Citations

Abstract Abstract 2859 Background: PTLD is the most common malignancy, other than melanomatous skin cancer complicating solid organ transplantation and has been one of the most commonly observed fatal consequences. The histologies are diverse and include B-cell, T-cell and Hodgkin lymphomas. Rituximab has affected the outcome in CD20+ patients with PTLD. This single institution study sought to identity the outcomes in patients of all histologies and presentations managed in the post-rituximab era. Methods: Patients with solid organ transplantation who were diagnosed with PTLD at Mayo Clinic (Rochester, MN) between December 1970 and October 2009 were identified through the Mayo Clinic Lymphoma Data Base. The rituximab era was defined as patients diagnosed after December 26, 2000, the date of diagnosis for the first patient treated with rituximab in our series. Cox proportional hazards models were used to assess the association of clinical factors and overall survival (OS). Results: 143 patients diagnosed with PTLD between December 1970 and October 2009 were identified. The median age at the time of diagnosis of PTLD was 50 years (range 15–84) with 41 patients (29%) over the age of 60. 93 were male (65%). At a median follow-up of 84 months (range 1–295), 95 patients (65%) have died. The types of organ transplant included renal (39%), liver (31%), cardiac (11%), lung (6%), renal/pancreas (6%), pancreas (4%), and multiorgan (4%). 83% of patients presented with extranodal disease. 28% had involvement of the engrafted organ. 76% of the patients developed PTLD that was EBV+ by in situ hybridization. 62% were stage 3–4. The IPI was intermediate-high in 39% of patients. Initial approaches to management included reduction in immunosuppression (45%), chemotherapy (12%), reduction in immunosuppression with rituximab (12%), rituximab (8%), and radiation therapy (6%). The overall response to therapeutic approaches was 46% in the pre-rituximab era and 56% in the post-rituximab era (chi-squared p=0.25). Patients treated with rituximab had an improved overall survival (HR = 1.66, 95% CI: 0.99–2.79). Patients treated in the rituximab era had improved 1 year survival (76%) compared to patients in the pre-rituximab era (59%) (chi-squared p=0.03). However, the survival advantage in the rituximab era was not maintained in longer follow-up. The median overall survival in the pre-rituximab era was 31 months compared to 56 months in the post-rituximab era (logrank p=0.63). Conclusion: The overall response rates and overall survival are improved with rituximab treatment in CD20+ PTLD, however, the natural history of all PTLD has not improved significantly in the post-rituximab era. New approaches are needed for the prevention and management of all the histologies of PTLD. Disclosures: No relevant conflicts of interest to declare.

Abstract Background: Follicular lymphoma (FL) is the most common indolent NHL with a heterogenous natural history of disease and a median survival of 8 to 12 y, albeit ranging between 1 to 20 y. Casulo et al. (2015) identified a high-risk FL cohort of patients with progression of disease (POD) at ≤24 months following initiation of immunochemotherapy with R-CHOP. Idelalisib (Zydelig) is a first-in-class, highly selective, oral inhibitor of PI3Kd which is indicated for relapsed FL or SLL following receipt of at least two lines of systemic chemotherapy. Retrospective subgroup analysis of the idelalisib registrational trial NCT01282424 (101-09) of a cohort with early POD following immunochemotherapy was performed to assess possible activity of idelalisib in this population. Methods: A subset of 46 patients enrolled in study 101-09 were identified as having been diagnosed with FL and having received first-line immunochemotherapy, of which 37 experienced early POD, defined as starting second-line treatment within 24 months of initial first-line treatment. For the latter group, descriptive statistics of demographic and baseline characteristics and inter-treatment intervals in months as well as Kaplan-Meier estimates of progression-free survival (PFS) and overall survival (OS) following initiation of immunochemotherapy and idelalisib were calculated. Population: Demographic characteristics of these 37 patients included median (range) age at initiation of idelalisib of 64 (33-84) y and 18 (48.6%) females. Histologic grade at diagnosis included 33 (89.2%) with grades 1 or 2 as well as 4 (10.8%) with grade 3A, while 21 (56.8%) patients had a FLIPI score ≥3. The mean (s.d.) number of prior therapies was 3.4±1.4, with a range of 2 to 8, while first-line therapies included 21 (56.8%) patients who received R-CHOP-based regimens, 7 (18.9%) who received BR, and 5 (13.5%) who received R-CVP. Mean (s.d.) inter-treatment intervals included 12.5±6.1 months between first- and second-line for all patients, 9.7±9.3 months between second- and third-line for all patients, 11.9±12.0 months between third- and fourth-line for 24 (64.9%) patients, and 11.8±7.6 months between fourth- and fifth-line for 15 (40.5%) patients. Median (range) time from first-line therapy to idelalisib initiation was 30.3 (8.9-94.7) months; no patient received idelalisib as second-line therapy. Results: Best responses included 5 (13.5%) patients with CR, 16 (43.2%) with PR, 2 (5.4%) with SD, and 1 (2.7%) with PD; median duration of response for those with CR or PR was 11.8 months (95% CI: 3.8 months, not evaluable). There were 7 (18.9%) deaths and 21 (56.8%) PFS events in this group. Estimated probabilities of survival (s.e.) and progression-free status at 2 y following initiation of idelalisib were 79%±7% and 29%±10%, respectively. Median PFS was 11.1 months (95% CI: 5.5, 19.3 months). Estimated probability of survival (s.e.) at 5 years following initiation of first-line treatment was 79%±8%. Median overall survival from both initiation of first-line immunochemotherapy as well as with idelalisib was not reached during the course of this study. Conclusions: Idelalisib may have significant clinical activity in high-risk and doubly-refractive FL following early relapse status post first-line immunochemotherapy. Given the small size of the studied subset population which may not be representative, further characterization in additional patients is warranted to ensure the generalizability of this finding, including consideration of further investigational protocols featuring targeted therapies employed both as single agents and in combination. Figure 1. Overall Survival From Initiation of First-line Treatment Figure 1. Overall Survival From Initiation of First-line Treatment Figure 2. Overall Survival From Initiation of Idelalisib Figure 2. Overall Survival From Initiation of Idelalisib Figure 3. Progression-Free Survival From Initiation of Idelalisib Figure 3. Progression-Free Survival From Initiation of Idelalisib Disclosures Gopal: Gilead, Spectrum, Pfizer, Janssen, Seattle Genetics: Consultancy; Spectrum, Pfizer, BioMarin, Cephalon/Teva, Emergent/Abbott. Gilead, Janssen., Merck, Milennium, Piramal, Seattle Genetics, Giogen Idec, BMS: Research Funding; Millennium, Seattle Genetics, Sanofi-Aventis: Honoraria. Kahl:Roche/Genentech: Consultancy; Seattle Genetics: Consultancy; Millennium: Consultancy; Cell Therapeutics: Consultancy; Celgene: Consultancy; Infinity: Consultancy; Pharmacyclics: Consultancy; Juno: Consultancy. Flowers:Infinity Pharmaceuticals: Research Funding; Genentech: Research Funding; Spectrum: Research Funding; Millennium/Takeda: Research Funding; Seattle Genetics: Consultancy; Spectrum: Research Funding; Pharmacyclics: Research Funding; AbbVie: Research Funding; AbbVie: Research Funding; Gilead Sciences: Research Funding; Pharmacyclics: Research Funding; Onyx Pharmaceuticals: Research Funding; Celegene: Other: Unpaid consultant, Research Funding; OptumRx: Consultancy; Gilead Sciences: Research Funding; Janssen: Research Funding; Acerta: Research Funding; Millennium/Takeda: Research Funding; Acerta: Research Funding; Infinity Pharmaceuticals: Research Funding; Janssen: Research Funding; Onyx Pharmaceuticals: Research Funding. Martin:Janssen: Consultancy, Honoraria; Acerta: Consultancy; Gilead: Consultancy; Celgene: Consultancy; Novartis: Consultancy; Bayer: Consultancy. Link:Genentech: Consultancy, Research Funding; Kite Pharma: Research Funding. Ansell:Bristol-Myers Squibb: Research Funding; Celldex: Research Funding. Ye:Gilead: Employment. Koh:Gilead: Employment. Abella:Gilead: Employment. Barr:Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; Abbvie: Consultancy; Gilead: Consultancy. Salles:Calistoga Pharmaceuticals, Inc.; Celgene Corporation; Genentech, Inc.; Janssen Pharmaceutica Products, L.P.; Roche: Consultancy; Celgene Corporation; Roche and Gilead Sciences: Research Funding; Celgene Corporation; Roche: Speakers Bureau.

Abstract Waldenstrom’s macroglobulinemia is a serious and frequently fatal illness, however many of the mechanisms leading to this disease are not yet known. It is clear, however, that there is dysregulation of the balance between cell proliferation and programmed cell death. BLyS (B-lymphocyte stimulator) is a newly identified TNF family member expressed by monocytes, macrophages, and dendritic cells. BLyS has been shown to be critical for maintenance of normal B cell development and homeostasis, and has been found to stimulate lymphocyte growth. BLyS is overexpressed in a variety of B-cell malignancies and has been shown to inhibit apoptosis in malignant B-cells. Studies of the effects of BLyS on B cell physiology have shown that it also regulates immunoglobulin secretion. To determine the relevance of the BLyS receptor-ligand system in Waldenstrom’s macroglobulinemia, we examined malignant B cells from 5 patients with Waldenstrom’s macroglobulinemia for their ability to bind soluble BLyS and for the expression of the known BLyS receptors, TACI, BAFF-R, or BCMA. The malignant B cells were found to bind BLyS and express BAFF-R and TACI. BCMA expression was undetectable. We then determined the expression of BLyS in bone marrow specimens from 5 patients with Waldenstrom’s macroglobulinemia by immunohistochemistry and compared it to the expression in 5 normal bone marrow specimens. The lymphoplasmacytic cell infiltrate in the bone marrow of patients with Waldenstrom’s macroglobulinemia showed significantly increased BLyS expression. We further determined the serum BLyS levels by ELISA in stored serum specimens from patients with Waldenstrom’s macroglobulinemia (n=20), and compared them to serum BLyS levels in other patients with lymphoplasmacytic lymphoma without elevated immunoglobulin levels (n=10) and to serum levels in normal controls (n=50). Serum BLyS levels in Waldenstrom’s patients (mean: 49.6ng/ml) as well as those in patients with lymphoplasmacytic lymphoma (mean; 46.7ng/ml) were significantly higher than normal controls (mean 12.6ng/ml). In conclusion, we have demonstrated that malignant B cells from patients with Waldenstrom’s macroglobulinemia express the receptors for BLyS and can bind soluble BLyS. Furthermore, we have found that serum BLyS levels are significantly elevated in patients with Waldenstrom’s macroglobulinemia when compared to controls. Strategies to inhibit BLyS may potentially have significant therapeutic efficacy in Waldenstrom’s macroglobulinemia.

Abstract Introduction Relapse in the central nervous system is an uncommon complication of diffuse large B cell lymphoma (DLBCL) associated with a poor prognosis. The addition of rituximab to chemotherapy has improved outcomes in patients with DLBCL but its effect on the outcome of patients with CNS relapse is not well characterized. Here we present the natural history of patients with CNS relapse in a large cohort of patients with DLBCL who were treated in the immunochemotherapy (IC) era. Methods Newly diagnosed patients with DLBCL or primary mediastinal B-cell lymphoma (PMBCL) and treated with primary anthracycline based IC were prospectively enrolled on the University of Iowa/Mayo Clinic SPORE Molecular Epidemiology Resource (MER) within 9 months of diagnosis and followed for relapse, retreatment, and death. Clinical management at diagnosis and subsequent therapies were per treating physician. Patients with documented CNS involvement at diagnosis, primary CNS lymphoma, or post-transplant lymphoproliferative disorder at diagnosis were excluded. All CNS relapse and retreatment details were verified by medical record review. Results 1017 patients with newly diagnosed DLBCL or PMBCL, no documented CNS disease at diagnosis, and treated with IC were enrolled in the MER between 2002 and 2012. At a median follow-up of 59 months (range 1-148), 36 patients had CNS relapse. The cumulative incidence of CNS relapse was 3.1% (95% CI: 2.2%-4.4%) at 2 years and 3.7% (95% CI: 2.7%-5.0%) at 5 years after diagnosis. CNS involvement was identified after first line IC in 25 patients, and after salvage therapy in 11 patients. 22 patients had an isolated CNS relapse, while 14 had both systemic and CNS disease at relapse. The incidence of isolated CNS relapse at two years from diagnosis was 1.9% (95% CI: 1.2%-3.0%, figure 1). CNS involvement was parenchymal in 22 patients, leptomeningeal in 11, and parenchymal and leptomeningeal in 3 patients. At diagnosis, this subset of 36 patients had a median age of 61 years (range 20-86); 25 (69%) were male. IPI was 0-1 in 6 patients, 2 in 13 patients, 3 in 11 patients and 4-5 in 6 patients. Cell of origin per Hans algorithm was available in 17 patients, 8 were GCB and 9 were non-GCB. Extranodal sites of disease at diagnosis included testicular (2), renal (5), bone (10) and bone marrow (6). 7 patients had no sites of extranodal disease. LDH was elevated in 71%. The German High-Grade Non-Hodgkin Lymphoma Study Group CNS risk score was low risk in 6 patients, intermediate risk in 22 patients, and high risk in 8 patients. 6 patients received CNS prophylaxis with their initial immunochemotherapy, including 3 of the 21 patients who subsequently developed isolated CNS disease. First line therapy after CNS relapse included high dose methotrexate based chemotherapy in 22 patients and other systemic regimens in 6, with intrathecal (IT) chemotherapy in 5. Overall survival in patients after CNS relapse was poor with a median survival of 6.3 months (95% CI: 2.9-15.5) and 12-month survival rate of 29% (95% CI: 17%-49%). Patients who had CNS relapse following initial IC had better subsequent survival (median OS = 7.6 months) compared to patients with first presentation of CNS relapse following salvage therapy (OS = 2.1 months, p=0.005, see figure 2). 10 patients (28%) proceeded to SCT after CNS relapse, of which 6 remain alive at a median follow-up of 39 months. There were no differences in post-CNS relapse survival by age, sex, CNS risk score, cell of origin, extranodal site involvement at diagnosis, or site of CNS relapse (all p>0.10), though power was limited due to small numbers. Conclusions The incidence of CNS relapse in DLBCL is approximately 4% in the immunochemotherapy era. The vast majority of CNS relapses occur within 2 years of diagnosis. Isolated relapse in patients without CNS involvement at diagnosis is a relatively rare event with an incidence of approximately 2% at 2 years of diagnosis. Outcomes remain poor, and standard clinical variables do not predict survival after CNS relapse. Novel therapeutic approaches are needed in this population, with consideration to autologous SCT, which produces durable remission in a subset of patients. Disclosures Maurer: Kite Pharma: Research Funding. Farooq:Kite Pharma: Research Funding. Thompson:Kite Pharma: Research Funding. Ansell:Bristol-Myers Squibb: Research Funding; Celldex: Research Funding. Cerhan:Kite Pharma: Research Funding. Link:Genentech: Consultancy, Research Funding; Kite Pharma: Research Funding.

Abstract Background: Despite advances in chemotherapy, R/R HL remains a significant clinical problem with over 1,000 primarily young lives lost annually. HL is a unique tumor in which a small number of malignant Hodgkin Reed-Sternberg (HRS) cells propagate an immunosuppressive microenvironment that augments HRS growth and survival. We hypothesized that immune checkpoint inhibitor therapy could activate the tumor immune microenvironment, while the CD30 expressing HRS cells could be targeted by brentuximab vedotin (BV), thereby overcoming tumor cell resistance and deepening clinical responses. E4412 is a phase 1 ECOG-ACRIN sponsored study of the combination of BV and the checkpoint inhibitors ipilimumab (IPI) and nivolumab (NIVO) in patients with relapsed/refractory (R/R) Hodgkin lymphoma (HL). Here we report the data on the patients treated with BV + IPI, the first cohort of the study. Methods: Patients with biopsy proven R/R HL were treated with BV 1.8mg/kg and two escalating doses of IPI: 1 mg/kg or 3mg/kg. After safety was determined an expanded cohort was treated with BV 1.8mg/kg IV and IPI 3mg/kg IV. The schedule consisted of BV administered every 21 days for 16 cycles and IPI every 21 days x 4 doses and thereafter every 3 months for up to a year. Dose limiting toxicity (DLT) was defined for purposes of dose escalation within the first cycle of therapy. Patients are followed for toxicity up to 30 days beyond their last treatment. Results: As of 7/2015 19 of 23 planned patients have been treated with BV + IPI. We report the data on the full dose escalation population (13 patients: Dose level 1 (6), Dose level 2 (7)). The median age was 33 years (range: 20-49). Seven patients were male. Patients were heavily pretreated with a median of 4 prior therapies (2-13). Fourpatients had prior treatment with BV; 8 patients had prior SCT (7 autologous, 1 allogeneic). Safety: Overall the regimen of BV + IPI was extremely well tolerated with no DLTs noted during dose escalation. Toxicities considered at least possibly related to drug during any cycle of treatment are shown according to grade in Table 1. The most common treatment related adverse events were: diarrhea, rash, and peripheral sensory neuropathy. Other AEs of interest included: alopecia, transaminitis, and uveitis. Grade 3 and 4 treatment related adverse events (AEs) included: Dose level 1: one grade 3 infusion reaction, which led to a protocol amendment to include premedication, no further grade 3 infusion reactions were noted; Dose level 2: one each: grade 3 rash, vomiting, and peripheral sensory neuropathy, and one grade 4 thrombocytopenia in patient with pre-existing thrombocytopenia. Response: For the 12 evaluable patients, the overall response (ORR) for the combination of BV + IPI was 67% with a complete response (CR) rate of 42% (5 of 12 patients). An additional 2 patients had stable disease (SD) giving a clinical benefit rate of 83%. Three of 5 of the CRs occurred at dose level 1 (1mg dose of IPI). The median progression free survival (PFS) is 0.74 years with a median follow-up of 0.66 years. Conclusion: In this first reported study of the combination of checkpoint inhibitor and ADC, toxicity was low, primarily grades 1 and 2. In a heavily pretreated patient population, 33% of whom had had prior BV and 67% of whom were s/p ASCT, the ORR of 67% and CR rate of 42% suggests a potential deepening of response compared to monotherapy. More than half of these CRs occurred at 1mg of IPI suggesting that in combination with ADC, low doses of immune stimulation may be highly active. Optimization of this combination strategy is planned with ongoing accrual to cohorts receiving BV + NIVO, and BV + IPI + NIVO. Data will be updated to include the full BV + IPI cohort by the time of the annual meeting. Table 1. Common and Immune Toxicities Toxicity Type Dose Level 1 (n=6) Dose Level 2 (n=7) Grade Grade 1,2 3 4 5 1,2 3 4 5 (n) (n) (n) (n) (n) (n) (n) (n) Fatigue 5 - - - 3 - - - Fever 1 - - - 3 - - - Pain 2 - - - 3 - - - Alopecia 2 - - - 1 - - - Pruritus 1 - - - 2 - - - Rash maculo-papular 4 - - - 2 1 - - Diarrhea 4 - - - 4 - - - Dyspepsia 2 - - - 1 - - - Nausea 6 - - - 4 - - - Vomiting 3 - - - 2 1 - - Papulopustular rash 1 - - - 1 - - - Alanine aminotransferase increased 3 - - - 3 - - - Aspartate aminotransferase increased 3 - - - 2 - - - Platelet count decreased - - - - - - 1 - Anorexia 3 - - - - - - - Headache 2 - - - 2 - - - Peripheral sensory neuropathy 5 - - - 4 1 - - Dry eye 2 - - - - - - - Uveitis 1 - - - - - - - Cough 2 - - - 1 - - - Disclosures Diefenbach: Molecular Templates: Research Funding; Immunogen: Consultancy; Celgene: Consultancy; Idera: Consultancy; Jannsen Oncology: Consultancy; Gilead: Equity Ownership, Research Funding, Speakers Bureau; Incyte: Research Funding; Genentech: Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding. Off Label Use: Presentation will discuss the experimental use of the checkpoint inhibitor Ipilimumab in relapsed/refractory Hodgkin lymphoma.. Cohen:Celgene: Consultancy; Millennium: Consultancy; Pharmacyclics: Consultancy; Seattle Genetics: Consultancy; BMS: Research Funding; Janssen: Research Funding. Robertson:Eli Lilly: Equity Ownership. Fenske:Pharmacyclics: Honoraria; Seattle Genetics: Honoraria; Millennium/Takeda: Research Funding; Celgene: Honoraria. Kahl:Roche/Genentech: Consultancy; Seattle Genetics: Consultancy; Millennium: Consultancy; Cell Therapeutics: Consultancy; Celgene: Consultancy; Infinity: Consultancy; Pharmacyclics: Consultancy; Juno: Consultancy. Ansell:Bristol-Myers Squibb: Research Funding; Celldex: Research Funding.

Abstract Abstract 2862 Follicular lymphoma (FL) is a B-cell malignancy that exhibits significant intratumoral infiltration by non-malignant T lymphocytes. The pathophysiological significance of infiltrating T cells is poorly understood but recent studies have suggested that CD4+CD25+ regulatory T (Treg) cells are highly represented in lymph nodes involved by FL. These Treg cells display the ability to suppress the proliferation and cytokine production of other tumor-infiltrating T cells and migrate to areas of B-cell lymphoma in response to chemotactic signals provided by the malignant B-cells. Denileukin diftitox, a chimeric immunotoxin composed of the modified cytotoxic domain of diphtheria toxin and human interleukin-2 (IL-2) protein, targets cells expressing CD25 and has proven efficacy in patients with relapsed B-cell lymphoma. In this study, we combined denileukin diftitox with rituximab in a cohort of previously untreated, advanced-stage follicular lymphoma patients. Our hypothesis was that denileukin diftitox would deplete the Treg cells, thereby removing the inhibition of the immune response, and rituximab would deplete the B-cells thereby preventing further recruitment of Treg cells to the areas of lymphoma. Between August 2008 and March 2010, twenty-four patients with stage III and IV follicular grade 1 or 2 non-Hodgkin lymphoma were accrued to the study. One patient died before treatment was given and is not included in the analysis. The median age was 60 years (range: 27 – 79), 12 (52%) of the patients were male, 19 (83%) had a PS of 0 and 4 (17%) had a PS of 1. Based on the Follicular Lymphoma International Prognostic Index (FLIPI), 3 (13%) were low risk, 14 (61%) were intermediate risk and 6 (26%) were high risk. Patients received rituximab 375 mg/m2 on days 1, 8, 15 and 22 and denileukin diftitox 18 mcg/kg/day on days 1–5 every 3 weeks for 4 cycles. A median of 4 cycles of therapy was given (range: 1 – 4). Thirteen patients completed treatment per protocol (57%), however 5 patients discontinued treatment due to adverse events (22%), 2 refused further treatment (9%) and 1 discontinued due to disease progression (4%). Nine of the 23 patients (39%; 95% CI: 21–61%) responded to treatment, 3 (13%) had a complete response and 6 (26%) had a partial response. Twenty-one patients (91%) are alive with a median follow-up of 8.7 months (range: 3.4–19.5). Seven (30%) patients have progressed and two (8.7%) has died. The median time to progression is 13.4 months (95% CI: 10.4 – NA). The combination, however, was associated with significant toxicity. Thirteen patients (57%) experienced grade 3 or greater adverse events. Six patients (26%) had symptoms of capillary leak syndrome, 1 of whom died. In correlative studies performed on the peripheral blood, the number of CD25+ T-cells decreased after treatment when compared to pretreatment numbers (median 24%; range: 8–44%). We conclude that while the addition of denileukin diftitox to rituximab decreased the numbers of CD25+ T-cells, denileukin diftitox contributed significantly to the toxicity of the combination. Furthermore, the overall response rate and time to progression in this study were no better than what would be expected in follicular lymphoma patients treated with rituximab alone. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 2721 Poster Board II-697 The role of the CD40 pathway in B-cell cancers is rather enigmatic due to having polar opposite roles in tumor biology. Stimulation of the CD40 receptor can reduce cell viability of NHL cell lines and xenograft tumor models, whereas, in sharp contrast, constitutive CD40 stimulation can actually promote proliferation of NHL cell lines, as well as drive lymphomagenesis and transformation of primary B-cells. Therefore, targeting the CD40 pathway has been challenging due to a knowledge gap in understanding the factors that may dictate a pro- or anti-tumor role. To address this directly, we employed a large panel of NHL cell lines and xenografts models to simulate a patient population and to define the molecular parameters to test in the context of clinical trials. Using baseline gene expression profiling, we found that the in vitro activity of an antibody that stimulates the CD40 pathway, Dacetuzumab (SGN-40), correlated strikingly with a transcriptional profile that was representative of an inactive CD40 pathway. Resistant cells, on the other hand, displayed a transcriptional profile indicative of an activated CD40 pathway. Consistent with these observations, constitutive phosphorylation of ERK, a node downstream of CD40 signaling, was present predominantly in cell lines that were resistant to Dacetuzumab. Fifteen genes, based on their association with in vitro activity and their biology as components of the CD40 network, were selected as a classifier from these pre-clinical data and independently tested in a panel of cell lines and xenografts models. Testing the selected gene classifier by qRT-PCR from baseline fixed tumor tissue of 39 patients treated with Dacetuzumab in phase I and II clinical trials revealed the ability to predict sensitivity in patients, as determined by tumor shrinkage >10%, with an overall accuracy of 80%. Consistent with the observed tumor shrinkage, the classifier positive, predicted to respond to Dacetuzumab, patients also exhibited a prolonged progression free survival (PFS) compared to classifier negative patients, predicted not to respond to Dacetuzumab (HR = 0.23, p = 0.001). Finally, using a novel microarray approach to genome-wide expression profiling on fixed tumor tissue revealed that CD40 pathway activation was indeed an important predictor of response. Overall, these data suggest that sensitivity to Dacetuzumab can be predicted by pre-determining the CD40 pathway activation status of tumors. Disclosures: Dornan: Genentech, Inc.: Employment, Equity Ownership. Burington:Genentech, Inc.: Employment, Equity Ownership. Yue:Genentech, Inc.: Employment, Equity Ownership. Shi:Genentech, Inc.: Employment, Equity Ownership. Advani:Seattle Genetics, Inc.: Research Funding. Yu:Genentech, Inc.: Employment, Equity Ownership. Lau:Genentech, Inc.: Employment, Equity Ownership. Yu:Genentech, Inc.: Employment, Equity Ownership. De Vos:Seattle Genetics, Inc.: Research Funding. Forero-Torres:Seattle Genetics, Inc.: Research Funding. Modrusan:Genentech, Inc.: Employment, Equity Ownership. Koeppen:Genentech, Inc.: Employment, Equity Ownership. Yang:Genentech, Inc.: Employment, Equity Ownership. Du:Genentech, Inc.: Employment, Equity Ownership. Elkins:Genentech, Inc.: Employment, Equity Ownership. Polson:Genentech, Inc.: Employment, Equity Ownership. Offringa:Genentech, Inc.: Employment, Equity Ownership. Whiting:Seattle Genetics, Inc.: Employment, Equity Ownership. Ebens:Genentech, Inc.: Employment, Equity Ownership.

Abstract Classic Hodgkin lymphoma (cHL) is characterized by a rich non-malignant immune infiltrate. T-cells are key components of the antitumoral immune response and studies characterizing subsets in cHL have yielded conflicting results. Initial studies suggested a predominance of TH2-polarized CD4+ T-cells, thought to allow tumor progression due to exhaustion and hypofunctionality. More recent data contest these findings, supporting the theory of tumor progression through evasion from a TH1-rich infiltrate that is potentially functional. The role of tumor evasion in cHL has been highlighted by compelling early clinical data with the use of PD-1 blockade in patients with advanced disease. A similar trial in patients with non-Hodgkin lymphoma (NHL) yielded far more modest results. Intrinsic differences in T-cell subpopulations in the tumor microenvironment may correlate to response to immune checkpoint inhibitor therapy. CyTOF or mass cytometry is a platform able to evaluate more than 45 simultaneous parameters on a single-cell level using nonradioactive nonbiological isotopes tagged to monoclonal antibodies. Measurements are made based on mass spectrometry, avoiding the hurdles of interference and spectral overlap experienced with fluorochromes. This constitutes an ideal tool for the study of the tumor microenvironment given its ability to assess a large number of parameters and resolve differences in a heterogeneous population. We hypothesize that the phenotype of intratumoral lymphocytes in cHL identifies T-cells that can effectively eradicate malignant cells. To test this hypothesis, we compared the phenotype of intratumoral T-cells in cHL to that of NHL and nodular lymphocyte-predominant Hodgkin Lymphoma (nlpHL). Tonsil and hyperplastic lymph node (LN) tissues were used as normal controls. Single-cell suspensions created from tumor specimens were stained with a metal-tagged antibody panel containing 31 surface markers and acquired on CyTOF. Multiparametric data analysis was performed on Cytobank using spanning-tree progression analysis of density-normalized events (SPADE) and t-Distributed Stochastic Neighbor Embedding (viSNE) algorithms. Inferential statistical analyses were performed with JMP®, Version 10.0.0 (SAS Institute Inc., Cary, NC, 1989-2007) using two-tailed tests and a 95% confidence interval. Cell subsets are expressed as percentages of parent population (CD45+CD3+CD19-). A total of 10 samples were studied (4 cHL, 1 nlpHL, 3 NHL, 1 tonsil, 1 LN). The total T-cell population ranged from 30.52 to 67.05% in cHL and 15.36 to 47% in NHL compared to 4.02% and 24.58% in tonsil and LN respectively. The CD4+ T-cell subset ranged from 58.05 to 35.3% in cHL, 50.03 to 82.61% in NHL and corresponded to 82.74% and 87.07% in tonsil and LN respectively. SPADE analysis identified two areas of asymmetric frequency of events amongst samples (figure 1 and 2). The CD4+ Tnaive subset (CD4+CD45RA+CCR7+) ranged from 7.8 to 31.2% of total T-cells in cHL compared to 10.7% in nlpHL, 0.17 to 3.02% in NHL and 6.2 to 6.7% in controls. The pooled mean frequency of CD4+ Tnaive subset was significantly higher in HL (cHL + nlpHL) compared to NHL (14.3% vs. 1.55%; p<0.05; figure 3A). The regulatory T-cell subset (Treg; CD25+CCR4+) ranged from 0.49 to 1.84% of total T-cells in HL compared to 9.3 to 21.04% in NHL, and 4.45 to 8.28% in controls. The pooled mean frequency of the Treg subset was significantly smaller in HL compared to NHL (1.28% vs. 16.23%; p<0.05; figure 3B). Our data supports the use of mass cytometry as a platform to study the tumor microenvironment in B-cell lymphomas. Multiparametric data analysis revealed significant differences in the intratumoral T-cell population between HL and NHL samples, namely in the CD4+ Tnaive and Treg subsets. Further validation in a larger sample is underway and will include panels to evaluate intracellular cytokine production and cell signaling pathways. Correlation between specific intratumoral T-cell phenotypic signatures and clinical outcomes may identify prognostic and predictive characteristics and provide insight to mechanisms of resistance to immunotherapy. Disclosures No relevant conflicts of interest to declare.

Abstract Abstract 1999 Recurrent chromosomal translocations involving the IGH locus are characteristic of B-cell non-Hodgkin lymphoma (NHL) and MALT lymphoma in particular has been pathologically characterized by specific IGH translocations. However, these translocations are present in only a subset of cases, suggesting that additional uncharacterized translocations might exist. In previous studies we characterized the novel t(X;14)(p11.4;q32) translocation in a patient with MALT lymphoma and found that GPR34, an orphan G-protein coupled receptor (GPCR), was highly expressed due to its juxtaposition to the IGHSA2 switch region. Although the t(X;14)(p11;q32) translocation was only identified in one patient, we wanted to determine its expression across a spectrum or normal and malignant lymphoma tissue, as other mechanisms may contribute to overexpression of genes. We measured GPR34 mRNA expression by quantitative PCR in tissue biopsies from a panel of lymphomas. As controls, we also measured GPR34 mRNA expression in normal resting or activated CD19+ B cells, resting and activated CD3+ T cells, and CD14+ monocytes. Expression of GPR34 was significantly increased in MALT (37-fold, n=35), LPL (23-fold, n=23), nodal marginal zone B cell lymphoma (18-fold, n=21), and splenic marginal zone B cell lymphoma (21 fold, n=33) compared to resting CD19+ B cells (n=11). In a gastric MALT lymphoma specimen we detected GPR34 expression at levels similar to the t(X;14)(p11;q32) patient and interphase FISH studies showed an extra intact GPR34 signal, but no translocation involving IGH or GPR34, suggesting that other mechanisms, including gene dosage effect, can upregulate GPR34. The receptor encoded by GPR34 is most similar to the PY2 receptor subfamily of GPCRs and signaling studies suggest that overexpression of GPR34 results in an accumulation of inositol phosphates and MAP-kinase activation. To further characterize the impact of GPR34 overexpression on cell signaling, HeLa cells were transduced with WT GPR34, a signaling deficient GPR34 (GPR34 DRY), or a vector control. To determine if MAPK activity was upregulated, the phosphorylation status of ERK1/2 in GPR34 WT, GPR34 DRY, and vector control cells was analyzed and we found that ERK1/2 was constitutively phosphorylated at higher levels (1.6-fold) in GRP34 WT cells compared to GRR34 DRY or vector control cells. To further explore which signaling pathways were affected by GPR34 overexpression, GPR34 WT or vector control cells were transfected with an AP-1, CRE, NF-kB, E2F, SRE, NFAT, or ISRE- luciferase reporter plasmid. GPR34 expressing cells had increased luciferase activity driven by AP-1 (5.35-fold), CRE (4.7-fold), NF-kB (2.6-fold), and E2F (2.1) when compared to vector control cells. GPR34 DRY was unable to activate these pathways. AP-1 and CRE have been implicated in a large variety of cellular processes, including transformation, and both AP-1 and CRE activity is induced upon activation of MAP kinases. In untreated cells, both AP-1 and CRE activity were significantly higher in GPR34 WT cells compared to GPR34 DRY cells and both AP-1 and CRE luciferase activity was inhibited by the MEK1 inhibitor PD98059, suggesting that activation of these pathways is MAP-kinase dependent. To determine the biologic impact of GRP34 overexpression, the proliferation rates of vector control, GPR34 WT, and GPR34 DRY cells were compared and we found that proliferation of GPR34 WT cells was significantly higher (5.6-fold) than that seen in GPR34 DRY cells. We next tested the effect of the MEK inhibitor on proliferation and saw a dose dependent decrease in proliferation of GPR34 WT expressing cells. These results suggest that GPR34-mediated proliferation is dependent on MAPK. The presence of elevated GPR34 expression in tumors and the increased proliferation mediated by GPR34 suggests that it may have oncogenic potential. We therefore tested the ability of GPR34 WT cells to generate tumors in a tumor colony-forming assay. Only the GRP34 WT cells had the ability to form tumors in soft agar suggesting that overexpression of GPR34 can result in tumor formation. Taken together, our results identify a novel translocation in MALT lymphoma, emphasize a novel role for GPR34 in tumor cell growth, and suggest that MEK inhibitors may be useful in a subset of translocation-harboring or GRP34 high-expressing tumors. Disclosures: Fonseca: Genzyme: Consultancy; Medtronic: Consultancy; BMS: Consultancy; AMGEN: Consultancy; Otsuka: Consultancy; Celgene: Consultancy, Research Funding; Intellikine: Consultancy; Cylene: Research Funding; Onyx: Research Funding; FISH probes prognostication in myeloma: Patents & Royalties.

Abstract Background Waldenströms macroglobulinemia (WM) is a lymphoplasmacytic subtype of Non-Hodgkins lymphoma in which specific molecular changes lead to unrestricted cell proliferation and overproduction of immunoglobulin-M. These processes require exquisite coordination between growth promoting transcription factors (NFkB) and cell homeostatic systems. The bioavailability of various transcription factors and cell cycle proteins is primarily regulated by the ubiquitin proteasome system (UPS). Moreover, the proteolytic machinery ensures proper elimination of unwanted or misfolded proteins, which when disrupted leads to protein accumulation and apoptotic cell death. The 26S proteasome is a barrel shaped structure with a 20S catalytic core that is flanked by 19S caps on either side. 26S proteasomes are critical for WM cell survival, which is clinically evident, as up to 80% of WM patients treated with the proteasome inhibitor (PI) bortezomib have derived significant benefit. Traditional PI such as bortezomib and carfilzomib have been designed to target the B5 catalytic core within the 26S proteasome. However, proteasomes are capable of altering conformation of their proteolytic subunits in response to inflammation and stress, which can lower the effectiveness of these PI. The 19S cap is the regulatory complex and functions in unfolding and deubiquitinating the proteins before their entry into the 20S complex using constitutive deubiquitinating enzymes (DUBS). Recently, it has been demonstrated that inhibition of the DUBS, UCHL5 and USP14 results in cell death in a variety of tumor types but more so in cancer cells that rapidly divide or have a high protein turnover rate. Aim To define the anti-WM activity of the novel DUB inhibitor, b-AP15 in preclinical models of WM. Methods The WM cell lines BCWM.1, RPCI-WM1 and MWCL-1 were used for experiments in this analysis. Proteasomal activity was measured using synthetic fluorogenic peptide substrates. Apoptosis was determined by annexin-V/PI staining and mitochondrial membrane permeability (MOMP) was assessed using TMRM followed by flow cytometry. Protein profiling was done via immunoblot analysis. Results As reported by D’Arcy et al in their characterization of the b-AP15 molecule, inhibition of UCHL5 and USP14 by b-AP15 does not disrupt proteasomal activity conferred by the b-catalytic subunits. We confirmed these findings by treating WM cells with single agent bortezomib (10nM), carfilzomib (10nM), b-AP15 (100nM) or all three agents in combination to assess chymotrypsin-like, caspase-like and trypsin-like proteasomal activity using fluorogenic peptide substrates. Further, when used in combination with the other PI, PI-mediated chymotrypsin-like activity remained inhibited in the presence of b-AP15. Next, we sought to determine if b-AP15 treatment could induce WM cell death. Annexin-v staining showed that b-AP15 (500uM) induced apoptosis in all WM cell lines (28 – 60% cell death) with variable responses noted among the 3 models. Treatment with b-AP15 increased MOMP while also inducing the cleavage of caspases-9 and 3 and PARP-1 suggesting that the anti-WM activity of b-AP15 is mediated through the intrinsic apoptotic pathway. As components of the NFkB signaling cascade lie downstream to the UPS, we examined the effects of b-AP15 on this pathway. When treated with the DUB-inhibitor, nuclear translocation of NFkB was reduced in a time dependent manner. Interestingly, treatment with b-AP15 increased the phosphorylation of the mitogen activated protein kinase-p38 (p38) in all the WM cell lines tested. Treatment of WM cells with b-AP15 in presence of the p38 inhibitor, SB203580, resulted in a synergistic induction of cell death. Conclusion b-AP15 is a novel DUB inhibitor that disrupts two regulatory enzymes (UCHL5 and USP14) present in the 19S proteasomal cap. Results presented here demonstrate that b-AP15 induces apoptosis in in vitro models of WM and with in vivo analysis underway, is a potential therapeutic in WM. We would like to acknowledge the Waterfall Waldenström Macroglobulinemia Research Fund, the Leukemia and Lymphoma Society and the International Waldenström Macroglobulinemia Foundation for their continued support. Disclosures: No relevant conflicts of interest to declare.