ALBERT

Description: Background: Patients (pts) with R/R aggressive large B cell NHL who fail first-line therapy with immunochemotherapy and are ineligible for high-dose chemotherapy and hematopoietic stem cell transplantation (HSCT) have a poor prognosis. Available treatment options include platinum/gemcitabine-based or bendamustine-based regimens in combination with rituximab, with or without radiotherapy, or clinical trials. However, long-term outcomes remain poor due to lack of a curative option. Liso-cel is an investigational, anti-CD19, defined composition, 4-1BB CAR T cell product administered at target doses of CD4+ and CD8+ CAR T cells. In the ongoing TRANSCEND NHL 001 study of liso-cel as third- or later-line treatment for pts with R/R large B cell NHL, preliminary data showed high overall response rates with a low incidence of grade ≥3 cytokine release syndrome (CRS) and neurological events (NEs) (Abramson et al, ASCO 2018). The open-label, phase 2 PILOT study is assessing the safety and efficacy of liso-cel as second-line therapy in TNE pts (NCT03483103). PILOT is the first study evaluating CAR T cell therapy focusing on this pt population. Methods: Eligible pts had R/R large B cell NHL (diffuse large B cell lymphoma [DLBCL], not otherwise specified [NOS], de novo or transformed indolent NHL, high-grade lymphoma with MYC and BCL2 and/or BCL6 [double/triple-hit lymphoma], or follicular lymphoma (FL) grade 3B) and had received only 1 prior line of immunochemotherapy containing an anthracycline and a CD20-targeted agent (eg, R-CHOP). Pts had to be deemed ineligible for high-dose chemotherapy followed by HSCT by meeting at least 1 of the following TNE criteria while still fulfilling the criteria for CAR T cell therapy: age ≥70 years, ECOG PS of 2, and/or impaired pulmonary (DLCO ≤60% but SaO2 ≥92% on room air and CTCAE ≤1 dyspnea), cardiac (LVEF ≥40% and 30 and 2 and ≤5 ×ULN). Liso-cel was administered at a target dose of 100×106 CAR+ T cells after lymphodepletion (LD) with fludarabine/cyclophosphamide for 3 days. Pts could be treated as outpatients at the investigator's discretion. Results: At data cutoff, 10 pts had been leukapheresed, and 9 pts had LD followed by liso-cel infusion; 1 pt is awaiting liso-cel treatment. Liso-cel was manufactured successfully in all pts. Five pts were infused and monitored as outpatients. Median age was 71 (range, 64-79) years; 5 pts were male. Histology included DLBCL NOS (n=7) and transformed FL (n=2); 2 pts had triple-hit, one of whom had transformed from FL. Five pts had relapsed from, and 4 pts had disease refractory to, prior therapy. Median SPD and LDH were 26.6 cm2 and 201 U/L, respectively. Four pts had high tumor burden with SPD ≥50 cm2 (n=4) and/or LDH ≥500 U/L (n=1). The median Hematopoietic Cell Transplantation Comorbidity Index (HCT-CI) score was 3 (range, 0-3). Six pts had 1 or more treatment-emergent adverse events (TEAEs) grade ≥3, which were primarily cytopenias. Three pts had prolonged grade ≥3 cytopenias at Day 29. Two pts had infections of any grade; no pts had grade ≥3 infections. No pts had CRS or NEs, and no pts received tocilizumab, corticosteroids, or vasopressors. There were no cases of macrophage activation syndrome, tumor lysis syndrome, infusion reactions, or grade 5 TEAEs. Among the 5 pts treated and monitored as outpatients, none were admitted to hospital for adverse events within the first 29 days post liso-cel infusion. All 9 pts achieved an objective response. Four pts achieved complete response; all are ongoing. Five pts achieved partial response (PR), with 2 PRs ongoing. Results were similar in inpatient vs outpatient pts. Median follow-up was 3.5 months. Median (range) time to peak CAR T cell expansion was 10 (7-21) days. Conclusions: These preliminary safety and efficacy data from the ongoing phase 2 PILOT study suggest that liso-cel can be successfully administered, including in the outpatient setting, as second-line therapy in pts with R/R aggressive B cell NHL who were ineligible for high-dose chemotherapy and HSCT by prespecified criteria. Updated safety and efficacy data with longer follow-up will be presented. Disclosures Sehgal: Kite/Gilead: Research Funding; Merck: Research Funding; Juno/Celgene: Research Funding. Pribble:Celgene/Juno: Employment. Wang:Celgene Corporation: Employment. Thorpe:Juno Therapeutics, a Celgene Company: Employment, Equity Ownership. Hildebrandt:Axim Biotechnologies: Equity Ownership; Abbvie: Equity Ownership; GW Pharmaceuticals: Equity Ownership; Endocyte: Equity Ownership; Clovis Oncology: Equity Ownership; Kite Pharma: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Other; CVS Health: Equity Ownership; Celgene: Equity Ownership; Axim Biotechnologies: Equity Ownership; Pharmacyclics: Research Funding; Sangamo: Equity Ownership; Cellectis: Equity Ownership; Bluebird Bio: Equity Ownership; Bristol-Myers-Squibb: Equity Ownership; crispr therapeutics: Equity Ownership; IDEXX laboratories: Equity Ownership; Johnson & Johnson: Equity Ownership; Pfizer: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Other: Travel; Procter & Gamble: Equity Ownership; Vertex: Equity Ownership; Scotts-Miracle: Equity Ownership; Takeda: Research Funding; Bayer: Equity Ownership; Astellas: Other: Travel; Kite Pharma: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Other: Travel; Novartis: Equity Ownership; Aetna: Equity Ownership; Juno Therapeutics: Equity Ownership; Cardinal Health: Equity Ownership; Novartis: Equity Ownership; Insys Therapeutics: Equity Ownership; Incyte: Membership on an entity's Board of Directors or advisory committees, Other: Travel; Jazz Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Research Funding; Immunomedics: Equity Ownership.

Description: Experimental and clinical data suggest that acute graft vs. host disease (aGVHD) after allogeneic (allo-) stem cell transplantation (SCT) predominantly involves a Th1-type cytokine response. Paradoxically, the production of Interleukin 13 (IL-13), a typical Th2 cytokine, by donor T cells responding to host antigen in vitro was recently shown to correlate with the severity of clinical aGVHD. We used a well-established murine SCT model (BALB/c → B6) and mice deficient in IL-13 to more clearly investigate the role of IL-13 produced by donor cells in the pathogenesis of GVHD. In our first set of experiments, B6, BALB/c IL-13+/+ and BALB/c IL-13−/− T cells were stimulated with B6 splenic dendritic cells. BALB/c IL-13+/+ and IL-13−/− T cells proliferated equally to alloantigens (123718±9038 vs.100565±3083 cpm) compared to syngeneic controls (2411±349 cpm). In addition, IL-13+/+ T cells produced significant amounts of IL-13 (1882.5±301.9 pg/ml), whereas IL-13 levels in wells with IL-13−/− T cells were very low (37.7±2.1 pg/ml) and did not differ from syngeneic controls (52.9±7.4 pg/ml). Next, lethally irradiated B6 mice received bone marrow and T cells from either syngeneic B6, or allogeneic BALB/c IL-13+/+ or BALB/c IL-13−/− donors and serum cytokine levels were determined on day +7. As shown in table 1, serum levels of IL-13, IL-5, IFNγ and TNFa were all elevated in mice receiving allo-SCT from IL-13+/+ donors compared to syngeneic controls. By contrast, analysis of sera from IL-13−/− SCT recipients revealed significant reductions in IL-13 and IL-5 levels, no change in IFNγ and a significant increase in TNFa levels compared to allo controls. Subsequent experiments revealed that the altered cytokine milieu observed early after allo-SCT correlated with enhanced GVHD; day 100 survival in allo-recipients of IL13−/− SCT was significantly decreased when compared to mice transplanted with IL-13+/+ donor cells (table 1) although GVHD of the gut (table 1) and liver (data not shown) did not differ in animals surviving at day +42. In summary our data demonstrate that donor T cell production of IL-13 does not predict the severity of GVHD and may instead have a protective effect on mortality from GVHD in this system. The decrease in survival observed in recipients of IL-13−/− donor cells may be explained by 1) the significant decrease in Th2 cytokines early after SCT, 2) loss of the strong immuno-modulatory effects of IL-13 on macrophage function, and 3) the associated increase in TNFa levels observed in these animals. The previously described correlation between the in vitro production of IL-13 by donor T cells and clinical aGVHD may therefore reflect the overall activation status of these T cells rather than a direct functional link to GVHD pathophysiology. Table 1: Serum cytokines (pg/ml) 7 days after SCT IL-13 IL-5 IFN γ α TNF survival (day 100) gut pathology (day 42) (** p〈 0.01; * p 〈 0.05; ND = not detectable) syngeneic 28.0±16.9 32.1±7.9 ND 2.2±1.5 100% 15.3±3.2 allogeneic wt 161.2±29.0 115.0±21.3 2059±320 38.5±5.1 40% 26.0±1.1 allogeneic IL-13−/− 13.7±4.8** 53.5±9.4* 2042±313 70.5±11.0* 0% 26.2±1.2

Description: Acute graft versus host disease (aGVHD) is the major complication of allogeneic stem cell transplantation (allo-SCT) and limits the utility of this treatment strategy. The pathophysiology of aGVHD involves injury to host tissues by inflammatory cytokines and donor-derived cellular effectors, the recruitment of which is likely mediated by chemokine receptor: ligand interactions. CCR1 is expressed on various cell types such as T cells, monocytes and macrophages and binds to a group of CC chemokines that includes RANTES (CCL5) and Mip-1a (CCL3). In light of the previously described role for both donor T cells and monocytes in the development of aGVHD, we tested the hypothesis that CCR1 expression on donor leukocytes contributes to systemic and target organ inflammation that occurs in this setting by using a well established murine SCT model (B6→B6D2F1) and mutant mice deficient in CCR1. Lethally (1100cGy) irradiated B6D2F1 mice received SCT either from syngeneic (B6D2F1) or allogeneic (B6) CCR1+/+ or CCR1−/− donors. The severity of GVHD was assessed after SCT by survival and a clinical scoring system that incorporates changes in weight loss, fur texture, skin integrity, mobility and posture. As expected, syngeneic SCT recipients all survived and where indistinguishable from naïve, untransplanted controls, whereas animals receiving allo-SCT from CCR1+/+ donors developed significant GVHD and only 50% of animals survived by day 35. By contrast, allo-SCT with CCR1−/− donor cells resulted in significantly improved survival (92% vs. 50%) and less severe clinical GVHD (1.0±0.3 vs. 3.0±0.5) compared to allo-CCR1+/+ controls. In addition, serum TNFa levels were significantly decreased by day +7 following CCR1−/− SCT (4.7±2.7 vs. 55.3±14.4 pg/ml) and correlated with a significant reduction in intestinal histopathology both on day 7 (16.3±1.0 vs. 21.5±0.9) and on day 14 (15.8±1.8 vs. 23.8±1.0). GVHD injury to liver and skin was mild at these time points and did not differ between allo groups. Next we investigated the impact of CCR1 expression on allo-specific T cell responses in vivo and found that by day +7 after SCT both splenic T cell expansion (3.7±0.4 vs. 9.6±0.9 x 106 cells) and serum IFNγ levels (4561±559 vs. 10028±681 pg/ml) were significantly lower when CCR1 was absent on donor cells. In summary, we describe a heretofore unknown role for CCR1 on donor leukocytes in the development of aGVHD. The improvement in systemic and target organ disease observed after CCR1−/− SCT may be attributed to 1) alterations in leukocyte recruitment to the intestinal tract resulting in improved intestinal integrity, reduced translocation of endotoxin and decreased TNFa production and 2) modulation of donor T cell responses to host allo-antigens. Experiments are ongoing to determine whether strategies targeting CCR1 signalling can be exploited to prevent GVHD but maintain GVL effects and thereby improve overall survival after allo-SCT.

Description: Background: Historically, Kentucky has had one of the highest rates of cancer mortality in USA. In non-hematologic malignancy, the Appalachian region of the eastern United States is also associated with poor outcomes, however, the relationship with hematologic malignancy is poorly understood. We aim to study the disparities of Plasma Cell Neoplasms (PCN) in this region utilizing the Surveillance, Epidemiology, and End Results Program (SEER) database. Methods: We identified patients with PCN (multiple myeloma [MM], solitary plasmacytomas [PC], and plasma cell leukemia [PCL]) from the SEER database between 2000-2015. Data obtained included demographics, state, residence in an Appalachian region, rural/urban continuum code, median annual household income, and overall survival (OS) outcomes. Kentucky and Georgia are the only states that report to SEER which have populations from Appalachia. Therefore, patients were classified into 5 groups: Appalachia/Kentucky, non-Appalachia/Kentucky, Appalachia/Georgia, non-Appalachia/Georgia, and other (non-Appalachian) states. We used Kaplan-Meier & Cox regression to analyze survival outcomes. Income was analyzed as a continuous variable. Variables with a p value 〈 0.1 in univariate analysis were included in a stepwise multivariate Cox proportional hazard ratio (HR) model. Results A total of 68,627 patients were identified and included in the study (5.5% [n=3806] in Kentucky and 94.5% in other states). 3028 were identified as Appalachian (1969 in Georgia and 1059 in Kentucky). Baseline characteristics were comparable between Kentucky and other states except for income and rural/urban code. Percentages of patients with an income of

Description: Background: To date, CAR T cell therapy has generally been limited to inpatient treatment at university medical centers. However, most patients (pts) in the US with R/R diffuse large B cell lymphoma receive therapy at non-university medical centers where outpatient delivery of cancer therapy is common. Infusion and management of CAR T cell therapies in the outpatient setting may lead to wider utilization in community/non-university centers and improve access. In TRANSCEND NHL 001, lisocabtagene maraleucel (liso-cel), an investigational, anti-CD19, defined composition, 4-1BB, CAR T cell product administered at target doses of CD4+ and CD8+ CAR T cells, demonstrated efficacy as ≥3rd-line therapy in pts with R/R large B cell NHL. With fewer than half of pts developing cytokine release syndrome (CRS) and/or neurological events (NE) and its delayed onset (median 5 and 10 days, respectively; Abramson, ASCO 2018; 7505) outpatient treatment was allowed with hospitalization at the first sign of fever or neurological symptoms. We report on pts with R/R large B cell NHL who were treated with liso-cel in the outpatient setting in TRANSCEND NHL 001 (NCT02631044) and in two phase 2 studies assessing the safety and efficacy of liso-cel, as ≥3rd-line therapy (OUTREACH; NCT03744676) or as therapy for 2nd-line transplant noneligible (TNE) pts (PILOT; NCT03483103). Methods: Eligible pts had R/R large B cell NHL, adequate organ function, and prior systemic chemoimmunotherapy (TRANSCEND and OUTREACH: ≥2 prior lines of therapy and ECOG PS ≤1; PILOT: 1 prior line of therapy and deemed TNE for autologous hematopoietic stem cell transplantation based on ECOG PS, organ function, and/or age). After lymphodepletion with fludarabine/cyclophosphamide, liso-cel was administered at 1 of 3 dose levels (DL) (DL1 = 50 × 106, DL2 = 100 × 106, DL3 = 150 × 106 total CAR+ T cells) in TRANSCEND and at DL2 in OUTREACH and PILOT. All studies allowed outpatient treatment at non-university (OUTREACH) or at both university and non-university medical centers (TRANSCEND, PILOT). Outpatient treatment required pts to have a caregiver for 30 days post-liso-cel infusion, receive safety-monitoring education (recognizing critical adverse events; eg, fever), and to stay within 1 h travel to the site of care. Outpatient treatment was at the discretion of the investigator. All sites had a multidisciplinary CAR T cell therapy team and standard operating procedures for outpatient administration and toxicity monitoring. CRS (Lee criteria, 2014) and NEs (defined as related to liso-cel; CTCAE criteria) were managed in the hospital. Results: At data cutoff, 37 pts across studies had received liso-cel on study Day 1 and were monitored as outpatients, including pts ≥65 yr old and those with high tumor burden. Patient characteristics are shown in the Table. The most frequent grade ≥3 treatment-emergent AEs were cytopenias (neutropenia 43%, anemia 30%, thrombocytopenia 14%). Sixteen pts had any grade CRS and 12 had any grade NE (19 pts had CRS and/or NE). Severe CRS and/or NE occurred in only 2 pts and were reversible (Table). Three pts received tocilizumab and corticosteroids and 4 pts received corticosteroids alone for CRS and/or NE. No pts received tocilizumab alone. Twenty-two of the 37 pts (59%) required hospitalization at any time; all pts were from TRANSCEND or OUTREACH. Three of those pts (8%) were admitted on study Day 3 or earlier, all for CRS; 1 patient required ICU-level care (length of stay, 3 days). Median (range) time to hospitalization post treatment was 5 (2‒22) days and median (range) length of stay was 6 (2‒23) days. Fifteen (41%) of the 37 pts, including all 5 pts from PILOT, were not admitted to hospital in the first 29 days post liso-cel infusion. Across all 3 studies, most pts achieved an objective response, including CR (Table). Median time to peak CAR+ T cell expansion in each study was 10 days (range: 3-21 in TRANSCEND; 7-10 in OUTREACH; 7-10 in PILOT). Conclusions: A subset of pts with R/R large B cell NHL were successfully treated with liso-cel and monitored for CAR T cell-related toxicity in the outpatient setting, including elderly pts and pts with high tumor burden. Severe CRS and NEs occurred with low incidence. The number of early hospitalizations was low, and 41% of pts did not require hospitalization in the first month post liso-cel infusion. Most pts (65%) achieved an objective response. Updated data with longer follow-up will be presented. Disclosures Bachier: Sanofi: Speakers Bureau; Viracyte: Consultancy; Kadmon Corporation, LLC: Consultancy. Palomba:Noble Insights: Consultancy; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Hemedicus: Speakers Bureau; Merck & Co Inc.: Consultancy; Seres Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; STRAXIMM: Membership on an entity's Board of Directors or advisory committees; Kite Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Evelo: Equity Ownership; MSK (IP for Juno and Seres): Patents & Royalties. Abramson:AbbVie Inc, Amgen Inc, Bayer HealthCare Pharmaceuticals, Celgene Corporation, EMD Serono Inc, Genentech, Gilead Sciences Inc, Janssen Biotech Inc, Juno Therapeutics, a Celgene Company, Karyopharm Therapeutics, Kite Pharma Inc, Merck, Novartis, Seattle Gen: Consultancy. Andreadis:Roche: Equity Ownership; Novartis: Research Funding; Celgene: Research Funding; Juno: Research Funding; Pharmacyclics: Research Funding; Merck: Research Funding; Kite: Consultancy; Genentech: Consultancy, Employment; Gilead: Consultancy; Jazz Pharmaceuticals: Consultancy. Sehgal:Juno/Celgene: Research Funding; Kite/Gilead: Research Funding; Merck: Research Funding. Hildebrandt:Juno Therapeutics: Equity Ownership; crispr therapeutics: Equity Ownership; CVS Health: Equity Ownership; Immunomedics: Equity Ownership; IDEXX laboratories: Equity Ownership; Pfizer: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Other: Travel; Cellectis: Equity Ownership; Clovis Oncology: Equity Ownership; Aetna: Equity Ownership; Bluebird Bio: Equity Ownership; Celgene: Equity Ownership; Abbvie: Equity Ownership; Cardinal Health: Equity Ownership; Johnson & Johnson: Equity Ownership; Insys Therapeutics: Equity Ownership; Axim Biotechnologies: Equity Ownership; Axim Biotechnologies: Equity Ownership; Novartis: Equity Ownership; Kite Pharma: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Other: Travel; Sangamo: Equity Ownership; Procter & Gamble: Equity Ownership; Vertex: Equity Ownership; Bristol-Myers-Squibb: Equity Ownership; Bayer: Equity Ownership; Scotts-Miracle: Equity Ownership; Incyte: Membership on an entity's Board of Directors or advisory committees, Other: Travel; Jazz Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Research Funding; Takeda: Research Funding; Pharmacyclics: Research Funding; Astellas: Other: Travel; Endocyte: Equity Ownership; GW Pharmaceuticals: Equity Ownership; Kite Pharma: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Other; Novartis: Equity Ownership. Siddiqi:PCYC: Consultancy, Research Funding, Speakers Bureau; AstraZeneca: Consultancy, Research Funding, Speakers Bureau; Janssen: Speakers Bureau; Seattle Genetics: Speakers Bureau; Kite, A Gilead Company: Research Funding; TG Therapeutics: Research Funding; Celgene: Research Funding; BeiGene: Research Funding; Juno Therapeutics: Consultancy, Other: travel support, Research Funding. Stevens:Astellas: Consultancy. Farazi:Juno Therapeutics/A Celgene Company: Employment. Kostic:Juno Therapeutics, a Celgene Company: Employment. Trede:Celgene Corporation: Employment, Equity Ownership. Wang:Celgene Corporation: Employment. Lymp:Celgene Corporation: Employment, Equity Ownership. Thelen:Celgene Corporation: Employment. Ogasawara:Celgene Corporation: Employment, Equity Ownership. Maloney:Juno Therapeutics: Honoraria, Patents & Royalties: patients pending , Research Funding; Celgene,Kite Pharma: Honoraria, Research Funding; A2 Biotherapeutics: Honoraria, Other: Stock options ; BioLine RX, Gilead,Genentech,Novartis: Honoraria.

Description: Key Points Over the last decade, allogeneic HCT has been increasingly administered in the United States to adults aged 70 and older with hematologic malignancies. Allogeneic transplant outcomes were reasonable; high comorbidity and ablative conditioning regimens were associated with inferior outcomes.

Description: Idiopathic pneumonia syndrome (IPS) is a major cause of mortality following allogeneic stem cell transplantation (allo-SCT). Clinical and experimental data support a role for conditioning-induced inflammation and alloreactive T-cell responses in IPS pathophysiology, but the mechanisms by which donor leukocytes are ultimately recruited to the lung are not fully understood. RANTES is a chemokine ligand that is up-regulated during inflammation and promotes the recruitment of T cells and macrophages to sites of tissue damage. Using a lethally irradiated murine SCT model (B6 → B6D2F1), we evaluated the role of donor leukocyte–derived RANTES in the development of IPS. Pulmonary mRNA and protein levels of RANTES were significantly elevated in allo-SCT recipients compared to syngeneic controls and were associated with enhanced mRNA expression of CCR5 and CCR1 and with inflammatory cell infiltration into the lung. Allo-SCT with RANTES-/- donor cells significantly decreased IPS and improved survival. Combinations of allogeneic wild-type or RANTES-/- bone marrow with wild-type or RANTES-/- T cells demonstrated that the expression of RANTES by donor T cells was critical to the development of lung injury after SCT. These data reveal that donor T cells can help regulate leukocyte recruitment to the lung after allo-SCT and provide a possible mechanism through which inflammation engendered by SCT conditioning regimens is linked to allo-specific T-cell responses during the development of IPS.

Description: B-cell Chronic Lymphocytic Leukemia (CLL) is the most common leukemia in the Western world, accounting for nearly one third of all leukemia cases. In CLL abnormal B-cells accumulate in the blood and lymphoid organs leading to serious immune dysfunction. This immune suppression is in part due to CLL-produced mediators that downregulate T-cell responses, such as the regulatory cytokine Interleukin-10 (IL-10). We previously found that eliminating T-cell IL-10 signaling enhanced their ability to control CLL growth in vivo. Therefore, we investigated the potential for IL-10 blockade to enhance the anti-tumor activity of CD8+ T-cells. In our studies we use human CLL cells as well as the Eμ-Tcl1 mouse model of CLL, in which the oncogene Tcl1 is expressed under the immunoglobulin VH promoter and µ-enhancer. IL-10 production by CLL cells depends on the transcription factor Sp1, and we found that the Sp1 inhibitor mithramycin (MTM) suppresses CLL IL-10 production. However, MTM is not well tolerated in vivo, so we synthesized novel, less toxic analogues of MTM to test for IL-10 suppression. One of these MTM analogues similarly suppresses mouse and human CLL IL-10 with little to no effect on effector T-cell cytokines and viability. Therefore, we treated mice with this analogue in the adoptive transfer model of Eμ-Tcl1, and later combined this with anti-PD-L1 checkpoint blockade to determine its effects on anti-tumor immunity. Here we show that this MTM analogue enhances the efficacy of anti-CLL T-cells in vivo by suppressing CLL IL-10 production, allowing for increased CD8+ T-cell proliferation, effector memory cell prevalence, and CD8+ interferon-γ (IFN-γ) production. Treatment slowed the growth of Eμ-TCL1 CLL cells in the spleen and blood and reduced the spread of CLL to the bone marrow. Furthermore, suppressing IL-10 in this manner improved responses to anti-PD-L1 treatment, decreasing the burden of CLL cells and the functionality of CD8+ T-cells in comparison to anti-PD-L1 alone. The overall number and frequency of CD8+ T-cells was higher in double treated mice, with more IFN-γ+ CD8+ cells, more effector memory cells, and fewer exhausted T-cells. This paradigm shifting approach is novel as current therapies for CLL do not target IL-10 and it may increase the efficacy of T-cell-based immunotherapies in human CLL. T-cell-based immunotherapies have experienced limited success in trials with CLL, and since there is no cure for this disease, our approach may provide a new avenue for combination therapies. Moreover, IL-10 blockade could be applicable to other B-cell malignancies and even solid tumors where T-cell suppression plays a significant role. Disclosures Hildebrandt: Axim Biotechnologies: Equity Ownership; Kite Pharma: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Other; Sangamo: Equity Ownership; Novartis: Equity Ownership; Axim Biotechnologies: Equity Ownership; Juno Therapeutics: Equity Ownership; Kite Pharma: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Other: Travel; Novartis: Equity Ownership; Insys Therapeutics: Equity Ownership; Abbvie: Equity Ownership; GW Pharmaceuticals: Equity Ownership; Cardinal Health: Equity Ownership; Immunomedics: Equity Ownership; Endocyte: Equity Ownership; Clovis Oncology: Equity Ownership; Cellectis: Equity Ownership; Aetna: Equity Ownership; CVS Health: Equity Ownership; Celgene: Equity Ownership; Bluebird Bio: Equity Ownership; Bristol-Myers-Squibb: Equity Ownership; crispr therapeutics: Equity Ownership; IDEXX laboratories: Equity Ownership; Johnson & Johnson: Equity Ownership; Pfizer: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Other: Travel; Procter & Gamble: Equity Ownership; Vertex: Equity Ownership; Bayer: Equity Ownership; Scotts-Miracle: Equity Ownership; Incyte: Membership on an entity's Board of Directors or advisory committees, Other: Travel; Jazz Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Research Funding; Takeda: Research Funding; Pharmacyclics: Research Funding; Astellas: Other: Travel.