ALBERT

Description: Introduction CTL019 is a novel, investigational, chimeric antigen receptor (CAR) immunotherapy whereby autologous T cells are genetically modified with a chimeric antigen receptor to target CD19 on the surface of malignant as well as healthy B cells. The cellular kinetics of CTL019 have been evaluated in several trials for patients with relapsed/refractory CD19+ leukemias, including pediatric acute lymphoblastic leukemia (pALL), adult ALL (aALL), and chronic lymphocytic leukemia (CLL) (Maude 2014, Porter 2015). Methods The cellular kinetic profile of CTL019 was determined in peripheral blood (PB) and bone marrow (BM) through serial measurements using flow cytometry and quantitative real-time polymerase-chain-reaction (qPCR) assay in 3 studies comprised of (i) 55 pALL patients (NCT01626495), (ii) 28 adult CLL patients from a dose selection study (NCT01747486), and (iii) 14 CLL and 6 adult ALL patients (NCT01029366). The flow cytometry assay used a CAR19-specific anti-idiotype antibody to enumerate CTL019 T cells as a % of CD3+ T cell (Porter 2015). Cellular kinetic parameters included: maximal extent of expansion as measured by peak copies of CTL019 DNA and peak % by flow cytometry (Cmax), area under the curve at day 28 (AUC0-28d) describing expansion and persistence in the first month, and time to reach Cmax (Tmax). Parameters were derived by non-compartmental methods. Where estimable, persistence was described by the half-life (T1/2) based on the slope of the terminal phase. Results Following infusion, CTL019, expansion and persistence was evident in the patients who responded to CTL019 as measured by both PK assays across all 3 studies. Table 1 summarizes (arithmetic mean (SD)) the CTL019 kinetic parameters. With complete remission (CR/CRi), CTL019 cells undergo rapid in vivo expansion beyond the original CTL019 dose with maximal expansion at a mean of 11 days in pALL and aALL and approximately 14-18 days in adult CLL as determined by qPCR and flow cytometry (Table 1). In CR/CRi patients the transgene level-profiles in PB reveal a kinetic profile with an initial rapid expansion followed by a slower decay function with some fluctuations of transgene over time resulting in higher AUC0-28d and Cmax, while non-responder (NR) patients tend to have a lower expansion and faster decay (shorter T1/2)of CAR positive T-cells resulting in lower AUC0-28d and Cmax by, leaving the mechanism to be further explored. In pALL, significantly higher AUC0-28d and Cmax were observed in CR/CRi patients compared to NR patients by flow cytometry; however, a wide range of mean AUC0-28d and Cmax was observed in NR patients (n=3) resulting from significant expansion in one NR patient as determined by qPCR. In CLL, the exposure metrics AUC0-28d and Cmax were approximately 12 times higher in CR/CRi patients compared with PRi/NR/PD in NCT01747486; a similar trend was observed in NCT01029366. Similar findings were captured by the flow cytometry based measurements as summarized in Table 1. In pALL and CLL, CR/CRi patients tend to maintain higher levels of CTL019 transgene over longer periods of time (〉6 months) compared to NR patients as demonstrated by the longer T1/2 value. Cellular kinetic parameters were not summarized by response category for aALL due to the small sample size (n=5 CR/CRi; n=1 NR). CTL019 transgene levels ranged from below the limit of quantification (BLQ) to 178,000 copies/ug in aALL patients with CR/CRi and BLQ to 21,900 copies/ug in the NR. CTL019 positive cells were also shown to traffic to BM at 1 month in responders (CR/CRi), irrespective of the disease. Conclusions Overall, significantly higher levels of in vivo proliferation and persistence were observed in patients who successfully responded to CTL019 (i.e. CR/CRi/PR) compared to NRs in both CLL and (adult and pediatric) ALL patients, as captured by both analytical measures, indicating that the kinetics of CTL019 T cells and that proliferation and persistence of CTL019 reasonably predicts response to therapy. These are the first three studies to demonstrate that cellular kinetics may predict responses to CAR based cellular therapy. These results imply that measures to increase proliferation and persistence of CAR T cells may enhance responses in resistant patients. Figure. CTL019 concentration-time profiles for %CD3+/CTL019+ measured by flow cytometry and cellular kinetic parameters for qPCR and flow cytometry for p-ALL and adult CLL Figure. CTL019 concentration-time profiles for %CD3+/CTL019+ measured by flow cytometry and cellular kinetic parameters for qPCR and flow cytometry for p-ALL and adult CLL Disclosures Mueller: Novartis Pharmaceuticals: Employment. Chakraborty:Novartis Pharmaceuticals: Employment, Equity Ownership. Wood:Novartis Pharmaceuticals: Employment, Other: Stock. Awasthi:Novartis Pharmaceuticals: Employment. Quintas-Cardama:Novartis Pharmaceuticals: Employment, Equity Ownership. Han:Novartis Pharmaceuticals: Employment, Equity Ownership. Maude:Novartis: Consultancy. Grupp:Jazz Pharmaceuticals: Consultancy; Pfizer: Consultancy; Novartis: Consultancy, Research Funding. Porter:Novartis: Patents & Royalties, Research Funding; Genentech: Employment. Frey:Novartis: Research Funding; Amgen: Consultancy. Marcucci:Novartis: Research Funding. Levine:GE Healthcare Bio-Sciences: Consultancy; Novartis: Patents & Royalties, Research Funding. Melenhorst:Novartis: Research Funding. June:Celldex: Consultancy, Equity Ownership; Immune Design: Consultancy, Equity Ownership; Pfizer: Honoraria; Novartis: Honoraria, Patents & Royalties: Immunology, Research Funding; University of Pennsylvania: Patents & Royalties; Tmunity: Equity Ownership, Other: Founder, stockholder ; Johnson & Johnson: Research Funding. Lacey:Novartis: Research Funding.

Description: New treatments directly targeting polymerization of sickle hemoglobin (HbS), the proximate event in the pathophysiology of sickle cell disease (SCD), are needed to address the severe morbidity and early mortality associated with the disease. Voxelotor (GBT440) is a first-in-class oral therapy specifically developed to treat SCD by modulating the affinity of hemoglobin (Hb) for oxygen, thus inhibiting HbS polymerization and downstream adverse effects of hemolytic anemia and vaso-occlusion. GBT440-001 was a phase 1/2 randomized, double-blind, placebo-controlled, single and multiple ascending dose study of voxelotor in adult healthy volunteers and patients with SCD, followed by a single-arm, open-label extension study. This report describes results of voxelotor (500-1000 mg per day) in patients with sickle cell anemia. The study evaluated the safety, tolerability, pharmacokinetic, and pharmacodynamic properties of voxelotor and established proof of concept by improving clinical measures of anemia, hemolysis, and sickling. Thirty-eight patients with SCD received 28 days of voxelotor 500, 700, or 1000 mg per day or placebo; 16 patients received 90 days of voxelotor 700 or 900 mg per day or placebo. Four patients from the 90-day cohort were subsequently enrolled in an extension study and treated with voxelotor 900 mg per day for 6 months. All patients who received multiple doses of voxelotor for ≥28 days experienced hematologic improvements including increased Hb and reduction in hemolysis and percentage of sickled red cells, supporting the potential of voxelotor to serve as a disease-modifying therapy for SCD. Voxelotor was well tolerated with no treatment-related serious adverse events and no evidence of tissue hypoxia. These trials were registered at www.clinicaltrials.gov as #NCT02285088 and #NCT03041909.

Description: In chronic lymphocytic leukemia (CLL), acquired T-cell dysfunction impedes development of effective immunotherapeutic strategies, through as-yet unresolved mechanisms. We have previously shown that CD8+ T cells in CLL exhibit impaired activation and reduced glucose uptake after stimulation. CD8+ T cells in CLL patients are chronically exposed to leukemic B cells, which potentially impacts metabolic homeostasis resulting in aberrant metabolic reprogramming upon stimulation. Here, we report that resting CD8+ T cells in CLL have reduced intracellular glucose transporter 1 (GLUT1) reserves, and have an altered mitochondrial metabolic profile as displayed by increased mitochondrial respiration, membrane potential, and levels of reactive oxygen species. This coincided with decreased levels of peroxisome proliferator-activated receptor γ coactivator 1-α, and in line with that, CLL-derived CD8+ T cells showed impaired mitochondrial biogenesis upon stimulation. In search of a therapeutic correlate of these findings, we analyzed mitochondrial biogenesis in CD19-directed chimeric antigen receptor (CAR) CD8+ T cells prior to infusion in CLL patients (who were enrolled in NCT01747486 and NCT01029366 [https://clinicaltrials.gov]). Interestingly, in cases with a subsequent complete response, the infused CD8+ CAR T cells had increased mitochondrial mass compared with nonresponders, which positively correlated with the expansion and persistence of CAR T cells. Our findings demonstrate that GLUT1 reserves and mitochondrial fitness of CD8+ T cells are impaired in CLL. Therefore, boosting mitochondrial biogenesis in CAR T cells might improve the efficacy of CAR T-cell therapy and other emerging cellular immunotherapies.

Description: Background Transfusion-dependent β-thalassemia (TDT) is a severe genetic disease caused by impaired β-globin production, leading to severe anemia, lifelong transfusion dependence with iron overload and serious comorbidities. Gene therapy (GT) offers a potentially transformative option for these patients. LentiGlobin GT contains autologous CD34+ hematopoietic stem cells (HSCs) transduced ex vivo with the BB305 lentiviral vector (LVV) encoding β-globin with a T87Q substitution. The safety and efficacy of LentiGlobin in patients with TDT was assessed in the phase 1/2 Northstar study in which 8/10 patients with non-β0/β0 genotypes and 3/8 patients with a β0/β0 genotype stopped transfusions. A refined manufacturing process to improve drug product (DP) characteristics is being evaluated in the studies presented here. Methods Northstar-2 (HGB-207; NCT02906202) and Northstar-3 (HGB-212; NCT03207009) are ongoing, international, single-arm, phase 3 studies in patients with TDT (≥ 100 mL/kg/yr of red blood cells [RBCs] or ≥ 8 RBC transfusions/yr) and non-β0/β0 genotypes or a β0/β0 genotype, respectively. HSCs were collected by apheresis after G-CSF and plerixafor mobilization. CD34+ HSCs were transduced with the BB305 LVV using a refined manufacturing process. Patients received single-agent, myeloablative busulfan conditioning and transduced cells were infused. The primary endpoint in Northstar-2 is the proportion of patients achieving transfusion independence (TI, weighted average hemoglobin [Hb] ≥ 9g/dL without RBC transfusions for ≥ 12 months continuously) and in Northstar-3 is the proportion of patients achieving transfusion reduction (≥ 60% reduction in transfused RBC volume post-DP infusion compared to pre-DP infusion). Patients were evaluated for engraftment, DP and peripheral blood vector copy number (VCN), GT-derived Hb (HbAT87Q), adverse events (AEs), vector integration, and evidence of replication competent lentivirus (RCL). Patients are followed for 2 years and offered participation in a long-term follow-up study. Results Eleven patients (median age 20 [min - max: 12 - 24] years) with TDT and non-β0/β0 genotypes (5 β+/β0, 4 βE/β0, 2 β+/β+) have been treated in Northstar-2 as of May 15, 2018 with a median follow-up of 8.5 (min - max: 0.3 - 16.2) months. DPs had a median cell dose of 7.4 x 106 (min - max: 5.0 - 19.4 x 106) CD34+ cells/kg, median VCN of 3.4 (min - max: 2.4 - 5.6) copies/diploid genome (c/dg) and a median of 82% (min - max: 53 - 90%) CD34+ cells were transduced. Median time to neutrophil and platelet engraftment was 21.5 (min - max: 16 - 28) and 44.5 (min - max: 34 - 84) days, respectively, in 10 patients; 1 patient was not yet evaluable. Serious AEs after DP infusion included 2 events of grade 4 liver veno-occlusive disease treated with defibrotide and 1 event each of hypotension, hypoxia, sepsis, and transfusion reaction, all resolved. Only 1 AE (grade 1 abdominal pain) was related to LentiGlobin. There were no deaths or graft failure and no evidence of vector-mediated RCL or clonal dominance. Of 8 patients with ≥ 6 months follow-up, 7 have stopped RBC transfusions. At last study visit, peripheral blood VCN was 1.1 - 5.0 c/dg and total Hb was 11.1 - 13.3 g/dL of which 7.6 - 10.2 g/dL (68 - 92%) was contributed by HbAT87Q. Median Hb at month 6 was 11.9 (min - max: 11.2 - 13.3) g/dL. The first treated patient achieved TI. The additional patient with ≥ 6 months follow-up had no transfusions for 11 months, however had a peripheral blood VCN of 0.2 c/dg and resumed transfusions due to symptomatic anemia. Bone marrow assessment of dyserythropoesis and data with longer follow-up will be presented. Two patients, 26- and 7- years old, have been treated in Northstar-3. Both had 2 DP lots manufactured with DP VCNs of 2.9/3.3 and 3.4/3.9 c/dg and 82%/85% and 78%/78% CD34+ cells were transduced, respectively. Both successfully engrafted. Additional data for these patients will be presented. Summary Seven of 8 patients with TDT and non-β0/β0 genotypes produced sufficient HbAT87Q to stop chronic transfusions following LentiGlobin GT in Northstar-2. The safety profile appears consistent with busulfan myeloablative conditioning with no grade ≥ 3 DP-related AEs. Initial results show DP characteristics in Northstar-3 are consistent with those in Northstar-2. Additional data from Northstar-3 will determine the impact of HbAT87Q production on transfusion reduction in patients without endogenous β-globin production. Disclosures Locatelli: bluebird bio: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Miltenyi: Honoraria; Bellicum: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Walters:AllCells Inc.: Other: Medical Director; ViaCord Processing Lab: Other: Medical Director; bluebird bio: Research Funding; Sangamo Therapeutics: Consultancy. Kwiatkowski:Terumo: Research Funding; Apopharma: Research Funding; Novartis: Research Funding; Agios Pharmaceuticals: Consultancy, Research Funding; bluebird bio: Consultancy, Honoraria, Research Funding. Porter:Agios: Honoraria; Cerus: Honoraria; Novartis: Consultancy. Thuret:Addmedica: Research Funding; bluebird bio: Research Funding; Novartis: Research Funding. Kulozik:bluebird bio: Consultancy, Honoraria. Lal:Terumo Corporation: Research Funding; Celgene Corporation: Research Funding; Insight Magnetics: Research Funding; Bluebird Bio: Research Funding; La Jolla Pharmaceutical Company: Consultancy, Research Funding; Novartis: Research Funding. Thrasher:Orchard Therapeutics: Consultancy, Equity Ownership; Generation Bio: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Rocket Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees. Elliot:bluebird bio: Employment, Equity Ownership. Tao:bluebird bio: Employment, Equity Ownership. Asmal:bluebird bio: Employment, Equity Ownership. Thompson:Amgen: Research Funding; Baxalta/Shire: Research Funding; La Jolla Pharmaceutical: Research Funding; Novartis: Research Funding; bluebird bio: Consultancy, Research Funding; Celgene: Research Funding; Biomarin: Research Funding.

Description: In vitro studies have suggested that AML cells are sensitive to treatment with the mammalian target of rapamycin (mTOR) inhibitor, rapamycin. In particular, mTOR inhibition is known to enhance the sensitivity of primary AML cells and AML stem cells to etoposide based chemotherapy leading to inhibition of leukemic SRC activity in NOD/SCID mice. To determine the feasibility of applying this approach in vivo, we performed a Phase I dose escalation study of the mTOR inhibitor sirolimus (rapamycin) with a combination chemotherapy induction regimen in adults with relapsed or refractory non-M3 AML. The purpose of this trial was to determine the safety and dose limiting toxicities of sirolimus and chemotherapy in this patient population. Patients received a loading dose of oral sirolimus on day 1 followed 24 hours later by daily doses of oral sirolimus on days 2–7 plus MEC (mitoxantrone 8 mg/m2/day IV, etoposide 100 mg/m2/day IV, and cytarabine 1000 mg/m2/day IV) on days 1–5. Five sirolimus dose levels were explored by a standard 3+3 design. Sirolimus was studied at loading doses from 3–15 mg and daily doses from 1–5 mg/d. Clinical response was assessed by bone marrow biopsy upon hematologic recovery or day 42, whichever occurred first. 23 adults (14 women, 9 men) of median age 58 (range 22 to 65) with relapsed, refractory, or secondary AML were treated with sirolimus and MEC. Five subjects had antecedent hematologic disorders or prior leukemogenic chemotherapy, 18 had relapsed or refractory disease. Sirolimus was well tolerated and did not increase non-hematologic toxicity of MEC chemotherapy. Asymptomatic, reversible liver transaminase or bilirubin elevations occurred in 4 patients, two of which were 〉 grade 2. One patient with a history of prior cytarabine cerebellar toxicity (unknown at the time of study entry) developed reversible cerebellar ataxia. Three patients died of complications related to bacterial infections during chemotherapy-induced aplasia. Dose limiting toxicity was prolonged myelosuppression at the highest planned dose level and was responsible for one treatment-related death due to infectious complications from unresolved aplasia on study day 119. For the first four dose levels the median time to ANC recovery 〉500/uL among evaluable patients was 27 days (range16–38). Pharmacokinetic data showed that doses of 3 mg and higher consistently achieved rapamycin levels considered therapeutic in solid organ transplantation (4–9.2 ug/L). Bone marrow studies in 2/2 evaluable patients on dose level 4 (12 mg loading dose and 4 mg per day sirolimus) showed inhibition of p70S6 kinase phosphorylation consistent with effective inhibition of mTOR at this dose level. Complete remissions occurred in four patients, all treated for first relapse. Two patients subsequently proceeded to allogeneic transplantation. These results indicate that the combination of mTOR inhibition and chemotherapy is feasible in human AML and establish an appropriate dose for phase II studies to be 12mg loading dose followed by 4 mg daily. Patient recruitment at this dose is ongoing. Confirmation of the efficacy of this regimen, which targets signal transduction in leukemic 〈 stem cells, is planned in a randomized phase II trial at the cooperative group level.

Description: Introduction: FL is generally responsive to conventional-dose chemotherapy but long term disease-free survival (DFS) is uncommon. High-dose chemo-radiotherapy followed by ASCT has the potential to induce remission in this disease but the long-term benefit of this modality remains to be determined. Methods: Between 1990 and 2003, we transplanted 52 pts originally diagnosed with low-grade FL (31 grade 1, 21 grade 2). Twenty-five (48%) had biopsy-proven large cell transformation (FL grade 3 or diffuse large cell lymphoma) before ASCT. The median number of prior therapies was 2 (range: 1 to 7). Prior to ASCT, 45 pts (87%) were responsive to salvage therapy with 20 pts (38%) in CR. Five pts (10%) had chemo-resistant disease at the time of ASCT. High-dose regimens included BCNU-cyclophosphamide-etoposide (31%), melphalan/TBI (27%), and cyclophosphamide/TBI (25%). Thirty-eight pts (73%) received peripheral stem cells (PSCT) and 14 pts (27%) received autologous bone marrow (BM) with 4-hydroxyperoxycyclophosphamide (4-hc) purging in 9 cases (17%). The median age was 49 yrs (range: 29–65). Results: There was 1 treatment-related death during the first 100 days. After ASCT, 36 pts (69%) achieved a CR, 2 (4%) had a PR, and 7 (13%) had stable disease. Among those in CR, 20 (56%) had a CR pre-ASCT, 14 (41%) had a lesser response, and 1 (3%) was chemo-resistant. Median follow-up (f/u) of survivors was 5.3 yrs (range: 1.7 months to 12.4 yrs). The median overall survival (OS) has not yet been reached. The median event-free survival (EFS) is 3.4 yrs (range: 1.7 months to 12.4 yrs). Among complete responders, more than 50% are disease free at last follow-up (range 1.7 months to 12.1 yrs). Variables favorably affecting EFS and OS are age 〈 60 yrs (p = 0.007, 0.015 respectively), achievement of a CR after ASCT (p = 0.002, 0.001), absence of transformation (p = 0.038, 0.017), BM vs. PSCT (p = 0.042, 0.086), and 4-hc BM purging (p = 0.044, 0.059). Number of prior regimens, response prior to ASCT, type of preparative regimen, and addition of TBI, were not significantly associated with EFS, DFS, or OS. In multivariable analysis, achievement of CR after ASCT and age 〈 60 yrs are the only significant predictors of EFS and OS. Adjusted for age, 53% of pts with a CR after ASCT are alive and event-free at last f/u (range: 2.4 months to 12.4 yrs) (Figure 1). In contrast, the median EFS among pts without a CR is 0.5 yrs (range: 1.7 months to 5.3 yrs). Conclusion: ASCT is a reasonable therapeutic approach to FL, resulting in long term EFS for some pts, even with relapsed, refractory and/or transformed disease. In our experience, significant predictors of EFS and OS after ASCT are complete response and age

Description: Introduction: Venous thromboembolism (VTE) is a significant adverse event in adults receiving pegaspargase (PEG) for acute lymphoblastic leukemia (ALL). PEG increases VTE risk by depletion of antithrombin III (AT). Heparin requires adequate AT for anticoagulation. Younger adults with T-cell ALL receiving prednisone may be particularly at risk. Retrospective series (most with L-asparaginase) suggest AT supplementation may decrease VTE, however prospective data in adults beyond induction is limited while the optimal dose of AT remains undefined and varies across series. We reviewed adults at our institution who received PEG for ALL to assess the incidence of VTE within our AT supplementation practice. Laboratory and cost data for AT repletion were also analyzed. Methods: Adults who received PEG for ALL between 11/2015 and 7/2018 were retrospectively identified. Institutional recommendations were to supplement AT if serum AT 〈 60% following PEG for at least the first 2 courses (induction/consolidation). AT levels were assessed twice weekly until normalized. AT supplementation following additional cycles was recommended for all patients receiving therapeutic anticoagulation. Pharmacists calculated the AT dose using a repletion factor of 80-120%, rounded to the nearest vial. After VTE, patients received therapeutic enoxaparin throughout all remaining PEG doses, with enoxaparin held only if platelets 〈 50,000/mcL or for procedures. After 3/2018, all patients receiving PEG also received enoxaparin prophylaxis when platelets 〉30,000/mcL. A retrospective analysis was done to assess the incidence of VTE. Secondary endpoints included an assessment of VTE risk factors, ability to achieve therapeutic AT levels with supplementation and to characterize drug therapy costs with AT supplementation. Results: Thirty-one patients (30 newly diagnosed, 1 in relapse) with ALL received ≥ 1 dose of PEG followed by AT supplementation. Seventeen of 31 patients were adolescent/young adults (AYA) and 13/31 had T cell ALL. Additional patient characteristics are summarized in table 1. The incidence of VTE was 19%, with 7 VTEs identified in 6 patients. Two patients developed CNS thrombosis (1 fatal), 1 had a pulmonary embolism, and the remainder were upper extremity VTE. Six of 7 VTE occurred during the first two courses at a mean of 66 days (range 6-225) following the first PEG dose. Patients with VTE had a median platelet count of 118/mcL (range 34-377) and a mean AT nadir of 53% (36-98) within 72 hours of VTE. Two of 7 events occurred despite enoxaparin prophylaxis. Five of 6 (83%) patients with VTE had T-ALL; which was more common in the VTE vs. no-VTE group (p = 0.01). The incidence of VTE within the T-ALL group was 38%. Patients with VTE were all AYA and were younger than those without VTE (median 31 vs. 42 years, p = 0.06). Patients with VTE received a higher mean PEG dose than patients without VTE (4589 vs. 3504 units, p 〈 0.0001), reflective of the more aggressive dosing in the AYA regimen. Six of 7 VTEs occurred during a course containing prednisone (p = 0.08 vs. dexamethasone). AT nadirs during cycles with VTE were similar to cycles without VTE. No clinically significant bleeding occurred. Characteristics of patients with VTE are summarized in table 2. Overall the mean time to AT nadir was 11 days. Therapeutic AT (〉 60%) following supplementation occurred 56% of the time. Most AT doses (89%) were calculated with a correction factor of 80-89%. The probability of obtaining a therapeutic AT increased when a higher repletion factor (〉 90%) was used (76% vs. 52%, p = 0.06). Patients received a mean of 1.9 (0-6) doses of AT per PEG dose, and a mean of 5.9 (1-21) AT doses throughout treatment. The mean AT supplementation cost per PEG dose was $11,663 with 186 doses administered ($3.22/unit). Conclusions: VTE occurred in 19% of patients receiving AT supplementation following PEG, with 2/7 events involving the CNS. The risk of VTE was greatest in younger adults with T-ALL receiving concurrent prednisone and higher doses of PEG. AT levels were low at the time of VTE in most patients, however nadirs were similar compared to courses not complicated by VTE. Routine or augmented VTE prophylaxis and a higher AT repletion goal (〉 90%) may further limit VTE risk but given the cost and patient inconvenience, prospective evaluation is needed to confirm the benefit. Disclosures Frey: Servier Consultancy: Consultancy; Novartis: Consultancy. Perl:Pfizer: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Consultancy; Actinium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees; Arog: Consultancy; Astellas: Consultancy; NewLink Genetics: Membership on an entity's Board of Directors or advisory committees. Porter:Genentech: Other: Spouse employment; Novartis: Other: Advisory board, Patents & Royalties, Research Funding; Kite Pharma: Other: Advisory board.

Description: CD4+CD25+ T-regulatory (Treg) cells have been shown to critically regulate self- and allograft tolerance in several model systems. Studies of human Treg cells have been restricted by the small number present in peripheral blood and their naturally hypoproliferative state. To better characterize Treg suppressor cell function, we determined methods for the isolation and expansion of these cells. Stringent magnetic microbead-based purification was required for potent suppressor cell line generation. Culture stimulation with cell-sized Dynabeads coated with anti-CD3 and anti-CD28 monoclonal antibodies, CD4+ feeder cells, and interleukin 2, provided for marked expansion in cell number (100-fold), with retention and enhancement of suppressor function. The potent Treg cell lines suppressed proliferation in dendritic cell-driven allo-mixed lymphocyte reaction (MLR) cultures by more than 90%. The Treg-derived suppressor cells functioned early in allo-MLR because expression of activation antigens and accumulation of cytokines was nearly completely prevented. Importantly, cultured Treg cells also suppressed activated and matured dendritic cell-driven responses. These results demonstrate that short-term suppressor cell lines can be generated, and they can express a very potent suppressive activity. This approach will enable more detailed biologic studies of Treg cells and facilitate the evaluation of cultured Treg cells as a novel form of immunosuppressive therapy. (Blood. 2004;104:453-461)

Description: Aleutian disease of mink, apparently of viral etiology, is characterized by an extreme diffuse proliferation of plasma cells, and a marked hypergammaglobulinemia, which is electrophoretically heterogeneous. In some mink with this disease serially followed by serum protein electrophoresis, a transition to a homogeneous myeloma-like hypergammaglobulinemia, together with the appearance of Bence Jones proteinuria, was observed late in their course. Thus, this viral disease shows plasma cell proliferation beginning as a multiclonal hyperplasia which may terminate as a monoclonal, possibly neoplastic overgrowth of the plasma cell system.

Description: Germ line mutations in ETV6 are responsible for a familial thrombocytopenia and leukemia predisposition syndrome. Thrombocytopenia is almost completely penetrant and is usually mild. Leukemia is reported in ∼30% of carriers and is most often B-cell acute lymphoblastic leukemia. The mechanisms by which ETV6 dysfunction promotes thrombocytopenia and leukemia remain unclear. Care for individuals with ETV6-related thrombocytopenia and leukemia predisposition includes genetic counseling, treatment or prevention of excessive bleeding and surveillance for the development of hematologic malignancy.