ki-67 had moderate/high expression. Of the 7 multiple myeloma (MM) patients, 6 (85.7%) presented as stage 1 and 1 (14.3%) as stage 3. Of the 3 SM patients, all 3 presented as low risk [12]. In addition, these patients were categorized as IgG-K (4; 40.0%), IgG-L (2; 20.0%), IgA-K (1; 10.0%), IgA-L (1; 10.0%), IgM (1; 10.0%), and biclonal IgG-L/IgA-L (1; 10.0%) [13]. Mutation statuses were identified by commercially tested myeloid or lymphoid molecular panels. As expected in this MPN subtype distribution, 11 (45.8%) are JAK2+, 2 (8.3%) are MPL+, 1 (4.2%) is BCR-ABL+, and 1 (4.2%) is CALR+ (Table 3). The risk of a co-occurrent MPN and LPN is higher than expected if they are mutually exclusive (Table 4A-4B, 5). Of interest, 13 (54.2%) patients were diagnosed with a MPN 11.8±18.8 years prior to a LPN; conversely, 11 (45.9%) were diagnosed with a LPN 6.5±6.2 years prior to a MPN. In addition, MPN therapy was started 2.0±2.3 years after a MPN diagnosis, and LPN therapy was started 2.6±4.0 years after a LPN diagnosis. A review of survival analysis requires larger subtype populations since the degree of survival can vary greatly, but it has been reported that patients with a MPN or LPN have significantly reduced life expectancy when compared to the general population. Median follow-up for our patient is 8.2 years (1.5-28.0) with 17/24 (70.8%) patients still being actively followed at our institution, 6 (25.0%) are been lost to follow-up, and 1 (4.2%) is deceased. The significant prevalence of these hematologic malignancies in combination emphasizes the importance of performing a bone marrow biopsy, which we espouse at our institution, cytogenetic analysis, and myeloid and lymphoid molecular testing to identify mutations. Disclosures Furman: Loxo Oncology: Consultancy; Gilead: Consultancy; Verastem: Consultancy; Acerta: Consultancy, Research Funding; TG Therapeutics: Consultancy; Incyte: Consultancy, Other: DSMB; Pharmacyclics LLC, an AbbVie Company: Consultancy; Genentech: Consultancy; Sunesis: Consultancy; Janssen: Consultancy; AbbVie: Consultancy. Niesvizky:Amgen Inc.: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Takeda: Consultancy, Research Funding. Ritchie:Bristol-Myers Squibb: Research Funding; Novartis: Consultancy, Other: Travel, Accommodations, Expenses, Research Funding, Speakers Bureau; Astellas Pharma: Research Funding; NS Pharma: Research Funding; Celgene: Consultancy, Other: Travel, Accommodations, Expenses, Speakers Bureau; Pfizer: Consultancy, Research Funding; Incyte: Consultancy, Speakers Bureau; ARIAD Pharmaceuticals: Speakers Bureau.

Description: Background: While CLL is commonly diagnosed in older patients, there are ~15% of patients diagnosed at ages younger than 50. Several past studies have investigated differences in clinical parameters and treatment outcomes in younger patients with CLL, including a shorter time to first treatment (TTFT) among younger patients (Parikh et al. 2014). However, few studies have reported on the genetic mutational differences between younger and older cohorts. To bridge this gap, we investigated the mutational landscape between younger and older patients and evaluated the clinical outcome TTFT, hypothesizing that our younger cohort of patients would associate with higher risk lesions and behave more aggressively. Methods: We conducted a single center retrospective database review of 557 patients diagnosed with CLL from 1980 to 2019 who underwent whole exome profiling between 2015 to 2019 with a lymphoid specific 75-gene next generation sequencing (NGS) panel (Genoptix Inc). A Pearson's chi-square test was used to compare categorical variables between groups and a Wilcoxon rank sum test was used to compare medians. The TTFT was estimated using Kaplan-Meier methods, and the difference between groups was compared using the log-rank test. Multivariate regression using a Cox proportional hazards model was used to compare TTFT between groups independent of well-accepted clinical risk factors for treatment initiation. Results: Of the 557 patients who underwent NGS testing, 92 (16.5%) were younger than 50 years old with a median age of 44.9 years old compared to a median age of 62.7 years old in the 465 (83.5%) patients older than 50 years old. There was no difference between the two groups with regards to previous treatment prior to NGS testing with 29.2% in the older patients and 26.1% in the younger patients having previously been treated (p=0.63). The median time from CLL diagnosis to initial NGS testing was 5.2 years in the younger cohort vs. 3.2 years in the older cohort (p=0.04). There were no differences in baseline prognostic factors between younger and older patients, including Rai stage, IGVH status, CD38 positivity, ZAP70 expression, and cytogenetic abnormalities. We found a lower frequency of TP53 mutations in younger compared to older patients (6.5% vs 15.7%, p=0.03) but otherwise found no differences in any other genetic mutations between the two groups, including NOTCH1, FAT1, ATM, and SF3B1 (Table 1). There was a longer TTFT in younger patients with a median TTFT of 7.61 years compared to 4.42 years in older patients (p=

Description: Introduction. Recent research in lymphoma has resulted in better outcomes for clinical trial populations. Population studies have suggested that some real-world patients (pts) have not benefited. We hypothesized that one reason for this discrepancy is the difference between trial participants and real-world pts. We aimed to: 1) Compare demographics and baseline clinical characteristics of real-world and clinical trial pts receiving first-line therapy for diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), and mantle cell lymphoma (MCL); and 2) Compare demographics and baseline clinical characteristics of real-world DLBCL, FL, and MCL pts with clinical trial eligibility criteria. Methods. Using ClinicalTrials.gov, we identified all phase 2 and 3 clinical trials that opened between 2002-2017 and included pts with DLBCL, FL, MCL. Published trials that included front-line immunotherapy and chemotherapy were selected, and eligibility criteria recorded. We reviewed publications and recorded pt numbers and characteristics. Using the Weill Cornell Medicine (WCM) Lymphoma Database, an IRB-approved, prospective cohort which started in 2010, we identified all pts diagnosed with DLBCL, FL, and MCL and recorded baseline characteristics. Descriptive statistics were used to describe clinical trial eligibility and pt characteristics. Fisher's exact test was used to compare pt characteristics. Results. We identified 642 phase 2 and 3 trials on Clinicaltrials.gov, 37 of which met predefined criteria. The most frequent exclusion criteria were HIV infection (n=33), pregnancy (n=25), HBV infection (n=21), history of non-lymphoma cancer (n=19), ECOG〉2 (n=16), HCV infection (n=16), serum creatinine 〉2 mg/dL or 〉2x ULN (n=15), active infection (n=12), history of MI (n=11), serum bilirubin 〉2 mg/dL or 〉2x ULN (n=7), congestive heart failure (n=4), hemoglobin (Hb)

Description: Background The B cell receptor (BCR) is a signaling complex composed of surface immunoglobulin and heterodimer subunits, Igα (CD79a) and Igβ (CD79b) (Sanchez, et al. 1993). Chronic lymphocytic leukemia (CLL) demonstrates dim surface staining of CD79b compared to normal B cells or other B cell malignancies, in part due to overexpression of a splice variant that lacks coding for the extracellular domain (Alfarano, et al. 1999; Cabezudo, et al. 1999). Aggressive lymphomas, like diffuse large B cell lymphomas of non-germinal center origin (DLBCL-ABC), overexpress surface CD79b and can harbor gain of function mutations (Schmitz, et al. 2018). Richter's transformation (RT), a complication of CLL is defined by transformation to a DLBCL-ABC subtype most commonly. Upon transformation outcomes are poor and survival is short with standard therapeutic approaches. Polatuzumab vedotin (Pv), an antibody drug conjugate, targets CD79b on the surface and has obtained FDA approval for relapsed DLBCL in combination with bendamustine and rituximab. Targeting CD79b may represent an attractive therapeutic strategy for patients (pts) with RT. To this end we sought to characterize CD79b expression in RT. Methods Pts with CLL or RT and available paraffin embedded tissue blocks were identified in coordination with Weill Cornell Medicine's (WCM) pathology department. Clone AT107-2 (Bio-Rad, USA) which targets an intracellular epitope was used to stain for CD79b in formalin fixed paraffin embedded (FFPE) tissue sections after optimization following institutional staining procedures. CD79b was classified as either positive (pos) or negative (neg) based on staining pattern and intensity as deemed by a board certified hematopathologist. RT pt derived xenografts (RT-PDXs) were assessed for surface expression of CD79b via flow cytometry. Nonpermabilized cells derived from RT-PDXs were stained using an anti-human CD79b-FITC conjugated antibody (clone CD3-1, Southern Biotech, USA). Mean fluorescence intensity (MFI) was established. RNA seq data was obtained from 2 of 3 RT-PDX models and has been reported previously (Vaisitti, et al. 2018). CD79b transcripts per million (TPM) were analyzed and compared to that of normal lymph node (LN) tissue deposited in the Human Protein Atlas RNA Seq database (HPA-RNA Seq). GraphPad Prism 8.0 was used to perform statistical analysis. Results Nineteen pts with RT and 5 pts with CLL were identified for the study. Median age at diagnosis of the 19 RT pts was 71 years compared to 67 years for the 5 CLL pts. Five RT pts (26%) were treatment naïve (TN) at time of RT. Ten (53%) RT pts transformed on targeted therapy, 6 on BTK inhibitors, 2 on IMiD based therapy, 2 on venetoclax. CD79b stained pos for 16 RT pts (84%) and all 5 (100%) CLL pts. We were not able to identify any correlations between CD79b expression due to low numbers of neg cases. Surface expression of CD79b was evaluated on RT-PDX models from different passages and found to be pos in all 3 models with a median percentage of CD79b+ cells of 45.9% (range 34.6-76%). The median MFI was 2028.5 (range MFI 860-4289). Two of the 3 three models had bimodal populations of cells (pos and neg) whereas the third model was more uniformly pos. RNA seq data from 2 RT-PDX models was available and compared to RNA-seq data from normal LN tissue deposited in the HPA-RNA Seq database. The mean TPM of CD79b for RT-PDX cases was 837.5 compared to 311.5 for normal LN tissue, p=0.028. Conclusion CD79b expression was pos in 84% of FFPE primary RT specimens evaluated. We were able to confirm extracellular CD79b expression with flow cytometry in all 3 RT-PDX models with a median MFI of 2028.5. Surface expression was found to be bimodal in 2 models and uniformly pos in 1 model suggesting tumor heterogeneity. Rna-seq data from RT-PDX models demonstrated higher TPM values in RT-PDX samples compared to normal LN tissue. We conclude that RT expresses CD79b at sufficient levels despite deriving from a CLL cell that historically has demonstrated low surface CD79b expression. Further studies will be undertaken characterizing pos and neg cellular populations focusing on mechanisms of expression and potential differences in splice variant expression. Disclosures Allan: Pharmacyclics LLC, an AbbVie company: Consultancy; Verastem Oncology, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy; Sunesis Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Acerta Pharma: Consultancy; Janssen: Consultancy, Honoraria; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees. Vaisitti:Verastem Inc: Research Funding; VelosBio Inc.: Research Funding. Joyce:Genentech: Employment. Schulz:Genentech, Inc.: Employment; Roche: Equity Ownership. Deaglio:Verastem Inc: Research Funding; iTeos Therapeutics: Research Funding; VelosBio Inc.: Research Funding. Furman:Genentech: Consultancy.