Eculizumab for Refractory Thrombosis in Antiphospholipid Syndrome

Introduction:Antiphospholipid syndrome (APS) is characterized by arterial and/or venous thrombosis in the presence of antiphospholipid antibodies. Recently, derangement in the complement pathway has been implicated in APS pathophysiology. Refractory cases of APS with recurrent and potentially fatal thrombosis have prompted use of the monoclonal antibody eculizumab, which inhibits generation of the terminal complement complex. We present the successful use of eculizumab in controlling and preventing recurrent thrombosis in a refractory case of APS. Case Description:An 18-year-old female received a diagnosis of antiphospholipid syndrome after developing extensive unprovoked deep vein thrombosis of axillary, inferior vena caval and brachiocephalic veins. Thrombophilia evaluation revealed triple positivity for lupus anti-coagulant (LA), beta-2 glycoprotein I (GP) IgG 84.9 SGU Units, IgM 76.5 SMU Units, IgA 66.7 SAU Units and strongly positive anti-cardiolipin (aCL) antibodies (each >>40U/mL) with persistent positive titers after 12 weeks of initial evaluation. She was refractory with trials of multiple anticoagulants alone and with antiplatelet and adjunctive therapies. Anticoagulants used were enoxaparin, fondaparinux, apixaban, rivaroxaban, and warfarin; antiplatelet agents used were aspirin and clopidogrel; and adjunctive therapies included hydroxychloroquine, immunosuppression with steroids and rituximab, and plasmapheresis. Despite these interventions, she continued to develop recurrent thrombosis of subclavian, femoral, common femoral, iliac, popliteal and saphenous veins. She additionally developed a potentially life-threatening hepatic infarction and pulmonary embolism, and 6 weeks of plasma exchange failed to decrease antiphospholipid antibody titers. Following this event, eculizumab (600mg weekly x 4 weeks, followed by 900mg once on week 5, followed by 900mg every 2 weeks) was initiated in combination with fondaparinux, aspirin, clopidogrel, and hydroxychloroquine. She has remained on this regimen with additional anticoagulation and antiplatelet therapy without recurrence of thrombosis over the subsequent year. Discussion:Recent evidence has shown complement activation playing a role in pathophysiology of antiphospholipid syndrome. This is thought to occur through C3 and C5a causing platelet and endothelial activation, leading to microvascular thrombosis. Histological evidence of such processes is supported by the demonstration of anti-beta-2 GP1 IgG-C5b-9 immune complexes in microvascular organ thrombi in individuals with APS leading to thrombotic microangiopathy and multiorgan failure. Such evidence of complement induced thrombosis in antiphospholipid syndrome led us to use eculizumab following failure of available therapies including anticoagulation, antiplatelet therapy, immune modulation and plasmapheresis in a potentially life-threatening event. Absence of recurrent thrombotic events over approximately one year with eculizumab combined with anticoagulation and antiplatelet therapy highlights the potential role of complement inhibition in preventing thrombosis in APS. While the role of complement in thrombosis continues to be elucidated, we have observed no decline in antiphospholipid antibody levels in a span of one year in our patient. Importantly, there has been no recurrent thrombosis during this time. Our case suggests that eculizumab may have a role as a therapeutic option in refractory thrombosis in APS. Chronology of Events:Eculizumab initiated on 9/5/2019. No evidence of venous or arterial thrombosis since 10/2019 to present. Figure Disclosures Tarantino: Pfizer:Other;Genentech:Membership on an entity's Board of Directors or advisory committees;Octapharma:Membership on an entity's Board of Directors or advisory committees;Dova:Membership on an entity's Board of Directors or advisory committees;CDC:Membership on an entity's Board of Directors or advisory committees;Grifols:Membership on an entity's Board of Directors or advisory committees, Speakers Bureau;Amgen:Membership on an entity's Board of Directors or advisory committees;Biomarin:Membership on an entity's Board of Directors or advisory committees;NovoNordisk:Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau;Takeda:Research Funding;HRSA:Membership on an entity's Board of Directors or advisory committees;Spark:Membership on an entity's Board of Directors or advisory committees;Sobi:Membership on an entity's Board of Directors or advisory committees.McCrae:Rigel:Consultancy;Novartis:Honoraria;Momenta Pharmaceuticals:Consultancy;Dova:Consultancy.Chaturvedi:Sanofi:Honoraria, Membership on an entity's Board of Directors or advisory committees;Alexion:Honoraria, Membership on an entity's Board of Directors or advisory committees.Roberts:Octapharma:Consultancy, Speakers Bureau;uniQure:Consultancy;Sanofi:Consultancy, Speakers Bureau;Novo Nordisk:Consultancy, Speakers Bureau;Pfizer:Consultancy;Takeda:Consultancy, Research Funding, Speakers Bureau. OffLabel Disclosure: eculizumab for treatment of refractory thrombosis in antiphospholipid syndrome

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A Study of the Role of Antiplatelet Therapy in the Prevention of Thrombosis in Patients with Calr-Mutated Low Risk Essential Thrombocythemia

Blood ◽

10.1182/blood.v126.23.1602.1602 ◽

2015 ◽

Vol 126 (23) ◽

pp. 1602-1602

Author(s):

Alberto Alvarez-Larrán ◽

Paola Guglielmelli ◽

Eduardo Arellano-Rodrigo ◽

Martin Griesshammer ◽

Chiara Paoli ◽

...

Keyword(s):

Multivariate Analysis ◽

Board Of Directors ◽

Antiplatelet Therapy ◽

Major Bleeding ◽

Research Funding ◽

Jak2 V617f ◽

Low Risk ◽

Advisory Committees ◽

Prevention Of Thrombosis

Abstract Young patients (age < 60 years) with essential thrombocythemia (ET) and no history of thrombosis are considered at low risk of thrombosis and therefore managed on a conservative approach with antiplatelet therapy or even without any treatment. JAK2 V617F and CALR exon 9 mutations are the most frequent molecular alterations observed in ET, with CALR-positive ET being considered a distinct clinical entity due to its higher platelet counts and lower incidence of thrombosis as compared with JAK2 V617F-positive ET. There is some evidence supporting a role for antiplatelet therapy in JAK2 V7617F-positive neoplasms. However, the role of antiplatelet therapy in CALR-positive ET has not been studied. The aim of the present study was to assess the effect of antiplatelet therapy in the primary prevention of thrombosis in patients with CALR-positive ET without indication of cytoreductive therapy. For such purpose, 240 patients (107 males, 133 females) diagnosed with ET at a median age of 42 years (range 13-59) were included in a multicenter retrospective study. Initial treatment consisted of antiplatelet therapy (n=109) or careful observation (n=108), whereas 23 patients received cytoreduction since diagnosis and were excluded. During a median follow up of 8 years, 137 patients were started on cytoreductive therapy because of the following indications: age > 60 years (n=10), thrombosis (n=10), bleeding (n=2), microvascular symptoms (n=18), extreme thrombocytosis (n=89), and others (n=8). Median time free of cytoreductive therapy was 3.2 years. Thrombosis-free survival restricted to the time of cytoreductive therapy abstention was calculated using the Kaplan-Meier method. Variables attaining a significant level at the univariate analysis were included in a Cox proportional hazard model. During the period of abstention of cytoreductive therapy, a total of 10 thrombotic events and 8 major bleeding episodes were registered. The probability of thrombosis at 3 years was 5% in patients managed with careful observation and 1% in those receiving antiplatelet therapy (p = 0.2). At multivariate analysis, antiplatelet therapy did not result in a lower risk of thrombosis after correction for age, sex and presence of cardiovascular risk factors. Interaction studies did not identify any subgroup of patients that benefited from antiplatelet therapy in thrombosis prevention. Regarding major bleeding, patients receiving antiplatelet therapy experienced a higher rate than those managed on observation (3-year probability of major bleeding, 5.5% and 0%, respectively, p=0.05). At multivariate analysis, antiplatelet therapy was associated with a tendency towards and increased risk of major bleeding (HR: 7.7, 95%CI: 0.9-66.2, p=0.06) independently of platelet count at diagnosis, age and gender. In conclusion, CALR-mutated low-risk ET patients under cytoreductive therapy abstention may not obtain a clear benefit from antiplatelet therapy since the increase in the rate of bleeding may offset the reduction in the rate of thrombosis Disclosures García-Gutierrez: Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Ariad: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Harrison:CTI Biopharma: Consultancy, Honoraria, Speakers Bureau; Novartis: Honoraria, Research Funding, Speakers Bureau; Gilead: Honoraria; Sanofi: Honoraria, Speakers Bureau; Shire: Speakers Bureau. Cervantes:Sanofi-Aventis: Consultancy; Novartis: Consultancy, Speakers Bureau; CTI-Baxter: Consultancy, Speakers Bureau. Vannucchi:Shire: Speakers Bureau; Baxalta: Membership on an entity's Board of Directors or advisory committees; Novartis Pharmaceuticals Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.

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A Cohort Study of Warfarin Administered to Achieve An INR of 2.0 to 3.0 for the Prevention of Recurrent Venous Thrombosis in Patients with An Antiphospholipid Antibody.

Blood ◽

10.1182/blood.v114.22.3123.3123 ◽

2009 ◽

Vol 114 (22) ◽

pp. 3123-3123

Author(s):

Madeline Song ◽

Michael J. Kovacs ◽

Mark A. Crowther

Keyword(s):

Venous Thrombosis ◽

Board Of Directors ◽

Research Funding ◽

Standardized Test ◽

Low Risk ◽

Antiphospholipid Antibody ◽

Minor Bleeding ◽

Recurrent Thrombosis ◽

Advisory Committees

Abstract Abstract 3123 Poster Board III-60 Introduction Despite recent evidence, controversy remains regarding the optimal method of recurrent thrombosis prevention in patients with antiphospholipid antibodies (APLA) and prior thrombosis. Specifically, although two randomized trials have supported the efficacy of “usual intensity warfarin” (administered to a target INR of 2.0 to 3.0) there remains a dearth of prospective data examining this treatment. The aim of our study was to confirm that patients with prior thrombosis and an APLA had a low risk of recurrent thrombosis while being treated with warfarin administered to achieve an INR of 2.0 to 3.0. Methods We examined the annual rate of recurrent thrombosis in patients with prior thrombosis and APLA who had all been treated with OAT (oral anticoagulant therapy) to achieve a target INR of 2.0 to 3.0. Eligible patients had to have had at least one prior objectively confirmed arterial or venous thrombosis and at least one positive standardized test for an APLA. Patients were selected from the Victoria Hospital, and follow up appointments were conducted through the hospital's thrombosis clinic. Consenting patients underwent a baseline clinical examination with the intent to be followed every six months for evidence of recurrent thrombosis, adverse consequences of anticoagulation therapy, or until death. Results Eighty three patients (mean age 50.5 years; 50 females) were enrolled; one patient was lost to follow up and did not contribute data to the analyses. Median follow up was 12 months (Range 5-18 months). No patients experienced a recurrent thrombotic event. 10 patients (12.2%) had a minor bleeding event (5 had significant ecchymosis, two had rectal bleeding, two had vaginal bleeding, and one had hematuria). No major bleeding events occurred. One patient had a presumed transient ischemic attack (TIA). One patient (1.2%) died during follow up due to multi-system organ failure in the context of a failing hepatic allograft. Conclusion Patients with previous thrombosis and an APLA have a low risk of recurrent thrombosis while having a target INR of 2.0 to 3.0. “Usual intensity warfarin” therapy appears to be an adequate method of thromboprophylaxis in these patients. Disclosures Crowther: BI: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria, Research Funding; Leo Pharma: Consultancy, Honoraria, Research Funding; Sanofi-Aventis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Artisan Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees.

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Role of Remission Status and Prior Transplant in Optimizing Survival Outcomes Following Allogeneic Hematopoietic Stem Transplantation (HSCT) in Patients Who Received Inotuzumab Ozogamicin (INO) for Relapsed / Refractory (R/R) Acute Lymphoblastic Leukemia (ALL)

Blood ◽

10.1182/blood.v130.suppl_1.886.886 ◽

2017 ◽

Vol 130 (Suppl_1) ◽

pp. 886-886

Author(s):

Partow Kebriaei ◽

Matthias Stelljes ◽

Daniel J. DeAngelo ◽

Nicola Goekbuget ◽

Hagop M. Kantarjian ◽

...

Keyword(s):

Board Of Directors ◽

Survival Probability ◽

Research Funding ◽

Employment Equity ◽

Inotuzumab Ozogamicin ◽

Advisory Committees ◽

Allogeneic Hsct ◽

Post Transplant ◽

Equity Ownership

Abstract Introduction: Attaining complete remission (CR) prior to HSCT is associated with better outcomes post-HSCT. Inotuzumab ozogamicin (INO), an anti-CD22 antibody conjugated to calicheamicin, has shown significantly higher remission rates (CR/CRi and MRD negativity) compared with standard chemotherapy (SC) in patients (pts) with R/R ALL (Kantarjian et al. N Engl J Med. 2016). Pts treated with INO were more likely to proceed to HSCT than SC, which allowed for a higher 2-yr probability of overall survival (OS) than patients receiving SC (39% vs 29%). We investigated the role of prior transplant and proceeding directly to HSCT after attaining remission from INO administration as potential factors in determining post-HSCT survival to inform when best to use INO in R/R ALL patients. Methods: The analysis population consisted of R/R ALL pts who were enrolled and treated with INO and proceeded to allogeneic HSCT as part of two clinical trials: Study 1010 is a Phase 1/2 trial (NCT01363297), while Study 1022 is the pivotal randomized Phase 3 (NCT01564784) trial. Full details of methods for both studies have been previously published (DeAngelo et al. Blood Adv. 2017). All reference to OS pertains to post-HSCT survival defined as time from HSCT to death from any cause. Results: As of March 2016, out of 236 pts administered INO in the two studies (Study 1010, n=72; Study 1022, n=164), 101 (43%) proceeded to allogeneic HSCT and were included in this analysis. Median age was 37 y (range 20-71) with 55% males. The majority of pts received INO as first salvage treatment (62%) and 85% had no prior SCT. Most pts received matched HSCTs (related = 25%; unrelated = 45%) with peripheral blood as the predominant cell source (62%). The conditioning regimens were mainly myeloablative regimens (60%) and predominantly TBI-based (62%). Dual alkylators were used in 13% of pts, while thiotepa was used in 8%. The Figure shows post-transplant survival in the different INO populations: The median OS post-HSCT for all pts (n=101) who received INO and proceeded to HSCT was 9.2 mos with a 2-yr survival probability of 41% (95% confidence interval [CI] 31-51%). In patients with first HSCT (n=86) the median OS post-HSCT was 11.8 mos with a 2-yr survival probability of 46% (95% CI 35-56%). Of note, some patients lost CR while waiting for HSCT and had to receive additional treatments before proceeding to HSCT (n=28). Those pts who went directly to first HSCT after attaining remission with no intervening additional treatment (n=73) fared best, with median OS post-HSCT not reached with a 2-yr survival probability of 51% (95% CI 39-62%). In the latter group, 59/73 (80%) attained MRD negativity, and 49/73 (67%) were in first salvage therapy. Of note, the post-HSCT 100-day survival probability was similar among the 3 groups, as shown in the Table. Multivariate analyses using Cox regression modelling confirmed that MRD negativity during INO treatment and no prior HSCT were associated with lower risk of mortality post-HSCT. Other prognostic factors associated with worse OS included older age, higher baseline LDH, higher last bilirubin measurement prior to HSCT, and use of thiotepa. Veno-occlusive disease post-transplant was noted in 19 of the 101 pts who received INO. Conclusion: Administration of INO in R/R ALL pts followed with allogeneic HSCT provided the best long-term survival benefit among those who went directly to HSCT after attaining remission and had no prior HSCT. Disclosures DeAngelo: Glycomimetics: Research Funding; Incyte: Consultancy, Honoraria; Blueprint Medicines: Honoraria, Research Funding; Takeda Pharmaceuticals U.S.A., Inc.: Honoraria; Shire: Honoraria; Pfizer Inc.: Consultancy, Honoraria, Research Funding; Novartis Pharmaceuticals Corporation: Consultancy, Honoraria, Research Funding; BMS: Consultancy; ARIAD: Consultancy, Research Funding; Immunogen: Honoraria, Research Funding; Celgene: Research Funding; Amgen: Consultancy, Research Funding. Kantarjian: Novartis: Research Funding; Amgen: Research Funding; Delta-Fly Pharma: Research Funding; Bristol-Meyers Squibb: Research Funding; Pfizer: Research Funding; ARIAD: Research Funding. Advani: Takeda/ Millenium: Research Funding; Pfizer: Consultancy. Merchant: Pfizer: Consultancy, Research Funding. Stock: Amgen: Consultancy; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Wang: Pfizer: Employment, Equity Ownership. Zhang: Pfizer: Employment, Equity Ownership. Loberiza: Pfizer: Employment, Equity Ownership. Vandendries: Pfizer: Employment, Equity Ownership. Marks: Pfizer: Consultancy, Honoraria, Speakers Bureau; Amgen: Consultancy, Honoraria, Speakers Bureau.

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Impact of Interim FDG-PET (iPET) in the Outcomes of Patients with Aggressive B-Cell Lymphomas Receiving DA-EPOCH-R

Blood ◽

10.1182/blood-2019-122393 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 2898-2898

Author(s):

Vania Phuoc ◽

Leidy Isenalumhe ◽

Hayder Saeed ◽

Celeste Bello ◽

Bijal Shah ◽

...

Keyword(s):

B Cell ◽

Board Of Directors ◽

Fdg Pet ◽

Research Funding ◽

Cell Lymphoma ◽

B Cell Lymphoma ◽

Advisory Committees ◽

End Of Treatment

Introduction: 2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) remains the standard of care for baseline and end of treatment scans for aggressive non-Hodgkin lymphomas (NHLs). However, the role of interim FDG-PET remains not as well defined across aggressive NHLs, especially in the era of high-intensity chemoimmunotherapy. Interim FDG-PET (iPET) can serve as an early prognostic tool, and prior studies evaluating the utility of iPET-guided treatment strategies primarily focused on diffuse large B-cell lymphomas (DLBCL) and frontline R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone). Classification criteria systems assessing response also differ between studies with no clear consensus between use of Deauville criteria (DC), International Harmonization Project (IHP), and the ΔSUVmax method. Methods: This study evaluates our institutional experience with iPET during treatment with DA-EPOCH ± R (dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin with or without Rituximab) in aggressive NHLs. We retrospectively evaluated 70 patients at Moffitt Cancer Center who started on DA-EPOCH ± R between 1/1/2014 to 12/31/2018 for aggressive NHLs. Response on interim and end-of-treatment (EOT) scans were graded per DC, IHP, and ΔSUVmax methods, and progression free survival (PFS) probability estimates were calculated with chi-square testing and Kaplan Meier method. PFS outcomes were compared between interim negative and positive scans based on each scoring method. Outcomes were also compared between groups based on interim versus EOT positive or negative scans. Results: We identified 70 patients with aggressive NHLs who received DA-EPOCH ± R at our institute. The most common diagnoses were DLBCL (61%) followed by Burkitt's lymphoma (10%), primary mediastinal B-cell lymphoma (9%), plasmablastic lymphoma (7%), gray zone lymphoma (6%), primary cutaneous large B-cell lymphoma (1%), primary effusion lymphoma (1%), and other high-grade NHL not otherwise specified (3%). Of the 43 patients with DLBCL, 21/43 (49%) had double hit lymphoma (DHL) while 7/43 (16%) had triple hit lymphoma (THL), and 3/43 (7%) had MYC-rearranged DLBCL while 2/43 (5%) had double expressor DLBCL. Thirty nine out of 70 (56%) were female, and median age at diagnosis was 58.39 years (range 22.99 - 86.86 years). Most patients had stage IV disease (49/70, 70%), and 43/70 (61%) had more than one extranodal site while 45/70 (64%) had IPI score ≥ 3. Forty-six out of 70 (66%) received central nervous system prophylaxis, most with intrathecal chemotherapy (44/70, 63%). Fifty-five out of 70 (79%) had iPET available while 6/70 (9%) had interim computerized tomography (CT) scans. Fifty-six out of 70 (80%) had EOT PET, and 4/70 (6%) had EOT CT scans. Sustained complete remission occurred in 46/70 (66%) after frontline DA-EPOCH ± R (CR1), and 12/70 (17%) were primary refractory while 5/70 (7%) had relapse after CR1. Four of 70 (6%) died before cycle 3, and 3/70 (4%) did not have long-term follow-up due to transition of care elsewhere. Median follow-up was 15.29 months (range 0.85 - 60.09 months). There was significantly better PFS observed if iPET showed DC 1-3 compared to DC 4-5 (Χ2=5.707, p=0.0169), and PFS was better if iPET was negative by IHP criteria (Χ2=4.254, p=0.0392) or ΔSUVmax method (Χ2=6.411, p=0.0113). Comparing iPET to EOT PET, there was significantly better PFS if iPET was negative with EOT PET negative (iPET-/EOT-) compared to iPET positive with EOT negative (iPET+/EOT-), and iPET+/EOT+ and iPET-/EOT+ had worse PFS after iPET-/EOT- and iPET+/EOT- respectively. This pattern in iPET/EOT PFS probability remained consistent when comparing DC (Χ2=30.041, p<0.0001), IHP (Χ2=49.078, p<0.0001), and ΔSUVmax method (Χ2=9.126, p=0.0104). These findings fit clinical expectations with positive EOT scans indicating primary refractory disease. There was no significant difference in PFS when comparing DLBCL versus non-DLBCL (Χ2=3.461, p=0.0628) or DHL/THL versus non-DHL/THL diagnoses (Χ2=2.850, p=0.0914). Conclusion: Our findings indicate a prognostic role of iPET during treatment with DA-EPOCH ± R for aggressive NHLs. Significant differences in PFS were seen when graded by DC, IHP, and ΔSUVmax methods used in prior studies and when comparing interim versus EOT response. Larger studies are needed to confirm these findings. Disclosures Bello: Celgene: Speakers Bureau. Shah:Novartis: Honoraria; AstraZeneca: Honoraria; Spectrum/Astrotech: Honoraria; Adaptive Biotechnologies: Honoraria; Pharmacyclics: Honoraria; Jazz Pharmaceuticals: Research Funding; Incyte: Research Funding; Kite/Gilead: Honoraria; Celgene/Juno: Honoraria. Sokol:EUSA: Consultancy. Chavez:Janssen Pharmaceuticals, Inc.: Speakers Bureau; Genentech: Speakers Bureau; Kite Pharmaceuticals, Inc.: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees.

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Long-Term Outcome Following B-Cell Depletion Therapy with Rituximab In Children and Adults with Immune Thrombocytopenia (ITP)

Blood ◽

10.1182/blood.v116.21.72.72 ◽

2010 ◽

Vol 116 (21) ◽

pp. 72-72 ◽

Cited By ~ 1

Author(s):

Vivek L. Patel ◽

Matthieu Mahévas ◽

Roberto Stasi ◽

Susanna Cunningham-Rundles ◽

Bertrand Godeau ◽

...

Keyword(s):

Board Of Directors ◽

Research Funding ◽

Response Rate ◽

Initial Response ◽

Response Rates ◽

Advisory Committees ◽

Term Outcome ◽

Long Term Outcome ◽

One Year

Abstract Abstract 72 Background: Studies of B-cell depletion using Rituximab in adults with ITP report responses lasting at least one year in almost all of the 30–40% of patients with complete responses (CR: platelet count >150 × 109/l) and also a small fraction of patients with partial responses (PR: platelet count 50–150 × 109/l). However data describing patients with ITP who are relapse-free and off-treatment beyond 1–2 years from initial Rituximab are almost entirely anecdotal and comparable response data are even less available for children. This study assessed the duration of unmaintained platelet response following rituximab treatment in 72 adults and 66 children with ITP, all of whom had had at least an initial response to rituximab. Long-term outcome was estimated from these data. Methods: Seventeen published studies including 486 patients, 376 adults and 110 children, were used to obtain the initial response rates to standard-dose rituximab treatment (375mg/m2 weekly for 4 weeks) in adults and children. Only 1 included study did not use the standard dose of rituximab. The Godeau study (Blood, 2008) was used to estimate the one-year response rate in adults with ITP. Only those adults whose responses persisted at least one year had follow up assessed whereas children who demonstrated even ephemeral responses were included. Only verified counts were used in this IRB-approved multicenter study. Results: 138 subjects with CR's or PR's after rituximab were included. All patients had starting platelet counts <30×109/l and 131 (95%) had ITP of > 6 months duration. Thirty-three (24%) had undergone splenectomy. Using the data from prior publications to obtain the initial response rates, children had a 56% initial response rate to rituximab treatment and adults had a 57% rate. Taking initial responders and then using the Godeau data for adults and Kaplan-Meier analysis of our data for children, 38% one-year response rates were obtained for both children and adults treated with rituximab. Both age groups also showed remarkable similarity at two years with 30% relapse-free response rates. However, all of the 26 eligible children maintained their response beyond two years whereas adults continued to relapse. Therefore the five-year response rate was 30% for children and only 21% for adults. Sex, duration of ITP, and age among adults did not affect long-term outcome. The rate of relapse was almost identical for splenectomized patients and non-splenectomized ones but the splenectomized patients appeared to relapse sooner (Figure). Patients with CR's (55 of the 72 adults with responses lasting at least one year were CR's) had better long-term outcomes than did patients with PR's even more than one year from initial treatment. B-cells returned significantly sooner to higher levels in subjects who relapsed compared to those whose responses were ongoing. No clinical long-term toxicity was observed but 2 patients were identified to have mild hypogammaglobulinemia > 30 months from initial treatment. Conclusions: In summary, only approximately 1 in 5 adults treated with rituximab will have an at least five-year relapse-free response rate which is disappointingly low; children have only a slightly higher five-year relapse-free response rate. A pilot study to improve outcomes using either R-CVP or double dose rituximab was unsuccessful (Hasan, Am J Hematol,2009) Current efforts to improve long-term response rates have focused on the combination of high dose dexamethasone and rituximab (or even by providing maintenance treatment with rituximab). A better understanding of the mechanism of effect of rituximab in patients with ITP might allow an improved treatment strategy to be developed. Fortunately, the toxicity of rituximab treatment in patients with uncomplicated ITP appears to be low; however, yearly testing for immunoglobulins for a minimum of five years might be appropriate. Disclosures: Neufeld: Novartis. Inc: Research Funding. Shenoy:Novartis Oncology: Honoraria. Bussel:Amgen: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding; Cangene: Research Funding; GlaxoSmithKline: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genzyme: Research Funding; Immunomedics: Research Funding; Ligand: Membership on an entity's Board of Directors or advisory committees, Research Funding; Eisai Inc: Membership on an entity's Board of Directors or advisory committees, Research Funding; Shionogi: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sysmex: Membership on an entity's Board of Directors or advisory committees, Research Funding; Portola: Consultancy.

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Investigational Agent MLN9708 Target Tumor Suppressor MicroRNA-33b in Multiple Myeloma Cells

Blood ◽

10.1182/blood.v118.21.136.136 ◽

2011 ◽

Vol 118 (21) ◽

pp. 136-136

Author(s):

Ze Tian ◽

Jian-Jun Zhao ◽

Jianhong Lin ◽

Dharminder Chauhan ◽

Kenneth C. Anderson

Keyword(s):

Multiple Myeloma ◽

Tumor Suppressor ◽

Board Of Directors ◽

Expression Profiling ◽

Research Funding ◽

Advisory Committees ◽

Myeloma Cells ◽

Investigational Agent ◽

Reporter Activity

Abstract Abstract 136 Investigational Agent MLN9708 Target Tumor Suppressor MicroRNA-33b in Multiple Myeloma Cells Ze Tian, Jianjun Zhao, Jianhong Lin, Dharminder Chauhan, Kenneth C. Anderson Medical Oncology, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, 02115 MicroRNAs (miRNAs) are 19–25 nucleotide-long noncoding RNA molecules that regulate gene expression both at the level of messenger RNA degradation and translation. Emerging evidence shows that miRNAs play a critical role in tumor pathogenesis by functioning as either oncogene or tumor suppressor genes. The role of miRNA and their regulation in response to proteasome inhibitors treatment in Multiple Myeloma (MM) is unclear. Here, we utilized MLN9708, a selective orally bio-available proteasome inhibitor to examine its effects on miRNA alterations in MM.1S MM cells. Upon exposure to aqueous solutions or plasma, MLN9708 rapidly hydrolyzes to its biologically active form MLN2238. Our previous study using both in vitro and in vivo models showed that MLN2238 inhibits tumor growth and triggers apoptosis via activation of caspases. Moreover, MLN2238 triggered apoptosis in bortezomib-resistant MM cells, and induced synergistic anti-MM activity when combined with HDAC inhibitor SAHA, dexamethasone, and lenalidomide. In the current study, we treated MM.1S cells with MLN2238 (12 nM) for 3 hours and harvested; total RNA was subjected to miRNA profiling using TaqMan® Array Human miRNA A-Card Set v3.0 and the data was analyzed using dChip analysis. Results showed that MLN2238 modulates miRNA expression with a total of 36 miRNA changing their expression profiling (δδCT>1.5 or δδCT <-1.5; 19 were upregulated and 17 showed a downregulation). Among all miRNA, miR-33b was highly (δδCT>7) upregulated in response to MLN2238 treatment. We therefore hypothesized that miR-33b may play a role in MM pathogenesis as well as during MLN2238-induced proteasome inhibition in MM cells. We first utilized quantitative polymerase chain reaction (q-PCR) to validate the changes in miRNA expression profiling. Results confirmed that MLN2238 treatment triggers significant increase in the miR-33b expression in MM.1S cells (2.1 and 2.2 folds at 3h and 6h, respectively; P<0.001). Examination of normal PBMCs and plasma cells showed higher expression of miR-33b than patient MM cells (P<0.001). We further investigated the functional role of miR-33b in MM cells at baseline and during MLN2238 treatment. Drug sensitivity, cell viability, apoptosis, colony formation, and migration assays were performed using cell TilTer-Glo, Annexin V-FITC/PI staining, MTT staining, and Transwell assays, respectively. Signaling pathways modulated post miR-33b overexpression were evaluated by q-PCR, immunoblot, and reporter assays. Our findings show that overexpression of miR-33b significantly decreased cell viability, cell migration, colony formation, as well as increased apoptosis and sensitivity of MM cells to MLN2238 treatment. Targetscan analysis predicted pim-1 as a putative downstream target of miR-33b. Overexpression of miR-33b downregulated pim-1 mRNA and protein expression. To further corroborate these data, we co-tranfected miR-33b and Pim-1-wt or Pim-1-mt in 293T and MM.1S cell lines. In concert with our earlier findings, miR-33b decreases pim-1-wt, but not pim-1-mt reporter activity in both cell lines. Reflecting the overexpression study results, MLN2238 treatment also decreases pim-1-wt, but not pim1-mt reporter activity. Moreover, a biochemical inhibitor of pim1/2 triggered apoptosis in MM cells. Finally, overexpression of miR-33b inhibits tumor growth (P<0.001) and prolongs survival (P<0.001) in both subcutaneous and disseminated human MM xenograft models. In summary, our study suggests that miR-33b is a tumor suppressor, which plays a role during MLN2238-induced apoptotic signaling in MM cells, and provide the basis for novel therapeutic strategies targeting miR-33b in MM. Disclosures: Anderson: Millennium: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Acetylon: Equity Ownership.

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Deregulation of TNFRSF18 (GITR) Through Promoter CpG Island Methylation Induces Tumor Proliferation in Multiple Myeloma

Blood ◽

10.1182/blood.v118.21.2424.2424 ◽

2011 ◽

Vol 118 (21) ◽

pp. 2424-2424

Author(s):

Yang Liu ◽

Yong Zhang ◽

Phong Quang ◽

Hai T Ngo ◽

Feda Azab ◽

...

Keyword(s):

Gene Expression ◽

Bone Marrow ◽

Flow Cytometry ◽

Board Of Directors ◽

Research Funding ◽

Plasma Cells ◽

Cpg Island ◽

Advisory Committees ◽

Brdu Assay

Abstract Abstract 2424 Introduction Tumor necrosis factor receptor super families (TNFRSFs) play an important role in activation of lymphocyte and cell apoptosis. However the function of TNFRSFs in multiple myeloma (MM) remains unknown. Loss of function mutation of Fas antigen (TNFRSF6) was identified in MM cells, thus suggesting the possible role of TNFRSFs in regulating MM pathogenesis. We therefore investigated the epigenetic mechanisms that may mediate inactivation of TNFRSFs and its functional role in MM. Methods Dchip software was utilized for analyzing gene expression dataset. DNA was extracted from both primary CD138+ MM plasma cells and MM cell lines using blood & tissue DNA isolation kit (Qiagen, Inc.). Expression of GITR in primary CD138+ plasma cells was detected by Imunohistochemistry (IHC) DNA methylation was analyzed by methylated DNA immunoprecipitation (Medip) assay and bisulfate sequencing. 5'azacytidine was used to demethylate genomic DNA. Gene expression was detected by qRT-PCR and confirmed at the protein level by flow cytometry and western-blot. Over-expression of GITR was obtained in MM1.S cells by using GITR recombinant plasmid and electroporation. Apoptosis was determined using Annexin/PI staining and flow cytometry analysis. Activation of apoptotic signaling was studied by western blot. Cell survival and proliferation were analyzed by MTT and BrdU assay, respectively. Recombinant GITR-lentivirus was obtained from the supernatant of culture medium after 72 hours transfection in 293 cells. GFP positive MM cells were sorted and analyzed by flow cytometry. In vivo effect of GITR on MM tumor growth was determined by injection of GITR over-expressing MM cells in null mice. Mice skull, femur and vertebrae were isolated after 4 weeks injection. Anti-human CD138+ mAb microbead was used to detect MM cells extracted from mice tissue by flow cytometry. Results Gene-expression profiling showed down-regulation of TNFRSFs, including TNFRSF11A, TNFRSF11B, TNFRSF8, TNFRSF10C, TNFRSF9, TNFRSF21, TNFRSF1B, TNFRSF1A and TNFRSF18, compared to normal plasma cells. Moreover, Our IHC results also showed that GITR expression was positive in primary CD138+ plasma cells from 9 normal bone marrow, but negative in 9 MM samples. Importantly, we found that low GITR expression significantly correlated with MM progression. Indeed, GITR gene levels were lower in smoldering and active MM patients compared to MGUS patients and normal donors. Promoter CpG island (CGI) methylation of GITR was indentified in 5 out of 7 MM primary bone marrow (BM)-derived CD138+ cells but not in normal BM-derived plasma cells. Bisulfate sequencing and Medip assay showed that methylation of GITR was significantly associated with GITR expression in 5 MM cell lines, including MM1.S, OPM1, U266, RPMI and INA6. Promoter CGI of GITR was highly methylated leading to complete silencing of GITR in MM1.S cell line. GITR expression was significantly up-regulated in MM cells upon treatment with the 5'azacytidine. MTT and BrdU assay revealed that the proliferation and survival of MM1.S cells was disrupted in the GITR over-expressing MM1.S cells, notably with inhibition of cell proliferation compared to control vector infected cells. Moreover induction of cytotoxicity in GITR over-expressing cells was confirmed by using GFP competition assay. GITR-induced apoptosis was supported by induction of caspase 8 and 3 cleavage. The inhibition of human CD138+ plasma cell growth in the bone marrow of SCID mice using a disseminated MM xenograft model was observed in the experimental group injected with GITR expressing cells compared to the control group after 4 weeks injection. Conclusion Our findings uncovered a novel epigenetic mechanism contributing to MM pathogenesis, showing the role of GITR methylation as a key regulator of MM cell survival. Disclosures: Roccaro: Roche:. Ghobrial:Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Research Funding; Noxxon: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding.

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Outcome and Prognostic Factors in Patients with Mantle Cell Lymphoma Relapsing After Autologous Stem Cell Transplantation: A Retrospective Study of the EBMT

Blood ◽

10.1182/blood.v120.21.474.474 ◽

2012 ◽

Vol 120 (21) ◽

pp. 474-474 ◽

Cited By ~ 1

Author(s):

Sascha Dietrich ◽

Herve Finel ◽

Ariane Boumendil ◽

Irit Avivi ◽

Liisa Volin ◽

...

Keyword(s):

Prognostic Factors ◽

Board Of Directors ◽

Research Funding ◽

Cell Lymphoma ◽

Salvage Chemotherapy ◽

Refractory Disease ◽

Advisory Committees ◽

Mantle Cell ◽

One Year

Abstract Abstract 474 BACKGROUND: Autologous stem cell transplantation (autoSCT) is considered as standard treatment for non-frail patients with mantle cell lymphoma (MCL). However, little is known about outcome of MCL recurrence after autoSCT. We therefore conducted a retrospective analysis of patients with MCL who failed autoSCT using the EBMT database. PRIMARY OBJECTIVE was to analyse outcome and prognostic factors after relapse following autoSCT for MCL in the rituximab era. PRIMARY ENDPOINT was overall survival (OS) from relapse. ELIGIBLE were patients aged 18 years or more who relapsed following an autoSCT for MCL performed between 2000 and 2010 and who were registered with the EBMT. Centres were contacted to provide additional information on relapse treatment. STATISTICAL ANALYSIS was based on log-rank comparisons and multivariable testing using Cox regression models. RESULTS: 1054 patients meeting the eligibility criteria could be identified in the EBMT registry. Of these, a full data set could be retrieved for 382 patients. Sixteen patients had to be excluded due to loss of follow up (n=7), wrong diagnosis (n=6), or falsely reported relapse (n=3). Median age at autoSCT of 366 evaluable patients was 59 years (range: 37 to 76), 290 patients (79%) were men. 64% had undergone autoSCT as part of 1st-line therapy; 68% and 49% had documented exposure to rituximab (RTX) and high-dose ara-C (HA) before autoSCT; and 12% had had refractory disease at autoSCT. Median time from autoSCT to relapse was 20 months (range: 0.4 to 117). 21 relapses (6%) occurred beyond 5 years after autoSCT. With a median observation time of 37 months (95% CI 32–43), median OS after relapse of the whole study group was 20 months. By univariate analysis, a long (>12mo) interval between autoSCT and relapse (p<0.001; HR 0.26; Figure 1A), 1st-line autoSCT (p=0.006; HR 0.7) refractory disease at autoSCT (p<0.001, HR 2.0) and more recent year of relapse (p<0.001, HR per year 0.9) significantly influenced OS from relapse, whereas age, gender, RTX and HA exposure did not. By multivariate analysis refractory disease at autoSCT (p<0.001, HR=2.14), remission duration after autoSCT (p<0.001 HR per 3 months 0.88) and calendar year of relapse (p<0.03, HR per year 0.93) were confirmed to be predictors for OS. In addition, HA exposure prior autoSCT adversely affected OS from relapse (p=0.06, HR 1.38). Salvage chemotherapy after relapse resulted in only 31% complete responses and 29% partial responses, whereas 40% of patients have been refractory to first salvage chemotherapy. 83 patients (23%) received an allogeneic SCT (alloSCT), whereas only 7 patients (2%) received a second autoSCT after relapse. Median time after relapse to second SCT was 7 months (range: 1 to 40). Survival after relapse for patients who received a second autoSCT was poor with no long-term survivor. AlloSCT performed for late relapse (>12mo) after autoSCT was associated with superior OS compared to patients who received an allograft upon a shorter remission duration after autoSCT (5-year OS from alloSCT 50% vs 0%; p=0.001; Figure 1B). Achievement of CR before alloSCT (p=0.05 HR=0.5), but not donor source, T-cell depletion or conditioning intensity affected OS after alloSCT. CONCLUSIONS: Patients with MCL who relapse within one year after autoSCT have an extremely dismal outcome even with alloSCT. In contrast, about half of the patients who have MCL recurrence beyond one year after autoSCT and can undergo salvage alloSCT enjoy long-term survival. It remains to be shown if a similarly good outcome can be achieved without alloSCT in this favourable selection of patients. A 2nd autoSCT does not appear to be a promising option in patients with MCL failing a 1st autoSCT. Disclosures: Walewski: Mundipharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Roche: Honoraria, Speakers Bureau; GSK: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Janssen-Cilag: Membership on an entity's Board of Directors or advisory committees; Cephalon: Research Funding.

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Absence Of Mutation In Cereblon (CRBN) and DNA Damage Binding Protein 1 (DDB1) Genes In Myeloma Cells and Patients and Its Clinical Significance

Blood ◽

10.1182/blood.v122.21.3139.3139 ◽

2013 ◽

Vol 122 (21) ◽

pp. 3139-3139

Author(s):

Anjan Thakurta ◽

Anita K Gandhi ◽

Michelle Waldman ◽

Chad C. Bjorklund ◽

Suzanne Lentzsch ◽

...

Keyword(s):

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Heterozygous Mutation ◽

Employment Equity ◽

Advisory Committees ◽

Single Nucleotide ◽

Truncating Mutation ◽

Equity Ownership

Abstract Background CRBN, a target of thalidomide and IMiDs® immunomodulatory agents lenalidomide (LEN) and pomalidomide (POM), is a component of the E3 ubiquitin cullin 4 ring ligase (CRL4) complex that also includes DDB1, Roc1, and Cul4. Two CRBN mutations have been reported in multiple myeloma (MM) patients: truncating mutation (Q99) and point mutation (R283K). One copy of the CRBN gene was shown to be deleted in the MM1S and MM1S.R cell lines. No DDB1 mutation has been described previously. Results We investigated the incidence of CRBN and DDB1 mutations by next-generation sequencing in 20 MM cell lines and MM subjects. Of 90 MM patients, 24 were newly diagnosed and 66 were relapsed and refractory of which 36 patients were LEN resistant. Out of the cell lines tested, 1 heterozygous CRBN mutation (D249Y) was found in the LEN-resistant ANBL6R cells, which is located in the putative DDB1 binding domain, and 2 single silent mutations were identified in the KMS-12-BM (rs17027638) and OPM-2 cells. One DDB1 heterozygous mutation (E303D) was identified in ANBL6 cells. In the cohort of patients assessed, no CRBN mutation was detected; however, 5 single nucleotide variations (SNV) were identified. Three of the 5 SNVs were at position 735 (Y245Y) and 1 each at position 219 (H73H) and 939 (C313C), respectively. The first 2 SNVs (rs17027638 and rs1045309) are described but not the last. We found a single SNV (P51P; rs2230356) in DDB1 gene the patient samples. Conclusion Mutations within the coding sequences of CRBN and DDB1 are rare in MM patients and cell lines. Most intrinsically LEN-resistant cells and cell lines made resistant to LEN or POM do not have CRBN or DDB1 mutations, suggesting the potential role of other sources, such as genetic or epigenetic pathways in developing resistance to IMiD drug–based therapy. Disclosures: Thakurta: Celgene: Employment, Equity Ownership. Gandhi:Celgene: Employment, Equity Ownership. Waldman:Celgene: Employment, Equity Ownership. Bjorklund:Celgene: Employment, Equity Ownership. Lentzsch:Celgene: Research Funding. Schey:Celgene: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau; NAPP: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau; BMS: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau. Orlowski:Bristol-Myers Squibb: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Millennium: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Onyx: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Resverlogix: Research Funding; Array: Honoraria, Membership on an entity’s Board of Directors or advisory committees; Genentech: Honoraria, Membership on an entity’s Board of Directors or advisory committees; Merck: Membership on an entity’s Board of Directors or advisory committees. Madan:Covance Genomics Lab: Employment. Ning:Celgene: Employment, Equity Ownership. Mendy:Celgene: Employment, Equity Ownership. Lopez-Girona:Celgene: Employment, Equity Ownership. Schafer:Celgene: Employment, Equity Ownership. Avet-Loiseau:Celgene: Research Funding. Chopra:Celgene: Employment, Equity Ownership.

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The Influence Of KIR Haplotype In ITP Incidence, Treatment Response and Bleeding Symptoms

Blood ◽

10.1182/blood.v122.21.2316.2316 ◽

2013 ◽

Vol 122 (21) ◽

pp. 2316-2316

Author(s):

Bethan Psaila ◽

Nayla Boulad ◽

Emily Leven ◽

Naznin Haq ◽

Christina Soo Lee ◽

...

Keyword(s):

Platelet Count ◽

B Cells ◽

Nk Cells ◽

Board Of Directors ◽

Research Funding ◽

Nk Cell ◽

Advisory Committees ◽

Kir Genes ◽

Number Of Patients

Abstract The pathogenesis of immune thrombocytopenia (ITP) is multifactorial, with both cellular and humoural immune dysfunction. The role of NK cells has not been well defined in ITP but in other diseases NK cells have a role in rejecting “foreign” eg transplanted organ or tumor, and also acting against self as occurs in autoimmunity. NK cell activity is orchestrated by the balance of activating vs. inhibitory signalling, in particular via the killer cell immunoglobulin-like receptor (KIR) family of receptors. Significant variation exists in KIR allelic subtype and copy number for the KIR between individuals, and associations have been made with certain haplotypes and a number of autoimmune disorders including rheumatoid arthritis, scleroderma and diabetes. Previous reports have demonstrated a reduction in natural killer (NK) cell number and function in ITP and expression of inhibitory KIR genes is increased in patients in remission vs. active ITP. Methods To explore whether a particular KIR haplotype might predispose to ITP, and also affect response to ITP treatment, we performed KIR genotyping using the Invitrogen SSP kit on 92 patients attending a haematology centre in New York and compared the results to data from 213 controls taken from the USA Eastern Database. Genomic DNA was typed for the inhibitory KIR genes KIR2DL1, KIR2DL2, KIR2DL5A (alleles 001 and 002), KIR2DL5B (alleles 002-004, 06, and 007), KIR3DL1, KIR3DL3; the activating KIR genes KIR2DS1, KIR2DS2, KIR2DS3, KIR2DS4, KIR2DS5, KIR3DS1; the framework genes KIR2DL3, KIR2DL4, KIR3DL2, KIR3DP1; and the pseudogene KIR2DP1. The patients with ITP had been or were receiving treatment with IVIG (n=64), corticosteroids (72) and rituximab (37). Bleeding symptoms were recorded. Response to treatment was defined as complete - platelet count increase to > 100 x 109/mL; partial - platelet count increase to > 50 x 109/mL; or no response. For the purpose of analysis, PRs and CRs were combined. A comprehensive database allowed a logistic regression, assessing both responses to treatments, platelet counts, neutrophil counts, CRP, lymphocyte subsets and bleeding symptoms. Results The expression of two inhibitory KIR genes, 2DL1 and 3DL1, was significantly lower in the patients with ITP as compared to controls (87% 2DL1 and 87% 3DL1 compared to 99% in controls - P < 0.02). Response to rituximab was strongly related to KIR haplotype expression. 2DL1 expression was higher among nonresponders to Rituximab (100% of non responders compared to 82% of responders), whereas 2DL3 expression was significantly lower (79% compared to 90%) (P < 0.05, Figure 1B). Separately, patients with the 2DS3 allele, an activatory KIR, were 5.5 times more likely to have experienced significant bleeding. Conclusions Although these findings are preliminary and require further investigation, these data suggest that increased cytotoxic autoimmunity due to reduced KIR inhibition may be associated with the development of ITP and possibly contribute importantly to the pathogenesis. Anti-CD20 targeting therapy directed at B cells was strongly influenced by 2 different KIRs (1 upregulated and one down-regulated) emphasizing the potential role of NK cells in elimination of tissue-based (nodal) B cells. Finally a more pronounced clinical phenotype with a markedly higher incidence of severe bleeding associated with an increased activatory KIR expression demonstrates the role of NK cells in bleeding presumably via their effects on either endothelial cells or platelet function. These exciting findings will be pursued for confirmation in a larger number of patients. Disclosures: Bussel: Amgen: Family owns stock Other, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Cangene: Research Funding; Genzyme: Research Funding; GlaxoSmithKline: Family owns stock, Family owns stock Other, Membership on an entity’s Board of Directors or advisory committees, Research Funding; IgG of America: Research Funding; Immunomedics: Research Funding; Ligand: Membership on an entity’s Board of Directors or advisory committees, Research Funding; Eisai: Membership on an entity’s Board of Directors or advisory committees, Research Funding; Shionogi: Membership on an entity’s Board of Directors or advisory committees, Research Funding; Sysmex: Research Funding; Symphogen: Membership on an entity’s Board of Directors or advisory committees.

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