ALBERT

Description: Background HCT cures thalassemia major (TM). In the absence of a family donor, marrow or less frequently umbilical cord blood (UCB) from unrelated donors (URD) has been used. Due to risks of graft rejection, myeloablative preparative regimens are primarily utilized. URD marrow and UCB HCT have 65-90% and 21-74% event free survival (EFS) and rejection rates of 9-17% and 17-57% respectively. The URTH trial was developed in collaboration with the Thalassemia Clinical Research Network (TCRN), National Heart, Lung and Blood Institute (NHLBI), Pediatric Blood and Marrow Transplant Consortium (PBMTC) and New England Research Institutes (NERI) to explore URD HCT for TM as a strategy to expand availability of HCT. It employed reduced intensity conditioning (RIC) as a means to decrease early and late toxicities. The study tested our hypothesis that an immunosuppressive RIC regimen was sufficient for engraftment in children with TM (age 〉 1 year to 〈 17 years) after URD HCT. The primary objective was to determine EFS at 1 year after URD marrow or UCB HCT. Methods Patients with transfusion dependent beta thalassemia and a suitable URD (matched at 8/8 HLA-alleles in marrow donors or 5 to 6/6 HLA antigens in UCB donors) were conditioned with hydroxyurea (30mg/kg x 30 days) (day -50 to -21), alemtuzumab (48 mg) (-22 to -19), fludarabine (150 mg/m2) (-8 to -4), thiotepa (8mg/kg) (-4), and melphalan (140mg/m2) (-3). Patients received tacrolimus or cyclosporine with methotrexate and methylprednisone (marrow) or mycophenolate mofetil (UCB) after HCT to prevent graft-versus-host disease (GVHD). Suitable UCB units were defined as having a pre-thaw total nucleated cell content 〉4.0x10E7/Kg recipient weight. Patients were eligible irrespective of Pesaro classification but the presence of liver fibrosis by histology was an exclusion criterion. Results Twenty-three patients from 11 US centers (11M: 12F) with a median age of 10 years (2–17 years) received unrelated donor allografts: marrow (14) or UCB matched at 6/6 (1) or 5/6 HLA antigens (8). The median follow up time was 12 months (range 120 days-2 years). The median time to neutrophil engraftment was 13 days (range 10-25) and 34 days (range 12-46) after marrow and UCB HCT respectively. The median time to platelet engraftment after marrow and UCB HCT was 24 days (range 18-34) and 54.5 days (range 32-234) respectively. Primary graft rejection occurred in 1 patient (4% of all patients) following UCB HCT and was accompanied by autologous hematopoietic recovery 35 days after HCT. All others had 〉90% donor chimerism and achieved transfusion independence. There were no late graft rejections. The overall and EFS probabilities were 82% and 78% respectively at the most recent encounter. One patient developed mild VOD which resolved uneventfully. Of 15 patients who had CMV reactivation, 13 responded to pre-emptive therapy and had no progression to CMV disease. The probabilities of grade II-IV and grade III-IV acute GVHD were 30% and 9% respectively. Limited chronic GVHD was noted in 35% of the cohort; 9% developed extensive cGVHD. Four patients died on days 25, 86, 106 and 366. The causes of death included 1) pulmonary hemorrhage associated with CMV, adenovirus, and Pneumocystis jiroveci infections, 2) diffuse alveolar pulmonary hemorrhage, 3) cGVHD with pneumonia associated with CMV and adenovirus infections, and 4) cGVHD with pulmonary failure associated with CMV and EBV infections and presumed central nervous system post-transplantation lymphoproliferative disease. Conclusion HCT after RIC for thalassemia is feasible and sufficient for engraftment after URD marrow and UCB transplantation with survival exceeding 80%. The principal transplant- related complications we observed were early opportunistic viral reactivations; otherwise the preparative regimen was tolerated well with very little early toxicity. Fatal and late viral infections were noted only in the setting of severe GVHD. Patients should be monitored carefully and treated promptly for infectious complications after HCT until there is adequate immune reconstitution. The risk of severe GVHD was low despite unrelated and mismatched (UCB) donor sources. Longer follow up will determine if this regimen can reduce late toxicities. An extension of this trial is ongoing and currently recruiting patients to evaluate additional HCT related and quality of life measures. Disclosures: Neufeld: Shire: Consultancy. Kwiatkowski:Resonance Health: Research Funding; Shire: Consultancy. Thompson:Novartis: Consultancy, Research Funding; ApoPharma: Consultancy, Honoraria; Glaxo Smith Kline: Research Funding; Eli Lilly: Research Funding; Amgen: Research Funding; bluebird bio: Research Funding.

Description: Key Points Children with sickle cell disease engrafted unrelated donor marrow after reduced intensity conditioning. A high incidence of GVHD and associated mortality compromised safety of the trial.

Description: Background: Myeloablative hematopoietic cell transplantation (HCT) provides a cure for children with hemoglobinopathies, but transplant related early and late morbidity remains a challenge. Toxicities associated with myeloablative chemotherapy include early complications such as mucositis, hemorrhagic cystitis, seizures, and hepatic injury. Late effects such as infertility and compromised linear growth impair long-term quality of life, often decreasing enthusiasm for the procedure. Reduced intensity preparative regimens are especially attractive in children with non-malignant disorders to mitigate these toxicities but have been associated with increased risk of graft rejection. The primary objective of this study was to determine the toxicity and efficacy of a non-myeloablative preparative regimen using alemtuzumab, fludarabine, and melphalan followed by HCT from HLA matched related donors (MRD) in children with hemoglobinopathies. Methods: Following institutional review board approval, and parent and/or patient consent, participants were enrolled at 18 centers. Children 〈 21 years of age with severe sickle cell disease (SCD) manifestations, or transfusion dependent (〉 8 red blood cell transfusions per year) thalassemia with a MRD and a performance status 〉 40 were eligible for inclusion. The preparative regimen included alemtuzumab (total dose 48 mg) IV (between days –22 and –19), fludarabine (30 mg/m2/day) (days –8 to –4) and melphalan (140 mg/m2) on day -3. Graft versus host disease (GVHD) prophylaxis included a calcineurin inhibitor (tapered after day 100, and methotrexate (7.5 mg/m2 on days 1, 3 and 6) or mycophenolate mofetil. Five patients also received methylprednisone (1 mg/kg/day) between days 1 and 28; this practice was discontinued in 2007. Results: A total of 52 children (43 with SCD and 9 with thalassemia), median age 11 years (range, 10m - 20y) underwent HCT between March 2003 and July 2014. Of these, 46 received bone marrow, 5 received marrow and cord blood (CB), and 1 received CB alone. Median follow up was 35.5 months (range, 3 – 136). Forty-nine children were alive at last follow up (Figure 1); 48 were symptom-free; one CB recipient had disease recurrence following graft rejection and successfully underwent a 2nd HCT. No hepatic veno-occlusive disease was noted. Three deaths 6, 11 and 21 months post HCT were from GVHD related causes [bronchiolitis obliterans (n=1); infection with GVHD (n=2)]. The cumulative incidence of graft failure and transplant related mortality was 1.9% and 5.7% respectively. The mean time to engraftment of neutrophils (ANC 〉500/cu mm) and platelets (〉50,000/cu mm) was 13.0 (range 5-21) and 25.9 (range 8-120) days respectively. Three patients had neurologic toxicity (seizures/PRES) post HCT. At the time of last follow up, 35 patients (67%) were complete donor chimera (〉90% donor) and 16 (31%) were mixed chimera (28-89% donor). Acute GVHD (grade 1-3) was noted in 30.8%. Four had grade I, 6 had grade II, and 6 had grade III GVHD. No patient developed grade IV aGVHD. Chronic GVHD was noted in 13%. Of 43 patients that were alive without disease and 〉6 months post HSCT, 38 had successfully discontinued all immune suppression and maintained donor chimerism post withdrawal. Immune reconstitution was robust by the end of the first year post transplant; infectious complications (23 of 30 CMV+ recipients had reactivation) were noted primarily in the first 3 months post HSCT. Conclusions: Children with hemoglobinopathies undergoing MRD HCT tolerated this non-myeloablative preparative regimen well, with minimal early toxicities. The event-free survival rate was comparable to those achieved with myeloablative regimens. Withdrawing immunosuppression was not associated with graft loss or recurrent GVHD. GVHD complications resulted in a low mortality rate. Alternative GVHD prophylaxis may further improve event-free survival. No gonadal toxicity (determined by hormone levels) has been identified to date in 15 HCT recipients of pubertal age (〉13 years). Follow up however is early and in progress to determine long-term toxicities. These results support consideration of reduced intensity conditioning regimens for HCT in children with hemoglobinopathies as an alternative to standard myeloablative regimens. Figure 1: Overall/Event-free survival following non-myeloablative conditioning andMRD transplants for hemoglobinopathy Figure 1:. Overall/Event-free survival following non-myeloablative conditioning andMRD transplants for hemoglobinopathy Disclosures No relevant conflicts of interest to declare.

Description: Background: Granulocyte colony-stimulating factor (G-CSF) is used after hematopoietic cell transplantation (HCT) to enhance neutrophil recovery in patients rendered neutropenic by the agents used in the preparative regimen (PMID: 9187067). G-CSF is contraindicated in patients with sickle cell disease (SCD) due to reported life-threatening complications ascribed to sickle vasculopathy, presumably secondary to leukocytosis and granulocyte activation (PMID: 11880644). Complications include severe vaso-occlusive pain crises, splenic engorgement, rupture, and death (PMID: 19513902). Individuals with sickle trait tolerate G-CSF without toxicity (PMID: 29743574, PMID: 27167356).The safety/toxicity of using G-CSF to enhance neutrophil recovery following HCT for SCD has not been previously described in the context of vasculopathy that is present in recipients but whose hematologic milieu is altered by transfusions and donor product infusion. Aim/Method: The hypothesis that G-CSF use would be safe in SCD patients following HCT was tested in a multicenter trial (NCT 03128996). Patients underwent HCT from matched or one-antigen mismatched (at HLA-A, -B, -C, -DRB1 if marrow; -A, -B, -DRB1 loci if cord) related or unrelated donor products between 2004 and 2019 following reduced intensity conditioning (RIC) which included hydroxyurea, alemtuzumab, fludarabine, melphalan +/- thiotepa. The regimen results in short-term marrow suppression followed by recovery. GVHD prophylaxis included tacrolimus, short-course methotrexate or mycophenolate or prednisone, and since 2018, abatacept. All patients underwent transfusions prior to commencing conditioning to reduce Hemoglobin S (Hb S) levels to 1.5x103 cells/mL on 3 successive days. The clinical course, outcomes, and toxicities in the first 100 days post-HCT were evaluated as best representing the period of G-CSF influence on SCD recipients. Results: Sixty-four patients with SCD were evaluated post-HCT. The median age at HCT was 10.67 years (range, 1-21). HCT was performed for stroke/increased transcranial doppler velocity (N=32), acute chest syndrome (N=24) and vaso-occlusive episodes (VOE) (N=38). Twenty-nine and 35 patients received related and unrelated donor HCT respectively; 24 were mismatched at one antigen or allele locus. Graft sources included marrow (46), cord (12), peripheral blood (3), marrow + cord (2) and CD34 selected graft with T cell add-back (1). G-CSF was administered for a median of 9.4 days (range 6-33 days) post HCT. Neutrophil engraftment occurred at a median of 14.35 days (range 10-38), platelets at median of 25.2 days (range 12-89). Three patients recovered platelets beyond day 100. Seven patients had primary graft rejection and autologous reconstitution of hematopoiesis. Chimerism analysis in the remaining patients included a median of 93% (range 41-100% in the myeloid lineage; N=30), 89% (range 26-100% in the lymphoid lineage; N=36) and 93% (range 48-100% in whole blood; N=45) on day 100. The incidence of grade I-II and III-IV acute GVHD was 23.4% and 17% respectively during first 100 days. A total of 23 episodes of bloodstream and 7 non-bloodstream sites of bacterial infection were observed in 22 patients. No patient developed SCD related symptoms following post-HCT G-CSF administration. Organ toxicities noted in 17 of the 64 patients were variable [most common were hypertension (4), posterior reversible encephalopathy (3), and renal dysfunction (3)] and expected as part of the transplant process. Conclusion: In this cohort of SCD patients who underwent HCT from different donor sources following RIC and G-CSF to enhance neutrophil recovery, we noted no toxicities attributable to G-CSF. Specifically, no SCD related symptoms or extended hospitalization were encountered in any patient attributable to G-CSF administration. Commencing conditioning at a Hb S level