Citations

Abstract Background Denintuzumab mafodotin (SGN-CD19A) is an antibody-drug conjugate (ADC) composed of a humanized anti-CD19 monoclonal antibody conjugated to the microtubule-disrupting agent monomethyl auristatin F (MMAF) via a maleimidocaproyl linker. CD19 is a B cell-specific marker that is expressed in nearly all patients (pts) with B-lineage acute leukemia or lymphoma. Methods A phase 1 dose-escalation study is ongoing to evaluate the safety, tolerability, pharmacokinetics, and antitumor activity of denintuzumab mafodotin in pts with relapsed or refractory (R/R) B-ALL, B-cell lymphoma (B-LBL), or Burkitt leukemia/lymphoma (NCT 01786096). Eligible pts are ≥1 year of age and are R/R to ≥1 prior systemic regimen; patients with Philadelphia chromosome-positive (Ph+) disease must have failed a 2nd-generation TKI. A modified continual reassessment method was used for dose allocation and maximum tolerated dose (MTD) estimation. The study evaluated 2 dosing schedules: first weekly (Days 1 and 8 of 21-day cycles) and then once every 3 weeks (q3wk). This report presents data from the adult subset of pts in the study (≥18 years). Results To date, 71 adult pts with R/R B-ALL (n=59), B-LBL (n=6) or Burkitt leukemia/lymphoma (n=6) have been treated; median age is 45 years (range 18−77). Pts received a median of 2 prior therapies (range 1−8); 20 pts (28%) had prior allogeneic stem cell transplant. On the weekly schedule (0.3−3 mg/kg), 40 pts received a median of 2 cycles (range 1−27); 2 pts remain on treatment. On the q3wk schedule (4−6 mg/kg), 31 pts received a median of 3 cycles (range 1−6); 4 pts remain on treatment. An MTD was identified at 5 mg/kg q3wk and was not reached with weekly dosing. Best clinical responses to date for pts with B-ALL are summarized below: Table 1.Response category per Cheson 2003Efficacy-evaluable adult pts with B-ALLweekly dosing, N=32 n (%)q3wk dosing, N=23 n (%)Complete remission (CR)6 (19)3 (13)CR with incomplete platelet recovery (CRp)−3 (13)CR with incomplete blood recovery (CRi)−2 (9)Partial remission (PR)1 (3)−Resistant disease with clinical benefit15 (47)12 (52)Resistant disease without clinical benefit2 (6)-Progression8 (25)3 (13)CRc (CR+CRi+CRp), % (95% CI)19% (95% CI 7, 36)35% (95% CI 16, 57) In the q3wk schedule, the CRc rate was similar at 4, 5, and 6 mg/kg. The median duration of response across schedules is currently 27 weeks (95% CI 7, −). Of 12 pts with CRc and available minimal residual disease (MRD) assessment, 7 were MRD negative. 3 patients with MRD-negative CRs have been in remission for >1 year, 2 of whom have been on continuous treatment for 19 and 22 months. In the subset of pts with Ph+ B-ALL, 4 of 8 pts achieved CR and 1 pt a PR. In 6 pts with Burkitt leukemia/lymphoma, 1 achieved a CR. In 6 pts with B-LBL, objective responses were 1 CR and 2 PR. The adverse event (AE) profiles were similar across both dosing schedules; the most frequently reported AEs were pyrexia (54%), nausea (52%), fatigue (51%), headache (44%), chills (38%), vomiting (37%), blurred vision (35%), and anemia (34%). Ocular symptoms and corneal exam findings consistent with superficial microcystic keratopathy were observed in 40 pts (56%); symptoms were less severe than the associated corneal exam findings. Keratopathy was managed with topical steroids and dose modifications, and improved/resolved within a median of ~3 wks (range 1-17) in pts with sufficient follow-up. ADC exposures increased with dose, and in leukemia patients, target-mediated disposition was observed that diminished with higher doses in the q3wk schedule. Post treatment, flow cytometry data demonstrate that unbound CD19 on peripheral blasts inversely correlates with ADC concentration in circulation, and is present in the majority of evaluable patients at the end of the q3wk cycle. Conclusions Denintuzumab mafodotin is generally well tolerated and demonstrates activity in heavily pretreated adult pts with B-ALL and B-lineage highly aggressive lymphomas, including durable MRD-negative responses. The results of this trial indicate that the q3wk schedule, with a CRc rate of 35% in B-ALL, warrants further clinical investigation. Based on the encouraging responses observed to date in Ph+ B-ALL (CRs in 4 of 8 pts), an expansion cohort of these pts is currently enrolling on the q3wk schedule. Disclosures Fathi: Exelexis: Research Funding; Agios: Membership on an entity's Board of Directors or advisory committees; Merck: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Ariad: Consultancy; Takeda Pharmaceuticals International Co.: Research Funding. Off Label Use: SGN-CD19A is an investigational agent being studied in patients with B-cell malignancies. SGN-CD19A is not approved for use.. Borate:Seattle Genetics: Research Funding; Genoptix: Consultancy; Alexion: Speakers Bureau; Gilead: Speakers Bureau; Novartis: Speakers Bureau; Amgen: Speakers Bureau. DeAngelo:Agios: Consultancy; Incyte: Consultancy; Celgene: Consultancy; Amgen: Consultancy; Pfizer: Consultancy; Bristol Myers Squibb: Consultancy; Ariad: Consultancy; Novartis: Consultancy. O'Brien:Seattle Genetics, Inc.: Research Funding. Trippett:OSI Pharmaceuticals: Research Funding; Seattle Genetics, Inc.: Research Funding. Shah:NCCN: Consultancy; SWOG: Consultancy; Seattle Genetics: Research Funding; Acetylon Pharmaceuticals, INC: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Speakers Bureau; Bayer: Honoraria; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Speakers Bureau; DeBartolo Institute for Personlaized Medicine: Research Funding; Rosetta Genomics: Research Funding; Plexus Communications: Honoraria; Spectrum: Speakers Bureau. Hale:Seattle Genetics, Inc.: Research Funding; Hyundai: Research Funding; V Foundation: Research Funding. Silverman:Seattle Genetics, Inc.: Research Funding. Pauly:Seattle Genetics, Inc.: Research Funding. Kim:Bayer: Consultancy; Seattle Genetics, Inc.: Consultancy, Research Funding; Eli Lilly: Consultancy. Kostic:Seattle Genetics, Inc.: Employment, Equity Ownership. Huang:Seattle Genetics, Inc.: Employment, Equity Ownership. Pan:Seattle Genetics, Inc.: Employment, Equity Ownership. Chen:Genentech: Consultancy, Speakers Bureau; Seattle Genetics, Inc.: Consultancy, Other: Travel expenses, Research Funding, Speakers Bureau; Millennium: Consultancy, Research Funding, Speakers Bureau.

Abstract Abstract 1554 T cells in the tumor microenvironment influence the biology of malignant cells in many hematologic malignancies, often through cytokine-mediated interactions. Recent studies involving healthy B cells and CD4+T cells identified an interplay between IL-6 and IL-21, whereby IL-6 increased IL-21 production by T cells, driving the differentiation and IL-6 secretion of nearby B cells. In addition to their known effects on healthy B cell function, IL-6 and IL-21 have also been implicated in the pathology of various lymphomas. In Waldenstrom's macroglobulinemia (WM), IL-6 is elevated in the bone marrow and is associated with increased IgM production. However, the function of IL-21 in the WM tumor microenvironment and its relationship to IL-6 is poorly understood. Our objective in this study was to characterize IL-21 production and function in WM and to examine the role of IL-6 and IL-21 in regulating interactions between malignant B cells and T cells in the tumor microenvironment. Immunohistochemistry revealed significant IL-21 staining in bone marrows of patients with WM (n=5), but the areas of infiltration by WM in the bone marrow sections appeared negative for IL-21 staining. To better understand the origin of IL-21 in in the tumor microenvironment, IL-21 expression was assessed by PCR in the CD19−CD138− fraction of cells remaining in patient bone marrow aspirates after positive selection for malignant B cells (n=5). IL-21 transcript was detected in 4/5 samples. CD19−CD138− cells activated with anti-CD3 and anti-CD28 antibodies expressed higher levels of IL-21 transcript and secreted significantly higher levels of IL-21 protein compared to unstimulated cells, suggesting that IL-21 in the WM bone marrow is derived from activated T cells. Intracellular expression of IL-21 protein was confirmed in CD4+ and CD8+ cells within the CD19−CD138− population using flow cytometry. Furthermore, dual staining of WM bone marrow sections with antibodies against IL-21 and CD3 or CD20 revealed co-staining of IL-21 with CD3+ T cells but not with CD20+ B cells. The response of WM B cells to T-cell derived IL-21 was then assessed in positively selected CD19+CD138+ WM B cells (n=5) and in the MWCL-1 cell line. Using flow cytometry, both the IL-21 receptor and the required common gamma chain subunit were detected on all patient samples as well as on MWCL-1 cells. Treatment of MWCL-1 cells with IL-21 (100 ng/mL) for 72 h increased proliferation by 35% (p<0.05) and IgM secretion by 80% (p<0.005). Similarly, in primary CD19+CD138+ WM cells (n=5), proliferation increased on average by 38% and IgM secretion by 71%. No apoptotic effects were associated with IL-21 in WM. Characterization of STAT activation in response to IL-21 revealed significant phosphorylation of STAT3 in both CD19+CD138+ WM cells and MWCL-1 cells and was associated with increases in BLIMP-1 and XBP-1 protein and decreases in PAX5. As STAT3 activation is known to regulate IL-6, we assessed the effect of IL-21 on B cell-mediated IL-6 secretion using ELISA. IL-21 significantly increased IL-6 secretion by both primary CD19+CD138+ WM cells (n=4) and MWCL-1 cells (87.9 +/− 10.9 ng/mL vs. 297.8 +/− 129.2 ng/mL, p<0.05). Treatment with IL-6 and IL-21 together had no additional effect over IL-21 alone on proliferation or IgM secretion in MWCL-1 cells, but culturing anti-CD3/anti-CD28-activated CD19−CD138−cells from WM bone marrows with IL-6 significantly increased IL-21 secretion (n=3). Overall, these data indicate that T-cell derived IL-21 significantly promotes growth and immunoglobulin production by malignant WM B cells and that subsequent IL-6 secretion by malignant B cells may enhance the secretion of IL-21 by T cells within the bone marrow microenvironment. Disclosures: No relevant conflicts of interest to declare.

Abstract Background: The incidence of secondary Acute Lymphoblastic leukemia (sALL) after a preceding first primary solid organ malignancy (1M) is not well defined. We undertook a Surveillance Epidemiology and End Results (SEER)-based analysis to describe the occurrence of sALL among adult patients with a history of common 1M's. We also evaluated differences in sALL survival on the basis of age, the site and extent of 1M, and for evidence of any underlying racial/ethnic disparity. Methods: The SEER-18 database (1973-2011) was interrogated for the current study. All confirmed cases of ALL (ICD-O-3 codes: 9811, 9812, 9814-18, 9826-28, 9835-37) in adult patients (age ≥18 years) were identified. De novo ALL vs. sALL was determined by using the SEER variable ‘First Malignant Primary Indicator'. 1M prior to the diagnosis of ALL was identified by merging all SEER databases together by patient ID number. Those with 1M stage of ‘in situ'; sALL cases reported <2 months after the diagnosis of 1M; and those with “unknown” information on 1M (n=471) were excluded. Standard race/ethnicity categories were used. Latency interval (time from diagnosis of 1M to sALL) was calculated for all patients. Overall survival (OS) was calculated as the interval from diagnosis to death, or censored at date of last contact, December 31st 2011, or 5 years after diagnosis, whichever came first. A proportional hazards Cox regression model was performed to evaluate the impact of sALL and latency on OS, adjusting for age at diagnosis, race/ethnicity, marital status, birthplace, SEER registry site, and year of diagnosis. All statistical tests were two-sided and utilized the SAS software (v9.4) with a two-sided significance level of 0.05. Results: A total of n=8,398 adult patients with primary ALL (1ALL) and n=414 with sALL were identified. Patient characteristics were significantly different between 1ALL & sALL (Table). Males comprised 49.8% of sALL patients as compared to 58% with 1ALL. Age at diagnosis of ALL was also significantly different, with 55.5% of sALL patients being ≥65 years as compared to 51.4% of 1ALL observed in the 18-44 years age group. Non-Whites comprised 27.3% of sALL and 40.4% of 1ALL, with Hispanics having the most differential distribution of 13.3% and 24.6%, respectively in the two groups. Distribution of sALL patients by latency from 1M is shown in Table. The majority of sALL patients had a diagnosis of local/regional (rather than advanced stage) 1M (Table). sALL patients had a significantly inferior OS when compared to 1ALL (HR 1.211, 95%CI 1.079-1.359) (Median OS 14 months vs. 18 months, Figure). sALL cases with longer latency interval (>5 year) appeared to have better median OS compared to shorter latency intervals, but this difference was not statistically significant (p=0.53). Conclusion: We have performed the largest population-based analysis identifying sALL after 1M, demonstrating that sALL patients are older and have significantly worse OS than 1ALL. We noted a lower relative incidence of sALL in Hispanics as compared with 1ALL, while the converse was true for Whites. Although detailed treatment data (specifically with respect to chemotherapeutic agents) is not available in SEER, it is possible that treatment for local/regional 1M - presumably adjuvant in nature - may be associated with the risk of sALL. Further analyses are required and are ongoing to confirm the relative incidence after specific 1M's, and the impact of both specific treatment modalities and the era of treatment for 1M on risk of developing sALL. Figure 1 Figure 1. Figure 2 Figure 2. Disclosures No relevant conflicts of interest to declare.

Abstract Background: Non-Hodgkin lymphomas (NHL) are increasing in incidence and are now the fifth most common tumor diagnosed each year in the United States. Most NHLs are of B-cell origin but the tumor tissue is variably infiltrated with T-cells. Our group has shown in diffuse B-cell large cell lymphoma, that a high number of intratumoral CD4+ T-cells predicts a better overall survival. It has been shown that recently-characterized CD4+CD25+ regulatory T-cells (Treg cells) played an important role in the mediation of anti-tumor immunity. However, there is no data on the role of intratumoral Treg cells in suppression of autologous infiltrating CD4+ T-cells in B-cell NHL. Goal: To investigate the effect of intratumoral Treg cells on the proliferation of tumor-infiltrating CD4+CD25- T-cells, to determine the underlying mechanism of the T-cell suppression, and evaluate the role that malignant B-cells may play in the recruitment of Treg cells to the site of B-cell NHL. Results: We identified a subset of CD4+CD25+ T-cells over-represented in biopsy specimens of B-cell NHL (these cells comprise 17% of cells in lymphoma biopsies, compared 7% of peripheral blood mononuclear cells, 12% of cells in inflammatory tonsil and 6% of cells in tumor free lymph nodes; p-value =0.001). These CD4+CD25+ T-cells are memory-like T-cells (CD45RO+ and CD45RA−) and express high levels of CTLA-4 and Foxp3 when compared to autologous tumor-infiltrating CD4+CD25- T-cells. Importantly, these CD4+CD25+ T-cells displayed the ability to suppress the proliferation and cytokine (IFN-g and IL-4) production of tumor-infiltrating CD4+CD25- T-cells in response to PHA stimulation. Treatment with anti-B7-H1 antibody or PD-1 fusion protein enhanced the proliferation of infiltrating CD4+CD25- T-cells when co-cultured with intratumoral CD4+CD25+ T-cells. Our results suggest that interaction between B7-H1 and PD-1 accounts for about 30% of intratumoral Treg cell-mediated inhibition of autologous infiltrating CD4+CD25- T-cells in tumor sites of B-cell NHL. Lastly, we found that CCL22 secreted by lymphoma B-cells is involved in the chemotaxis and migration of intratumoral CD4+CD25+ T-cells which express chemokine receptor CCR4, but not CCR8. Conclusion: Our results suggest that tumor microenvironmental CD4+CD25+ regulatory T-cells are important regulators of tumor immunity and that these cells are recruited to the area of lymphoma involvement by the malignant B-cells.

Abstract BACKGROUND Monocytes and macrophages (mo/mΦ) are a key part of the composition of peripheral blood (PB) and tissues and increased numbers of mo/mΦ have been associated with patient outcome in non-Hodgkin lymphoma (NHL). Because CD14 is abundantly expressed on the surface of human mo/mΦ, it is often used to identify or isolate human mo/mΦ, and immunosuppressive CD14+HLA-DRlow monocytes have been shown to be increased in the peripheral blood of NHL patients. However, we have previously shown that CD14 expression on mo/mΦ is substantially lower than CD68 expression suggesting that many CD68+ mo/mΦ are CD14 negative, especially in spleen and lymph node tissues. To characterize both CD14+ and CD14- mo/mΦ in PB and tissues, we isolated all mo/mΦ from B-cell NHL specimens and normal controls and assessed their phenotype and function. METHODS Human mo/mΦ were isolated by negative selection from PB and tissue biopsy specimens (B-cell NHL and normal tissues) using the immunomagnetic isolation (monocyte enrichment kit). Morphological and immunophenotypic characteristics of isolated mo/mΦ were determined by Giemsa stain and flow cytometry. Phagocytosis and migration assays were used to determine the function of isolated mo/mΦ. T cells were co-cultured with mo/mΦ and T cell proliferation was evaluated by CFSE staining and detected by flow cytometry. RESULTS Using a monocyte enrichment kit to isolate all mo/mΦ, the purity of isolated mo/mϕ was 85~99%, which was defined by the percentage of lineage-negative cells (i.e. cells without expression of CD3,CD19, CD20, and CD56). We found that these isolated mo/mΦ constituted 2 populations: a more frequent population of larger cells and a less common population of smaller cells. In contrast to PB, CD14 positive mo/mΦ constituted less than 40% of the tissue mo/mΦ from the isolated population. Furthermore, we found that the cell size from CD14+ mo/mΦ were larger than CD14- mo/mΦ. Using CD14 and SIRP-α, we could identify 3 populations of mo/mΦ: CD14+SIRP-αhigh, CD14-SIRP-αdim and CD14-SIRP-α- cells. CD14+SIRP-αhigh cells and CD14-SIRP-αdim cells typically constituted the population of larger cells, while CD14-SIRP-α- cells constituted the population of smaller cells. CD14-SIRP-α- cells lacked the typical phenotypic markers and had decreased phagocytic and migratory ability compared to CD14+SIRP-αhigh and CD14-SIRP-αdim cells. Furthermore, we found that these 3 populations of mo/mΦ had a differential effect on activated T-cells and that the CD14-SIRP-α- cells appeared increased number in biopsy specimens from NHL when compared to normal tissues. CONCLUSIONS We have identified a unique population of small CD68+ mo/mΦ that lack expression of CD14, SIRP-α, and other FcγR markers. This subset of mo/mΦ is more prevalent in NHL tissues and has limited phagocytic and migratory functions. This CD14-SIRP-α- mo/mΦ subpopulation may play an inhibitory role in anti-cancer and inflammatory responses. Disclosures No relevant conflicts of interest to declare.

Abstract Background: Numerous studies have shown that lymphoma B-cells are resistant to CTL-mediated death, however the underlying mechanism for this resistance is not clear. In previous work, we have identified a subset of CD4+CD25+ T-cells overrepresented in the tumor sites of B-cell NHL that display a phenotype compatible with regulatory T cells (Treg cells). These cells express high levels of Foxp3 and CTLA-4, and are capable of suppressing the proliferation and cytokine production of autologous infiltrating CD4+CD25- T cells in B-cell NHL. Goal: To explore whether Treg cells exert a suppressive effect on the induction and function of autologous tumor-infiltrating CD8+ T-cells in B-cell NHL. Results: Using fresh specimens obtained from patients with B-cell lymphoma, we found that intratumoral Treg cells had a significantly suppressive effect on autologous tumor-infiltrating CD8+ T-cells in B-cell NHL. When activated CD8+ T-cells were cocultured with infiltrating CD4+CD25- T-cells, they displayed less proliferation than CD8+ T-cells cultured alone. However, we found that with a 1:4 ratio of stimulating cells (Treg cells) to responding cells (CD8+ T-cells), intratumoral Treg cells completely inhibited the proliferation of autologous tumor-infiltrating CD8+ T-cells activated with PHA. Furthermore, we have observed that 20% of infiltrating CD8+ T-cells in fresh isolated samples from B-cell NHL coexpress perforin and granzyme B. When intratumoral Treg cells were cocultured with CD8+ T-cells, the Treg cells inhibited the activation-induced production of perforin and granzyme B of autologous tumor-infiltrating CD8+ T-cells in a dose-dependent fashion. We also found that cytokine treatment (IL-2 and IL-12) or PHA activation induced the capability of tumor-infiltrating CD8+ T-cells to kill lymphoma B-cells, which was accompanied by upregulation of expression of CD107a on the surface of cytotoxic CD8+ T-cells. Intratumoral Treg cells significantly inhibit cytotoxicity of activated infiltrating CD8+ T-cells to lymphoma B-cells. Finally, we found that there was an inverse correlation of cell frequencies between intratumoral Treg cells and tumor-infiltrating CD8+ T cells in patients with B-cell NHL, suggesting that Treg cells may inhibit the migration of cytotoxic T-cells to the sites of B-cell lymphoma. Conclusion: Intratumoral Treg cells dramatically suppress the proliferation and activation-induced production of granules in infiltrating CD8+ T-cells in B-cell NHL. These Treg cells also inhibit the ability of activated tumor-infiltrating CD8+ T-cells to kill lymphoma B-cells in vitro, and may prevent the migration of CD8+ cells to the sites of lymphoma. Taken together, these data indicate an important role for intratumoral Treg cells in CTL-mediated anti-tumor immunity in B-cell NHL.

Abstract Background: We have previously reported on ethnic disparities in outcomes of multiple myeloma (MM) pts (pts) and shown that Hispanics have the shortest median overall survival (OS) and myeloma-specific survival (MMS) while Asians have the longest. Ethnic minorities are increasing in number in the United States (US) and have been historically underrepresented in population databases with limited follow up since the introduction of novel agents for MM. We did an updated analysis with longer follow up for ethnic minorities to explore the changes in outcomes by race and also explored MM incidence rates, not reported previously. Methods: Surveillance Epidemiology and End Results (SEER) 13 Registry data (1973-2013) for adult pts (>18 yr) with confirmed diagnosis of MM was utilized. To avoid bias of under representation of ethnic minorities, analysis was restricted to pts diagnosed in 1992 or later. Years of diagnosis were 1992-1995 (pre-stem cell transplant; SCT), 1996-2002 (after SCT but before novel therapeutics) and 2003-2013 (after introduction of novel therapeutics). Cases that received a diagnosis at death certificate/autopsy, without follow-up records, lacking documentation on age at diagnosis, sex, or race/ethnicity were excluded. Cox proportional hazards models were used to evaluate association between patient characteristics and survival. All statistical tests utilized the SAS software (v9.4) and were two-sided with a significance level of 0.05. Results: The final analysis included 68431 MM pts (37300 males; 55%, 31131 females; 45%). Age-group cohorts included: 18-44 yr (2519; 4%), 45-54 yr (8131; 12%), 55-64 yr (15416; 23%), 65-74 yr (20214; 30%), and ≥75 yr (22151; 32%). Mutually exclusive racial subgroups included: non-Hispanic White (NHW; 44618, 65%), non-Hispanic African-American (AA; 13164, 19%), non-Hispanic Asian/Pacific Islanders (API; 3570, 5%), Hispanic (H; 6759, 10%) and Native American (NA; 320, 0.5%). Trends in age-specific incidence rates were similar for all races but except the 20-24 yr group, were highest for AA and lowest for API. (Figure 1) Survival analysis showed that females had a better median OS (3.4 vs 3 yr; p<0.001) and MMS (4.7 vs 4.4 yr; p<0.001) than males. Age was an independent predictor of OS (p<0.001) with the median OS changing from 7.3 yr in 18-44 to 1.9 yr in ≥75 age group. Similar results were seen for age groups and MMS as well (p<0.001). During the three pre-specified time periods for year of diagnosis, both the median OS and MMS progressively improved (P<0.001) suggesting improved outcomes secondary to treatment advancements. H and AA had the worst median OS (3.1 yr) as compared to NHW and API (3.3 yr) (p<0.001) and H had the worst median MMS (4.3 yr) while API had the best (5.1 yr) (p<0.001). Survival analyses were performed for ≥75 age group separately since it was the largest and traditionally with worst outcomes. The difference in median OS by gender was still significant (p<0.001) but less pronounced (1.8 vs 1.9 yr) and was not significant for MMS (p=0.33). Due to less SCT utilization, no incremental OS or MMS benefit was seen prior to advent of novel agents but since 2003 the ≥75 group did have a small benefit for OS (2 vs 1.6 yr, p<0.001) and MMS (3 vs 2.3 yr, p<0.001). Race no longer predicted for a statistically significant OS difference (p=0.52) while for MMS, H continued to have the worst (2.5 yr) and NA the best (3.8 yr) outcome (p<0.001). 5-year relative survival rates (RSR) over time showed an incremental improvement in recent years for all racial groups except API ≥70 yr (Figure 2) with generally an increased incremental benefit for the <70 yr age group than the elderly. For majority of races no incremental benefit was seen in 5-yr RSR for ≥70 yr pts between 1992-1995 and 1996-2003 but improvement was seen in 2004-2013. Conclusions: In a fast changing US demographic mix, significant disparities for MM incidence and outcomes exist by race/ethnicity. As compared to our previous analyses, new trends have emerged with Whites having an improved median OS than AA while H continue to have the worst MMS and API the best. Differences in median OS among races are no longer significant in elderly pts. A modest benefit in OS is being seen for elderly pts since the advent of novel therapeutics. Studies of ethnic disparities are important for evaluating management needs of specific patient populations as well as optimal triaging of healthcare resources. Figure 1 Figure 1. Figure 2 Figure 2. Disclosures Kelly: Novartis: Consultancy, Speakers Bureau; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Consultancy, Speakers Bureau. Ailawadhi:Pharmacyclics: Consultancy; Novartis: Consultancy; Amgen Inc: Consultancy; Takeda Oncology: Consultancy.

Abstract Programmed death 1 (PD-1) is a T cell co-inhibitory receptor with two ligands, PD-L1 and PD-L2. In B-cell malignancies, this pathway plays a major role in immune resistance in the tumor environment by promoting the differentiation of regulatory T-cells and inducing T-cell exhaustion. Recent data have shown that blockade of this pathway can enhance antitumor immune responses. While interactions between PD-1 and its ligands have been studied in various lymphoid tissues, little data exist regarding these interactions in the bone marrow, particularly in patients with Waldenstrom macroglobulinemia (WM). The goal of this study was therefore to determine the expression of PD-1 and its ligands in the bone marrow of patients with WM and to assess the functional role of PD-1 signaling in this disease. Using immunohistochemistry, the expression of PD-1, PD-L1 and PD-L2 in bone marrow (BM) specimens from patients with WM (n=6) was compared to normal control BM. PD-1 expression was modest and the pattern of staining in WM was similar to normal BM. In contrast however, intense staining for PD-L1 and PD-L2 was seen in WM compared to controls. When analyzed by flow cytometry, PD-L1 and PD-L2 expression was seen on malignant B-cells and also on dendritic cells, monocytes and macrophages isolated from the bone marrow. To determine the functional effect of PD-1 signaling in WM, we stably transfected PD-L1 and PD-L2 into the HEK-293 cell line. The WM cell lines, MWCL-1, BCWM.1 and RPCI-WM1 as well as patient specimens, were then cocultured with either the PD-L1 or PD-L2 expressing HEK-293 cells. When compared to cells expressing an empty vector control, proliferation and viability of WM cells was increased when they were cocultured with cells expressing PD-L1 or PD-L2. Addition of blocking antibodies abrogated the increase in proliferation. These results show that PD-L1 and PD-L2 are highly expressed on both malignant B-cells and non-malignant cells within the BM microenvironment in WM and promote malignant B-cell growth. Inhibition of PD-1 signaling may therefore be a promising therapeutic strategy in patients with WM. Disclosures: No relevant conflicts of interest to declare.

Abstract To date, whole genome and exome sequencing studies of follicular lymphoma (FL) have primarily focused on identification of small site mutations that are recurrent in FL tumorigenesis or involved in tumor clonal evolution. A comprehensive genomic and transcriptomic survey of various mutation types including large structural variants (SVs) in FL cases with detailed clinical annotations and long-term follow-up has not been accomplished. To gain insight into genetic biomarkers that may predict clinical features, we performed exome and whole genome mate-pair sequencing of fresh frozen tumor and paired peripheral blood DNAs, and transcriptome sequencing of tumor RNAs, from 8 FL patients. The patients we selected were either below the median age of FL onset (n=7, median 54.5 yrs) or had a family history of lymphoma (n=1). These patients were clinically diverse, and included patients who had Grade 1 or 2 disease (n=4), classified as “indolent”; and patients with Grade 3a disease (n=2) or who subsequently had pathologic transformation (n=2), classified as “aggressive”. The coding regions of the genome (exome) were captured using Agilent SureSelect Target Capture Kit V2.0, and sequenced at 100-bp paired-end. The single nucleotide variants (SNVs) and small insertions and deletions (INDELs) were called using The Genome Analysis Toolkit (GATK), and the exon level copy number variants (CNVs) we identified using patternCNV. The whole-genome mate-pair libraries of both normal and tumor DNAs with 3kb insert sizes were sequenced paired end at 50-bp. The large SVs of CNVs, large INDELs, translocations, and inversions were identified using the SnowShoes-SV algorithm. The RNA sequencing libraries of 8 FL tumors were constructed using Illumina TruSeq protocol, and sequenced at 50-bp paired end. The RNA-Seq data were analyzed using TopHat and the fusion transcripts were identified using SnowShoes-FTD. Our analysis of SNVs and INDELs revealed mutations in previously reported genes including MLL2, CREBBP, TNFRSF14, and histone cluster genes (HIST1H2AM, HIST1H2BD). In addition, we identified novel recurrent mutations in cysteine-rich PAK1 inhibitor (CRIPAK) in 25% of the tumors. In a secondary analysis performed by Sanger sequencing or re-analysis of publically available RNA sequencing data, we identified CRIPAK mutations in 44% of FL (n=32) and 28% of DLBCL tumors (n=102). Bioinformatics analysis shows that the coding region of CRIPAK is highly enriched with the protein functional domain, post-SET, which is usually found in histone lysine methyltransferases (HMTase) genes including MLL2 and EZH2 that are known to be important in lymphomagenesis. Interestingly, CRIPAK is part of the same regulatory network consisted of previously identified lymphoma genes including MLL2, EZH2, CREBBP, and EP300, according to the shortest path algorithm by MetaCore (Philadelphia, Pennsylvania). Recurrent SVs identified in the FL tumors included the well-known IGH-BCL2 translocation, or t(14;18), in 6 out of 8 cases (75%) and the chr1q amplifications in 4 out of 8 (50%) tumors. Other non-recurrent large CNVs involving entire chromosomes or chromosome arms, as well as other inter- and intra-chromosomal structural variants were detected in individual tumors. In addition, we identified and validated 6 fusion transcripts from the transcriptome sequencing data in 3 out of 8 cases (38%). While our sample size is small, we found that SNVs and INDELs in MLL2, CREBBP, TNFRSF14, CRIPAK, and histone cluster genes, as well as t(14;18), did not distinguish indolent or aggressive tumors. However, all aggressive (4/4, 100%) and none of the indolent tumors had gains in chr1q; and the presence of RNA fusion transcripts were observed in aggressive tumors only (3/4, 75%). Additionally, we found that aggressive tumors had higher numbers of genes with point mutations (SNVs and short INDELs) (40 ± 7.6 vs. 26 ± 2.6; aggressive vs. indolent), higher numbers of genes impacted by copy number aberrations (1060 ± 263.7 vs. 233 ± 133.9), and higher numbers of large SVs (24 ± 10 vs. 6 ± 1.6). Taken together, our comprehensive analysis of 8 FL tumors reveals genetic diversity among newly diagnosed FL patients, identifies novel and recurrent mutations in CRIPAK, and finds that high tumor complexity and DNA instability may be indicators of aggressive disease. Disclosures No relevant conflicts of interest to declare.

Previous large registry studies have demonstrated inferior outcomes for simultaneous liver‐kidney transplantation (SLKT) recipients of grafts from donation after circulatory death (DCD) donors compared with those from donation after brain death (DBD) donors in the era from 2000 to 2010. Given the improving national results in liver transplantation alone using grafts from DCD donors, the present study aimed to investigate if results with DCD‐SLKT have improved in the modern era. Patients undergoing SLKT between 2000 and 2018 were obtained from the United Network for Organ Sharing Standard Analysis and Research file and divided into 2 eras based on the date of SLKT: era 1 (2000‐2010) and era 2 (2011‐2018). Improvement in DCD‐SLKT patient, liver graft, and kidney graft survival rates was seen between era 1 and era 2 (P < 0.001). Concurrently, there was a decrease in the proportion of critically ill (P = 0.02) and retransplant (P = 0.006) candidates undergoing DCD‐SLKT. When DCD‐SLKT in era 2 was compared with a propensity‐matched cohort of DBD‐SLKT in era 2, no differences in patient (P = 0.99), liver graft (P = 0.19), or kidney graft (P = 0.90) survival were observed. In addition, both bilirubin (0.5 versus 0.5 mg/dL; P = 0.86) and creatinine (1.2 versus 1.2 mg/dL; P = 0.68) at last follow‐up were not different between the DCD‐SLKT and DBD‐SLKT patients in era 2. In conclusion, in the most recent era, patients undergoing DCD‐SLKT were able to achieve similar outcomes compared with matched patients undergoing DBD‐SLKT. DCD‐SLKT represents a viable option for appropriately selected recipients.