ALBERT

Description: Abstract 44 CALGB (now part of the Alliance for Clinical Trials in Oncology) performed a non-randomized phase II study testing one year (yr) of investigational maintenance therapy with decitabine for newly diagnosed adult AML patients (pts) 1 × 109/L, platelets 〉75 × 109/L, and be within 90 days after day 1 of the final consolidation. Decitabine 20mg/m2 was given IV over 1 hour for 4–5 days, every 6 weeks, for 8 cycles. 546 pts enrolled with a median age of 48 yrs (range, 17–60) and median presenting white blood count (WBC) of 12.6 × 109/L (range, 0.3–380 × 109/L). 75% achieved CR (412/546). Reasons for CR pts not receiving maintenance were mainly early relapse, alloHCT in 1st CR, inadequate count recovery, and patient refusal (Blum et al. ASH 2011). 33% of CR pts (134/412) received investigational maintenance. Of these, 46 (34%) were favorable risk; among the remaining 88 pts, 73 were consolidated with autoHCT, and 15 received HiDAC-based consolidation. The median time from initial study registration to initiation of maintenance therapy was 6.3 months. Pts receiving decitabine had a median age of 45 yrs (range, 18–60) and presenting WBC of 13.5 × 109/L (range, 0.4–221 × 109/L). Treatment with decitabine maintenance was feasible and reasonably well tolerated; the primary toxicity was myelosuppression. Preplanned dose reduction criteria for neutropenia were met after the first 20 pts had been treated. After this early timepoint, all subsequent pts who had been consolidated with autoHCT received only 4 days of decitabine per cycle (HiDAC consolidated pts continued to receive 5 days per cycle). The median number of cycles of decitabine received was 7 (range, 1–8); 46% of pts (62/134) received all 8 cycles, and 75% completed at least 4 cycles. Reasons for discontinuation of decitabine before completing 8 cycles included relapse (28%, 38/134), pt refusal (13%), adverse events (4%), and others. In this selected cohort of pts who received post-CR maintenance with decitabine, 1-yr and 3-yr overall survival (OS) were 96% and 66%; 1-yr and 3-yr disease-free survival (DFS) were 80% and 53%. 1-yr “failure-free survival” calculated from the time of registration to decitabine was 68% (70% for favorable risk, 68% for others). These results are similar to the outcomes for comparable pts enrolled on our prior CALGB study 19808 who received identical chemotherapy for induction and consolidation and then were randomized to observation or maintenance with interleukin-2 (3-yr OS 61% and 68%, 3-yr DFS 45% and 56%, for observation and IL-2 respectively). Post-consolidation maintenance with decitabine appears to provide only modest, if any, benefit overall. Correlative studies for CALGB 10503 are ongoing, including investigations into the impact of decitabine in unique molecular and cytogenetic subsets of disease, the prognostic/predictive value of aberrant methylation and other molecular markers, and assessment of minimal residual disease. Supported by CA33601 and CA128377. Disclosures: No relevant conflicts of interest to declare.

Description: Background: Donor grafts with more naive T cells and plasmacytoid dendritic cells were associated with improved overall survival after unrelated donor bone marrow, but not peripheral blood stem cell (PBSC) transplants (Waller, E JCO 2014). Here we present results on influence of innate and adaptive immune subsets in G-CSF mobilized allografts on incidence of acute GVHD (aGVHD) and chronic GVHD (cGVHD) in 238 patients (pts). Methods: We analyzed the absolute numbers and percentages of T, NK, NKT and B cells along with an extensive immunophenotypic characterization of their activation status in consecutive PBSC allografts obtained from sibling and unrelated donors between 2010 - 2014 and studied their association with the incidence of aGVHD and cGVHD. Wilcoxon rank sum tests were used to screen differential marker expression between those who did vs. did not develop aGVHD and similarly for cGVHD. Significant markers were evaluated in the multivariable (m.v.) setting along with known prognostic factors, including: recipient age, related vs. unrelated donor, female donor vs. not, Anti-thymocyte globulin (ATG) use (yes vs. no), and Reduced-intensity conditioning (RIC) vs. not. Cutpoints for markers were generated using recursive partitioning algorithms and evaluated in m.v. models. Results: Of the 238 alloSCT pts evaluated, most (71%) had unrelated donors, 64% received ATG, where most pts with unrelated donors received ATG (83%), and 78% received RIC. The incidence of aGVHD and cGVHD was 58% and 38% respectively. A total of 107 pts had grade II-IV aGVHD reported (71 II, 28 III, 8 IV), and 92 of 192 evaluable for cGVHD (at least 100 days of f/u) had reported cGVHD. Median follow-up in living pts was 21 months (range: 1.4 to 41.1 months). Table 1 shows dichotomized markers most influential on aGVHD. Higher absolute numbers of T cells, activated T cells, CD8+ cells, CD8+ cells expressing IL-7 receptor and CD27 were associated with higher incidence of aGVHD. Higher number of Stage 4 NK cells expressing stem cell factor receptor, and T-regs were associated with a lower incidence of aGVHD. Similar analyses were done for cGVHD (Table 2). Higher absolute numbers of activated T lymphocytes, activated B lymphocytes, KIR expressing CD3+ cells, CD8+ lymphocytes and activated NK cells were associated with higher incidence of cGVHD. When the percent of these makers in relation to total lymphocytes was evaluated regarding association with aGVHD, higher percent of T-regs (OR: 0.204, p=0.0018), effector memory T cells (OR: 0.45, p=0.024) and NKG2D positive NK cells (OR: 0.38, p=0.0008) conferred protection from aGVHD . Similar analysis for cGVHD showed higher percent of naïve CD4+ T cells conferred protection from cGVHD (OR: 0.44; p=0.0062) while higher percent of CD8+ cells (OR: 3.93; p=0.0032) and activated NK cells (OR: 2.08; p=0.024) was associated with cGVHD. Conclusions: These results show a protective role of donor T-regs, CD4+ T cells and Stage 4 NK cells from aGVHD. Additionally, higher content of activated T cells, CD8+ cells and B lymphocytes are associated with higher incidence of cGVHD. Higher content of activated NK cells seems to protect from aGVHD, but not from cGVHD. Updated results including multivariable analyses will be presented. These findings showing the influence of specific subsets in the allograft on aGVHD and cGVHD may provide opportunities for therapeutic interventions for graft engineering or pharmacologic methods for targeting specific immune subsets to decrease incidence of aGVHD and cGVHD. Table 1 Univariate model results for aGVHD with dichotomized markers using cutpoints: Marker Absolute OR p-value CD3+/CD5616- (T lymphocytes) 3.07 0.0013 CD3+/HLA DR+ (Activated T lymphocytes) 3.26 0.012 CD8+/CD45RA- (CD 8+ lymphocytes) 2.56 0.012 CD8+/CD27+ (Effector Memory CD8 cells) 3.25 0.0082 CD8+/CD127+ ( CD8 cells expressing IL-7 receptor) 2.92 0.073 CD4+/CD25+/CD127-(T regs) 0.43 0.057 CD3-/CD16-/CD56+/CD117+ (Stage 4 NK cells expressing Stem cell factor receptor) 0.12 0.0007 Table 2 Univariate model results for cGVHD with dichotomized markers using cutpoints: Marker Absolute OR p-value CD3+/HLA DR+ (Activated T lymphocytes) 4.41

Description: Key Points High miR-10 family expression levels in AML patients are associated with achieving complete remission to induction chemotherapy. Functional experiments did not show any impact of miR-10a-5p in AML blast growth or survival at baseline conditions or after chemotherapy.

Description: Abstract 2693 Background: Aggressive B-cell NHL harboring a c-MYC rearrangement (myc+) with or without t(14;18) is associated with shortened PFS and overall survival (OS) (Savage, Blood 2009; Johnson, Blood 2009). Clinical presentation, risk-assessment, and therapies vary among pts and institutions. We reviewed pts with myc+ and double hit NHL treated at the Ohio State University (OSU) from Aug 2008-Jan 2012 to determine factors associated with prolonged PFS and OS. Methods: Pts with de-novo B-cell NHL who were myc+ by FISH break-apart probe were included. Pts with Burkitt's, follicular, and transformed NHL were excluded. Most pts were also evaluated for presence of t(14;18) by FISH, and those myc+ pts with t(14;18) were classified as double hit NHL. Response was determined by PET/CT at the completion of first-line therapy. Associations between myc+ and clinical characteristics were described. PFS and OS were defined from date of diagnosis to date of relapse or death. Univariable and multivariable Cox regression models were performed to assess relationships of selected clinical variables with PFS and OS. Results: Of 49 myc+ pts, 55% were male, and median age at diagnosis was 62 (range: 23–83). Morphologically, 30 pts had diffuse large B-cell lymphoma (DLBCL), 10 pts had B cell lymphoma unclassifiable with features intermediate between diffuse large B cell and Burkitt lymphoma (BCLU), and 9 pts had high grade NHL not otherwise specified. Twenty-eight pts had ECOG performance status ≤1, and 40 pts had stage III-IV disease. Twelve pts had bone marrow involvement, and 26 pts had bulky disease ≥5cm. IPI was ≥3 in 24 pts, and median Ki-67 was 90% (range: 45–100). Twenty-nine of 43 assessed pts (67%) were positive for t(14;18). Therapies included R-CHOP (N=17), R-EPOCH (N=17), Burkitt's-like (ie, R-HyperCVAD, R-CODOXM/IVAC, or R-CHOP with high dose methotrexate; N=11), or other (N=4). No pts underwent autologous transplant in first remission. Twenty-nine pts (59%) achieved a complete response (CR), 2 pts had a partial response, 1 pt had stable disease, 8 pts had progressive disease (PD), and 9 pts died before response assessment (5 pts after cycle 1, 3 pts after cycle 2, and 1 pt after cycle 3). With a median follow-up of 26.2 months (mos; range: 4.8–45.0), the median PFS for all pts was 16.6 mos (95%CI: 9.6 - not reached=NR), and median OS was 37.7 mos (95%CI: 15.7–NR). Median PFS was 3.9 mos for pts without CR vs. not yet reached in pts with CR (p

Description: Abstract 2955 Introduction: Deacetylase (DAC) inhibitors show promise as anti-neoplastic agents, the approved drugs are weak inhibitors of class I and II DACs or potent inhibitors of class I DAC only, and have suboptimal activity or unacceptable toxicities. AR-42 is a class I/II DAC-I designed at OSU that demonstrates a 20,000-fold improvement in DAC inhibitory potency relative to the parent molecule (IC50=16 nM) with greater antiproliferative effects than Vorinostat in vitro and in vivo (Kulp et al, Clin Cancer Res, 2006 and Lucas et al, PLoS One, 2010). Methods: OSU 09102 (NCI 9119) is a first-in-man single agent, cohorts-of-3 phase I dose escalation study in adult patients with relapsed CLL, lymphoma (NHL), or multiple myeloma (MM) with normal kidney and liver function. Patients received AR-42 orally M-W-F in cycles of 28 days (3 weeks of 3-times-per-week dosing followed by a 7-day break). Moderate cell count suppression was allowed with an absolute neutrophil cutoff of 1000/μL, platelets 3 50,000/μL and hemoglobin 3 10 g/dL. In the first stage of dose escalation, each dose level increased by 100% until the first grade 2, drug-related toxicity was observed. Subsequent dose increases will be approximately 33% increase with accrual in cohorts of 3 patients. For pharmacokinetic analysis, plasma was obtained at 0 (pre-dose), 0.25, 0.5, 1, 1.5, 2, 4, 8, 10, 24, and 48 hours after dosing on day 1 and day 19 (only up to 24 h), and then kept at –80°C until analysis. Results: We enrolled 3 patients at 20 mg (MM, MM, NHL), 3 patients at 40 mg (MM) with a transition to a slower dose escalation due to a grade 2 thrombocytopenia. Three more patients were enrolled at 40 mg (MM, MM, T-cell NHL), then 7 patients at 50 mg (MM × 4, follicular × 1, T-cell NHL × 2). One myeloma patient was enrolled at 70 mg. In the 40 mg cohort, related toxicities include 2 grade 3 and 2 grade 2 thrombocytopenia, 1 grade 3 neutropenia, 1 grade 2 vomiting, and 2 grade 1 QTc prolongation. In the 50 mg cohort 1 grade 4 and 3 grade 3 thrombocytopenia, 2 grade 3 neutropenia, 4 grade 2 fatigue, 2 grade 2 muscle spasm, 1 grade 2 blurred vision/dizziness, 3 grade 1 QTc prolongation, and 3 grade 1 nausea. Accrual was temporarily halted for a safety analysis Mar-2012 focused on the 50 mg cohort toxicities – one grade 4 thrombocytopenia considered a DLT, one patient found dead on cycle 2 day 10 without prior evidence of QTc prolongation, and one patient with reproducible dizziness and blurry vision. AR-42 was detected 15 mins after dose in 12 of 17 patients, suggesting rapid absorption. The time to reach the peak concentration in plasma (Tmax) varied from 1.5 hours to 4 hours. The Cmax (see chart) and AUC of AR-42 was not increased proportionally with doses, suggesting that the PK of AR-42 is not linear in the 20–50 mg range. Conclusion: The Cmax achieved at the 40 mg and 50 mg dose levels is adequate for HDAC inhibition in vitro and minor clinical responses were observed in myeloma and T-cell lymphoma as a single agent in the 40 mg cohort (see monoclonal proteins chart), hence 40 mg TIW 3-weeks-on and 1-week-off was declared the MTD. Complete pharmacokinetic, toxicity, and results from brief fatigue inventory will be presented at the meeting. AR-42 does not have the severe fatigue and gastrointestinal side effects of other broad DAC inhibitors and may be suitable for combination phase Ib trials in T-cell lymphoma and myeloma. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 4308 VWF function has long been implicated in TTP's pathogenesis. Initial study reported unusually large (UL)VWF multimers in patients with relapsing TTP. Later, ULVWF were demonstrated in TTP patients during remission that are acutely consumed at the onset of disease. However, many detailed steps concerning the timely relationship between VWF multimerization and clinical courses such as disease onset, mortality, disease refractoriness, and treatment response are still missing. In this study, we performed VWF multimeric analyses in over 400 serial samples longitudinally collected from more than 20 TTP patients at various clinical stages, including initial presentation, acute treatment, clinical remission, and clinical visits prior to TTP relapses. At the time of acute presentation, approximately 50% of cases show presence of ULVWF multimer patterns, while around 35% demonstrate acute consumption of UL and high molecular weight VWF multimers. The other 15% of cases however reveal normal VWF multimer patterns at the time of disease presentation. For the TTP patients who normally respond to plasma exchange (PE) therapy, a mild ULVWF multimer pattern may be present after discontinuation of daily PE therapy. Upon restoration of ADAMTS13 activity and achievement of sustained remission, VWF multimer patterns are normalized. During the period of daily plasma exchange for acute episodes of TTP, a persistent presence of ULVWF multimer patterns appears indicative of disease refractoriness and is associated with disease mortality. In the course of this study, ADAMTS13 activity levels (reportable range of 0.5 % –100%) in these longitudinal samples were also precisely determined using SELDI-TOF mass spectrometry to establish the correlation between ADAMTS13 activity measured in vitro and VWF multimeric patterns formed in vivo. Our study for the first time defines the dynamic changes of VWF multimeric patterns in relation to the evolution and natural history of TTP in a large well-defined clinical cohort. These novel observations provide new implications into the pathobiology of TTP and may help to develop new biomarkers for monitoring therapeutic responses and for screening for TTP relapses. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 4094 Background: Our group has previously reported the benefits of thalidomide-prednisone based regimens for improvement of anemia, thrombocytopenia, and splenomegaly for patients with MF; both primary myelofibrosis (PMF), and arising from essential thrombocythemia and polycythemia (Post ET/PV MF). We sought to evaluate the overall efficacy of these commonly used regimens by evaluating long-term outcomes and applying the IWG-MRT response criteria (Tefferi et. al. Blood 2006) which arose after completion of these trials. Methods: We retrospectively analyzed the long-term outcomes, and assessed the initial therapeutic responses using IWG-MRT criteria from three parallel completed trials of MF using a thalidomide (THAL-50 mg/day) and prednisone (3 month taper beginning at 40mg, stopped at 3 months) backbone. The trials had identical eligibility criteria including adequate organ function and need for MF therapy (defined as symptomatic: anemia and/or splenomegaly). The trials were 1) THAL-PRED alone, THAL only after 3 months 2) THAL-PRED-etanercept (ETAN - TNF- alpha inhibitor at 25 micrograms subcutaneously twice a week), THAL and ETAN only after 3 months and 3) THAL-PRED – oral cyclophosphamide (CTX 25mg daily orally), THAL alone after 3 months. Results: Patients: A total of 50 pts were enrolled in these 3 trials (Males n=36, 72%) with median age of 68.5 years (Range 43–85), with 79% having PMF. Patients had advanced disease in general with 88% having intermediate 2 or high risk MF by IWG criteria (Cervantes et. al. Blood 2009), 62% patients with red cell transfusion dependence and 50% with an abnormal karyotype. Therapy initial results: 80 % of patients reached the three month juncture on the trials, with 40% reaching 6 months. Initial toxicity was myelosuppression with 3 cases of grade 3 anemia, 3 cases of grade 3 neutropenia and 4 cases of grade 3 thrombocytopenia. There were no grade 4 or higher hematological toxicities noted. Initial neuropathy was uncommon and seen in only 4% of patients. No complete responses were observed and only 1 patient had partial response (by IWG-MRT criteria). 14 patients (28% overall) met the new IWG-MRT criteria for clinical improvement; 11 for anemia (22%), 2 for thrombocytopenia (4%) and 3 for splenomegaly (6%). Responses occurred relatively quickly at an overall median of 8 weeks (range 4–12) after enrollment. Long Term Outcomes: After a median follow-up of 36 months across this cohort we observed an overall median duration of response of 8.5 months (range 3–42). Responses to THAL based regimens can lead to periods of prolonged stabilization after cessation of therapy. We observed an overall median time to institution of next therapy of 3 months (range 1–50). At the time of this analysis 14 patients (28%) have expired of their MF and median survival across the entire cohort was 36 months (3-106). Comparison of Regimens: Comparison of these three independent trials (Table 1) suggests greater toxicity and inferior response rate, duration of response, and time to next therapy with the cyclophosphamide containing regimen. Conclusion: THAL-PRED based regimens are active in a subset of MF patients for therapy primarily of anemia, and for some patients a response of good duration (even after cessation of therapy) may be obtained. IWG-MRT response assessment demonstrates utilizing additional agents to a THAL-PRED regimen do not appear to augment (and may detract from responses). Newer agents such as pomalidomide may have similar to greater efficacy without neuropathy and less myelosuppression. Disclosures: Off Label Use: There is no FDA approved agent in Myelofibrosis. All the drugs discussed; Thalidomide, Prednisone, Etanarcept and Cyclophosphamide are off-label. Mesa:SBio: Research Funding; Novartis: Research Funding; Celgene: Research Funding; Incyte: Research Funding; Roche: Research Funding; eisai: Research Funding; telik: Research Funding.

Description: Abstract 204 Treatment of chronic myeloid leukemia (CML) patients with tyrosine kinase inhibitors (TKIs), such as imatinib, nilotinib, and dasatinib, results in a dramatic reduction in proliferating BCR-ABL expressing leukemia cells. However, these agents do not eliminate the CML stem cell population, indicating that inhibiting BCR-ABL kinase activity alone is not sufficient to eradicate the disease. In vitro studies of human CML cell lines and CD34+ cells isolated from CML patients, have shown that bone marrow stromal cell factor (BMSF) conditioned media can maintain important pro-survival and self-renewal activities downstream of BCR-ABL in the presence of TKIs, suggesting a role for secreted BMSFs in innate resistance to BCR-ABL kinase inhibition. However, the ability of BMSFs to maintain the leukemic potential of CML stem cells upon exposure to TKIs has not been reported. We used a standard murine retroviral transduction system to model CML blast crisis (BC-CML) and obtain cells highly enriched for leukemia initiating potential. Purified LIN-, Sca-1+, CD117+ cells (LSKs) were isolated from the bone marrow of C57BL6/J mice and retrovirally-transduced with BCR-ABL-GFP and Nup98/HoxA9-YFP then injected intravenously into recipient C57BL6/J mice. All animals developed leukemia within 21 days characterized by leukocytosis and extensive infiltration of bone marrow and spleen with leukemic blasts. LSKs expressing both BCR-ABL-GFP and Nup98/HoxA9-YFP (GFP+/YFP+ LSKs) were purified from the spleens or bone marrows of leukemic mice and cultured for 72 hrs in BMSF conditioned media across a range of concentrations (0% - 50%) in the presence and absence of imatinib (0 - 1000 nM). BMSF conditioned media reduced the cytotoxic effects of imatinib on GFP+/YFP+ LSKs as assessed by cell counts, trypan blue viability assays, and Annexin V expression by flow cytometry. Furthermore, BMSF conditioned media reduced the inhibitory effects of imatinib on GFP+/YFP+ LSK colony formation in methylcellulose, and beta-catenin expression as assessed by flow cytometry. These observations strongly suggest that signaling by stromal cell-derived soluble factors protects BC-CML stem cells from imatinib therapy by re-activating pro-survival and self-renewal pathways. The ability of BMSFs to reduce the inhibitory effect of imatinib on BC-CML stem cell self-renewal in vivo was assessed by performing secondary transplantation assays. GFP+/YFP+ LSKs were purified from primary CML mice and transplanted into secondary recipients following in vitro exposure to BMSF conditioned media in the presence and absence of 1000 nM imatinib. Survival after transplantation was compared in cohorts of 5 mice per experimental condition: Group 1 (0% BMSF, 0 nM imatinib), Group 2 (50% BMSF, 0 nM imatinib), Group 3 (50% BMSF, 1000 nM imatinib) and Group 4 (0% BMSF, 1000 nM imatinib). Survival was significantly prolonged in Group 4 mice treated with 1000 nM imatinib and this effect was abrogated by treatment with 50% BMSF conditioned media, indicating that cell-derived soluble factors contribute to maintaining BC-CML stem cell function in the presence of imatinib. Our findings strongly suggest that signaling by soluble BMSFs plays an important role in the innate imatinib resistance of CML stem cells, implicating these factors in disease relapse. Genetically defined murine models of CML provide a powerful in vivo system to identify and target soluble factors that contribute to stromal-mediated cytoprotection of CML stem cells from TKIs. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 3504 The only known curative therapy for patients with SCD is a matched family donor AlloSCT (Walters et al, NEJM, 1996). Complications after myeloablative AlloSCT are numerous and include death, graft versus host disease (GVHD), and infections, making reduced toxicity conditioning regimens more appealing. A major obstacle allowing most SCD patients to undergo SCT is the lack of an unaffected, HLA-matched identical sibling (Bhatia et al, BMT, 2008). Umbilical cord blood (UCB) has been proven to be an excellent alternate donor source that can safely reconstitute hematopoiesis after AlloSCT in pediatric recipients with non-malignant conditions (Cairo et al, BBMT, 2008). In this study, we report the results of a RTC regimen followed by an AlloSCT from matched family and unrelated UCB donors in selected patients with symptomatic SCD. Between August 27, 2004 and March 2, 2010, 18 patients (14M:2F) with symptomatic SCD (HbSS=10, HbSC=4, HbSßThal=4) underwent an AlloSCT. Indications for SCT included: ACS (n=8), CVA (n=2), multiple VOC (n=9), splenic sequestration (n=6) and retinopathy (n=1). Conditioning was Bu (4mg/kg × 4d 〈 4 yrs and 12.8mg/kg × 4d 〉 4 yrs), Flu (30mg/m2 × 6d), and Alemtuzumab (2mg/m2 × 1d, 6mg/m2 × 2d, and 20mg/m2 × 2d). Median age was 6.29 yrs(1.3–19.2). Median follow-up was 26 months. Donor sources: 8-6/6 HLA-matched sibling bone marrow (BM), 2–6/6 sibling UCB, 1–6/6, 4–5/6 and 3–4/6 unrelated UCB. Donors were HbAA (n=13), HbAC (n=1), HbAS(n=3), or ßThal trait (n=1). Sibling BM recipients received a median total nucleated cell (TNC) dose/kg of 7.16 × 108 (range 2.27–11.31) and a median CD34 cell dose/kg of 5.38 × 106 (range 1.50–6.83). Recipients of related or unrelated UCB received a median TNC dose/kg of 4.35 × 107 (range 3.40–9.10) and a median CD34 cell dose/kg of 2.21 × 105 (range 0.60–7.94). All received tacrolimus and mycophenolate mofetil as GVHD prophylaxis (Bhatia/Cairo et al, BBMT, 2009) and phenytoin or keppra as seizure prophylaxis for 180 days post SCT. Patients receiving sibling donor AlloSCT had a median time to neutrophil engraftment of 16 days (range 13–41). Among evaluable unrelated UCBT recipients, median time to neutrophil engraftment was 34 days (range 27–47). Four patients (all unrelated UCBT) experienced primary graft failure at day +60 post-SCT secondary to CMV (n=2), adenovirus, and low Bu Css levels with early withdrawal of MMF. Patients with sibling donors had a median time to platelet engraftment of 26 days (range 17–75). Of evaluable unrelated UCB recipients, median time to platelet engraftment was 54 days (range 43–70). Patients achieved mean whole blood donor chimerism of 71.0, 79.6, 85.7, 92.9, 90.7% and 93.2% at days 30, 60, 100, 180, 365 and 730 post-transplant, respectively. Mean erythroid (CD71) donor chimerism at these time points was 78.1, 81.1, 86.6, 90.5, 87.9% and 94.0%, respectively. Patients with non-sickle cell trait donors had median HbS levels of 0% at 1 yr (n=8) and 2 yrs (n=3) post-SCT; those with sickle cell trait donors had median HbS levels of 38.3% at 1 yr (n=3) and 39% at 2yrs (n=3) post-SCT. Among evaluable patients, the Kaplan-Meier probability of grade II-IV acute GVHD is 33.3% and of chronic GVHD is 8.3%. Among the ten donor-recipient pairs in which at least one member of the pair had CMV positivity, four experienced CMV reactivation on days +13, +26, +30 and +32 (BM: n=2, unrelated UCB: n=2). Of the four patients with primary graft failure (all unrelated UCBT recipients), one resumed chronic transfusions, two died of complications from disseminated CMV and adenoviral infections, and one received a second myeloablative SCT 1 yr after initial SCT and died of fungal sepsis. Among all patients, the Kaplan-Meier probability of OS is 81.8% (100% with sibling donors, 62.5% with UCB donors) and of EFS is 77.8% (100% with sibling donors, 50% with UCB donors) with none of these patients showing any evidence of SCD symptomatology post-SCT. The longest follow-up is 2134 days. In summary, we report the largest experience of RTC and matched family AlloSCT in selected children with symptomatic SCD with persistent long-term donor chimerism and absence of SCD symptoms or progression of disease. However, with the high incidence of viral infections and toxic deaths following unrelated UCBT, it is too premature to extend this treatment option to those SCD patients lacking a sibling donor. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 2224 Background: Acquired TTP is characterized by a significant risk for exacerbation (recurrent TTP within 30 days of last plasma exchange (PEX)). An algorithm applied early in the course of treatment that detects patients at increased risk for exacerbation could identify patients most likely to benefit from more intensive upfront therapy (PEX, immune-suppressive therapy) to prevent recurrence of disease after tapering PEX. We have previously reported in a small cohort study that pretreatment ADAMTS13 activity was significantly lower (0.8% v. 1.4%) in patients suffering an exacerbation, but the difference was primarily mediated by race (EJH 2009 Dec 1;83(6):559–64). We performed a study to analyze data from a large cohort of TTP patients to assess the potential prognostic utility of pretreatment ADAMTS13 activity for risk of exacerbation. Patients: Patients presenting with a clinical diagnosis of acquired TTP (platelets 〈 100K/uL, microangiopathic hemolytic anemia) between May 2002 and August 2010 with pretreatment ADAMTS13 activity data (86 acute TTP episodes from 49 patients evaluable for exacerbation, and 94 episodes for other factors associated with ADAMTS13 activity) were included in these analyses. Methods: Demographic and laboratory data obtained prior to starting PEX in patients with acute TTP were analyzed retrospectively to determine their relationship to early recurrences (exacerbation) of TTP. Based on these data, ROC analysis and recursive partitioning algorithms were used to determine an optimal cutoff of pretreatment ADAMTS13 activity that was prognostic for exacerbation of TTP. Subsequently, the acute TTP episodes with pretreatment ADAMTS13 1.15% with respect to clinical outcomes and presenting clinical symptoms and laboratory data. Impact of these factors on exacerbation were also analyzed using generalized estimating equation models to account for multiple episodes from the same patients. Results: Overall, there were 22 exacerbation events observed in the 86 TTP episodes. There were no significant differences between subjects that suffered an exacerbation in terms of clinical laboratory data (platelet count, LDH, creatinine) at presentation. However, mean ADAMTS13 activity at presentation was significantly lower in patients that suffered exacerbations compared to those that did not [1.4% (0.5 –7.2) v. 2.9% (0.5–13.3); p=0.002]. ROC analysis of all study subjects indicated that the optimal threshold for pretreatment ADAMTS13 activity to predict the risk of exacerbation is 1.15%, which provides a test sensitivity of 64% and specificity of 62%. Subset analyses also defined the optimal threshold for AA and female populations to predict an increased risk of relapse to be 2% for both groups, giving rise to a sensitivity of 100% (AA)/82%(F) and specificity of 42% (AA)/50% (F), respectively. When using an ADAMTS13 activity threshold of 1.15% to risk stratify for increased risk for exacerbation, there were no significant differences in presenting clinical symptoms and laboratory values (Table 1). However, subjects with pretreatment ADAMTS13 activity 150 K/uL). Conclusions: These data are among the first to suggest pretreatment ADAMTS13 activity may predict clinical outcome from an acute episode of TTP. The optimal ADAMTS13 activity threshold was 1.15%, with ADAMTS13 activity below this level being associated with an increased risk for exacerbation. Furthermore, incorporating this threshold of ADAMTS13 activity into a model with race and gender will significantly improve risk stratification and identify patients at greatest risk for early treatment failure who may be more likely to benefit from the early addition of immune-based therapy to PEX. Disclosures: No relevant conflicts of interest to declare.