Efficacy of Remestemcel-L Treatment in Steroid Refractory Acute Graft-Versus-Host Disease in Children: An Aggregate Analysis

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 12-12
Author(s):  
Joanne Kurtzberg ◽  
Paul J Martin ◽  
Susan Prockop ◽  
Elizabeth Burke ◽  
Karen Segal

Introduction: Steroid-refractory acute graft-versus-host dose disease (SR-aGVHD) is a frequent and potentially fatal complication of hematopoietic stem cell transplantation (HSCT). There are no approved therapies specifically indicated for use in children with SR-aGVHD < 12 years old. Treatment with culture-expanded, adult human allogeneic bone marrow (BM)-derived mesenchymal stromal cells (remestemcel-L) has shown excellent safety and efficacy in clinical trials conducted over the past 10 years. Here we describe aggregate results of remestemcel-L treatment of SR-aGVHD in the pediatric population. Methods: 309 pediatric subjects with SR-aGVHD were treated with remestemcel-L across 3 protocols. Data were derived from a phase 3, single arm study as first line after steroid failure with no other second line aGVHD therapies added through day 28 (NCT02336230, n=54), an expanded access program in subjects with aGVHD that had not responded to multiple other treatments (NCT00759018, n=241) and the pediatric subset of a randomized controlled trial (NCT00366145, n=14) in which remestemcel or placebo were given with a concomitant second line aGVHD therapy. Subjects in each protocol received 8 intravenous infusions of remestemcel-L (2 x 106 cells/kg twice weekly for 4 weeks). Those achieving a partial response could receive an additional 4 doses (once weekly for the subsequent 4 weeks). This analysis included 309 subjects who received at least one remestemcel-L dose. Response was assessed 28 days after the first dose. Survival was evaluated through day 100. Results: At baseline, mean age was 8.9 years (range 0.3 to 18.2 years) and aGVHD severity by IBMTR grade was C or D in n=252 (82%). Sources of grafts were bone marrow (BM: 46%), mobilized blood (MB: 20%) and cord blood (CB: 31%). Donor grafts were HLA matched related (9%) or unrelated (44%) or HLA-mismatched (46%). Subjects received a mean (standard deviation) of 10.3 (4.2) remestemcel-L infusions for a mean cumulative dose of 660.8 (484.1) x 106 cells. The primary endpoint, overall response (complete + partial response) at day 28 (OR) was observed in 66% of subjects (204/309) and survival at day 100 (OS) was 68% (211/309). Day 28 OR strongly predicted day 100 survival. Among subjects who were alive at day 28 (N=284), 170 of the 204 (83%) responders survived through day 100. In contrast, 41/80 (51%) of non-responders survived through day 100. Day 28 OR frequencies and day 100 OS rates were consistent across baseline aGVHD grades: Grade B OR 70%, OS 77%; Grade C or D OR 65%, OS 66%. Comparable day 28 response frequencies and day 100 survival rates were observed across type of HSCT: OR was achieved in 65%, 64% and 71% of BM, MB and CB, respectively and 67%, 70% and 70% of BM, MB and CB recipients survived through day 100. Comparable OR and OS were observed in HLA compatibility and donor types with OR in 71%, 66% and 66% and day 100 OS in 64%, 66% and 71% of matched related or unrelated and mismatched, respectively. Remestemcel-L was well tolerated with no infusion-related toxicity or other safety concerns. Most treatment-emergent serious adverse events were attributable to aGVHD or the underlying pre-transplant disease. Conclusions: In this large, diverse sample of pediatric subjects with SR- aGVHD, treatment with remestemcel-L was associated with a high and consistent overall response rate and survival rate through 100 days. Day 28 OR was highly predictive of day 100 survival. Remestemcel-L was well tolerated and effective across transplant types, donor sources, moderate to severe grades of GVHD and prior or concurrent treatment paradigms as defined by the individual protocols in this aggregate analysis. Remestemcel-L is a safe and effective treatment for children with SR- aGVHD addressing an unmet medical need for this highly vulnerable population. Disclosures Kurtzberg: Mesoblast, Inc,: Consultancy, Honoraria. Martin:Abgenomics: Research Funding; Enlivex: Consultancy; Procter and Gamble: Current equity holder in publicly-traded company; Pharmacyclics LLC: Membership on an entity's Board of Directors or advisory committees; Neovii: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfzier: Membership on an entity's Board of Directors or advisory committees; Xenikos: Research Funding; Talaris: Consultancy; Rigel: Consultancy; Mesoblast, Inc.: Consultancy; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria. Prockop:Atara: Research Funding; Jasper: Research Funding; Mesoblast, Inc,: Consultancy, Honoraria, Research Funding. Burke:Mesoblast, Inc,: Current Employment. Segal:Mesoblast, Inc,: Current Employment.

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 1688-1688
Author(s):  
Teresa Lopes Ramos ◽  
Sara B. Wagers ◽  
Po-Yu Lin ◽  
Toshihito Hirai ◽  
Leon Su ◽  
...  

Abstract Regulatory T cells are a critical population for the maintenance of self-tolerance and the use of these cells for therapeutic purpose in transplantation has emerged based on their capacity to control immune activation, exhibiting positive therapeutic potential to ameliorate acute graft-versus-host disease (GvHD), one of the major complications after allogeneic bone marrow transplantation (allo-BMT). One of the remaining technical challenges in the clinical practice of Treg administration is the number of Treg required to effectively prevent GvHD. In this study, we engineered murine Treg cells to express an altered IL-2 receptor β subunit that selectively interacts with an orthogonal mutant IL-2 (oIL2) without interacting with the natural cytokine or receptor counterparts, thus preventing acute -GvHD. For investigation of the suppressive function of Treg orthogonal IL-2/IL-2 receptor system in a murine major mismatch of acute GvHD model, the BALB/c mice were lethally irradiated (8.8 Gy) and transplanted with 5x10 6 T cell-depleted bone marrow cells (TCD-BM) from C57Bl/6 mice alone or together with fresh 1x10 6 C57Bl/6 FoxP3 DRT-GFP-luc+ Treg cells (fTreg) or with 0.2x10 6 and 1x10 6 oTreg (transduced with the construct for murine oIL-2 receptor β chain) on day 0. On day 2, C57Bl/6 Tcon cells (1x10 6) were injected to induce GvHD. Recipients were treated with PBS or oIL-2 (25K IU/daily) for 14 days and then 3 times a week for another 14 days. Using bioluminescence imaging, we observed that ortho IL2Rβ +Treg not only maintains migration ability to the gut, mLN and LN but also exhibited significant expansion ability treated with oIL2 at day 7 post-transplant. The expansion of oTreg with PBS and fTreg was observed on day 14 after allo-BMT. The administration of oTreg-oIL2 and fTreg (1:1 Tcon:Treg ratio) significantly increased the survival of the mice compared to Tcon group (P<0.0001 and P=0.0001, respectively). Furthermore, the group oTreg-oIL2 (1:1) showed a significant increase in the survival curve compared to the fTreg group (P=0.03). When decreasing the number of oTreg administrated (5:1 Tcon:Treg ratio) a significant increase in the survival (Tcon vs Tcon:oTreg (5:1)+oIL2; P<0.0001) in the oIL2 group. Similar survival curves were observed between this group and fTreg group (1:1). oIL-2 protein injection was able to selectively expand the oTreg in vivo, with a significantly increased percentage of Foxp3 GFP+ in CD4 + T cells (PBS;14.96±2.4%, oIL-2; 27.76±23.6%, P=0.02) in the peripheral blood (PB) and spleen after 7 days post-transplant. We also observed a significant decrease in the percentage of effector T cells in the LN, mLN and spleen of the mice transplanted with oTreg and oIL-2 administration after 7 days post transplantation compared with GvHD group. We further demonstrated that ortho-IL2 administration-maintained graft-versus-leukemia (GvL) responses against lymphoma cells (A20). Engineered orthogonal cytokine receptor improves the suppressing abilities of Treg potential in a murine model of acute GvHD with the ability to maintain GvL, representing a novel approach to the utilization of Treg in Allogeneic Hematopoietic Stem Cell Transplant. Disclosures Garcia: Synthekine: Membership on an entity's Board of Directors or advisory committees. Blazar: Tmunity Therapeutics: Other: Co-founder; Equilibre Pharmaceuticals Corp: Research Funding; Carisma Therapeutics, Inc: Research Funding; Rheos Medicines: Research Funding; BlueRock Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Magenta Therapeutics: Membership on an entity's Board of Directors or advisory committees.


Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 3160-3160
Author(s):  
Ondine Walter ◽  
Agnès Ribes ◽  
Johanne Germain ◽  
Jean-Baptiste Rieu ◽  
Thibault Comont ◽  
...  

Abstract Introduction: Immune thrombocytopenia (ITP) is an autoimmune disease due to peripheral destruction but also impaired central production of platelets. Autoimmune reaction directed against megakaryocytes (MKs) has been described, and may explain morphological abnormalities of MKs observed in some patients with primary ITP. Thrombopoietin receptor agonists (TPO-RAs) are indicated as second-line treatments for ITP, but no predictive factors of response used in clinical routine practice has been demonstrated. The utility of systematic bone marrow smears (BMS) at ITP diagnosis is discussed. Howerer, it is usually recommended before second-line treatments. Two studies have suggested an association between MK abnormalities and response to corticosteroids in primary ITP, but none have investigated this association for TPO-RAs. This study aimed to investigate the association between MK abnormalities and response to TPO-RAs in adult patients with primary ITP. Methods: The source of population was the CARMEN registry. The CARMEN (Cytopénies Auto-immunes: Registre Midi-PyréneEN) registry is aimed at the prospective follow-up of all incident ITP adults in the French Midi-Pyrénées region (South-West of France, 3 million inhabitants) since June 2013. Each investigator follows all adult patients (aged ≥18 years) with incident ITP in routine visit or hospital stay. ITP was defined by international definition (platelet count <100 x 10 9/L and exclusion of other causes of thrombocytopenia). The study population consisted in all patients included in the CARMEN registry between June 2013 and March 2018 with primary ITP, treated by TPO-RA and with a BMS before initiating TPO-RA. We excluded the patients with a number of MKs <10 MK on the BMS. Morphological abnormalities were established based on literature and defined by consensus among 3 expert cytologists (AR, JBR and VDM). All MKs present on each smear were analyzed. MKs were categorized by the presence of dysplasia (monolobed MK and/or separated nuclei and/or microMKs), and according to their stage of maturation (basophilic, granular and thrombocytogenic). All patients' medical charts were reviewed by two experts in ITP (OW and GM) to determine the response to TPO-RAs. Response was defined by a platelet count between 30 and 100 G/L with at least a doubling of basal platelet count according to the international definition. In case of subsequent exposure to both TPORAs in a single patient, response was defined by response to at least one TPO-RA in the main analysis. We performed a subgroup analysis by TPORAs. Results: During the study period, 451 patients with incident ITP were included in CARMEN-registry. Among them, 105 had been treated by TPO-RAs, including 65 with BMS before the exposure to TPORA. We then excluded 20 patients with secondary ITP and 7 with less than 10 MKs on the BMS. We finally included 38 patients in the analysis. Median age at diagnosis was 71 years (interquartile range - IQR: 31 - 94) and 34.2% were women. Thirty-three patients were treated with eltrombopag, 17 with romiplostim including 13 who were exposed to both TPORAs. Thirty-four (89.4%) achieved response. The median number of MKs analyzed per patient was 137 (IQR: 50 - 265). All results are presented in Table 1. In the main analysis, there was no significant difference in the median percentage of dysplastic MKs in responders (4.0%, 95% confidence interval - CI: 2.3 - 6.4) and non-responders (4.5%, 95% CI: 0.7 - 7.1). There was a trend for a higher proportion of granular MKs (4.5%, 95% CI: 3 - 6) and basophilic MKs (30.1%, 95% CI: 21.9 - 39.1) in non-responders comparing to responders (granular: 2.0%, 95% CI: 0 - 4.1; basophilic: 21.3%, 95% CI: 11.4 - 40.7). Results were similar in the subgroup of patients treated with eltrombopag (data not shown; the low number of patients treated with romiplostim precluded any analysis). Conclusion: In this study, neither MK abnormalities nor the pattern of MK maturation stages were significantly associated with response to TPO-RAs. These results do not support a systematic bone marrow smear in patients with primary ITP to look for morphological predictive factors of response to TPO-RA. Figure 1 Figure 1. Disclosures Comont: AstraZeneca: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding. Moulis: Amgen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Grifols: 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, Research Funding; Sobi: Membership on an entity's Board of Directors or advisory committees; Argenx: Membership on an entity's Board of Directors or advisory committees.


Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 599-599
Author(s):  
Caitlin W Elgarten ◽  
Yimei Li ◽  
Yuan-Shung V. Huang ◽  
Richard Aplenc ◽  
Michael T. Hemmer ◽  
...  

Background Variation in the gastrointestinal microbiota after hematopoietic cell transplantation (HCT) has been associated with acute graft-versus-host disease (aGVHD). The significant immunosuppression associated with HCT leads to frequent broad-spectrum antibiotic exposures that in turn drive host microbiota composition. We sought to explore the association of different antipseudomonal antibiotic classes, commonly administered as empiric therapy for neutropenic fever, with subsequent aGVHD-risk in a large, multicenter cohort of children undergoing HCT for acute leukemia. We hypothesized that antibiotic classes that retain broad anti-anaerobic activity would increase aGVHD due to the greater potential impact of these agents on the microbiota. Methods Children 1-21 years old who underwent first HCT for acute leukemia from 2004 to 2017 were identified in 2 databases: CIBMTR, an observational database with demographic, transplant and outcomes information, and PHIS, an administrative database with resource utilization data from freestanding children's hospitals. Patients were then merged based on date of birth, date of transplant, sex and disease. The outcome was grade 2-4 aGVHD by day +100. The primary exposures were 3 distinct classes of antibiotics commonly used for empiric therapy: (1) antipseudomonal cephalosporins, (2) antipseudomonal penicillins and (3) carbapenems. They were captured as days of therapy from conditioning start to day +7, and classified as no, low (1-3 days), or high (>3 days) exposure. Logistic regression was applied to evaluate the association between aGVHD and each exposure, controlling for exposure to the other two classes. For the subset of patients with data on date of GVHD onset, a time to event analysis was performed considering death without GVHD as a competing event. For both analyses, we constructed multivariable models that were informed by a directed acyclic graph and included covariates representing demographics, transplant characteristics and GVHD risk factors associated with both exposure and outcome. The adjusted models also included exposure to other antibiotics within the same window, captured as fluoroquinolones, intravenous vancomycin and other adjunctive antibiotics, with and without anti-anaerobic activity. Generalized estimating equations with robust variance estimates were employed to account for clustering at the hospital level. Results The assembled cohort included 2,501 patients at 35 hospitals. One-third of patients (36.6%) developed aGVHD, 4.4% died without GVHD and no patients were lost to follow-up. The proportion of patients exposed to at least 1 day of an antipseudomonal cephalosporin was 52.2%, but was lower for antipseudomonal penicillins (24.1%) and carbapenems (18.2%). Table 1 shows patient characteristics by exposure to the antibiotic classes of interest. The unadjusted and adjusted associations between the three antibiotic classes and aGVHD are shown in table 2. In the unadjusted model, high exposure to cephalosporins and carbapenems was statistically associated with increased aGVHD risk. For antipseudomonal penicillins, the direction of association was the same but not statistically significant. After adjustment, most point estimates reverted towards the null. The time to event analysis included 1,146 patients that were similar to the overall cohort with a similar incidence of aGVHD (35.5%) diagnosed a median of 28 (range: 8-100) days after HCT. This group had a higher proportion of mismatched donors (40.9 vs 30.2%), cord blood transplants (40.0 vs 23.5%) and receipt of growth factors (50.5% vs 38.9%). Table 2 also shows the unadjusted and adjusted associations for this analysis. As above, the unadjusted point estimates of association between cephalosporins and carbapenems and aGVHD were suggestive of an association but reverted towards the null with adjustment. Conclusions After controlling for other antibiotic exposures and GHVD-risk factors, there was not a statistically significant association between antibiotic exposure and aGVHD for any of three antibiotic classes commonly used for empiric therapy. However, the adjusted point estimates suggest exposure to carbapenems may confer some additional aGHVD risk. Further exploration of different exposure windows is planned to understand if the identified associations change with capture of earlier or later antibiotic exposures. Disclosures Jagasia: Kadmon: Consultancy; Incyte: Consultancy; Janssen: Research Funding. MacMillan:Alpine Immune Sciences: Consultancy; Angiocrine: Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy; Equillium: Membership on an entity's Board of Directors or advisory committees. Fisher:Pfizer: Research Funding; Astellas: Other: Data Safety Monitoring Board Chair for an antifungal study; Merck: Research Funding.


Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 390-390 ◽  
Author(s):  
Mark A. Schroeder ◽  
H. Jean Khoury ◽  
Madan Jagasia ◽  
Haris Ali ◽  
Gary J. Schiller ◽  
...  

Abstract Background: Corticosteroids are considered standard first-line systemic therapy for patients with aGVHD, but this approach is effective in only approximately half of all cases. For patients who progress or do not respond to corticosteroids, no specific agent has been identified as standard, and regimens are typically selected based on investigator experience and patient co-morbidities. In preclinical models, JAK inhibition has been shown to impair production of cytokines as well as the differentiation and trafficking of T cells implicated in the pathogenesis of aGVHD. Retrospective studies have suggested that JAK1/JAK2 inhibition with ruxolitinib treatment provides clinical benefit in patients with steroid-refractory GVHD (Zeiser et al, Leukemia 2015;29:2062-2068). Herein, we report preliminary safety results from a prospective randomized, parallel-cohort, open-label phase 1 trial evaluating the potent and selective JAK 1 inhibitor INCB039110 in patients with aGVHD. Methods: Male or female patients 18 years or older who underwent their first allo-hematopoietic stem cell transplant (HSCT) from any donor source and developed grades IIB-IVD aGVHD were eligible for the study. Patients were randomized 1:1 to either a 200 or 300 mg oral daily dose of INCB039110 in combination with corticosteroids, and were stratified based on prior treatment status (treatment-naive [TN] versus steroid-refractory [SR]). The primary endpoint of the study was safety and tolerability; secondary endpoints included overall response rate at Days 14, 28, 56, and 100, non-relapse mortality, and pharmacokinetic (PK) evaluations. Patients were assessed through Day 28 for dose-limiting toxicities (DLTs) and response. A Bayesian approach was used for continuous monitoring of DLTs from Days 1-28. Treatment continued until GVHD progression, unacceptable toxicity, or withdrawal from the study. Acute GVHD was graded according to MN-CIBMTR criteria; adverse events (AEs) were graded according to NCICTCAE v 4.03. Results: Between January and June 2016, 31 patients (TN, n=14; SR, n= 17) were randomized. As of July 25, 2016, data were available from 30 patients who received an oral daily dose of 200 mg (n=14) or 300 mg (n=16) INCB039110 in combination with 2 mg/kg methylprednisolone (or equivalent dose of prednisone). The median durations of treatment were 60.8 days and 56.5 days for patients receiving a daily dose of 200 mg and 300 mg INCB039110, respectively. One DLT of Grade 3 thrombocytopenia was reported. The most frequently reported AEs included thrombocytopenia/platelet count decrease (26.7%), diarrhea (23.3%), peripheral edema (20%), fatigue (16.7%), and hyperglycemia (16.7%). Grade 3 or 4 AEs occurred in 77% of patients and with similar frequency across dose groups and included cytomegalovirus infections (n=3), gastrointestinal hemorrhage (n=3), and sepsis (n=3). Five patients had AEs leading to a fatal outcome, including multi-organ failure (n=2), sepsis (n=1), disease progression (n=1), and bibasilar atelectasis, cardiopulmonary arrest, and respiratory distress (n=1); none of the fatal events was attributed to INCB039110. Efficacy and PK evaluations are ongoing and will be updated at the time of presentation. Conclusion: The oral, selective JAK1 inhibitor INCB039110 can be given safely to steroid-naive or steroid-refractory aGVHD patients. The safety profile was generally consistent in both dose groups. Biomarker evaluation, PK, and cellular phenotyping studies are ongoing. The recommended phase 2 dose will be selected and reported based on PK studies and final safety data. Disclosures Schroeder: Incyte Corporation: Honoraria, Research Funding. Khoury:Incyte Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding. Jagasia:Incyte Corporation: Research Funding; Therakos: Research Funding; Janssen: Research Funding. Ali:Incyte Corporation: Research Funding. Schiller:Incyte Corporation: Research Funding. Arbushites:Incyte Corporation: Employment, Equity Ownership. Delaite:Incyte Corporation: Employment, Equity Ownership. Yan:Incyte Corporation: Employment, Equity Ownership. Rhein:Incyte Corporation: Employment, Equity Ownership. Perales:Merck: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Chen:Incyte Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding. DiPersio:Incyte Corporation: Research Funding.


Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 47-48
Author(s):  
Grigori Okoev ◽  
Daniel J. Weisdorf ◽  
John E Wagner ◽  
Bruce R. Blazar ◽  
Margaret L. MacMillan ◽  
...  

Introduction: Chronic Graft-versus-Host Disease (cGvHD) frequently requires prolonged immune suppressive therapy (IST) with > 50% still on IST at 5 years. The IST typically involves a slow taper of steroids often with flare of cGvHD, necessitating augmentation of previous therapy or addition of new IST. Studies describing cGvHD flares are limited. We analyzed patients with cGvHD who flared during the treatment with systemic IST, their overall survival (OS) and non-relapse mortality (NRM). Methods: This study included all adult patients with cGvHD (n=145) following an allogeneic transplant (2010 - 2017) from a matched sibling donor peripheral blood stem cell transplant (MSD, n=104 (72%) or double/single umbilical cord blood transplant (UCBT, n=41 (28%). The 2014 NIH Consensus Criteria were used to classify organ/overall cGvHD severity. Flare of cGvHD was defined as progression in cGvHD manifestations (after initial response), which was less severe than at diagnosis. Multivariate regression of flares was based on the Prentice, Williams and Peterson model for ordered multiple events (flares). Time-dependent effects on OS and NRM were analyzed by Cox and Fine and Gray regression with propensity scoring to control for confounding. Results: Flares occurred in 87 patients; the cumulative incidence of flares was 60% (95% CI: 51-70%) at a median of 188 days (range 16-751) after diagnosis of cGvHD. The median dose of prednisone was 1 mg/kg/day (range 0-4.2) at diagnosis of cGvHD. At the diagnosis of flare, 36 (41%) of the patients were off prednisone, 50 (57%) were receiving 0.1-0.5 mg/kg /day, and 2 patients > 0.5 mg/kg /day. Thirty two of the 87 (36%) patients experienced multiple flares (2 to 4). The most common organs involved at cGvHD flare were skin (n=45; 51%), mouth (n=27; 31%), GI tract (n=22; 25%) and liver (n=12; 14%); often in combinations of skin/mouth in 11 cases (13%), skin/GI in 6 (7%) and liver/mouth in 4 (5%) cases. Treatment for flare was mostly increase in dose of prednisone to 0.5 mg/kg/day (range 0.3-1.0) in 77 patients (88%) plus the addition of another line of IST in 48 patients (55%). In multiple regression analysis, only donor type was significant predictor of flare in cGvHD. UCBT was associated with 2-fold lower probability of flaring (HR 0.5; 95% CI: 0.3-0.9; p=0.03) compared to MSD. cGvHD severity, organ involvement, platelet count at diagnosis and type of onset were not significant predictors of cGvHD flares. At 2 years after the initial flare, the OS was 77% (95% CI: 66-84%) and NRM 19% (95% CI: 11-28%). Multiple regression analysis evaluating OS and NRM from onset of cGvHD comparing flare to non-flare were performed using flare as a time dependent variable. Compared to cGvHD patients without flare at 2 years, those with flare of cGvHD had a similar risk of NRM (HR 1.2; 95% CI: 0.2-6.1, p=0.86) and OS (HR 0.9; 95% CI: 0.4-2.3, p=0.85). At 2 years from cGvHD onset, the cumulative incidence of resolved cGvHD (durable discontinuation of steroids for ≥ 6 consecutive months) was 31% (95% CI: 21-41%) in those who flared vs. 86% (95% CI: 75-96%) in those without flare. Conclusions: Though cGvHD patients with flare had similar risk of NRM and OS as those without a flare, patients with flare required extended steroids, along with clinical monitoring and intensified IST. cGvHD after UCBT was associated with significantly lower risk of flaring compared to MSD. The ongoing burden of IST, risk of infection and morbidity of cGvHD is substantial and needs better approaches than chronic slow taper of steroids. Disclosures Weisdorf: Incyte: Research Funding; FATE Therapeutics: Consultancy. Wagner:Novartis: Research Funding; Rocket Pharmaceuticals, Inc.: Consultancy, Current equity holder in publicly-traded company; Magenta Therapeutics: Consultancy, Research Funding; BlueRock: Research Funding; Gadeta: Membership on an entity's Board of Directors or advisory committees. Blazar:Fate Therapeutics Inc.: Research Funding; Childrens' Cancer Research Fund: Research Funding; BlueRock Therapeutics: Research Funding; BlueRock Therapeuetic: Consultancy; Magenta Therapeutics: Consultancy; KidsFirst Fund: Research Funding; Tmunity: Other: Co-founder. MacMillan:Mesoblast: Consultancy; Angiocrine Biosciences, Inc.: Consultancy; Equillium, Inc.: Consultancy; Talaris Therapeutics, Inc: Consultancy; Fate Therapeutics, Inc.: Consultancy. Holtan:Generon: Consultancy; BMS: Consultancy; CSL Behring: Other: Clinical trial data adjudication; Incyte: Consultancy. Brunstein:AlloVir: Other: Advisory board; Gamida: Research Funding; Astex: Research Funding; Magenta: Research Funding. Betts:Patent Pending: Patents & Royalties: Dr. Betts has a pending patent WO2017058950A1: Methods of treating transplant rejection. This includes the use of JAK inhibitors. Neither he nor his institution have received payment related to claims described in the patent.. Bachanova:FATE: Research Funding; Karyopharma: Membership on an entity's Board of Directors or advisory committees; Incyte: Research Funding; Gamida Cell: Membership on an entity's Board of Directors or advisory committees, Research Funding; Kite: Membership on an entity's Board of Directors or advisory committees; BMS: Research Funding. Rashidi:Synthetic Biologics: Other: DSMC member (1 trial) and related honorarium. Arora:Fate Therapeutics: Consultancy; Kadmon: Research Funding; Pharmacyclics: Research Funding; Syndax: Research Funding.


Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 32-33
Author(s):  
Aikaterini Poulaki ◽  
Theodora Katsila ◽  
Ioanna E Stergiou ◽  
Stavroula Giannouli ◽  
Jose Carlos Gόmez Tamayo ◽  
...  

Despite its major role in cellular biology, metabolism has only recently acquired a principal role in the research of the most profound cellular cycle disturbance, cancerous transformation. Myelodysplastic syndromes (MDS), a massively heterogeneous group of Hematopoietic Stem/ Progenitor Cell (HSC/HPC) disorders lie at the interface of normal differentiation and malignant transformation and have thus drew great attention due to their polymorphic presentation and elusive pathophysiology. Failure to establish a direct etiopathogenic relationship with specific genetic aberrations, along with the novel finding of a highly deregulated HIF1 activity by several unrelated research groups worldwide, including ours, urged us to investigate the metabolomic status of human bone marrow derived differentiating myeloid lineage in comparison with one another as well as with control samples. BM aspiration samples collected from 14 previously untreated MDS patients (10 patients with <5% (1 SLD, 8MLD, 1del5q, group 1- G1) and 4 with >5% BM blasts (2 EB1, 2 EB2group 2 - G2)) and 5 age matched controls. Myeloid lineage cells were isolated through ficoll bilayer protocol. All samples contained homogenous myeloid lineage subpopulations, assessedthrough optical microscopy. Two different metabolite extraction protocols were applied. The one with the best metabolites yield (50% MeOH, 30% ACN, 20% H2O) was chosen. LC-MS/MS analysis was performed using UPLC 1290 system (Agilent Technologies) coupled to a TripleTOF 5600+ mass spectrometer (SCIEX) equipped with SWATH acquisition, SelexION technology and an electrospray ionization source (ESI). A threshold of a minimum of three samples expressing a given metabolite was set against data sparsity. Data tables were scaled by data centering and setting unit variance. Log2 Foldcalculation and PLS analysis were performed for the two datasets (positive and negative ion-modes). R2 and Q2 for positive ion-mode and negative-ion mode analyses were determined. Both datasets were merged in a unique data table by taking into account maximum absolute log2 foldvalues, when a metabolite was found in both datasets. Warburg effect was evidently present in both the G1 and G2 vs control comparisons, yet the role of this stem like aerobic glycolysis seems markedly different in the two groups. While in the G2 group it serves to rescue glucose from complete burn in the mitochondrion and thus shuts it towards nucleotide synthesis (Pentose Phosphate Pathway found upregulated) with the added benefit of increased reduced Glutathione synthesis and improved redox state, in the G1 group proves detrimental. This greatly variable effect of the same phenomenon in the cellular fate lies upon the quality and functionality of the cellular mitochondrial content. G2 precursors presented functional mitochondrial (decreased NAD/NADH and FAD/FADH2) contrary to the G1 ones (Table). Failing TCA cycle, with increased NAD/NADH and FAD/FADH2 ratios and markedly increased ADP/ATP levels leads to FAs accumulation due to failure of effective adequate β oxidation. The uncontrolled increase in the NAD/NADH ratio stimulates upper glycolysis into a turbo mode further increasing the ADP/ATP, depleting cellular energy contents, engaging it to a never-ending deadly metabolism. The enormous abundance of upper glycolytic intermediates is relieved through phospholipid and ceramide synthesis, all found massively upregulated in both the MDS vs control yet also in the G1 vs G2 comparisons. FAs, mostly phospholipid and ceramide accumulation, interrupt the mitochondrial membrane lipidome further incapacitating metabolic integrity and inducing their autophagic degradation which further stimulates the Warburg effect. This type of metabolic reprogramming is eventually targeted to epigenetic modifier production, increased S-adenosyl-methionine, the major methyl group donor, 2-HydroxyGlutarate, a potent epigenetic modifier and notorious oncometabolite, Acetyl-Lysine, the major acetyl- group donor, even glutathione. We therefore present a model of an uncontrolled Warburg effect which in the G1 group confers premature death of the hematopoietic precursors, the ineffective hematopoiesis of MDS. Yet, under the pressure of the vastly upregulated epigenetic modifiers cellular fate changes, the G1 precursors adapt and transform to the G2 ones yet eventually to Acute Myeloid Leukemia blasts. Table Disclosures Vassilopoulos: Genesis pharma SA: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; Gilead: Research Funding; Abbvie: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees.


Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 196-196
Author(s):  
Bishwas Shrestha ◽  
Kelly Walton ◽  
Jordan Reff ◽  
Elizabeth M. Sagatys ◽  
Nhan Tu ◽  
...  

Distinct from pharmacologic immunosuppression, we designed a programmed cytolytic effector T cell that prevents graft versus host disease (GVHD). CD83 is expressed on allo-activated conventional T cells (Tconv) and pro-inflammatory dendritic cells (DCs), which are implicated in GVHD pathogenesis. Therefore we developed a novel human CD83 targeted chimeric antigen receptor (CAR) T cell for GVHD prophylaxis. Here we demonstrate that human CD83 CAR T cells eradicate cell mediators of GVHD, significantly increase the ratio of regulatory T cells (Treg) to allo-activated Tconv, and provide lasting protection from xenogeneic GVHD. Further, we show human, acute myeloid leukemia (AML) expresses CD83 and can be targeted by CD83 CAR T cells. A 2nd generation CD83 CAR was generated with CD3ζ and 41BB costimulatory domain that was retrovirally transduced in human T cells to generate CD83 CAR T cells. The CD83 CAR construct exhibited a high degree of transduction efficiency of about 60%. The CD83 CAR T cells demonstrated robust IFN-γ and IL-2 production, killing, and proliferation when cultured with CD83+ target cells. To test whether human CD83 CAR T cells reduce alloreactivity in vitro, we investigated their suppressive function in allogeneic mixed leukocyte reactions (alloMLR). CD83 CAR T cells were added to 5-day alloMLRs consisting of autologous T cells and allogeneic monocyte-derived DCs at ratios ranging from 3:1 to 1:10. The CD83 CAR T cells potently reduced alloreactive T cell proliferation compared to mock transduced and CD19 CAR T cells. We identified that CD83 is differentially expressed on alloreactive Tconv, compared to Tregs. Moreover, the CD83 CAR T cell efficiently depletes CD83+ Tconv and proinflammatory DCs with 48 hours of engagement. To test the efficacy of human CD83 CAR T cells in vivo, we used an established xenogeneic GVHD model, where mice were inoculated with human PBMCs (25x106) and autologous CD83 CAR (1-10x106) or mock transduced T cells. The CD83 CAR T cells were well tolerated by the mice, and significantly improved survival compared to mock transduced T cells (Figure 1A). Mice treated with CD83 CAR T cells exhibited negligible GVHD target organ damage at day +21 (Figure 1B). Mice inoculated with CD83 CAR T cells demonstrated significantly fewer CD1c+, CD83+ DCs (1.7x106 v 6.2x105, P=0.002), CD4+, CD83+ T cells (4.8x103 v 5.8x102, P=0.005), and pathogenic Th1 cells (3.1x105 v 1.1x102, P=0.005) at day +21, compared to mice treated with mock transduced T cells. Moreover, the ratio of Treg to alloreactive Tconv (CD25+ non-Treg) was significantly increased among mice treated with CD83 CAR T cells (78 v 346, P=0.02), compared to mice injected with mock transduced T cells. Further, CD83 appears to be a promising candidate to target myeloid malignancies. We observed CD83 expression on malignant myeloid K562, Thp-1, U937, and MOLM-13 cells. Moreover, the CD83 CAR T cells effectively killed AML cell lines. Many AML antigens are expressed on progenitor stem cells. Thus, we evaluated for stem cell killing in human colony forming unit (CFU) assays, which demonstrated negligible on-target, off-tumor toxicity. Therefore, the human CD83 CAR T cell is an innovative cell-based approach to prevent GVHD, while providing direct anti-tumor activity against myeloid malignancies. Figure Disclosures Blazar: Kamon Pharmaceuticals, Inc: Membership on an entity's Board of Directors or advisory committees; Five Prime Therapeutics Inc: Co-Founder, Membership on an entity's Board of Directors or advisory committees; BlueRock Therapeutics: Membership on an entity's Board of Directors or advisory committees; Abbvie Inc: Research Funding; Leukemia and Lymphoma Society: Research Funding; Childrens' Cancer Research Fund: Research Funding; KidsFirst Fund: Research Funding; Tmunity: Other: Co-Founder; Alpine Immune Sciences, Inc.: Research Funding; RXi Pharmaceuticals: Research Funding; Fate Therapeutics, Inc.: Research Funding; Magenta Therapeutics and BlueRock Therapeuetics: Membership on an entity's Board of Directors or advisory committees; Regeneron Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Davila:Atara: Research Funding; Celgene: Research Funding; Precision Biosciences: Consultancy; Bellicum: Consultancy; GlaxoSmithKline: Consultancy; Adaptive: Consultancy; Anixa: Consultancy; Novartis: Research Funding.


Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 523-523
Author(s):  
Rasoul Pourebrahimabadi ◽  
Zoe Alaniz ◽  
Lauren B Ostermann ◽  
Hung Alex Luong ◽  
Rafael Heinz Montoya ◽  
...  

Acute myeloid leukemia (AML) is a heterogeneous disease that develops within a complex microenvironment. Reciprocal interactions between the bone marrow mesenchymal stem/stromal cells (BM-MSCs) and AML cells can promote AML progression and resistance to chemotherapy (Jacamo et al., 2014). We have recently reported that BM-MSCs derived from AML patients (n=103) highly express p53 and p21 compared to their normal counterparts (n=73 p<0.0001) (Hematologica, 2018). To assess the function of p53 in BM-MSCs, we generated traceable lineage specific mouse models targeting Mdm2 or Trp53 alleles in MSCs (Osx-Cre;mTmG;p53fl/fl and Osx-Cre;mTmG;Mdm2fl/+) or hematopoietic cells (Vav-Cre;mTmG;p53fl/fl and Vav-Cre;mTmG;Mdm2fl/+). Homozygote deletion of Mdm2 (Osx-Cre;Mdm2fl/fl) resulted in death at birth and displayed skeletal defects as well as lack of intramedullary hematopoiesis. Heterozygote deletion of Mdm2 in MSCs was dispensable for normal hematopoiesis in adult mice, however, resulted in bone marrow failure and thrombocytopenia after irradiation. Homozygote deletion of Mdm2 in hematopoietic cells (Vav-Cre;Mdm2fl/fl) was embryonically lethal but the heterozygotes were radiosensitive. We next sought to examine if p53 levels in BM-MSCs change after cellular stress imposed by AML. We generated a traceable syngeneic AML model using AML-ETO leukemia cells transplanted into Osx-Cre;mTmG mice. We found that p53 was highly induced in BM-MSCs of AML mice, further confirming our findings in primary patient samples. The population of BM-MSCs was significantly increased in bone marrow Osx-Cre;mTmG transplanted with syngeneic AML cells. Tunnel staining of bone marrow samples in this traceable syngeneic AML model showed a block in apoptosis of BM-MSCs suggesting that the expansion of BM-MSCs in AML is partly due to inhibition of apoptosis. As the leukemia progressed the number of Td-Tomato positive cells which represents hematopoietic lineage and endothelial cells were significantly decreased indicating failure of normal hematopoiesis induced by leukemia. SA-β-gal activity was significantly induced in osteoblasts derived from leukemia mice in comparison to normal mice further supporting our observation in human leukemia samples that AML induces senescence of BM-MSCs. To examine the effect of p53 on the senescence associated secretory profile (SASP) of BM-MSCs, we measured fifteen SASP cytokines by qPCR and found significant decrease in Ccl4, Cxcl12, S100a8, Il6 and Il1b upon p53 deletion in BM-MSCs (Osx-Cre;mTmG;p53fl/fl) compared to p53 wildtype mice. To functionally evaluate the effects of p53 in BM-MSCs on AML, we deleted p53 in BM-MSCs (Osx-Cre;mTmG;p53fl/fl) and transplanted them with syngeneic AML-ETO-Turquoise AML cells. Deletion of p53 in BM-MSCs strongly inhibited the expansion of BM-MSCs in AML and resulted in osteoblast differentiation. This suggests that expansion of BM-MSCs in AML is dependent on p53 and that deletion of p53 results in osteoblast differentiation of BM-MSCs. Importantly, deletion of p53 in BM-MSCs significantly increased the survival of AML mice. We further evaluated the effect of a Mdm2 inhibitor, DS-5272, on BM-MSCs in our traceable mouse models. DS-5272 treatment of Osx-cre;Mdm2fl/+ mice resulted in complete loss of normal hematopoietic cells indicating a non-cell autonomous regulation of apoptosis of hematopoietic cells mediated by p53 in BM-MSCs. Loss of p53 in BM-MSCs (Osx-Cre;p53fl/fl) completely rescued hematopoietic failure following Mdm2 inhibitor treatment. In conclusion, we identified p53 activation as a novel mechanism by which BM-MSCs regulate proliferation and apoptosis of hematopoietic cells. This knowledge highlights a new mechanism of hematopoietic failure after AML therapy and informs new therapeutic strategies to eliminate AML. Disclosures Khoury: Angle: Research Funding; Stemline Therapeutics: Research Funding; Kiromic: Research Funding. Bueso-Ramos:Incyte: Consultancy. Andreeff:BiolineRx: Membership on an entity's Board of Directors or advisory committees; CLL Foundation: Membership on an entity's Board of Directors or advisory committees; NCI-RDCRN (Rare Disease Cliln Network): Membership on an entity's Board of Directors or advisory committees; Leukemia Lymphoma Society: Membership on an entity's Board of Directors or advisory committees; German Research Council: Membership on an entity's Board of Directors or advisory committees; NCI-CTEP: Membership on an entity's Board of Directors or advisory committees; Cancer UK: Membership on an entity's Board of Directors or advisory committees; Center for Drug Research & Development: Membership on an entity's Board of Directors or advisory committees; NIH/NCI: Research Funding; CPRIT: Research Funding; Breast Cancer Research Foundation: Research Funding; Oncolyze: Equity Ownership; Oncoceutics: Equity Ownership; Senti Bio: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Eutropics: Equity Ownership; Aptose: Equity Ownership; Reata: Equity Ownership; 6 Dimensions Capital: Consultancy; AstaZeneca: Consultancy; Amgen: Consultancy; Daiichi Sankyo, Inc.: Consultancy, Patents & Royalties: Patents licensed, royalty bearing, Research Funding; Jazz Pharmaceuticals: Consultancy; Celgene: Consultancy. OffLabel Disclosure: Mdm2 inhibitor-DS 5272


Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 45-47
Author(s):  
Josu de la Fuente ◽  
Dirk-Jan Eikema ◽  
Paul Bosman ◽  
Robert F Wynn ◽  
Miguel Díaz ◽  
...  

Congenital sideroblastic anaemias (CSA) are a rare group of disorders characterized by the presence of pathologic iron deposits within the mitochondria of erythroid precursors (ring sideroblasts) in the bone marrow due to heterogenous germline mutations leading to defects in mitochondrial heme synthesis, iron-sulfur (Fe-S) cluster biogenesis, or protein synthesis. Patients present with anaemia and relative reticulocytopenia, and systemic iron overload secondary to chronic ineffective erythropoiesis, leading to end-organ damage. The disease is heterogenous underlying the genetic variability and the variable response to treatment. Although a number of CSA patients have received a bone marrow transplant, the outcomes and toxicities are not known. This status makes it very difficult to understand the role of BMT in the management of CSA. A search in the EBMT database identified 28 patients receiving a HSCT for CSA between 1998 to 2018 by 24 participating centres. The median year of transplantation was 2014 (IQR 2004-2016). The distribution was equal between males (n=14) and females (n=14). The median age at transplantation was 7 years of age (3-10 years). Fifteen patients had a sibling HSCT (88%), one a family matched donor HSCT (6%) and one an unrelated matched (6%), the type of transplant being unknown in others (n=11). The source of stem cells was bone marrow in 20 cases (74%), peripheral blood in 4 cases (15%), cord blood in 2 (7%) and combined bone marrow and cord in one (4%). Five cases had a Bu/Cy based conditioning regimen, 4 had Bu/fludarabine based regimen and three fludarabine/treosulfan based conditioning with the rest having a variety of approaches. Eighty-six percent of cases had serotherapy with ATG or alemtuzumab. The median follow-up was 31.6 months (95% CI, 12.2-74.1%). The overall survival at 12 and 24 months was 88% (76-100) and 82% (66-99), respectively (figure 1). The median neutrophil engraftment was 18 (15-21) days and platelet engraftment >20 x 109/L was 29 (20-51) days, with a graft failure incidence of 7% (0-17) at 12 months. Two patients suffered from VOD. There were four deaths, three of which were related to transplant complications. The event free survival (survival without graft failure, relapse and second transplant) at 12 and 24 months was 85% (72-99) (figure 2). Six patients developed acute GvHD grade II and one case grade III; giving a grade II/III incidence of 28% (10-46). There was one case of limited and one of chronic GvHD, giving an incidence of 11% (0-26%) at 12 months and 24 months. In conclusion, whilst HSCT for CSA is a rare occurrence, these data demonstrate that HSCT for this condition is feasible and the outcomes are in keeping with those obtained for transplantation for transfusion dependent anaemias during the same time-period. Disclosures Handgretinger: Amgen: Honoraria. Moraleda:Gilead: Consultancy, Other: Travel Expenses; Jazz Pharmaceuticals: Consultancy, Research Funding; Novartis: Consultancy, Other: Travel Expenses; Sandoz: Consultancy, Other: Travel Expenses; Takeda: Consultancy, Other: Travel Expenses. Risitano:Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Alnylam: Research Funding; Alexion: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Jazz: Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees; Samsung: Membership on an entity's Board of Directors or advisory committees; Amyndas: Consultancy; RA pharma: Research Funding; Biocryst: Membership on an entity's Board of Directors or advisory committees; Apellis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Achillion: Membership on an entity's Board of Directors or advisory committees; Pfizer: Speakers Bureau. Peffault De Latour:Amgen: Research Funding; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Apellis: Membership on an entity's Board of Directors or advisory committees; Alexion Pharmaceuticals Inc.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.


Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 4496-4496 ◽  
Author(s):  
Luke Eastburg ◽  
David A. Russler-Germain ◽  
Ramzi Abboud ◽  
Peter Westervelt ◽  
John F. DiPersio ◽  
...  

The use of post-transplant cyclophosphamide (PTCy) in the context of haploidentical stem cell transplant (haplo-SCT) has led to drastically reduced rates of Graft-vs-Host (GvH) disease through selective depletion of highly allo-reactive donor T-cells. Early trials utilized a reduced-intensity Flu/Cy/TBI preparative regimen and bone marrow grafts; however, relapse rates remained relatively high (Luznik et al. BBMT. 2008). This led to the increased use of myeloablative (MA) regimens for haplo-SCT, which have been associated with decreased relapse rates (Bashey et al. J Clin Oncol. 2013). Most studies have used a MA total body irradiation (TBI) based regimen for haplo-SCT. Preparative regimens using fludarabine and melphalan (FluMel), with or without thiotepa, ATG, and/or low dose TBI have also been reported using bone marrow grafts. Reports on the safety and toxicity of FluMel in the haplo-SCT setting with PTCy and peripheral blood stem cell (PBSC) grafts are lacking. In this two-center retrospective analysis, the safety/toxicity of FluMel as conditioning for haplo-SCT was evaluated. We report increased early mortality and toxicity using standard FluMel conditioning and PBSC grafts for patients undergoing haplo-SCT with PTCy. 38 patients at the University of Rochester Medical Center and the Washington University School of Medicine underwent haplo-SCT with FluMel conditioning and PBSC grafts between 2015-2019. Outcomes were measured by retrospective chart review through July 2019. 34 patients (89.5%) received FluMel(140 mg/m2). Two patients received FluMel(100 mg/m2) and two patients received FluMel(140 mg/m2) + ATG. The median age at time of haplo-SCT was 60 years (range 21-73). 20 patients were transplanted for AML, eight for MDS, two for PMF, two for NHL, and five for other malignancies. The median Hematopoietic Cell Transplantation-specific Comorbidity Index (HCT-CI) score was 4 (≥3 indicates high risk). 11 patients had a history of prior stem cell transplant, and 16 patients had active disease prior to their haplo-SCT. Seven patients had sex mismatch with their stem cell donor. Median donor age was 42 (range 21-71). 20 patient deaths occurred by July 2019 with a median follow up of 244 days for surviving patients. Nine patients died before day +100 (D100, "early mortality"), with a D100 non-relapse mortality (NRM) rate of 24%. Median overall and relapse free survival (OS and RFS, respectively) were 197 days (95% CI 142-not reached) and 180 days (95% CI 141-not reached), respectively, for the entire cohort. The 1 year OS and NRM were 29% and 50%. The incidence of grades 2-4cytokine release syndrome (CRS) was 66%, and 52% of these patients were treated with tocilizumab. CRS was strongly associated with early mortality, with D100 NRM of 36% in patients with grade 2-4 CRS compared to 0% in those with grade 0-1. The incidence of acute kidney injury (AKI) was 64% in patients with grade 2-4 CRS, and 8% in those without (p < 0.001). 28% of patients with AKI required dialysis. Grade 2-4 CRS was seen in 54% of patients in remission prior to haplo-SCT and in 92% of those with active disease (p = 0.02). Of the 9 patients with early mortality, 89% had AKI, 44% needed dialysis, and 100% had grade 2-4 CRS, compared to 31%, 10%, and 55% in those without early mortality (p = 0.002, p = 0.02, p = 0.01). Early mortality was not significantly associated with age, HCT-CI score, second transplant, disease status at transplant, total dose of melphalan, volume overload/diuretic use, or post-transplant infection. In conclusion, we observed a very high rate of NRM with FluMel conditioning and PBSC grafts for haplo-SCT with PTCy. The pattern of toxicity was strongly associated with grade 2-4 CRS, AKI, and need for dialysis. These complications may be mediated by excessive inflammation in the context of allo-reactive donor T-cell over-activation. Consistent with this, multiple groups have shown that FluMel conditioning in haplo-SCT is safe when using bone marrow or T-cell depleted grafts. Based on our institutional experiences, we would discourage the use of FluMel as conditioning for haplo-SCT with PTCy with T-cell replete PBSC grafts. Alternative regimens or variations on melphalan-based regimens, such as fractionated melphalan dosing or inclusion of TBI may improve outcomes but further study and randomized controlled trials are needed. This study is limited in its retrospective design and sample size. Figure Disclosures DiPersio: WUGEN: Equity Ownership, Patents & Royalties, Research Funding; Karyopharm Therapeutics: Consultancy; Magenta Therapeutics: Equity Ownership; Celgene: Consultancy; Cellworks Group, Inc.: Membership on an entity's Board of Directors or advisory committees; NeoImmune Tech: Research Funding; Amphivena Therapeutics: Consultancy, Research Funding; Bioline Rx: Research Funding, Speakers Bureau; Macrogenics: Research Funding, Speakers Bureau; Incyte: Consultancy, Research Funding; RiverVest Venture Partners Arch Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees. Liesveld:Onconova: Other: Data safety monitoring board; Abbvie: Membership on an entity's Board of Directors or advisory committees.


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