Abstract: Background: Deletional a+-thalassemia comprising of -a3.7 and -a4.2 deletions is commonly encountered in the Indian sub-continent but HbH disease, resulting from the co-inheritance of a+-thalassemia trait and ao-thalassemia trait, is uncommon with just a few cases reported. Few recent reports on the molecular characterization of patients with HbH disease from India has been published which includes both deletional a-thalassemia and non-deletional a-thalassemia. This report highlights the clinical and molecular heterogeneity of HbH disease from north India. Materials and Methods: We encountered 34 patients with HbH disease in 28 families from north India over 15 years and performed the molecular analysis to determine the frequency of both deletional and non-deletional alpha gene defects. Patients as well as parents and affected siblings were also studied for automated complete blood cell counts, reticulocyte counts and HbH inclusions using 1% brilliant cresyl blue. Cation exchange HPLC (Bio-Rad Laboratories, Hercules, CA, USA) and hemoglobin electrophoresis at pH 8.6 were performed. Genomic DNA from peripheral blood leucocytes was extracted by the phenol-chloroform method. A multiplex Gap-PCR was carried out as an initial screen which tested for deletions a3.7, a4.2, aSEA, aMED and aSA. Southern Blot for alpha and zeta probes with Bam H1 digest was performed on 20 subjects. PCR followed by sequencing for both a1 and a2 genes were done. The a–GlobinXS MLPA kit (MRC Holland) with 35 probes was used to screen for the extent of deletions. Results: Homozygous Hb Sallanches (a2 codon 104 G 〉 A; Cys →Tyr) in 6 cases in 5 families was found. Homozygous polyadenylation signal mutation of a2(-AA) AATAAA →AATAwas detected in 3 cases. One patient each showed double heterozygosity for -a3.7/aHb Sallanches a, a76 +Ta/aHb Sallanches a. PolyAa/ aHb Sun Prairie a, aPolyAa/ a76 +Ta, and -a3.7/aHb Seal Rocka and aSeal Rock a/--. Three patients were double heterozygous for -a3.7/--SA. Fifteen patients from 12 families had a0 deletion of varying lengths in combination with -a3.7 based on the MLPA analysis. The extent of deletions was variable ranging from a0 starts upstream of z gene & extends downstream of a1, deletion of probes 1-18, deletion of probes 1-22 and deletion of probes 8-18.The genotype phenotype correlation illustrating the clinical heterogeneity of HbH disease is detailed in Table 1. Discussion: This is the largest series of cases of HbH disease encountered in Indians. Since HbH disease is uncommon in India, the clinical recognition of the diagnosis is limited to few centres and molecular characterization is incomplete. Our study shows considerable heterogeneity both at the molecular level as well as the clinical presentation. Alpha2 gene sequencing revealed a novel mutation with addition of +T at codon 76 leading to a frameshift mutation .MLPA will be useful in characterizing the approximate location of the breakpoints and designing simple GAP PCR assays to identify the deletion. Increased awareness amongst the clinicians as well as more diagnostic laboratories will help to identify more patients with HbH disease. Table 1: Genotype and phenotype correlation of cases with HbH Number of cases Clinical Severity Homozygous Hb Sallanches 6 cases (5 families) Severe anemia with early presentation Homozygous aPolyAa/ aPolyAa 3 cases Moderate anemia with presentation in the second decade Double heterozygous -a3.7/aHb Sallanches a 1 case Moderate anemia Double heterozygous a76 +Ta/aHb Sallanches a 1 case Moderate anemia with presentation in the third decade Double heterozygous aPolyAa/ aHb Sun Prairie a 1 case Moderate anemia with early presentation Double heterozygous aPolyAa/ a76 +Ta 1 case Moderate anemia with early presentation Homozygous a2 Codon 19 (-G) 1 case Severe anemia with early presentation Double heterozygous for -a3.7/--SA 3 cases Moderate anemia with presentation in the third decade Double heterozygous for aSeal Rock a/-- 1 case Severe anemia with early presentation Double heterozygous for -a3.7/aSeal Rock a 1 case Mild presentation at family screening in forth decade with mild anemia Double heterozygosity for -a3.7/-- 15 cases (13 families) Larger deletions showed early presentation with severe anemia and shorter deletions showed mild anemia Disclosures No relevant conflicts of interest to declare.

Abstract: Introduction Global transcriptome analysis of circulating reticulocytes using microarrays is challenging due to the high abundance of globin transcripts. In order to accurately measure the transcriptome in reticulocytes, we planned to study the reticulocytes transcriptome profile before and after globin depletion. Patients with Hereditary Spherocytosis (HS) were recruited because of high reticulocytosis and also there was no global trancriptome profile available for the disease to the best of our knowledge. Methods Reticulocytes were purified by passing EDTA anticoagulated red cell suspensions through a column of microcrystalline cellulose and α-cellulose mixture. The extraction of total RNA was done fresh prior to microarray analysis using TRIzol reagent (Invitrogen) and RNeasy columns as per manufacturer's instruction. The globin transcripts were depleted with starting quantity of 3 µg of total RNA.using GLOBINclearTMHuman kit (Ambion, Austin, TX). RNA quality were assessed before and after depletion using Agilent Technologies 2100 Bioanalyzer in each sample used for the study. The Agilent Low Input Quick Amp Labelling kit was used to generate cRNA with a sample input of 200 ng total RNA in single-color microarray analysis (SurePrint G3 Human Gene Expression v3 8x60K Microarray, G4858A- 072363). cRNA was hybridized for 17 hours at 65˚C. After thorough washing, the results were extracted with Feature Extraction Project software and analysed using GeneSpring v13.0. For this study, differentially expressed genes were identified according to the criteria: t-test unpaired p (Corr) cut-off = 0.05 and fold-change cut-off of 2.0. These differentially expressed genes were imported in PANTHER (Protein Analysis Through Evolutionary Relationships) classification system to classify the genes. Results Transcriptome profiling of reticulocyte RNA from HS patients revealed 5318 annotated transcripts and 2744 lnc-RNA/uncharacterized transcripts to be differentially regulated before globin depletion. After globin depletion increase (8196 annotated transcripts and 4292 lnc-RNA) in the number of differentially regulated genes were observed. An increase of 54% and 56% was seen in annotated transcripts and noncoding transcripts respectively after globin depletion. This increased coverage may be attributed to the removal of the globin transcript. Gene Ontology analysis for molecular function, biological process, cellular component and protein class did not reveal any difference in the percentage of the category, though the number of transcripts was more after depletion. There were approximately 7% more pathways in the globin transcript depleted samples. Namely, 2-arachidonoylglycerol biosynthesis, biotin biosynthesis, carnitine metabolism, cobalamin biosynthesis, coenzyme a linked carnitine metabolism, cysteine biosynthesis, flavin biosynthesis, phenylalanine biosynthesis, sulfate assimilation, tyrosine biosynthesis pathways, etc. were elucidated only after globin depletion. Conclusions The globin transcript reduction followed by microarray analysis represents a robust methodology for studying pathophysiology of hematologic diseases which are not related to globin chain disorders. Furthermore we describe the global transcriptome profile of HS for the first time. Globin transcript depletion elucidates the better number of the transcripts and eventually the pathways which may have been earlier masked under the abundance of globin mRNAs. Pathway analysis and validation experiments are required to explain the role of these differentially expressed genes in the pathophysiology of HS. Disclosures No relevant conflicts of interest to declare.

Abstract: We compared outcomes among adult matched related donor (MRD) patients undergoing peripheral blood stem cell transplantation and adult patients undergoing double unit cord blood transplantation (CBT) at our center between 2010 and 2017. A total of 190 CBT patients were compared with 123 MRD patients. Median follow-up was 896 days (range, 169-3350) among surviving CBT patients and 1262 days (range, 249-3327) among surviving MRD patients. Comparing all CBT with all MRD patients, overall survival (OS) was comparable (P = .61) and graft-versus-host disease (GVHD) relapse-free survival (GRFS) was significantly improved among CBT patients (P = .0056), primarily because of decreased moderate to severe chronic GVHD following CBT (P & lt; .0001; hazard ratio [HR], 3.99; 95% confidence interval [CI] , 2.26-7.04). Among patients undergoing our most commonly used MRD and umbilical cord blood (CB) myeloablative regimens, OS was comparable (P = .136) and GRFS was significantly improved among CBT patients (P = .006). Cumulative incidence of relapse trended toward decreased in the CBT group (P = .075; HR, 1.85; CI 0.94-3.67), whereas transplant-related mortality (TRM) was comparable (P = .55; HR, 0.75; CI, 0.29-1.95). Among patients undergoing our most commonly used nonmyeloablative regimens, OS and GRFS were comparable (P = .158 and P = .697). Cumulative incidence of both relapse and TRM were comparable (P = .32; HR, 1.35; CI, 0.75-2.5 for relapse and P = .14; HR, 0.482; CI, 0.18-1.23 for TRM). Our outcomes support the efficacy of CBT and suggest that among patients able to tolerate more intensive conditioning regimens at high risk for relapse, CB may be the preferred donor source.

Abstract: Aims: To evaluate AMG 701, a BiTE® molecule binding BCMA on MM cells and CD3 on T cells, in RR MM (Amgen, NCT03287908); primary objective was to evaluate safety and tolerability and estimate a biologically active dose; secondary objectives were to characterize pharmacokinetics (PK), anti-myeloma activity per IMWG criteria, and response duration. Methods: Patients with MM RR or intolerant to ≥3 lines [proteasome inhibitor (PI), IMiD, anti-CD38 Ab as available] received AMG 701 IV infusions weekly in 4-week cycles until disease progression (PD). A 0.8-mg step dose was added prior to target doses ≥1.2 mg to prevent severe cytokine release syndrome (CRS). Target dose was achieved by day 8 or sooner with earlier escalation. Exclusion criteria included: solely extramedullary disease; prior allogeneic stem cell transplant (SCT) in the past 6 months; prior autologous SCT in the past 90 days; CNS involvement; prior anti-BCMA therapy. The first 3 cohorts (dose 5-45 μg) had 1 patient each, the next cohorts (0.14-1.2 mg) had 3-4 patients each, and subsequent cohorts (1.6-12 mg) were to have 3-10 pa tients each. Minimal residual disease (MRD) was measured by next-generation sequencing (NGS, ≤10-5 per IMWG) or flow cytometry (≤3×10-5). Results: As of July 2, 2020, 75 patients received AMG 701. Patients had a median age of 63 years, a median time since diagnosis of 5.9 years, and a median (range) of 6 (1-25) prior lines of therapy; 27% of patients had extramedullary disease, 83% prior SCT, and 93% prior anti-CD38 Ab; 68% were triple refractory to a PI, an IMiD, and an anti-CD38 Ab. Median (Q1, Q3) treatment duration was 6.1 (3.1, 15.3) weeks and median follow-up on treatment was 1.7 (1.0, 3.7) months. Patients discontinued drug for PD (n=47), AEs (adverse events, n=4, 3 CRS, 1 CMV / PCP pneumonia), withdrew consent (4), other therapy (1), investigator discretion (1), and CNS disease (1); 17 patients remain on AMG 701. The most common hematological AEs were anemia (43%), neutropenia (23%), and thrombocytopenia (20%). The most common non-hematological AEs were CRS (61%), diarrhea (31%), fatigue (25%), and fever (25%). CRS was mostly grade 1 (n=19) or 2 (n=21) per Lee Blood 2014 criteria. All grade 3 CRS (n=5, 7%) were assessed as dose-limiting toxicities (DLTs); all were reversible with corticosteroids and tocilizumab, with median duration of 2 days. CRS grade 3 drivers included transient LFT increases in 3 patients and hypoxia in 2 patients. Other DLTs were 1 case each of transient grade 3 atrial fibrillation, transient grade 3 acidosis, and grade 4 thrombocytopenia. Serious AEs (n=29, 39%) included infections (13), CRS (7), and asymptomatic pancreatic enzyme rise (2, no imaging changes, 1 treatment related). There were 4 deaths from AEs, none related to AMG 701 (2 cases of sepsis, 1 of retroperitoneal bleeding, and 1 of subdural hematoma). Reversible treatment-related neurotoxicity was seen in 6 patients, with median duration of 1 day, all grade 1-2, and associated with CRS in 4 patients. The response rate was 36% (16/45) at doses of 3-12 mg; at ≤1.6 mg (n=27), there was 1 response at 0.8 mg in a patient with low baseline soluble BCMA (sBCMA). With earlier dose escalation with 9 mg, the response rate was 83% (5/6, 3 PRs, 2 VGPRs), with 4/5 responders being triple refractory and 1 DLT of grade 3 CRS in this group. Across the study, responses included 4 stringent CRs (3 MRD-negative, 1 not yet tested), 1 MRD-negative CR, 6 VGPRs, and 6 PRs (Table). Median (Q1, Q3) time to response was 1.0 (1.0, 1.9) month, time to best response was 2.8 (1.0, 3.7) months, and response duration was 3.8 (1.9, 7.4) months, with maximum duration of 23 months; responses were ongoing at last assessment in 14/17 patients (Figure). MRD was tested in 4 patients (3 sCR, 1 CR) and all were negative (3 by NGS, 1 by flow); MRD negativity was ongoing at last observations up to 20 months later. AMG 701 exhibited a favorable PK profile in its target patient population of RR MM, with AMG 701 exposures increasing in a dose-related manner. Patient baseline sBCMA levels were identified as a determinant of AMG 701 free drug exposures; at higher doses, encouraging preliminary responses were seen even at the higher end of baseline sBCMA values. Summary: In this FIH study with ongoing dose escalation, AMG 701, an anti-BCMA BiTE® molecule, demonstrated a manageable safety profile, encouraging activity, and a favorable PK profile in patients with heavily pre-treated RR MM, supporting further evaluation of AMG 701. Disclosures Harrison: Janssen: Honoraria; Novartis: Consultancy, Honoraria, Patents & Royalties: wrt panobinostat; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Honoraria; CRISPR Therapeutics: Consultancy, Honoraria; Haemalogix: Consultancy; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen-Cilag: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; F. Hoffmann-La Roche: Consultancy, Honoraria. Minnema:Amgen: Honoraria; Servier: Honoraria; Gilead: Honoraria; Celgene Corporation: Honoraria, Research Funding; Janssen Cilag: Honoraria. Lee:Celgene: Consultancy, Research Funding; Genentech: Consultancy; GlaxoSmithKline: Consultancy, Research Funding; Genentech: Consultancy; Regeneron: Research Funding; Takeda: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Sanofi: Consultancy; Daiichi Sankyo: Research Funding; Amgen: Consultancy, Research Funding. Spencer:AbbVie: Consultancy, Honoraria, Research Funding; Roche: Honoraria; Takeda: Honoraria, Research Funding, Speakers Bureau; Sanofi: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Secura Bio: Consultancy, Honoraria; Servier: Consultancy, Honoraria, Research Funding; HaemaLogiX: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding, Speakers Bureau; Pfizer: Consultancy, Honoraria; Pharmamar: Research Funding. Kapoor:Cellectar: Consultancy; Amgen: Research Funding; Janssen: Research Funding; Sanofi: Consultancy, Research Funding; Takeda: Honoraria, Research Funding; GlaxoSmithKline: Research Funding; Celgene: Honoraria. Madduri:Takeda: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Foundation Medicine: Consultancy, Honoraria; GSK: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Speaking Engagement, Speakers Bureau; Kinevant: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Speaking Engagement, Speakers Bureau; Legend: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Speaking Engagement, Speakers Bureau; Celgene: Consultancy, Honoraria. Larsen:Janssen Oncology: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees. Ailawadhi:Cellectar: Research Funding; BMS: Research Funding; Medimmune: Research Funding; Amgen: Research Funding; Takeda: Honoraria; Janssen: Research Funding; Pharmacyclics: Research Funding; Celgene: Honoraria; Phosplatin: Research Funding. Kaufman:Amgen: Consultancy, Honoraria; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Consultancy, Honoraria; AbbVie: Consultancy; Celgene: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Tecnopharma: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sanofi/Genyzme: Consultancy, Honoraria. Raab:Takeda: Membership on an entity's Board of Directors or advisory committees; Heidelberg Pharma: Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees, Research Funding. Hari:BMS: Consultancy; Amgen: Consultancy; GSK: Consultancy; Janssen: Consultancy; Incyte Corporation: Consultancy; Takeda: Consultancy. Iida:AbbVie: Research Funding; Merck Sharpe Dohme: Research Funding; Kyowa Kirin: Research Funding; Chugai: Research Funding; Sanofi: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Daiichi Sankyo: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; Ono: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Janssen: Honoraria, Research Funding. Davies:Celgene/BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Oncopeptides: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotech: Honoraria; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees. Lesley:Amgen Inc.: Current Employment, Current equity holder in publicly-traded company. Upreti:Amgen Inc.: Current Employment, Current equity holder in publicly-traded company. Yang:Amgen Inc.: Current Employment, Current equity holder in publicly-traded company. Sharma:Amgen Inc.: Current Employment, Current equity holder in publicly-traded company. Minella:Amgen Inc.: Current equity holder in publicly-traded company, Ended employment in the past 24 months; Beam Therapeutics Inc.: Current Employment, Current equity holder in publicly-traded company. Lentzsch:Mesoblast: Divested equity in a private or publicly-traded company in the past 24 months; Janssen: Consultancy; Caelum Biosciences: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; Magenta: Current equity holder in private company; Sanofi: Research Funding; Karyopharm: Research Funding; Celularity: Consultancy; Sorrento: Consultancy. OffLabel Disclosure: AMG 701, a half-life extended BiTE® (bispecific T-cell engager) molecule is an investigational agent for multiple myeloma.

Abstract: Introduction Stomatocytes in peripheral blood are pathognomonic findings in multiple conditions along with hemolysis and reticulocytosis, often suggestive of erythrocyte membrane transport defects. These uncommon disorders are usually difficult to diagnose due to a wide range of overlapping phenotypes and a perception of stomatocytes being artefacts. Genes involved in these disorders are multiple (RHAG,SLC4A1, ABCG5, ABCG8, PIEZO1,KCNN4, ABCB6, SLC2A1 etc) rendering Sanger sequencing costly and labor intensive. Phenotypes vary from transfusion-dependent anemia to compensated hemolysis. Methods Seventeen patients were encountered in 12 families and enrolled in this study. Majority of the cases showed the presence of significant numbers of red blood cells showing stomatocytes with or without thrombocytopenia. Various hematological, biochemical and molecular tests were used to exclude thalassemia syndromes and hemoglobinopathies, glucose-6-phosphate dehydrogenase (G6PD) deficiency, autoimmune hemolytic anemia, hereditary spherocytosis (HS) and pyruvate kinase deficiency. Genomic DNA was extracted by the QIAamp DNA Blood Midi Kit and quantified on NanoDrop 2000 spectrophotometer and QubitFluorometer. DNA libraries were prepared using Illumina's custom panels (TruSight One Sequencing Panel and TruSeq Custom Amplicon v1.5) and sequenced on a MiSeq Sequencing System. MiSeq Reporter and VariantStudio were used for analysis, classification, and reporting of variants. Variants which were predicted pathogenic by in silico analysis using PolyPhen-2, SIFT, PROVEAN (http://provean.jcvi.org/), Mutpred (http://mutpred.mutdb.org/) and Human Splicing Finder as indicated, were subjected to Sanger sequencing in the patient and family members (where available). Results Of these 17 patients, 10 patients in 6 families were diagnosed to have Mediterranean stomatocytosis/ macrothrombocytopenia. All had the presence of stomatocytes along with macrothrombocytopenia, short stature, continuous abdominal discomfort and marked pleiotropic effects in different cases. This is a syndromic form of stomatocytosis and defects in ABCG5/ABCG8 genes were found and showed an autosomal recessive inheritance pattern. One case did not show any mutation. This number of cases suggests that this disorder is not rare in India and is probably underdiagnosed as patients have mild or moderate anemia and are often misdiagnosed as cases with HS. One of the patients also had coinheritance of G6PD deficiency (G6PD Kerela Kalyan). Patients with Mediterranean stomatocytosis/macrothrombocytopenia are advised to take sterol-absorption inhibitor 'ezetimibe' to reduce sterol accumulation. We also found 2 unrelated patients with stomatocytosis, reticulocytosis and splenomegaly with overhydrated hereditary stomatocytosis (OHSt) and pathogenic mutation in RHAG gene was found in both of them. The pattern of inheritance is sporadic or autosomal dominant. Splenectomy was deferred in a patient with OHSt as postsplenectomy thrombotic complications are known to occur and is contraindicated. Four patients in 3 families were found to have mutations in PIEZO1 gene which translates to red cell membrane mechanosensitive cation channel protein, causing xerocytosis/dehydrated hereditary stomatocytosis and 3 patients had severe anemia and were transfusion dependent. One patient showed the presence of stomatocytes and macrothrombocytopenia was found to have probably disease causing variant in SLC2A1 gene. She was incidentally undergoing treatment for infertility when the stomatocytosis was noted. Conclusions Stomatocytic disorders appear to be underdiagnosed in India which is compounded by the protean clinical manifestations, milder phenotypes, low index of suspicion and non-availability of molecular confirmation. Astute phenotype characterization is critical as it will help in establishing the causality of the variants identified and appropriate genetic counseling. Recently NGS for hemolytic anemias has led to rapid molecular characterization and accurate phenotypic correlation. Disclosures No relevant conflicts of interest to declare.

Abstract: Background: Although matched related donors (MRD) are the preferred source of stem cells for allogeneic hematopoietic cell transplantation, umbilical cord blood (UCB) is a well-established donor source in patients without a MRD or matched unrelated donor (MUD). Prior studies (Eapen et al, Lancet Oncology 2010; Rocha et al, NEJM 2004) have shown similar overall survival and relapse rates after umbilical cord blood transplant (UCBT), and our group (Gutman et al, BMT 2016) has shown lower chronic graft-versus-host-disease (GVHD) when compared to MUD transplant. Based on these data, our preferred donor source is MRD followed by UCB. Here, we evaluate our data comparing transplant outcomes in UCBT recipients versus MRD recipients. Methods: We compared outcomes in all consecutive adult patients undergoing first MRD transplant versus first double UCBT from January 2010 to December 2017. Patient selection, graft-versus-host disease prophylaxis and transfusions were per institutional standards. Graft-versus-host-disease free, relapse free survival (GRFS) was defined by events that includedgrade 3-4 acute GVHD, moderate to severe chronic GVHD, relapse or any death. Results: Of the 296 patients studied, 187 underwent UCBT and 109 received MRD transplant. Graft failure occurred in 6 (3%) UCBT recipients (5 of whom received reduced intensity conditioning) and did not occur in any MRD transplant recipients. While the incidence of grade 2-4 acute GVHD was higher in UCBT recipients (p= 0.006), grade 3-4 acute GVHD was comparable (p= 0.36) between the two groups. Any chronic GVHD (p= 0.0000001) and moderate to severe chronic GVHD (p= 0.00011) was significantly higher in MRD transplant recipients (figure 1a and 1b). There were significantly lower disease relapses in UCBT recipients (n= 51, 27% versus n= 46, 42%; p= 0.0036) compared to MRD transplant recipients. Transplant related mortality was higher in UCBT recipients (n= 33, 42% versus n= 11, 23% in MRD transplant recipients; p= 0.03). There was no difference in GRFS (p=0.15, figure 1c) and overall survival (OS) in the 2 study cohorts (p=0.31, figure 1d). Conclusions: UCBT recipients as compared to MRD recipients had lower chronic GVHD and lower relapse rates with no difference in OS and the composite endpoint of GRFS. Based on these results, UCB remains an appropriate alternative donor source for hematopoietic cell transplantation and might result in improved quality of life by virtue of lower incidence of chronic GVHD in long-term transplant survivors. Disclosures Haverkos: Viracta Therapeutics: Membership on an entity's Board of Directors or advisory committees. Pollyea:Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Consultancy; Celgene: Membership on an entity's Board of Directors or advisory committees; Argenx: Consultancy, Membership on an entity's Board of Directors or advisory committees; Curis: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Celyad: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Research Funding. Kamdar:Seattle Genetics: Membership on an entity's Board of Directors or advisory committees. Mark:Janssen, Takeda, Celgene, Amgen: Consultancy; BMS, Celgene: Research Funding; Celgene: Honoraria.

Abstract: Introduction Hemolytic anemias are a group of disorders caused by the premature destruction of red blood cells with reticulocytosis. Common causes of inherited/congenital hemolysis are hemoglobinopathies and thalassemia syndromes, red blood cell membrane, and enzyme disorders. Most of the common causes (thalassemia, glucose-6-phosphate dehydrogenase (G6PD) deficiency, hereditary spherocytosis, etc.) are diagnosed based on laboratory testing; however, for remaining causes laboratory tests are either inaccessible or cumbersome. We follow a stepwise diagnostic pipeline and red cell morphology is helpful with membrane disorders. Phenotypes vary from severe hemolysis (transfusion-dependent) to mild/asymptomatic patients. Undiagnosed haemolytic anemias are taken up for multi-gene panel-based targeted resequencing which is rapid, accurate, and cost-effective. The use of these panels expedites the diagnoses of inherited hemolytic anemias and is eventually helpful for evidence-based genetic counseling. Objectives This study aimed to determine the genetic defects in inherited/congenital hemolytic anemias which remained unexplained after routine laboratory tests. Methods Seventy-five families were enrolled based on the clinical and laboratory features of inherited/congenital hemolytic anemias. Common causes of inherited hemolysis are G6PD deficiency, hemoglobinopathies and thalassemia syndromes, autoimmune hemolytic anemias, hereditary spherocytosis, and pyruvate kinase (PK) deficiency were excluded on the basis of biochemical and molecular tests. DNA extraction was done QIAamp DNA Blood Mini Kit. Quantity and quality of DNA were verified using NanoDrop and Qubit Fluorometer respectively. DNA libraries were prepared using Amplicon custom panels for genes implicated in hemolytic anemias and sequenced on Illumina MiSeq Sequencer. Alignment and variant calling were done in Illumina Local run Manager and Variant annotation was done in Basespace VariantInterpretor. Sanger sequencing was done as orthogonal validation in the index case. Predictive testing was performed for the family members. Results After targeted resequencing of the total 75 index cases, 19 patients were found to have red blood cell enzymopathies, 15 patients had stomatocytosis, 13 had membranopathies and three patients had unstable hemoglobins. In 8 patients cause was not established either only heterozygous variant was found for autosomal recessive or due to the lack of samples of family members for screening. Seventeen cases remained unexplained even after next-generation sequencing. Out of 19 patients, unexpected PK deficiency was found in 12 patients and G6PD deficiency was found in 3 patients; despite the enzyme assay being normal in these cases. We also found 2 patients with glucose-6-phosphate isomerase deficiency. One case each with hexokinase deficiency and glutathione synthetase deficiency was found. Among 15 patients with stomatocytosis, 8 had Mediterranean stomatocytosis/macrothrombocytopenia (ABCG5/ABCG8). These 8 patients showed the presence of stomatocytosis along with giant platelets on peripheral smear evaluation. Of the remaining 7 cases , 2 were found to have overhydrated hereditary stomatocytosis (RHAG) and dehydrated Stomatocytosis/xerocytosis was found in 5 (PIEZO1/KCNN4). We also found 13 cases of hemolytic anemia to have a genetic defect in red blood cell membrane protein-coding genes. Of these 5 had probably pathogenic variants in the ANK1 gene, 5 had a pathogenic variant in SPTA1, 2 had SPTB 2, and 1 patient SLC4A1. We also encountered 3 cases of unstable hemoglobins where no abnormality was noted in Hb-HPLC patterns. A total of seven patients underwent splenectomy and are transfusion free. Conclusions Our cohort of 75 families of hemolytic anemia of unexplained etiology showed a highly heterogeneous genetic spectrum. Of the total cases, the confirmed diagnosis was achieved in 67% of the patients. This approach of using a multi-gene panel is cost-effective and can provide a rapid and accurate diagnosis. Unexpected PK deficiency, G6PD deficiency, and unstable hemoglobins suggest that such cases can be missed. Providing accurate diagnosis in such cases provides evidence-based counseling and saves the families from inappropriate treatments. Disclosures No relevant conflicts of interest to declare.