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Refractory acute myeloid leukemia (AML), defined as failure of 2 cycles of induction therapy at diagnosis or of 1 cycle at relapse, represents a subgroup with poor clinical outcomes. In our transplant cohort, the 5-year overall survival in this subgroup was 16% (Ganapule at al. JGO 2017). Haploidentical natural killer cell (NK) therapy is a strategy that is being explored in refractory malignancies. Our in-vitro and animal model data suggest that exposure to arsenic trioxide (ATO) results in enhanced NK cytotoxicity (Alex AA et al. Front. Immunol 2018). Historically, at our center, patients with refractory AML have been treated with cytoreductive therapy (FLAG ± idarubicin or mitoxantrone + etoposide for 3 to 5 days) followed by 1-week rest and then a reduced-intensity transplant with fludarabine + melphalan conditioning while in peak cytopenia. From February 2019, we initiated a phase II single arm clinical trial (CTRI/2019/02/017505) enrolling patients with refractory AML planned for a stem cell transplant in peak cytopenia. Patients received CD56-positive cells from an HLA haploidentical related family donor (other than the stem cell donor, wherever feasible) following cytoreductive chemotherapy. The NK cell donor preference strategy included presence of KIR ligand mismatch, greater number of KIR B motifs (or the B score), lower donor age, and negative donor specific antibodies tested using flowcytometry crossmatch (Figure 1a). CD56-positive selection was done using CliniMACS prodigy system. This was followed by overnight incubation of the CD56 positive cells in autologous plasma with 2 micromolar ATO and 500 U/mL of interleukin-2. The CD56 positive cells were then infused to the patient 1-day after the completion of cytoreductive chemotherapy. This was followed by a reduced intensity stem cell transplant (Figure 1b). The primary outcome variable was 1-year relapse free survival. From February 2019, 14 patients with median age 28 years (IQR: 15.75-31.5) were enrolled in this trial. Six were females. Six had primary-refractory AML while 8 had relapsed-refractory AML. The cytoreductive chemotherapy was FLAG ± idarubicin (n=7), Mitoxantrone + Etoposide (n=6) and GCLAC (n=1). The median blast percentage on flowcytometry MRD testing prior to NK infusion was 15.9% (IQR: 9.1%-54.5%) (n=11). The median B score for the NK cell donors was 2 (IQR: 1-3). The median age of the NK cell donor was 43 years (IQR: 36-49.5). KIR ligand mismatch with the patient was noted in 2 donors. The median CD56-cell dose infused was 46.16 x 10 6/kg (IQR: 25.06-70.36) (Figure 1c). Pre-defined release criteria, including sterile cultures, and endotoxin negativity were met in all cases. There was no infusion related toxicity. The median blast percentage on flowcytometry MRD testing done following NK cell infusion was 11.9% (IQR: 4.9%-47.6%) (n=8). One patient withdrew consent after NK cell infusion and did not undergo transplant. For the remaining 13 patients, the stem cell donor was HLA matched (n=4), HLA 9/10 matched (n=1) or HLA haplomatched (n=8). The median CD34 cell dose infused was 10 x 10 6/kg (IQR:7.51-11.6). Five (38.5%) patients died of immediate post-transplant complications (sepsis (n=3) on days 1, 2 and 28, cerebral venous sinus thrombosis (n=1) on day 1 in a patient treated with hormonal contraceptives for menorrhagia, and veno-occlusive disease (n=1) on day 15 in a patient undergoing a second transplant) while 2 (15.4%) did not engraft (both subsequently died of infective complications following engraftment post-second transplant). Of the remaining 6 (46.2%) patients who engrafted and survived beyond 1 month of the transplant, the day 28 post-transplant MRD was negative for 5 patients while it was positive in 1 patient (0.13%). On follow up, 2 (15.4%) patients developed disease relapse (on days 54 and 218 respectively) and died. The remaining 4 (30.8%) patients are alive and relapse free at last follow up (mean follow up of surviving patients is 16 months). One patient received a CD34 cell boost on day 96 (cell dose - 8.55 x 10 6/kg) for poor graft function. For the entire cohort, the estimated 1-year event free survival is 28.8% ± 13.1%(Figure 1d). Whereas, acute GVHD was noted in 3 patients (50%; out of 6 evaluable patients) and chronic GVHD was noted in 3 patients (50%; out of the 6 evaluable patients). Thus, haploidentical NK cell therapy as an adjunct to transplant is safe and merits further evaluation in patients with AML. Figure 1 Figure 1. Disclosures Mathews: Christian Medical College: Patents & Royalties: US 2020/0345770 A1 - Pub.Date Nov.5, 2020; AML: Other: Co-Inventor.

Introduction Aplastic anemia (AA) is characterized by a hypoplastic marrow and bone marrow failure (BMF), leading to peripheral pancytopenia. The treatment for AA currently consists of either hematopoietic stem cell transplant (HSCT) or immunosuppressive therapy (IST) with anti-thymocyte globulin and cyclosporine. We have previously reported poor responses to IST in Indian children with AA while adults (>15 years) show responses of 60%. Therefore, we wanted to study if we could identify constitutional variants in children and young adults with AA. Methods We included 102 young patients (≤40 years of age) diagnosed to have AA between year Jan 2006 to April 2021. Genomic DNA was extracted from peripheral blood and relative telomere length (rTL) was measured using quantitative real-time PCR (qPCR). The DNA was used to perform targeted gene capture using a custom capture kit which covered 2196 genes associated with various hematological disorders. Among the 2196 genes, the analysis was restricted to 96 genes associated with AA/IBMFS. Bioinformatics analysis was carried out using Genome Analysis ToolKit (GATK) best practices pipeline. Based on the American College of Medical Genetics and Genomics (ACMG) guidelines, the variants were labelled as pathogenic/likely pathogenic/variant of uncertain significance (VUS)/likely benign/benign. The candidate variants were validated by Sanger sequencing. Results The median age of patients was 9 (0-40) years, including 56 males (55%) and 46 females (45%). There were 15 patients with non-severe AA (NSAA) (15%), 63 with severe AA (SAA) (62%) and 24 with very severe AA (VSAA) (23%). The median relative telomere length of the entire cohort was 0.85 (0.21-3.10). The characteristics of patients age-wise are mentioned in Table 1. Genetic variants were identified in 34 patients (33.3%). This included germline pathological (PAT) genetic variants in 12.7%, variants of limited significance in 9.8% and variants of uncertain significance (VUS) in 10.7% patients. Of the 13 patients who had PAT variants, 6 patients had variants in telomere associated genes. This includes 2 patients with splice site and missense mutation in TINF2 (c.1221+5G>A & R282H); 2 patients with missense mutation in TERT (C828W & S947C); and 2 patients with frameshift and nonsense mutation in RTEL1 (L962S & R1010X). Homozygous MPL mutations [L79Q, R522T & P530L(n=3)] were observed in 5 patients. Two patients had PAT variants in DNAJC21 and NLRP12. Eleven VUS variants were present in the following genes, ATM (n=3), TINF2 (n=1), WRAP53 (n=1), BRCA2 (n=1), AK2 (n=1), FANCA (n=1), FANCN (n=1), ERCC6L2 (n=1) & PRF1 (n=1). The incidence of mutations in the age group ≤5, 6-10, 11-15 and 16-30 years were 51.8%, 25.6%, 27.8% & 33.4% respectively. There was significant difference in median rTL between patients with variants and no variants in the age-group 11-15 years (p=0.043). Discussion Genetic analyses studies in aplastic anemia patients were confined to single genes or limited gene sets. Keel et al., reported 5.1% of AA patients carried pathogenic variants in inherited BMF/MDS genes. We observed a high frequency of causative genetic variants (37%) in children ( Figure 1 Figure 1. Disclosures Mathews: Christian Medical College: Patents & Royalties: US 2020/0345770 A1 - Pub.Date Nov.5, 2020; AML: Other: Co-Inventor.

In the setting of clinical trials, high cure rates have been reported for acute promyelocytic leukemia (APL) with the chemotherapy-free combination of arsenic trioxide (ATO) and all-trans retinoic acid (ATRA) for low-intermediate risk disease, and with the addition of gemtuzumab ozogamicin or minimal anthracycline for high-risk disease. Despite clear in-vitro synergy between ATO and ATRA, most clinical trial protocols in APL have not used these drugs concurrently beyond induction. There is limited real world data on the use of chemotherapy-free combination of ATO and ATRA with minimal anthracycline use in the treatment of APL, especially in the high risk group. We did a retrospective analysis of the clinical outcomes of patients with newly diagnosed APL treated at our center from January 2015 to May 2020 using concurrent ATO, ATRA and minimal anthracycline in a risk stratified manner. The data was frozen and analyzed as on 1st June 2021. During the study period, 167 patients were diagnosed to have APL at our hospital. Of these, we excluded 5 patients who had presented with relapsed disease and 28 patients who were treated with single agent ATO. The remaining 134 patients were treated with a uniform protocol as summarized in Figure 1a. Figure 1b shows the KM plot for EFS (2 year: 90.8±2.5%) for these 134 patients. For analysis of regimen safety and efficacy, we excluded patients who wished to pursue treatment elsewhere within the first 1 week of treatment (n=7), and patients who had severe infections or life-threatening bleeding at presentation or before therapy initiation and subsequently died (n=4). Thus, a total of 123 patients with newly diagnosed APL were included for further analysis. The median age was 35 years (IQR: 24 to 45 years). Forty-six (37.4%) were females. The median duration of symptoms prior to admission was 14 days (IQR: 7 to 28 days). Sixty-one (49.6%) had high risk APL while the remaining 62 (50.4%) had low-intermediate risk APL. During induction, 28 (22.7%) patients had major bleeding while 5 (4%) patients developed major thrombosis. Sixty-seven (55%) patients had at least one documented infection during induction therapy. The median number of packed red cell concentrates, fresh frozen plasma, platelet rich concentrates and cryoprecipitates transfused during induction therapy was 5 (IQR: 3 to 6.5), 10 (IQR: 3 to 30), 40 (IQR: 23 to 55) and 6 (IQR: 0 to 18) respectively. Nineteen (15.4%) patients developed differentiation syndrome; all were treated with steroids, 8 required transient cessation of treatment and 6 required intensive care. Eight (6.5%) patients died during induction. During induction, grade 3 hepatotoxicity was noted in 8 (6.5%) patients, 10 (8.1%) patients had ATRA related headache or benign intracranial hypertension of which 5 required transient cessation of ATRA, while 11 (8.9%) patients had transient QTc prolongation of which 6 required transient cessation of ATO. Seventeen (13.8%) patients developed symptomatic sensory neuropathy requiring treatment. None required permanent discontinuation of therapy. At a median follow up of 854 days, there were 2 (1.6%) hematologic relapses and no deaths beyond induction therapy. The 2-year OS and EFS for the cohort (n=123) are 93.4% ± 2.3% and 91.6% ± 2.6% respectively (Figure 1c). Two (1.6%) patients have developed second malignancies. In a real world setting, concurrently administered ATO and ATRA with minimal anthracycline use results in excellent long term survival, even in the high risk group. Early deaths due to delayed presentation with infections and life threatening bleeding remain an unmet need for future research along with the need for strategies to reduce treatment-related toxicities. Figure 1 Figure 1. Disclosures Mathews: Christian Medical College: Patents & Royalties: US 2020/0345770 A1 - Pub.Date Nov.5, 2020; AML: Other: Co-Inventor.

Objective: Fanconi anaemia is a genotypically heterogeneous disease. A fast and reliable genetic diagnosis method helps is important for the clinical care of these patients. The objective of this study was to establish a strategy for expeditious molecular diagnosis for the Indian FA patients. Methods: Exome sequencing was performed for 119 FA patients on Illumina HiSeq X system and the data was analysed by Sentieon (v201808.01) to identify germline variants. Single nucleotide variants (SNVs) with an allele frequency of Results: SNVs associated with FA were identified in heterozygous states in 93 (78%) patients. Of the remaining 20 patients, 8 had homozygous deletions, and twelve were compound heterozygous with deletions and SNVs. We detected deletions in 20 patients: 7 with heterozygous and 12 with homozygous deletions in FANCA, and one with a homozygous deletion in FANCT (UBE2T). MLPA confirmed the deletions in the FANCA gene. The homozygous deletion in the FANCT gene was confirmed by the lack of amplification by PCR using the primers binding to the deleted region. By combining the SNVs and deletions, disease-causing genotypes were identified in 113 of 119 (95%) patients. A large number of our patients (81.5 %) were homozygous (Figure) due to the high rate of consanguinity in the population. FANCA was found to be the most frequently mutated gene in (57.5%) while mutations in FANCG gene accounted for 14.2% of our patients. FANCC mutations were found at a very low frequency (1.8%) in our patients. Although mutations in FANCL are rare in all the populations, 24 (21.2%) patients with FANCL mutations were identified in our study. A previously reported synonymous splicing mutation FANCL c.1092G>A;p.K364= was found in homozygous state in 22 (19.5%) patients. Two other FANCL mutations identified includes a missense mutation c.827C>T; p.Pro281Leu in the homozygous state in one patient and a nonsense mutation c.997C>T; p.Gln333Ter in the compound heterozygous state with the common FANCL c.1092G>A;p.K364= mutation in another patient. Mutations in rarely mutated FA genes included 1 patient each in FANCT/UBE2T and FANCI and two each in FANCJ/BRIP1 and FANCF gene. Based on the comprehensive genotype analysis, we could design an algorithm for FA in the Indian population. ~20% of the FA patients who have FANCL c.1092G>A;p.K364= mutation can be diagnosed by Sanger sequencing. MLPA can detect FANCA deletions (16.5% of the overall mutations). The results from these two tests can be obtained in 48 hours. For those who are negative for the mutations by these two methods, LA-NGS can detect SNVs in the FANCA and FANCG genes, which constitute >55% of the FA mutations in the population. We have tested this algorithm for expedited molecular diagnosis in 27 FA patients and found that the disease genotypes could be established in 94% of the patients in less than two weeks. Conclusion/Clinical applicability: Exome sequencing identified several novel mutations in the FA pathway genes in the FA patients. A cost-effective and time-saving algorithm was explicitly established for molecular diagnosis of FA in the Indian population. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Allogeneic stem cell transplantation (SCT) is a curative treatment for beta-thalassemia major. The Pesaro risk stratification classifies patients with thalassemia into three groups (class I, II, and III) to predict the transplant-related mortality (TRM) and graft rejection after myeloablative conditioning with busulfan and cyclophosphamide. However, in developing countries, where inadequate chelation therapy prior to transplant is common, most patients would fall under the class III category. There is heterogeneity in the clinical outcomes in this group. Hence, our center introduced a further refinement in this risk stratification, identifying a subset of "class III high risk" as those with age greater than or equal to 7 years and liver size > 5cm (Mathews V et al. BBMT 2007). Subsequently, we showed that the use of a conditioning regimen containing thiotepa, treosulfan, and fludarabine (TTF) along with a peripheral blood stem cell graft led to improved outcomes in this subset with a reduction in early TRM from 46% (with busulfan-cyclophosphamide) to 13% (Mathews V et al. PLoS One 2013). There is still a need to identify predictors of poor clinical outcomes to optimize further the clinical outcomes of these class III high-risk thalassemia patients. Endothelial activation and stress index (EASIX) is a simple biomarker calculated using lactate dehydrogenase, creatinine, and platelet counts. EASIX has been shown to be predictive of overall survival in various settings like GVHD following reduced-intensity transplants for malignancies in adults, veno-occlusive disease, and nonrelapse mortality following SCT (Luft T et al. Lancet Haem 2017; Jiang S et al. Haematologica 2021; Luft T et al. BMT 2020). Here, we evaluated the role of EASIX (measured before conditioning therapy) as a biomarker in predicting early TRM in patients with thalassemia major who have undergone SCT with a uniform conditioning regimen using TTF at our center. During the study period from January 2012 to December 2019, 281 patients with thalassemia major underwent SCT with a uniform TTF protocol at our center. The median age was nine years (range 1 to 25 years). One hundred and nine (38.8%) were females. As per Pesaro classification (with Vellore modification), three (1.1%) were class I, 34 (12.1%) were class II, 134 (47.7%) were class III low risk, and 110 (39.1%) were class III high risk. The stem cell donors were matched sibling (n=218, 77.6%), matched related non-sibling (n=23, 8.2%), or matched unrelated donors (n=40, 14.2%). The stem cell donor was HLA matched in all cases except 21 (7.5%), wherein there was a mismatch at one locus. Five (1.8%) had a bone marrow graft, while others had peripheral blood stem cell grafts. Thirty-eight (13.5%) patients had transplant-related mortality by day 100 (TRM100). The median follow-up of the cohort was 31 months (range 0 to 103 months). EASIX score pre-transplant was available for 184 (65.5%) patients. There was no difference in the rate of TRM100 in patients where EASIX was available compared to those where EASIX was not available (14.7% versus 11.3%, p 0.47). Also, there was no difference in overall mortality rate in patients where EASIX was available compared to those where EASIX was not available (21.2% versus 17.5%, p 0.53). Among patients with TRM100 vis-à-vis those who did not, the median EASIX score was significantly higher (1.09 versus 0.75, p 0.008). We then plotted a receiver operating characteristics (ROC) curve for predicting TRM100 using the EASIX score. The area under the curve was 0.661 (Figure 1a). A cut-off of 0.85 for the EASIX score had a 70.4% sensitivity and 62% specificity for predicting TRM100. The TRM100 for patients with EASIX above 0.85 was significantly higher than those with EASIX less than 0.85 (24.4% versus 7.5%, p 0.003). On multivariable logistic regression analysis, the factors independently predicting TRM100 were pre-transplant EASIX score, pre-transplant ferritin, unrelated donor source, and chimerism at day 60 (Figure 1b). In patients with thalassemia major undergoing SCT using a uniform TTF conditioning, EASIX score measured pre-transplant can identify patients at greater risk for Day100 TRM. Figure 1 Figure 1. Disclosures Mathews: Christian Medical College: Patents & Royalties: US 2020/0345770 A1 - Pub.Date Nov.5, 2020; AML: Other: Co-Inventor.

Patients and methods All patients with haemophilia A or B who underwent major surgery, either as elective or as emergency, with rFVIIIFc or rFIXFc as the clotting factor concentrate (CFC) for hemostasis were included in this study. None of them were positive for inhibitors before. The factor was administered once daily or once every 36-48 hours depending on the product. The factor assays were done with a one stage APTT method. The CFC support was continued till suture removal, usually 10 days. Other supportive measures included tranexamic acid,at physician discretion. Results A total of 57 patients underwent surgery. There were 45 patients with haemophilia A and 12 with haemophilia B. Of those with haemophilia A, - 37 (82.2%) had severe, 3 (11.1%) moderate and 5 (6.7%) mild disease. Of those with haemophilia B, 7 (58.3%) had severe,3 (25 %) moderate and 2 (16.7%) mild disease. The median age was 30 years (range: 1-70). Among those with haemophilia A, there were 4 with inhibitor titre 5 BU, requiring bypassing agents. None with haemophilia B had inhibitor. The surgical procedures included 40 (70.1%) orthopaedic, 6 (10.5%) abdomino-perineal, 4(7%) urological and 3(5.2%) neurosurgical and 1(1.7%) each - venricular septal defect repair, skin graft, tympanoplasty and coronary angioplasty. The orthopaedic surgeries included pseudotumour excision (n=9), bilateral total knee replacement (bilateral n=4, unilateral n=1), total hip replacement (n=3), open reduction and internal fixation of fracture (n=11), corrective osteotomies/soft tissue release (n=6), amputation (n=1), arthrodesis (n=1), laminectomy (n=1), implant removal (n=1),intra articular repair(n=1)and curettage (n=1). For those with haemophilia A, the median recovery assay pre-op was 108% (range: 50-200).The median trough levels for post- operative days +1,+3,+5 ,+7 were 40% (11-138), 36.5% (13-94), 36.4% (1.4-118), and 27%(1.6-77) respectively. Among 35 patients with severe haemophilia undergoing major surgery, the median total factor used was 305 (125-563)IU/kg. The median recovery assay for those with haemophilia B prior to surgery was 70.1%(50-165).The median trough levels for post operative days+1,+3,+5 ,+7 were 49.8% (28-70.7), 40.7%(31.6-56.2), 42.3%(11.6-58.2), and 40.5%(24.5-59.4) respectively. The median total factor used was 400 (134-1000)IU/kg. Seventeen of those with haemophilia A (37.8%) required transfusion of at least 1 packed red cell each as per expected blood loss in those surgeries. Two patients required FFP and 1 patient required platelet transfusion as well for DIC. One patient had sustained injury to axillary artery during surgery and the other one had undergone resection of extensive pseudotumour. There was no unexpected post-operative bleeding. In those with haemophilia B, 2(16.7%) patients required transfusion of packed red cell as per expected blood loss in those surgeries. No other blood product was required. There was no excessive bleed during the perioperative period. Conclusions Modest doses of rFVIIIFc and rFIXFc can be used safely for major surgery in haemophilia with effective haemostasis and monitored with one stage APTT based assays. The less frequent administration makes these agents a more convenient option. Disclosures No relevant conflicts of interest to declare.

Background: Fludarabine based conditioning protocols are increasingly being used for transplant (SCT) in patients with aplastic anaemia (AA) especially in those who have received multiple transfusions. Patients and Methods: Between January 2004 and June 2019, 229 patients with AA and HLA identical sibling donors underwent SCT at CMC Vellore India using Fludarabine [180 mg/m2 over 6 days] and Cyclophosphamide [120 mg/kg over 2 days]. Few patients received low dose ATG [ATGAM 40 mg/kg]. Data on HSCT and outcomes were collected from the institutional database and individual medical records. Results: The median age was 23.9 years (range: 1.5 - 58) including 151 males and 78 females including 78 children (33.4%). Donors were matched sibling (n = 215) or family donors (n = 14). The graft source was Bone marrow in 11 and peripheral blood stem cells in 218. GVHD prophylaxis consisted mainly of cyclosporine and methotrexate mainly with few receiving post-transplant cyclophosphamide. Engraftment occurred in 90% with graft failure in 2.6% and early death in 7.4%. Regimen related toxicity (RRT) was seen in 4.7% and included veno-occlusive disease of liver and hemorrhagic cystitis. Acute GVHD (grade 2-4) occurred in 26.4% while chronic GVHD was seen in 40.3%. The 5 year overall survival (OS) for the entire group is 75.9 + 4.9%. The 5 yr OS was 81.4 + 3.9% for ages 0 - 20, 76.3 + 4.4% for ages 21-40 and 55.3 + 9.3% for ages > 40 years. Age > 40 years (p = 0.000), presence of fever requiring hospital admission within 4 weeks prior to SCT (p = 0.001) and acute GVHD (p = 0.051) were identified as risk factors associated with a poor outcome on a univariate analysis while on a multivariate analysis, older age and fever continued to remain significant. Conclusion: This is the largest series of patients with AA undergoing SCT using a fludarabine based conditioning and is associated with improved survival following sibling donor HSCT for AA. Presence of fever requiring a hospital admission immediately prior to SCT is associated with poor outcomes. Disclosures No relevant conflicts of interest to declare.

Among transplant related complications, graft versus host disease (GvHD) significantly affects survival among patients undergoing allogeneic hematopoietic stem cell transplantation (aHSCT). There is limited data on GvHD and its impact on outcomes of aHSCT in patients with thalassemia major (TM). We have reviewed the incidence and outcome of GVHD among patients with TM who underwent aHSCT at our center. All patients with TM undergoing their first aHSCT between January 2007 and December 2017 were included in this analysis. Till 2009, all patients received conditioning with busulfan (16mg/kg over 4 days) with cyclophosphamide (200mg/kg over 4 days). From 2010, most patients received treosulfan (42 G/m2 over 3 days) with thiotepa (8mg/Kg for one day) and fludarabine (160mg/m2over 4 days) based conditioning regimen. All patients receiving busulfan conditioning received bone marrow (BM) as the graft while most patients receiving treosulfan conditioning received mobilized peripheral blood stem cells (PBSC). GvHD prophylaxis was with short-course methotrexate (10mg/m2 on day +1, and 7mg/m2 on days 3, 6 and 11) with cyclosporine. Thymoglobulin was added for matched unrelated donors (MUD). GvHD was prospectively recorded and graded according to the Glucksberg classification. Between January 2007 and December 2017, 363 first transplants were done for patients with TM with HLA identical donors. There were 12(3.3%) class 1, 105(28.9%) class 2 and 246(67.8%) class 3 (Pesaro risk stratification), with 115(46.7%) of the latter being high risk (Vellore risk stratification - BBMT, 2007; 13: 889). The median age was 8 years (range: 1-25) with a male predominance (60%). 331 (91.2%) patients had matched related donors (MRD) and 32 (8.8%) had MUDs. Donor gender was mismatched in 207 (57%) of which 129 (35.5%) were female to male transplants. The graft was obtained from the bone marrow in 137 (37.7%) of whom 53 (38.7%) were class III, and from mobilized peripheral blood in 226 (62.3%) of whom 193 (85.4% were class III. 149 (41%) patients developed GvHD - acute GvHD (aGvHD) in 115 (31.7%) and chronic GvHD (cGvHD) in 80 (22%). aGvHD was grade I in 32 patients (27.8%), grade II in 36patients (31.3%), grade III in 16 patients (13.9%) and grade IV in 25 patients (21.7%), while 6 patients (5.2%) had features of overlap GvHD only (oral lichen planus). First line treatment was with steroids in all patients with grade II and above aGvHD (n=83) with 43 (51.8%) of them responding adequately. There were 37 patients (44.5%) who required various second line agents for aGvHD with 20 (24%) receiving more than one immunosuppressive agent. 20 patients (24%) with persistent aGvHD went on to develop cGvHD. Out of the total of 80 patients with cGvHD, 13 (16.3%) had limited and 67 (83.7%) had extensive cGvHD. 26 patients (32.5%) developed de novo cGvHD, 8 (10%) of them after donor lymphocyte infusion (DLI) for potential rejection. The other 46 patients (57.5%) had chronic overlap GvHD following previous aGvHD. Among the different variables evaluated for association with aGvHD (patient/donor age, gender mismatch, MUD vs MRD), none were significant. Among those with MRD, aGVHd occurred in 36/135 patients (26.7%) of patients receiving BM grafts compared to 65/196 patients (33.2%) who received PBSC grafts (p=ns). cGvHD occurred in 23/106 patients (21.7%) in those receiving BM grafts vs 52/171 patients (30.4%) receiving PBSC (p=ns). 30 patients (8.3%) persisted to have cGvHD at last follow-up but only 20 (5.2%) required treatment. Mortality of the whole cohort was 66 (18.2%), out of which 32 (8.8%) were related to GvHD - 24 (6.6%) due to aGvHD and 8 (2.2%) due to cGvHD. At a median follow up of 41 months (range: 0-148), the 5-year and 10-year overall survival (OS) was 81.1±2.1% each for the whole cohort. The 5-year OS of those with grade 2-4 aGvHD was significantly lower than those with grade 0/1 aGvHD (65.7±5.3% vs 85.7±2.2%, p=0.000) [figure 1]. The 5 year OS of those with cGvHD was 88.9% ± 3.8% as compared to those without cGVHD was 96.9% ± 1.2% (P=0.009) [figure 2]. There was no significant difference in OS among those with limited and extensive cGvHD (90.9±3.6% vs 88.4±4.2% (p=ns). Our data shows that, as expected, severe aGvHD and extensive cGvHD significantly lowers survival in patients with TM undergoing aHSCT. However, PBSC graft did not result in higher acute or chronic GVHD compared to BM. Disclosures No relevant conflicts of interest to declare.

Only 25-30% of patients with Thalassemia major (TM) will have a suitable HLA-matched sibling donor for an allogeneic SCT. In the absence of a HLA-matched sibling, an extended donor search within the family may yield a suitable donor, especially in societies with a high prevalence of consanguinity. We have previously reported inferior outcomes in patients who had a transplant from a non-sibling family donor. One of the criticisms of this was the issue of low resolution typing, which may have adversely impacted outcomes in some patients. We interrogated this data further to assess whether the poorer outcomes held up to scrutiny with the availability of high resolution HLA typing. Towards this we undertook a retrospective case-control study, adjusting controls for age and Lucarelli risk group (common confounders for clinical outcomes post-transplant in TM) with a 4:1 ratio of controls to cases. All consecutive patients with TM who had a stem cell transplant between the time periods 2007-2017, were included in this retrospective analysis. A total of 371 transplants were done with 281 matched sibling donor, 58 related donors (32 fully matched and 26 with 1-2 antigen mismatch), and 32 MUD donors (24 fully matched (10/10) and 8 with 1-antigen mismatch (9/10)). Subsequent to 2012, high resolution typing was done for all non-sibling related family donors. Of the 58 related donors, high resolution typing was available in 45, with twenty four 10/10 donors, nineteen 9/10 donors and two 8/10 donors. Further analysis was done in this sub-group (excluding the 8/10 donors), with rejection and death being considered as events. A control group from the fully matched sibling donor cohort was generated randomly after adjusting for age and Lucarelli Class. All patients received a myeloablative conditioning regimen (Busulphan/Treosulfan based). In-vivo T-cell depletion was done in 11 (45.8%) of matched related transplants and 54 (56.2%) of matched sibling donor transplants (P=0.359). A PBSC graft was used in 16 (66.7%) of matched related donor transplants compared with 36 (27.5%) of matched sibling donor transplants (P=0.012). There was no difference in the median CD34 cell dose achieved in both groups (Table 1). Table 1 shows baseline characteristics, transplant details and outcomes in the 10/10 matched related donors and fully matched sibling donor groups. Table 2 shows univariate and multivariate analysis for risk factors adversely affecting Thalassemia-free survival (TFS) using Cox regression analysis. The 2-year TFS in the 10/10 matched related donor group, 9/10 matched related donor group and fully matched sibling donor group was 56.8%±10.5%, 56.1%±11.9% and 81.8%±4% respectively (P=0.011) (Figure 1A). The 2-year overall survival (OS) in the 10/10 matched related donor group and 9/10 matched related donor group and the fully matched sibling donor group was 75.4%±9.9%, 64.5%±12.1% and 85.0%±3.7% respectively (P=0.168) (Figure 1B). This data on allogeneic transplants confirms our previous observations that there is a higher risk of graft rejection when the donor is a non-sibling related donor, even if fully matched on high-resolution typing (OR 4.8 ; 95% CI=1.3-18.2 : P=0.02). Transplant physicians must be aware this increased risk and counsel families appropriately. Further modifications in conditioning regimens and GVHD prophylaxis could potentially help in improving these outcomes. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Combination of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) is currently considered the standard of care in the management of acute promyelocytic leukemia (APL). While APL is considered a highly curable malignancy there is recognition that the outcome in pediatric patients is inferior to that reported in young adults. There have been concerns raised in the past on the potential long term side effects of the use of ATO, especially in a pediatric population. There is limited long term follow up data on the use of ATO in the pediatric population. At our center we have been using ATO based regimens to treat pediatric and adult patients with APL since 1998 and hence we undertook this retrospective analysis to evaluate the long term clinical outcomes and toxicity profile in the pediatric cohort. Data on all consecutive pediatric patients (age ≤18yrs) diagnosed with APL and treated in the Department of Haematology, Christian Medical College, Vellore, from January, 1998 to December, 2017 were included in this retrospective analysis. Of the total 73 patients with age ≤ 18yrs diagnosed during this period, 5 refused treatment and were discharged against medical advice. Treatment in the remaining 68 patients consisted of single agent ATO until 2015 (n=57), as reported previously by us (Mathews et al. Blood 2016). From 2015 combination of ATO, ATRA ± an anthracycline in induction and consolidation was administered in a risk adjusted manner (n=11). The median age was 2 years (range: 2-18) with equal gender distribution (50% each). Sixty two (91.2%) achieved complete hematologic remission (CR), 5 (7.4%) early deaths occurred from intracranial hemorrhage (n=3), neutropenic sepsis (n=1) and pulmonary thrombo-embolism (n=1), one patient did not achieve CR at the end of induction. The median time to CR was 45 days (range: 25- 62). Other acute ATO-related toxicities were low grade, transient and not associated with any mortality (transaminitis = 12 [17.6%]; ATRA like syndrome = 6 [8.8%]). With a median follow-up of 71 months, the 5 year OS and EFS of pediatric cohort (n=68) was 78.9±5.2% and 61.8±6.4% respectively (Fig 1). Among the 62 patients in CR, 21 (33.9%) relapsed at a median of 18 months (range: 5-126) from the initial diagnosis; 16 bone marrow, 3 bone marrow+CNS and 2 molecular relapses; an additional 2 patients died in remission (one viral encephalitis and another data not available). Nineteen out of 21 (90.5%) patients who relapsed received ATO based re-induction while 2 refused treatment and were discharged at request. Out of the 19 treated patients, all attained second CR. CR was consolidated with an autologous SCT (n=10) or ATO based chemotherapy (n=9). The OS and EFS of the 19 relapsed patients was 72.9±10.4% and 68±10.8% respectively. On long term follow up of this pediatric cohort (median follow up 71 months; 18 (26.5%) > 10 years follow up and 37 (54.5%) > 5 years follow up) there were no long term renal, hepatic, metabolic complications or second malignancies noted. Our results indicate the high efficacy and long term safety of ATO based regimens in the treatment of children with APL. Even among the relapse pediatric APL patients treated with upfront ATO, salvage chemotherapy with ATO based regimen followed by autologous stem cell transplantation is associated with excellent long term survival and is not associated with any major long term complications. Disclosures No relevant conflicts of interest to declare.

Introduction: Haploidentical transplants are increasingly being used in patients who need a transplant but do not have a matched sibling or unrelated donor. The easy availability of a family donor makes it very attractive but it is associated with its own specific complications. We present the outcomes of haplo-identical transplants from a single centre in India Patients and methods: We reviewed the outcomes of all patients who underwent Haplo-identical transplant at the Christian Medical College, Vellore, India between 2010 to 2017 using post transplant Cyclophosphamide (PTCY) as graft versus host disease (GVHD) prophylaxis. Data was collected from individual medical records and databases available in the department. The disease status of all patients was classified into early, intermediate and advanced disease based on a modification of the CIBMTR criteria for malignant disease. Early disease included patients transplanted in CR1 for malignant disease, patients with aplastic anemia (AA) with 20 transfusions and primary immunodeficiency syndromes (PID) who have had previous infection. Patients who were transplanted >CR2 or refractory disease, second transplants or presence of active infection were classified as Advanced disease. Results: Between 2010 and 2017, 149 patients underwent 158 haplo-identical transplants. This included 101 males and 48 females with a median age of 18.1 years (range: 0.9 - 58). Seventy patients (46.9%) were children (< 15 years of age). Patients underwent transplants for both malignant (n = 85) and non-malignant (n = 73) indications. Disease status was classified as Early in 20, Intermediate in 84 and Advanced in 54. Conditioning included both myeloablative (n = 90) and non-myeloablative conditioning (n = 68) and graft source was predominantly peripheral blood stem cells (PBSC in 93%). Engraftment was seen in 90.9% while graft failure occurred in 8% and death prior to engraftment occurred in 2%. Acute GVHD was seen in 32% of evaluable patients. Infections were a major problem with bacteraemia seen in 41% (majority were gram negative) and viral infections in 68% (CMV and BK virus). The 1 year OS for the entire cohort is 44.1 + 4.1% while the 2 year OS is 39.2 + 2.1%. The 1 and 2 yr OS for early disease was 71.8 + 1.1 and 63.8 + 1.2% respectively compared to 50 + 5.8% and 48 + 5.9% for intermediate disease and 23.4 + 5.9% and 18.2 + 5.6% for advanced disease. Conclusions: Haplo-identical transplants are feasible and associated with moderate outcomes in a developing country like India. Infectious complications are the major challenge with haploSCT and early transplantation remains the key to improving outcomes. Figure 1 - 2 year overall survival of patients with the early, intermediate and advanced disease Disclosures No relevant conflicts of interest to declare.

Allogeneic hematopoietic stem cell transplantation (Allo-SCT) with fludarabine based reduced intensity or toxicity reduced conditioning regimen with Busulfan or Melphalan (Flu/Bu; Flu/Mel) has improved HSCT outcome in patients with AML. Limited reports on the PK of Flu in patients with malignant hematological diseases undergoing Allo-SCT suggest that Flu AUC is associated with transplant related mortality (TRM) (Long-Boyle et al, 2011). We prospectively analyzed the PK and pharmacogenetics (PG) of Flu and Bu on Allo-SCT outcome in patients with AML receiving Flu/Bu or Flu/Mel based regimen. Forty-eight adult AML patients receiving Flu/Bu(targeted) (Flu 40mg/m2 /day intravenously from day-5 to -2 and intravenous Bu 130mg/m2 /day from day-5 to-2; n=27) or Flu/Mel (Flu 30mg/m2 /day intravenously from day -6 to -2 and Mel 140mg/m2 intravenously on day -1; n=21) regimen prior to Allo-SCT between January 2012 and 2015 were enrolled in this study. Peripheral blood was collected for PK analysis at serial time points and plasma was separated and analyzed the same day (for Bu TDM). Bu dose was adjusted based on the first dose PK to achieve target cumulative total AUC (22000mmoles*min). Flu plasma levels was analyzed using LC-MS/MS and the concentration was expressed as mmol/ml. Genetic polymorphisms that influence Flu and Bu PK (NT5E 5'-UTR variant rs2295890 and GSTA1*B polymorphism) were screened using pre- HSCT genomic DNA. The influence of Flu/Bu PK and PG on clinical outcome endpoints such as overall survival (OS) and event-free survival (EFS) was evaluated using cox regression analysis. The demographics of the patients is listed in the Table. There was a significant inter-individual variation in the flu clearance (1.2mL/h/m2(0.5-4.3); 8.6 fold) and AUC (46mmol*h/ml (24-101); 4.2 fold). Fludarabine AUC trended higher in Flu/Bu group when compared to Flu/Mel group (median AUC 52 vs. 43 mmol*h/ml respectively; p=0.08). Neither of the polymorphisms significantly explained the variation in Bu or Flu PK in this cohort and none of the PK parameters was associated with EFS/OS. However, patients carrying variant genotype of the NT5E 5'UTR polymorphism (rs2295890) showed significantly better OS (p=0.016) and EFS (p=0.007) (Figure) compared to those carrying wild type genotype. We have previously reported that this variant is associated with decreased Flu Clearance in patients with aplastic anemia and thalassemia receiving Flu based conditioning regimen (Mohanan et al, December 06, 2014; 124 (21): 3884; Mohanan et al, December 03, 2015; 126 (23): 3120). Although not significant, the Flu clearance was lower in the NT5E variants in this cohort as well. It can be extrapolated that patients carrying the variant genotype of the NT5E polymorphism, have decreased relapse incidence (Wild type-8; Variants-1) and hence better EFS and OS post HSCT, due to decreased clearance and increased systemic exposure to Flu. This finding need to be validated in a larger number and in patients with other disease conditions undergoing HSCT with Flu based regimen, in order to achieve the goal of personalizing conditioning regimen. Table Table. Disclosures No relevant conflicts of interest to declare.

Graft rejection (GR) following an allo-SCT occurs in 10-20% of patients with β thalassemia major (TM). The reported clinical outcome following second transplants have been associated with a high incidence of graft rejection, treatment related mortality, and graft versus host disease [Haematologica 2009; 94(9)]. There is limited data on the clinical profile and long term outcome of patients who have had a graft rejection. We undertook a retrospective analysis of patients who had a graft failure post allogeneic SCT for TM at our center. From October, 1991 to June 2016, 506 HLA matched related transplants for TM were done at our center. Of these 55 (11%) patients had a graft failure. An additional 7 patients with graft failure following an allo-SCT done at other centers were referred to us for a second transplant. Of the 62 patients with graft failure 32 (52.4%) were primary graft failures (PGF; 15 with aplasia and 17 with autologous recovery) while 30 (47.6%) were secondary graft failures (SGF; 5 with aplasia and 25 with autologous recovery). The median age of the patients who had graft failure was 8 years (range:1-19) and there were 38 (60.3%) males. On conventional risk stratification 40 (63.5%) were Class III. Eighteen (54.5%) cases with PGF and 16 (53.3%) with SGF did not receive a second transplant. From Oct 2009, at our center, a reduced toxicity myeloablative (MAC) treosulfan based conditioning regimen with a PBSC graft was offered to all high risk patients and for second transplants at the treating physician's discretion. Twenty nine (46%) of the patients with GR underwent a second allo-SCT. With the exception of one patient (first allo-SCT with an unrelated cord blood product) the donor for the second transplant was the same as the first transplant. Conditioning regimen for second SCT was busulfan based MAC in 7 (24%), treosulfan based MAC in 12 (41.3%) and the remaining received non-myeloablative conditioning regimens (fludarabine based, low dose TBI, OKT3, Cy-OKT3) often in view of pancytopenia and perceived inability to tolerate a MAC. All patients receiving a treosulfan based regimen had a PBSC graft. A BM graft was used in 7 (41%) of the remaining cases. None of the patients conditioned with a treosulfan based regimen had a graft rejection though one patient died of Grade IV acute GVHD. Of the remaining 17 patients 10 died following a second GR, 3 died of regimen related toxicity. Four are alive of which one has recurrent TM and the rest are well and transfusion independent at 55, 80 and 204 months from second transplant (all busulfan based MAC). The baseline characteristics and clinical outcomes of patients who received a treosulfan based MAC regimen versus the rest is summarized in table 1 and figure 1. On a univariate analysis a non-treosulfan based conditioning regimen and time from GR to second transplant of In conclusion there has been a significant improvement in clinical outcomes in our experience with the use of a treosulfan based reduced toxicity MAC regimen for second allo-SCT for TM. It would be reasonable, where feasible, to defer the second transplant by a year following the first graft rejection. Disclosures No relevant conflicts of interest to declare.

An allogeneic stem cell transplant (SCT) remains the only curative option for patients with β thalassemia major (TM). Conventional pre-transplant risk stratification is limited by its subjective nature of definition of hepatomegaly, adequacy of chelation therapy and also the need for an invasive liver biopsy. We have previously reported on the significant limitations in applying this risk stratification in our population (developing country) where the majority will fall into the high risk Class III group and further there is significant heterogeneity within this Class III subset that is not recognized by the conventional risk stratification (BBMT 2007;13:889). The major determinant of pre-transplant risk in patients with TM is related to iron overload, in organs such as the liver and heart. T2* magnetic resonance imaging (T2*MRI) has been widely utilized as a non-invasive measure of iron overload in these organs and has been reported to predict organ dysfunction and to guide adequacy of therapy. There is however no data available on the role of T2*MRI in pre-transplant risk assessment of patients with TM. From Jan 2014 to June 2016, in 69 patients with TM undergoing an allo-SCT a pre-transplant a T2*MRI cardiac and hepatic value was generated using standard techniques and validated software. The median age of this cohort was 7 years (range: 2-20) and there were 43 (62.3%) males. Twenty four (34.8%) were Lucarelli Class I/II while 45 (65.2%) were Class III. Of the Class III patients 15 (33.3%) were Class III high risk (Class III-HR) as previously defined by us. All Class III patients received a treosulfan based reduced toxicity myelo-ablative conditioning regimen. In this cohort 5 (7.2%) had graft failure, 12 (17.4%) had acute GVHD, 10 (14.5%) had sinusoidal obstruction syndrome (SOS) and 5 (7.2%) patients died. The cause of death was related to GVHD in 4 and in one it was due to uncontrolled sepsis. The 3 year KM estimate of OS and TFS for this cohort was 91.4±4.0% and 84.7±4.9% respectively. The median T2*MRI cardiac and hepatic value was 17.3 msec (range: 0.06-65) and 3 msec (range: 0.44-27) respectively. The correlation coefficient between T2*MRI cardiac and liver values was 0.169; P-value=0.164 (Fig 1A). It was of biological interest to note that there were patients in whom there was preferential hepatic or cardiac iron overloading as seen in Figure 1A. There was a trend to correlation with age and T2*MRI cardiac values (Fig 1C) similarly there was a significant though weak correlation between T2*MRI cardiac values and conventional risk stratification (Fig 1B). There was no significant correlation between either T2*MRI cardiac or hepatic values on graft rejection, SOS, GVHD or death nor did either of this parameters stand out as significant on linear regression analysis. In conclusion, with currently used reduced toxicity regimens, in the absence of organ dysfunction there is limited prognostic values of T2*MRI cardiac and hepatic readings on immediate peri-transplant events. Its impact on long term follow up post-transplantation on organ function and its role in directing post-transplant chelation therapy remains to be analyzed. Further evaluation is also required to understand the genetic and environmental factors that favor iron over load in one over the other organ as clearly seen in a proportion of cases. Disclosures No relevant conflicts of interest to declare.

Recent evidences suggests that the efficacy of Lenalidomide (LEN) depends upon its ability to degrade IKZF1 and IKZF3 proteins via cereblon dependent ubiquitin proteasome pathway [Science. 2014 Jan 17; 343(6168): 301-305]. Based on this model it would theoretically be antagonistic to combine LEN with proteasome inhibitors (PI). However, it is well recognized that there is significant synergism when LEN is combined with PI and this combination is routinely and effectively used in the clinic. The mechanism of synergy and the fate of IKZF1 and IKZF3 when these two agents are combined is poorly understood. We undertook a series of experiments to study the fate of IKZF1 when this combination of drugs was used in multiple myeloma cells. Combining LEN (1uM) along with bortezomib (BTZ; 1nM) a PI showed a significant kill on U266 cells (myeloma cell line) on day 5 post treatment (n=3; P=0.02) when compared to either of the agents alone. In an MTT assay, the synergism was well documented with a combination index of 0.5 (Fig 1a). Next we assessed the function of proteasome (chymotrypsin activity) when LEN was combined with PI. We observed that LEN alone does not interfere with proteasome activity. It was noted that BTZ alone at the concentration used (5 nM) was able to effectively inhibit the activity of proteasome (Fig 1b). It was also observed that combining these two agents does not interfere with BTZ action in inhibiting proteasome complex (Fig 1b). As a result of efficient proteasome inhibition, we observed an accumulation of ubiquitinated proteins in the BTZ and LEN + BTZ treated cells when compared to control and LEN alone treated cells (Fig 1c). Next, we looked for the fate of IKZF1 in U266 cells treated with LEN, BTZ and in combination of both the drugs. As reported, we observed a degradation of IKZF1 in U266 cells upon treatment with LEN. While we did not see any degradation of IKZF1 in BTZ alone treated cells. It was noted that in combination treated cells (LEN+BTZ) there was a degradation of IKZF1 (Fig 1c). In spite of significant proteasome complex inhibition, degradation of IKZF1 was observed which suggested a proteasome independent mechanism. It is well known that proteasome inhibition results in upregulation of the autophagy pathway which in turn can degrade the accumulated ubiquitinated proteins. We noted that upon treatment with BTZ or LEN+BTZ an induction of autophagy was observed, as evidenced by an increase in generation of LC3II bands on an immunoblot (Fig 1c). To support our hypothesis that IKZF1 is degraded by autophagy in the absence of proteasome complex, we pre-treated the U266 cells with an autophagy inhibitor (3-methyladenine) followed by treatment with LEN and BTZ and noted an accumulation of IKZF1 proteins (Fig 1d). We also observed a downregulation of IKZF1 target genes IRF4 and c-MYC by 12 and 24 hours in the combination treated cells (data not shown). Taken together this data demonstrates that there is (i) significant in-vitro synergism between the two agents (ii) the combination additively induces autophagy pathway (iii) IKZF1 protein can be degraded via this autophagy pathway in the presence of effective proteasome inhibition. While additional mechanisms of synergy between these two agents cannot be excluded, further enhancing autophagy pathway in these cells by drugs like sirolimus (autophagy inducer in myeloma cells) could potentially improve the synergy between these two drugs. Disclosures No relevant conflicts of interest to declare.

Introduction: The use of fecal surveillance cultures in predicting bacteremia in patients undergoing intensive chemotherapy and stem cell transplant is an unsettled issue (Neshar et al. Transpl. Infect Dis. 2015). With the increasing incidence of multi-drug resistant (MDR) organisms and high mortality rates with these infections, we sought to describe the spectrum of MDR identified in fecal surveillance, and re-visit the use of fecal surveillance in predicting infection with MDR organisms post-allogeneic stem cell transplant (allo-SCT). Methods: We analyzed data from all patients who underwent allogeneic stem cell transplant during a 2 year period (2014-2015). Patients with MDR strains of bacteria (defined in this study as defined as Vancomycin resistant enterococcus (VRE), Extended spectrum Beta-Lactamases (ESBL) and Carbapenem resistant enterobacteriacea (CRE)) in fecal surveillance were compared with patients who did not have MDR in fecal surveillance cultures. Baseline characteristics and post allo-SCT outcomes including MDR blood culture positivity, severe sepsis and 100-day transplant related mortality (TRM) were compared. Multivariate analysis using logistic regression model was used to determine independent predictors of outcome. Results: A total of 313 allogeneic stem cell transplants were performed in 299 patients, of which data on pre-transplant fecal surveillance cultures were available in 232 transplants. The incidence of MDR isolates in fecal surveillance cultures was 56% (134/232, with E.Coli 118, Klebsiella 33 and Enterococcus 13). Of these, 129 were ESBL alone (78.6%), 17 were CRE alone (10.3%), 10 were ESBL + CRE (6%), 6 (3.6%) were VRE alone. More than one drug resistant organism was isolated in fecal surveillance in 31 patients. The incidence of any MDR positivity in post-transplant blood cultures in all patients was 13.8% (32/232), with 9.4% CRE, 2.6% ESBL, and 1.7% VRE. Thirty-one patients had severe sepsis without any MDR organism isolated on blood culture, but of these 3 had CRE in sputum, 2 had Colistin resistant Acetinobacter (sputum), 2 had candidemia, 3 had NF-GNB and one had Enterococcus. Baseline characteristics between patients who were positive and negative for MDR in fecal surveillance were similar in relation in relation to age (p=0.058), diagnosis (0.133), type of transplant - matched family/MUD/Haplo (p=0.610), stem cell source (0.370), grade 3-4 GVHD (0.834). There was a significantly higher subsequent blood MDR positivity (any MDR) (p=0.012), 100-day mortality (p=0.012) and poor outcome (severe sepsis or 100 day mortality) (p=0.006) in patients who had MDR detected in fecal surveillance cultures. However, of the 25 patients who had MDR isolated in both fecal surveillance culture as well as subsequent blood cultures, only 9 patients had the same organism and susceptibility pattern in both. Factors influencing 100-day mortality included patient's age (p=0.001), MDR positivity in blood (p=0.0001), MDR in fecal surveillance (p=0.01), use of an alternate (Haplo/MUD/family) donor (p=0.0001), GVHD grade 3-4 (p=0.000) and severe sepsis (p=0.000). On multivariate analysis, only patient's age (p=0.015), alternate donor (0.009), severe sepsis (p=0.000) and grade 3-4 GVHD (p=0.001) retained significance in predicting 100-day mortality. Conclusion: Multidrug resistant organisms are frequently seen on fecal surveillance in the pre-transplant setting. MDR in fecal surveillance is associated with a higher incidence of MDR positive blood cultures but not with the same organism, and on univariate analysis is associated with higher incidence of 100 day mortality. Newer strategies to reduce bacteremia and mortality in this group of high risk patients need to be considered. Disclosures No relevant conflicts of interest to declare.