Severe Severe Sickle Cell Disease Research Articles

Favorable outcome of non-myeloablative allogeneic transplantation in adult patients with severe sickle cell disease: A single center experience of 200 patients.

Allogeneic hematopoietic stem cell transplant (HSCT) for adults with severe sickle cell disease (SCD) is potentially curative but not commonly utilized therapy due to complications such as graft failure (GF) and organ toxicity. Herein, we are reporting our long-term outcome data of non-myeloablative (NMA) HSCT in adults with severe SCD with emphasis on factors predicting event free survival (EFS). Adults with severe SCD undergoing NMA match-related donor allogeneic HSCT from 2015 to 2021 with at least 12 months of follow-up were included. A total of 200 patients were included with a median age of 26 years (14-43) and 56% were male. The median infused CD34 dose was 13.7 (5.07-25.8), respectively. Median absolute neutrophil count engraftment was 19 (13-39) days with 51% of patients receiving GCSF to expedite recovery. A total of 17 patients experienced GF; 3 as primary and 14 as secondary within a median time of 204 days (40-905). A 76% successfully discontinued sirolimus at the last follow-up. Median follow-up for the cohort is 29.2 (2.1-71.4) months. Estimated 3-year EFS and OS were 88.2% (81.9-92.5) and 94.6% (89.2-97.3). At multivariable analysis, minor ABC incompatibility hazard ratio (HR) 4 (1.3-12.1; 0.014) and allo-antibody against non-ABO donor antigens HR 4.3 (1.3-14.1; 0.016) were significant for EFS. No clonal evolution or myeloid malignancies were seen. This largest single-center report of NMA HSCT in adults with severe SCD further delineated its feasibility, potential toxicities, and fertility outcomes. GF remains a major impediment and appears dependent on ABO matching and non-ABO antibodies.

Exagamglogene Autotemcel for Severe Sickle Cell Disease

Background: Exagamglogene autotemcel (exa-cel) is a non-viral cell therapy designed to reactivate fetal hemoglobin via ex vivo CRISPR-Cas9 gene-editing of autologous CD34+ hematopoietic stem and progenitor cells (HSPCs) at the erythroid-specific enhancer region of the BCL11A gene in patients (pts) with severe sickle cell disease (SCD). We report that in a pre-specified interim analysis, the pivotal CLIMB SCD-121 trial of exa-cel met primary and key secondary endpoints. Methods: CLIMB SCD-121 is an ongoing, 24-mo, phase 3 trial of exa-cel in pts age 12-35y with SCD and a history of ≥2 VOCs/y in 2y prior to screening. Primary efficacy endpoint is proportion of pts free of severe VOCs for ≥12 consecutive months (mos) (VF12); key secondary efficacy endpoints are proportion of pts free from inpatient hospitalization for severe VOCs for ≥12 consecutive mos (HF12) and proportion of pts free from severe VOCs for ≥9 consecutive mos (VF9). Evaluable pts for VF12 and HF12 had ≥16 mos follow-up after exa-cel infusion; pts evaluable for VF9 had ≥12 mos follow-up after infusion. Evaluation of primary and key secondary endpoints began 60 days after last RBC transfusion for post-transplant support or SCD management. Pts completing trial enrolled in long-term follow-up Study 131. Mean (SD) are shown except where noted. Results: As of 10 Feb 2023, 42 pts with SCD (age 21.2[range 12-34]y; 12[28.6%] age ≥12 to <18y; 4.2 VOCs/y at baseline) received exa-cel. Following infusion, all pts engrafted neutrophils and platelets (median 27 and 34.5 days, respectively). 19/20 (95.0%) pts evaluable for primary endpoint were free of VOCs for ≥12 consecutive mos (VF12; 95% CI, 75.1% to 99.9%; P<0.0001), 20/20 (100%) were free from hospitalizations for VOCs for ≥12 consecutive mos (HF12; 95% CI, 83.2 to 100.0; P<0.0001), and 29/30 (96.7%) were free of VOCs for ≥9 consecutive mos (VF9; 95% CI, 82.8 to 99.9; P<0.0001). In pts achieving VF12, VOC free duration was 21.8 (range 12.3-41.4) mos; 18 pts remained VOC free through follow-up and 1 pt had an adjudicated VOC in the setting of parvovirus infection ~22.8 mos after exa-cel; pt recovered fully and has since been VOC free (Fig). For all pts, total Hb was 12.1 g/dL at Month 3 and was maintained at ≥11.0 g/dL from Month 6 onward; HbF was 36.0% at Month 3 and was generally maintained at ≥ 40.0% from Month 6 onward with pancellular distribution (≥95% RBCs expressing HbF). Proportion of edited BCL11A alleles was stable over time in bone marrow CD34 + and peripheral blood nucleated cells. 36/39 pts with ≥60 days follow-up after last RBC transfusion (including those not yet evaluable) remained VOC free (up to 41.4 mos; Fig). Quality-of-life (QOL) measures showed clinically significant improvements from baseline. All pts had ≥1 adverse event (AE), most were Grade 1 or 2; 40 (95.2%) pts had AEs of Grade 3 or 4 severity. Most common AEs were nausea (66.7%), stomatitis (61.9%), febrile neutropenia (52.4%), headache (52.4%), and vomiting (52.4%). Most AEs and serious AEs (SAEs) occurred within first 6 mos after infusion. No pts had SAEs considered related to exa-cel. As previously reported, 1 pt died from respiratory failure due to COVID-19 unrelated to exa-cel. There were no study discontinuations or malignancies. Conclusions: The CLIMB SCD-121 trial met primary and key secondary endpoints, with exa-cel treatment resulting in early and sustained increases in Hb and HbF leading to elimination of VOCs in 95% of pts, elimination of inpatient hospitalization for VOCs in 100% of pts and improved QOL. Safety profile of exa-cel was generally consistent with myeloablative busulfan conditioning and autologous transplantation. These results show exa-cel has the potential to deliver a one-time functional cure to pts with severe SCD.

Hematopoietic Stem Cell Transplantation Stabilizes Cerebral Vasculopathy in High-Risk Pediatric Sickle Cell Disease Patients: Evidence From a Referral Transplant Center.

BackgroundSevere sickle cell disease (SCD) can present with different vaso-occlusive manifestations with cerebral vasculopathy (CV) as one of the most serious complications. Hematopoietic stem cell transplant (HSCT) is the ultimate therapy for this complication. The aim of this study was to assess the outcome and impact of HSCT on severe SCD patients with CV complications.MethodsTwenty-five consecutive transplants-naive pediatric SCD patients with CV complications underwent HSCT at our institution between 1993 and 2015, using bone marrow as stem cells source from fully match related donors were included. Neurologic evaluation was done both clinically and radiologically before transplantation and regularly following the HSCT.ResultsWith a median follow-up of 52.2 ± 5.8 months, the cumulative probability of overall survival (OS) at 3 years was 92.0% and event-free survival (EFS) was 88%. Significant neurologic improvements were observed in most of the patients clinically. Different neurologic complications were assessed. The neurologic manifestations before and after HSCT were hemiparesis (11, 1), seizures (13, 8), focal neurologic deficit (4, 2), loss of conscious (2, 1) headache (6, 1), and psychological symptoms (5, 2). Post-HSCT radiological imaging was done in 15 patients, which showed stabilization of CV among all.ConclusionsAllogeneic HSCT in patients with severe SCD presenting with CV complications including moyamoya vasculopathy showed favorable outcome with significant clinical neurologic improvement and stabilization of the disease. None of the patients with severe vasculopathy underwent neurological vascular by-pass surgery prior to HSCT.

Longer Term Follow-up on the First Patients with Severe Hemoglobinopathies Treated with Lentiglobin Gene Therapy

Background: LentiGlobin Drug Product (DP) contains autologous CD34+ cells transduced with the betibeglogene darolentivec (BB305) lentiviral vector, encoding a human β-globin gene with a point mutation (AT87Q) that confers anti-sickling properties similar to those with γ-globin. Human proof of concept for LentiGlobin treatment in transfusion-dependent β-thalassemia (TDT) and severe sickle cell disease (SCD) has been established in HGB-205 (NCT02151526), the original clinical study of gene therapy for hemoglobinopathies. Here, we provide an update on 5 previously-reported patients (4 TDT, 1 SCD) as well as early data from 2 additional treated patients with SCD.Methods: HGB-205 enrolled patients (5−35 years old) with TDT (≥100 mL/kg of packed red blood cells [pRBCs] per year) or severe SCD (e.g., failed hydroxyurea treatment and ≥2 acute chest syndrome episodes [ACS] or ≥2 vaso-occlusive crises [VOC] in the preceding year/year prior to regular transfusions). Following mobilization/apheresis for TDT or bone marrow harvest for SCD, autologous CD34+ cells were transduced with the BB305 lentiviral vector. Patients underwent myeloablative conditioning with busulfan, were infused with transduced cells and monitored for hematologic engraftment, vector copy number (VCN), transgenic hemoglobin (HbAT87Q) levels, and adverse events (AEs). Transfusion requirements and biological markers for TDT, and VOCs for SCD were also assessed.Results: As of June 2, 2017, 4 patients with TDT and 3 patients with severe SCD have received LentiGlobin DP; median follow-up is 23.4 (range, 3.4 - 42.2) months. Patient and DP characteristics and key outcomes for these 7 patients are shown in Table 1. All patients engrafted successfully. The toxicity profile was consistent with myeloablative conditioning with single-agent busulfan, with no DP-related ≥ grade 3 AEs or serious AEs and no evidence of clonal dominance reported to date. For patients with TDT, VCN, total Hb and HbAT87Q levels in peripheral blood remain stable, with no evidence of decreasing efficacy (Table 1). All patients with TDT remain free of RBC transfusions. In all 3 β0/βE patients, Hb levels are stable near or within the normal range. Importantly, iron burden and biological hallmarks of dyserythropoiesis have largely returned to normal. Two patients with TDT have discontinued iron chelation therapy and transitioned to therapeutic phlebotomy while the third patient (1202) has been able to discontinue both.All 3 patients with SCD showed increase in HbAT87Q production through 6 months or last follow-up. The first treated patient with severe SCD (1204) had no clinical symptoms or complications of SCD until, at about 30 months post-treatment, the patient developed a VOC following an episode of acute gastroenteritis with fever and dehydration, and was subsequently hospitalized. His total Hb levels (12.4 g/dL), HbAT87Q (6.1 g/dL) and peripheral blood VCN levels (2.3) have remained stable at 30 months of follow-up. The 2 recently treated patients with SCD (1207 and 1208) have 6 and 3 months of follow-up, have not undergone transfusions since Day 21 and 15 post-infusion, and have total Hb of 8.8 g/dL and 9.8 g/dL and HbAT87Q of 1.8 and 1.5 g/dL, respectively as of last follow-up. At approximately 6 months post-treatment, patient 1207 experienced an episode of ACS and was hospitalized. Total % anti-sickling Hb ([HbAT87Q + HbF + HbA2]/Total Hb * 100) in the 3 patients with SCD was 52%, 39% and 36% as of last follow-up. Levels of unconjugated bilirubin, lactate dehydrogenase and reticulocyte count had improved compared to screening in the 2 patients with SCD (1204 and 1207) who had ≥ 6 months follow-up.Summary: Data from this pioneering phase 1/2 clinical study continue to suggest that treatment with LentiGlobin DP elicits sustained HbAT87Q levels which may be sufficient to alleviate the clinical and biochemical effects of severe SCD and TDT, with an acceptable safety profile. In patients with TDT, sustained levels of HbAT87Q with longer term follow-up, abatement of dyserythropoeisis and discontinuation of iron chelation therapy confirm the results seen to date. For patients with SCD, the marked clinical improvement in 1 patient with nearly 2.5 years of follow-up and increasing HbAT87Q levels in recently treated patients suggest gene therapy may be a promising option. Follow-up data on the 3 patients with SCD and 2-year primary follow-up for patients with TDT will be presented. [Display omitted] DisclosuresPayen:bluebird bio: Honoraria, Research Funding. Brousse:Add Medica: Membership on an entity's Board of Directors or advisory committees. Bartolucci:Novartis: Consultancy; AddMedica: Consultancy, Research Funding. Beuzard:bluebird bio: Consultancy, Equity Ownership. Asmal:bluebird bio: Employment, Equity Ownership. Miller:bluebird bio: Employment, Equity Ownership. De Montalembert:Addmedica: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Leboulch:bluebird bio: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties. Ribeil:Addmedica: Membership on an entity's Board of Directors or advisory committees; Vitalaire: Other: Non-financial support; Novartis: Other: Non-financial support.

A “Shot in the Arm” for Sickle Cell Disease

A “Shot in the Arm” for Sickle Cell Disease

Abatacept Is Effective for Gvhd Prophylaxis after Unrelated Donor Stem Cell Transplantation (URD SCT) for Severe Sickle Cell Disease (SCD)

Background In 2016, results from the first URD SCT for SCD (the SCURT Trial) revealed a 2-year overall survival (OS) and event-free survival (EFS) of 79% (95% CI 59-90) and 69% (95% CI, 48-82) respectively following reduced intensity conditioning (RIC).1 Though the RIC approach provided successful engraftment in the majority, the transplant approach was not considered safe for widespread adoption due to high rates of graft-versus-host disease (GVHD) especially in children >13 years, a predominant cause of mortality. Strategies to minimize GVHD were essential if URD SCT was to be considered with curative intent in SCD. Aim/Method Multicenter trial (NCT03128996) with the primary objective of determining EFS in non-malignant disorders at one-year was amended as follows. The phase I SCD cohort included conditioning with hydroxyurea, proximal alemtuzumab, fludarabine, and melphalan in patients with 8/8 HLA-matched URD (-A, -B, - C and -DRB1).1 Thiotepa (8 mg/kg) was added in 7/8 HLA-mismatched SCT. GVHD prophylaxis included a calcineurin inhibitor and methotrexate as previously described. Abatacept (10 mg/kg) was administered on days -1, +5, +14, +28, +60, +100, +180, +270 and +365 based on efficacy described against acute GVHD with early dosing after SCT for malignant disorders.2,3 The latter 3 doses were omitted in cord transplant recipients. Result Thirteen children (7-21 years) underwent SCT (8/8 URD marrow- 7; 7/8 URD marrow or cord-6) primarily for stroke (N=6), ≥3 severe vaso-occlusive pain crises (N=4) or ≥2 acute chest syndrome episodes per year (N=3). The conditioning regimen was well tolerated. One patient had primary graft rejection after CMV infection (7%) and had autologous recovery. All other patients engrafted; neutrophils at median of 18 days (10-24), platelets at median of 28 days (16-39) and are surviving free of SCD with median follow-up of 12 months (range 4-59). Myeloid lineage donor chimerism was >95% and lymphoid was 39%- 100% at day+100. Two-year OS and EFS was 100% and 92.3% (95% CI, 6.57-35.7), respectively. The day+100 incidence of grade II-IV and III-IV acute GVHD incidence was 23% and 15% respectively. One-year incidence of chronic GVHD was 38%. However, only one patient (7%) developed extensive cGVHD. One patient (7%) developed posterior reversible encephalopathy syndrome and recovered. Viral replication in blood was detected in 7 of 13 patients (7 CMV, 1 EBV reactivation). No patient developed EBV PTLD or required EBV-related intervention. Conclusion In comparison to previous experience1 with RIC and URD SCT, our early observations are (1) a lower incidence of PRES (7 vs 34%) (2) low incidence of severe acute GVHD (15% vs 17% grade III -IV) despite mismatched donors, (3) low incidence of extensive chronic GVHD (7% vs 38%) and (4) no mortality despite patient age (10/13 were >13 years old). We attribute this gain to avoiding steroid use, and the benefit of including abatacept into the treatment regimen. The engraftment, safety, and immune reconstitution profile continue to be monitored in this ongoing trial now accruing in a Phase II cohort. As we and others work toward expanding donor options for SCD transplants, we submit that all alternate donor transplants for severe SCD are experimental and should be performed on clinical trials that track success and pitfalls. Reference: 1. Shenoy S et al. A trial of unrelated donor marrow transplantation for children with severe sickle cell disease. Blood. 2016 Nov 24; 128(21): 2561-2567. 2. Koura et al. In vivo T cell costimulation blockade with abataceptfor acute graft-versus-host disease prevention: a first-in-disease trial. Biol Blood Marrow Transplant. 2013 Nov; 19(11): 1638-49. 3. Watkins BK et al. T cell co-stimulation blockade with CTLA-4 Ig (Abatacept) for acute GVHD prevention in HLA-matched and mismatched unrelated donor transplantation: Results of a Phase 2 trial. Abstract 65. ASTCT Meetings, Houston 2019. Figure Disclosures Shah: Jazz pharmaceuticals: Speakers Bureau. OffLabel Disclosure: Abatacept, FDA approved for rheumatoid arthritis is a fusion protein that inhibits T-cell activation by binding to CD80/CD86 on antigen-presenting cells (APCs).It is used for acute graft-versus-host disease (aGVHD) prevention during unrelated-donor hematopoietic cell transplantation in this study

Successful Plerixafor-Mediated Mobilization, Apheresis, and Lentiviral Vector Transduction of Hematopoietic Stem Cells in Patients with Severe Sickle Cell Disease

Background Patients with severe sickle cell disease (SCD) may benefit from β-globin gene transfer into autologous hematopoietic stem cells (HSC). Successful HBB gene transfer requires vector-mediated transduction of primitive HSCs. Steady-state bone marrow (BM) is the default HSC source in patients with SCD. Normal human BM contains up to 30% CD34+CD19+ pro-B cells and other lineage-committed cell types (CD34dim) that will not contribute to improved long-term erythropoiesis via gene therapy; these cells mobilize at low rates. CD34+ cell yields from BM harvest (BMH) are typically lower than those after mobilization and peripheral blood (PB) apheresis; multiple rounds of BMH may be required to obtain adequate cell doses for autologous gene therapy (GT) protocols. As G-CSF can cause life-threatening SCD complications and is contraindicated, plerixafor, a CXCR4 receptor antagonist, may accomplish HSC mobilization without the neutrophil or endothelial activation that elicit vaso-occlusion. We modified the protocol for the HGB-206 phase 1 study of LentiGlobin GT in severe SCD (NCT02140554) to assess HSC mobilization with plerixafor alone, followed by apheresis and transduction of mobilized cells. We also characterized BM-derived and plerixafor-mobilized HSC populations from patients with SCD. Methods HGB-206 is a phase 1 study of LentiGlobin Drug Product (DP), which contains autologous HSCs transduced ex vivo with the betibeglogene darolentivec (BB305) lentiviral vector, in patients with severe SCD (defined as a history of recurrent vaso-occlusive crisis [VOC], acute chest syndrome, stroke, or tricuspid regurgitant jet velocity of >2.5 m/s). Patients in group B receive 240 µg/kg plerixafor followed 4-6 hours later by apheresis, processing ~3 total blood volumes to collect backup HSCs. If Results To date, 3 patients have undergone plerixafor mobilization. Patients had a transient 1.5- to 3-fold increase in peak white blood cell and absolute neutrophil levels after plerixafor. Peak absolute CD34+ cell counts in PB were 170, 58, and 160 x 106 CD34+ cells/liter. A total of 15.3, 5.6, and 9.0 x 106 CD34+ cells/kg were collected in a single day of apheresis, and no subsequent apheresis or mobilization was required. In the same study, a mean of 5.0 (range 0.3-10.8) x 106 CD34+ cells/kg were collected per BMH (N=21). The mobilization and apheresis procedures had an acceptable toxicity profile. No dose-limiting toxicities were observed after plerixafor dosing. One patient had a single VOC approximately 48 hours after receiving plerixafor; this patient also experienced VOCs of similar severity after BMH. In contrast, after 21 BMHs in 9 patients, 18 ≥ grade 3 AEs were reported in 6 patients, primarily pain. Ex vivo cultured CD34+ cells isolated from BMH consisted of an average of 41.0% (17.3%-50.7%) CD34dim cells, with 16%-50% of the CD34dim cells expressing lymphoid markers. In contrast, ex vivo cultured CD34+ cells isolated from plerixafor mobilized PB contained an average of 8.2% (1.5-19.5%) CD34dim cells. Similar drug product vector copy numbers were obtained after research-scale transduction of CD34+ cells from marrow and PB from the same patient. Conclusion Initial results suggest that obtaining adequate doses of CD34+ cells from plerixafor-mobilized PB of patients with SCD may be safe and feasible, without the life-threatening complications associated with G-CSF, and with fewer, less invasive procedures compared with BMH. PB-derived CD34+ cells may contain lower proportions of lineage-committed CD34+ cells than BM-derived cells from patients with SCD. Cells collected by BMH and PB mobilization/apheresis appear to have an equivalent transduction efficiency. Together these results indicate that it may be possible to use plerixafor-only mobilization in clinical studies of autologous HSC GT in SCD. Results of mobilization, apheresis, and DP manufacturing at clinical scale for additional patients will be available for presentation. Disclosures Pierciey: bluebird bio: Employment. Kanter: American Society of Hematology (Sickle Cell Disease Guideline Panel): Membership on an entity9s Board of Directors or advisory committees; AstraZeneca: Membership on an entity9s Board of Directors or advisory committees; Novartis: Membership on an entity9s Board of Directors or advisory committees, Research Funding; MUSC: Other: The site PI for sponsored research conducted at MUSC who receives funds from: Novartis, bluebird bio, GBT, Sancillo, Apopharma, Pfizer; NHLBI (sickle cell disease research advisory committee): Membership on an entity9s Board of Directors or advisory committees, Research Funding; Sancillo: Research Funding; Apopharma: Research Funding; Pfizer: Research Funding; GBT: Research Funding; Bluebird Bio: Membership on an entity9s Board of Directors or advisory committees, Research Funding. Kwiatkowski: Novartis: Research Funding; Bluebird Bio: Research Funding; Apopharma: Research Funding; Agios: Consultancy, Honoraria; Ionis: Consultancy, Honoraria. Thompson: Novartis: Consultancy, Research Funding; bluebird bio: Consultancy, Research Funding; Baxalta: Research Funding; Celgene: Consultancy, Research Funding. Shestopalov: bluebird bio: Employment, Equity Ownership. Bonner: bluebird bio: Employment, Equity Ownership. Joseney-Antoine: bluebird bio: Employment, Equity Ownership. Asmal: bluebird bio: Employment, Equity Ownership. Walters: bluebird bio: Research Funding; ViaCord Processing Lab: Other: Medical Director; Sangamo Therapeutics: Consultancy; AllCells, Inc: Other: Medical Director.

Update from the Hgb-205 Phase 1/2 Clinical Study of Lentiglobin Gene Therapy: Sustained Clinical Benefit in Severe Hemoglobinopathies

Introduction: β-globin gene transfer into hematopoietic stem cells (HSCs) has the potential to reduce or eliminate the symptoms of severe sickle cell disease (SCD) and reduce or eliminate transfusion requirements in transfusion-dependent β-thalassemia (TDT). LentiGlobin Drug Product (DP) contains autologous CD34+ cells transduced with the BB305 lentiviral vector, which encodes a human β-globin gene containing a single point mutation (AT87Q) designed to confer anti-sickling properties similar to those observed with γ-globin. We previously reported proof of concept for LentiGlobin DP treatment in severe SCD and early data from 4 treated patients with TDT. We now report 18 months of follow-up for the patient with SCD and between 9 and 30 months of follow-up for the 4 patients with TDT.Patients (5-35 years of age) with severe SCD (e.g. ≥2 acute chest syndrome episodes or ≥2 vaso-occlusive crises [VOC] in preceding year/in year prior to regular transfusions) or TDT (≥100mL/kg of packed red blood cells [RBCs] per year) were enrolled. Following mobilization and apheresis (for TDT) or bone marrow harvest (for SCD), autologous CD34+ cells were transduced with the BB305 lentiviral vector. Patients underwent myeloablative conditioning with busulfan prior to infusion of the transduced cells. After infusion, patients were monitored for hematologic engraftment, vector copy number (VCN), and HbAT87Q expression. Disease-specific assessments included transfusion requirements for TDT, or VOCs and hospitalizations for SCD. Safety assessments included adverse events (AEs) and integration site analysis.Results: As of July 2016, 1 patient with severe SCD (male; 13 years old) and 4 patients with TDT (2 male, 2 female; 16-19 years old) have received LentiGlobin DP in Study HGB-205. The median LentiGlobin DP cell dose was 8.9 (range 5.6-13.6) x 106 CD34+ cells/kg with a DP VCN of 1.2 (range: 0.8-2.0) vector copies/diploid genome. Median post-infusion follow-up as of July 6, 2016 is 20.8 months (range 9.5-31.3). All subjects successfully engrafted after receiving LentiGlobin DP, with a median time to neutrophil engraftment of 17 days (range 14-38 days). VCN in peripheral blood has remained generally consistent from Month 3 in all patients with a range of 0.2 to 3.4 at last measurement. The toxicity profile observed from start of conditioning to latest follow-up remains consistent with myeloablative conditioning with single-agent busulfan, with no DP-related ≥Grade 3 AEs or serious AEs and no evidence of clonal dominance reported to date.Three patients with TDT have β0/βE genotypes and 1 is homozygous for the severe β+ mutation IVS1 nt 110 G>A. The 2 patients who have completed the 2-year primary follow-up period (both β0/βE) have not required RBC transfusions for 31 and 28 months, with total Hb of 10.9 and 13.5 g/dL, and HbAT87Q expression of 7.7 and 10.1 g/dL, respectively, at most recent study visit. Iron chelation has been discontinued and phlebotomy initiated for 1 of the patients. The remaining patient with β0/βE genotype has 9 months of follow-up and has not required transfusions since 4 days post-LentiGlobin DP infusion, achieving a total Hb of 11.3 g/dL at last study visit. The patient with the severe IVS1 genotype has 12 months of follow-up and has been free of transfusions for 9 months, with a total Hb of 8.3 g/dL at last study visit.The patient with severe SCD, who prior to study enrollment received regular RBC transfusions, has experienced no clinical symptoms or complications of SCD in the 18 months since treatment, despite discontinuing transfusions 3 months after LentiGlobin DP infusion. Total Hb in this patient was 12.5 g/dL, with 6.6 g/dL HbAT87Q (53%) and 5.7 g/dL HbS (45%) at last study visit. Compared with values at screening, unconjugated bilirubin had dropped 78% (50 to 11 μmol/L), lactate dehydrogenase had dropped 54% (626 to 287 U/L), and reticulocyte count had dropped 45% (238x109/L to 132x109/L) by Month 18.Conclusions: Data from this ongoing Phase 1/2 clinical study suggest that treatment with LentiGlobin DP can result in sustained production of therapeutic HbAT87Q, which ameliorates the clinical and biochemical effects of severe SCD and TDT, with an acceptable safety profile. Gene therapy presents a potentially promising therapy for patients with severe hemoglobinopathies. Further follow-up and additional data from patients are needed to confirm the encouraging results seen to date in this study. DisclosuresRibeil:Bluebirdbio: Consultancy; Addmedica: Research Funding. Payen:bluebird bio: Patents & Royalties. Hermine:Alexion: Research Funding; Celgene: Research Funding; Novartis: Research Funding; AB science: Consultancy, Equity Ownership, Membership on an entity’s Board of Directors or advisory committees, Patents & Royalties, Research Funding, Speakers Bureau. Asmal:bluebird bio: Employment, Equity Ownership. Joseney-Antoine:bluebird bio: Employment, Equity Ownership. De Montalembert:Addmedica: Research Funding; Novartis: Research Funding, Speakers Bureau. Leboulch:bluebird bio, Inc: Consultancy, Equity Ownership, Membership on an entity’s Board of Directors or advisory committees, Patents & Royalties, Research Funding.

Interim Results from a Phase 1/2 Clinical Study of Lentiglobin Gene Therapy for Severe Sickle Cell Disease

Interim Results from a Phase 1/2 Clinical Study of Lentiglobin Gene Therapy for Severe Sickle Cell Disease

Initial Results from Study Hgb-206: A Phase 1 Study Evaluating Gene Therapy By Transplantation of Autologous CD34+ Stem Cells Transduced Ex Vivo with the Lentiglobin BB305 Lentiviral Vector in Subjects with Severe Sickle Cell Disease

Background: Hematopoietic stem cell (HSC) gene transfer has the potential to reduce or eliminate the symptoms of severe sickle cell disease (SCD). Previously reported early results in a single subject with severe SCD from the ongoing study HGB-205 suggested that transplantation with autologous CD34+ cells transduced with a replication-defective, self-inactivating LentiGlobin BB305 lentiviral vector containing an engineered βA-T87Q -globin gene (LentiGlobin BB305 Drug Product) is well-tolerated and yields robust production of anti-sickling HbAT87Q at 6 months post-transplant. Here we provide initial data on subjects with severe SCD enrolled in the multi-center HGB-206 Study.Subjects and Methods: Subjects with severe SCD undergo HSC collection via bone marrow harvest. CD34+ cells are selected and transduced with LentiGlobin BB305 lentiviral vector. Subjects undergo myeloablation with intravenous busulfan, followed by infusion of LentiGlobin BB305 transduced cells. Subjects are monitored for hematologic engraftment, vector copy number (VCN), βA-T87Q -globinexpression and adverse events. Integration site analysis (ISA) and replication-competent lentivirus (RCL) assays are also performed. Prophylactic pRBC transfusions are continued in subjects with SCD who are on chronic transfusion pre-transplant to maintain HbS <30%, followed by gradual taper over time.Results: As of 31 July 2015, LentiGlobin BB305 drug product has been manufactured for 2 subjects with severe SCD, and 1 subject has been infused. Additional subjects are undergoing screening. Patient data are presented in Table 1. To date, the safety profile is consistent with autologous transplantation, without ≥ Grade 3 LentiGlobin BB305 Drug Product related adverse events.Follow-up of the infused subject and available data on additional subjects who may have undergone drug product infusion in the coming months will be presented.Conclusions: LentiGlobin BB305 transduced cells have been manufactured for 2 subjects with severe SCD, and 1 subject has been infused with the drug product. LentiGlobin BB305 gene therapy is a promising approach to decrease the HbS levels in patients with severe sickle cell disease. Table 1Preliminary dosing parameters and transplantation outcomesSubjectAge (years)/ Sex (M/F)GenotypeVCN in Drug ProductaCD34+ cell dose (x106/kg)Day of Neutrophil EngraftmentDrug Product- related Adverse EventsLast Study Visit (Months Post-infusion)206-113-130125/FβS/βS0.5/0.62.7NANAPending infusion206-114-130342/MβS/βS1.32.9Day +16None1MAs of 31 July 2015.F=female; M= Male for gender, and months post-infusion for visit; NA, not applicable; VCN, vector copy number;aIf more than one drug product was manufactured, the VCN of each drug product lot is presented. DisclosuresWalters:ViaCord and AllCells, Inc: Other: Medical director. Thompson:bluebird bio, Inc.: Consultancy, Research Funding. Kwiatkowski:ISIS: Membership on an entity's Board of Directors or advisory committees; Shire Pharmaceuticals and Sideris Pharmaceuticals: Consultancy; Sideris Pharmaceuticals: Consultancy; Novartis: Research Funding. von Kalle:bluebird bio, Inc.: Consultancy. Leboulch:bluebird bio: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding. Sandler:bluebird bio, Inc.: Employment, Equity Ownership. Soni:bluebird bio, Inc.: Employment, Equity Ownership.

A Multicenter Phase II Trial of Unrelated Donor Reduced Intensity Bone Marrow Transplantation for Children with Severe Sickle Cell Disease (SCURT): Results of the Blood and Marrow Transplant Clinical Trials Network (BMT CTN 0601) Study

▪Background:Children with severe sickle cell disease (SCD) experience organ damage, poor quality of life, and a risk of premature mortality. Allogeneic bone marrow transplantation (BMT) halts disease progression when stable donor erythropoiesis is established. Myeloablative conditioning (MAC) followed by HLA matched sibling donor BMT is effective, but most patients with SCD lack a matched sibling donor and long term side effects from MAC (e.g., infertility) can be barriers to patient acceptance of BMT. The SCURT trial was designed as a prospective, multicenter phase II trial to evaluate outcomes after HLA matched unrelated donor (MUD) BMT with reduced intensity conditioning (RIC). We hypothesized that an intensely immunosuppressive RIC regimen would be sufficient for donor engraftment and could limit toxicity. The primary endpoint was one year event free survival (EFS) (alive and disease free) ≥75%. All patients were evaluable for the primary endpoint for the purpose of this report.Methods:Children between 3 and 19.75 years of age who had ≥1of the following complications - stroke, high transcranial doppler velocity, recurrent acute chest syndrome, or significant vaso-occlusive pain crises were eligible. An independent review committee confirmed eligibility. The preparative regimen consisted of alemtuzumab (48 mg) (day-22 to -19), fludarabine (150 mg/m2) (day-8 to -4), and melphalan (140mg/m2) (day-3). Donors and recipients were matched at the HLA allele-level at HLA-A, -B, -C and -DRB1 loci. Graft-versus-host disease (GVHD) prophylaxis consisted of tacrolimus or cyclosporine, methotrexate (7.5 mg/m2)on days +1, +3 and +6, and methylprednisolone (1 mg/kg/day) from day +7, tapered after day +28.Results:Thirty patients were enrolled between 2008 and 2014. One patient was excluded from analysis for a major eligibility violation at the DSMB's recommendation. Twenty-nine patients (16 M, 13F), 5.9-19.3 years old (median 14.0 years) from 19 centers were evaluable with median follow up of 25.2 months (range, 12-61.5 months). All patients recovered neutrophils (median 12 days) and platelets >50x109/L (median 24 days). Graft rejection (GR) in 3 patients (10%) occurred before day +100, and was followed by autologous hematopoietic recovery. No late GR has been observed. The primary endpoint was met with1-year EFS of 76% (Figure 1A). The 1-year probability of overall survival (OS) was 86% (Figure 1B). The cumulative incidence (CINC) of grade II-IV and III-IV acute GVHD at day 180 were 31% and 17% respectively (Figure 2A). The CINC of chronic GVHD at 1-year was 62%. Chronic GVHD was extensive in 38% (Figure 2B). GVHD when present was noted by 12 months post-BMT. There were 7 deaths, all in patients >14 years at time of BMT. One death occurred after a second transplant for graft rejection. The other 6 deaths occurred between 143 and 960 days post BMT, from GVHD. Non-fatal toxicities included posterior reversible encephalopathy syndrome (PRES) associated with hypertension and seizures in 35%. All cases were observed in the first 6 months post-BMT; all patients recovered with no obvious sequelae. No patient developed veno-occlusive disease, idiopathic pneumonia syndrome or cerebral hemorrhage. Infections were common, and occurred in 76% of patients. CMV and EBV reactivation each occurred in 23% of recipients. Surviving patients report performance scores of 100% (n=14), 90% (n=5), and 80% (n=3) at 2 years or at the time of last assessment. At last follow up, 13 patients had successfully discontinued immunosuppressive therapy.Conclusion:In summary, the RIC regimen employed in this trial of MUD BMT in children with severe SCD resulted in low rates of regimen-related organ toxicity (other than a high rate of PRES) and 1-year EFS of 76%, associated with regression of SCD manifestations. . The risk of graft rejection/disease recurrence was similar to that observed after conventional HLA-identical sibling donor BMT. Chronic GVHD occurred in 62% of patients and was the leading cause of toxicity and mortality. Future trials should focus on effective GVHD prophylaxis after URD BMT. Secondary outcome analyses including health-related quality of life and neurocognitive performance are ongoing. [Display omitted] [Display omitted] DisclosuresWalters:ViaCord and AllCells, Inc: Other: Medical director. Levine:Novartis: Consultancy.

Unrelated Donor Cord Blood Transplantation for Children with Severe Sickle Cell Disease: Results of One Cohort from the Phase II Study from the Blood and Marrow Transplant Clinical Trials Network (BMT CTN)

The Sickle Cell Unrelated Donor Transplant Trial (SCURT trial) of the Blood and Marrow Transplant Clinical Trials Network (BMT CTN) is a phase II study of the toxicity and efficacy of unrelated donor hematopoietic cell transplantation in children with severe sickle cell disease (SCD) using a reduced-intensity conditioning regimen. Here we report the results for the cord blood cohort of this trial. Eight children with severe SCD underwent unrelated donor cord blood transplantation (CBT) following alemtuzumab, fludarabine, and melphalan. Cyclosporine or tacrolimus and mycophenolate mofetil were administered for graft-versus-host disease (GVHD) prophylaxis. Donor/recipient HLA match status was 6 of 6 (n = 1) or 5 of 6 (n = 7), based on low/intermediate-resolution molecular typing at HLA -A, -B, and high-resolution typing at -DRB1. Median recipient age was 13.7 years (range: 7.4-16.2 years), and median weight was 35.0 kg (range: 25.2-90.2 kg). The median pre-cryopreservation total nucleated cell dose was 6.4 × 10(7) /kg (range: 3.1-7.6), and the median postthaw infused CD34 cell dose was 1.5 × 10(5) /kg (range: 0.2-2.3). All patients achieved neutrophil recovery (absolute neutrophil count >500/mm(3)) by day 33 (median: 22 days). Three patients who engrafted had 100% donor cells by day 100, which was sustained, and 5 patients had autologous hematopoietic recovery. Six of 8 patients had a platelet recovery to >50,000/mm(3) by day 100. Two patients developed grade II acute GVHD. Of these, 1 developed extensive chronic GVHD and died of respiratory failure 14 months posttransplantation. With a median follow-up of 1.8 years (range: 1-2.6), 7 patients are alive with a 1-year survival of 100%, and 3 of 8 are alive without graft failure or disease recurrence. Based upon the high incidence of graft rejection after unrelated donor CBT, enrollment onto the cord blood arm of the SCURT trial was suspended. However, because this reduced-intensity regimen has demonstrated a favorable safety profile, this trial remains open to enrollment for unrelated marrow donor transplants. Novel approaches aimed at improving engraftment will be needed before unrelated CBT can be widely adopted for transplanting patients with severe SCD.

Complications of PORT-A-CATH® in patients with sickle cell disease

Red cell exchange/transfusion is frequently used in the management of patients with medical complications related to acute severe sickle cell disease (SCD). However, peripheral venous access is often difficult without central venous catheters (CVCs) in adult patients with moderate or severe SCD. To review our experience with the use of the PORT-A-CATH(®) device in sixteen patients with SCD undergoing exchange or simple transfusions. Among a cohort of 550 patients who frequently visited the inpatient service, sixteen SCD patients required the insertion of a PORT-A-CATH(®) device. These patients included 3 males and 13 females, aged 25-44 years [31.1 ± 2.3; mean ± SD]. A total of 24 PORT-A-CATH(®) devices were implanted in these 16 patients during the study period. Eleven patients had 1 device implanted, three patients had 2 devices, one patient had 3 devices, and one patient had 4 devices implanted. Out of the 24 devices implanted, 17 required removal, due to either infection associated with sepsis and/or thrombosis. The organisms involved were Candida spp. (3), C. Parapsilosis (2), C. albicans (1), C. famata (1), C. lusitanice (1), Staphylococcus spp. (6), and S. aureus (3), as well as the coagulase-negative Staphylococcus (2), alpha hemolytic Streptococcus (1), Diphtheroid bacilli (2), Pseudomonas aeruginosa (2), Ps. Spp. (3), Escherichia coli (3), Klebsiella oxytoca (1), Klebsiella pneumoniae (1), Klebsiella spp. (1), Serratia liquefaciens (1), Serratia fanticola (1), Achromobacter spp. (2) Chromobacterium violaceum (1), Delftia acidovirans (1), Stenotrophomonas maltophile (1), Alcaligenes faecalis (1), and Enterobacter cloacae (1). Two episodes of documented thrombosis were observed. One case presented with right atrial thrombosis/SVC syndrome and the other case presented with left upper arm thrombosis. Two patients died with ports in situ, while five patients had ports in place at the time of this study. The median working life of the ports was 688.5 days (range: 39-3925). The rate of infective complications was 2.63 infections per 1000 catheter days, and the number of infections was significantly correlated with the number of ports [Pearson's r=0.66; p<0.01]. Our results suggest that patients with SCD suffer infective complications associated with the PORT-A-CATH(®), which often necessitate its removal. Although these devices are extremely useful, their optimal beneficial potential is only realized if the patients receive proper care at special centers well-versed in the maintenance of such devices by experienced staff.

Non-Myeloablative Allogeneic Hematopoietic Stem Cell Transplantation (allo-HSCT) for Patients with Severe Sickle Cell Disease (SCD)

Abstract 10▪▪This icon denotes a clinically relevant abstractAllo-HSCT remains the only curative approach for patients with SCD, yet a high risk of procedural toxicities and graft-versus-host disease (GvHD) limit this approach in adult patients with end organ damage from SCD. We chose a low-dose radiation approach utilizing sirolimus based upon its unique ability to promote T cell tolerance. Entry criteria include irreversible SCD-related complications (stroke, nephropathy, or tricuspid regurgitant jet velocity >2.5 m/s), or reversible complications not ameliorated by a 6-month course of hydroxyurea (frequent vaso-occlusive crises or acute chest syndrome). Conditioning was achieved with 1mg/kg of alemtuzumab divided over 5 days, a single total body irradiation dose of 300cGy, and oral sirolimus targeting trough levels between 10–15 ng/ml. Donor chimerism was measured by microsatellite PCR among CD3 and CD14/15 positive white cells. Twenty-three patients have been transplanted to date, and their ages ranged from 17 to 64 years (median 28). All are alive at 2 months to 7 years post allo-HSCT. Conditioning was well-tolerated. All received unmanipulated G-CSF mobilized peripheral blood progenitors obtained from 8/8 HLA-matched siblings. CD34+ cell doses ranged from 5.5 to 31 × 10e6/kg (median 14.4), and CD3+ cell doses ranged from 1.6 to 5.4 × 10e8/kg (median 3.4). Three patients engrafted temporarily but lost their grafts between the 2nd and 3rd months post transplant and had recurrent SCD. Twenty patients engrafted with mean myeloid chimerism of 97.5% (median 89%) and CD3 chimerism of 42% (median 49%). Improvements in laboratory parameters of engrafted patients are as follows: pre vs post HSCT hemoglobin, 8.7 vs 12.1 g/dL; reticulocyte count, 181 vs 74 k/uL; LDH, 328 vs 202 units/L; total bilirubin, 2.87 vs 1.0 mg/dL. Hemoglobin electrophoresis revealed replacement by donor type hemoglobin in 19 patients by 1 year, with amelioration of the SCD phenotype allowing for therapeutic phlebotomy. In 17 patients at 1 year or more post allo-HSCT, 5 had CD3 chimerism >50% which allowed complete withdrawal of immunosuppression; they have maintained stable mixed chimerism. Two patients received preemptive treatment with ganciclovir or foscarnet for presumed CMV reactivation (blood PCR >300 genome/mL) before day 30. Treatment in both patients was discontinued 1 week later with negative blood PCR and prophylaxis with acyclovir was resumed. There were 2 patients with zoster at 2 and 3 years post allo-HSCT. Finally, no engrafted patient to date has developed any evidence of acute or chronic GVHD. Our results demonstrate that this relatively simple conditioning regimen is well-tolerated across a broad age range of adults with severe SCD, is effective in achieving stable mixed chimerism without the development of GVHD, and is sufficient to induce functional tolerance. Disclosures:No relevant conflicts of interest to declare.

Post-Transplant Cyclophosphamide and Sirolimus Are Synergistic in Preventing Rejection and Inducing Stable Mixed Chimerism Independently of Regulatory T Cells.

Abstract 3540Poster Board III-477A strategy that can induce stable mixed chimerism across human leukocyte antigen (HLA) barriers would be beneficial in extending the application of hematopoietic stem cell transplantation (HSCT) to patients with severe sickle cell disease (SCD) who are in need of this potentially curative procedure. Indeed, we have recently demonstrated the feasibility of an HLA-matched sibling protocol employing low dose total body irradiation (TBI, 300cGy), the lymphocyte depleting agent alemtuzumab, and sirolimus to reverse the phenotype with minimal side effects. Due to the lack of HLA-matched siblings in the majority of patients, our goal is to develop a safe haploidentical regimen. In this work, we focused on determining optimal postgrafting immunosuppression and examined sirolimus and post-transplant cyclophosphamide (PT-cy), agents known to induce transplantation tolerance. To determine the optimal sequence for combining these drugs and whether this combination is synergistic in promoting stable donor chimerism despite the antiproliferative effects of sirolimus, we used a mismatched murine model with BalbC donors and C57Bl6 recipients. Twenty-five to 40 recipient mice received 200cGy TBI and PT-cy (200mg/kg intraperitoneally (IP) 2 days post transplant) with or without sirolimus (3mg/kg IP) for 14 to 30 days starting 1 day before or 4, 6, or 10 days post transplant. We found that in contrast to sirolimus or PT-cy alone, the combination of PT-cy and a limited course of sirolimus resulted in stable mixed chimerism: all mice that received PT-cy and sirolimus starting between 1 day before and 6 days after transplant attained donor chimerism levels ranging from 15-35%. Further, a 14 day course of sirolimus was sufficient to maintain stable mixed chimerism in our model (See Figures 1 and 2). To examine whether this synergistic effect is mediated by regulatory T cells, we administered anti-CD25 monoclonal antibody (CD25 mAb), an agent known to transiently deplete these cells in vivo. Fifteen mice received 200cGy TBI, sirolimus, PT-Cy, and either no CD25 mab, CD25 mab (1mg IP) on 7 and 3 days before and 1 day after transplant, or CD25 mab starting 14 days after transplant. CD25 mab was given biweekly for 5 weeks to mice in both groups. Donor engraftment levels did not differ in the three groups, with donor chimerism levels ranging from 30-40%. Our data show that the anti-proliferative effects of sirolimus do not inhibit the efficacy of the cytotoxic agent cyclophosphamide. Rather, our data demonstrate that the combination of PT-cy and a limited course of sirolimus synergistically promote mixed bone marrow chimerism in a complete mismatched setting. Further, the synergistic effect of this drug combination appears to be mediated independently from CD25+ regulatory T cell expression. In light of our previous success using sirolimus in an HLA-matched HSCT protocol, these findings lay the groundwork for developing PT-cy and sirolimus as a novel, safe, and effective means of promoting stable mixed chimerism in the haploidentical setting and thus greatly enhancing our ability to successfully apply this approach to patients with severe SCD. [Display omitted] [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Results of Alternative Donor Search in Adult Patients with Severe Sickle Cell Disease (SCD) Eligible for Hematopoietic Stem Cell Transplantation (HSCT).

Supportive care has improved the outlook for patients with SCD, but life expectancy remains considerably shorter than those without SCD. The major causes of mortality are end-organ failure, stroke, pulmonary disease, and acute vaso-occlusive crises (VOC). Myeloablative allogeneic HSCT in children under age 16 is curative in the majority. However organ damage that meets severity criteria for HSCT may not become evident until adulthood, at which time conventional myeloablative transplant is no longer an option. Additionally, the great majority of SCD patients do not have a 6/6 HLA-matched sibling donor available. Reduced-intensity conditioning may extend this potentially curative treatment to adults with SCD. Since non-myeloablative transplants may result in mixed donor chimerism, major ABO-mismatch may lead to red cell aplasia, and therefore should be avoided. Finally, cell dose is likely an important parameter in non-myeloablative transplant regimens, potentially further limiting donor availability. We initiated an IRB approved non-myeloablative allogeneic HSCT program for adults with severe SCD for whom a matched sibling donor is available. For those without related donors, we devised a search strategy for alternative donors to establish the feasibility of matched unrelated donor (MUD) or umbilical cord blood (UCB) HSCT. HLA typing was performed for potential donors and patients who on initial screen met at least one the following criteria: stroke, pulmonary hypertension, sickle related nephropathy, or frequent VOC/ACS not improved by HU. Typing at the serologic level was performed for HLA-A,-B, and at the allele level for HLA-DR B1. For patients without matched sibling donors, searches in the National Marrow Donor Program for marrow and cord blood donors were initiated. Since 2003, we performed initial screening in >100 patients, typed 58 potential recipients and 85 donors, and identified 13 potential recipients (age ≥ 16 years) with matched sibling donors. Two were excluded because of major ABO incompatibility. Among the remaining 43, 10 patients who met all study criteria on full screening were selected for alternative donor searching. MUD search results identified a median of 2.5 (range 0–18) 6/6 HLA-matched donor available. Five individuals had 0, four had 4–6, and one had >15 potential donors. UCB search revealed no patient had a 6/6 HLA-matched, two had 15–16 5/6 HLA-matched, and five had 11–190 4/6 potential donor UCB units. The median UCB units containing ≥ 2 × 10e7 nucleated cells per kg were 0 for 6/6 HLA-matched (range 0–1), 0 for 5/6 HLA-matched (range 0–19), and 8.5 for 4/6 HLA-matched (range 0–190). When ethnic haplotype and allelic frequency, the available ABO status, the likelihood of requiring two UCB units for each adult recipient were considered, 5 had neither MUD nor UCB units available, 2 only had potential UCB units available, and 3 had both MUD and UCB units available. The majority of adults with severe SCD who are eligible for non-ablative allo-HSCT do not have matched sibling donors. Our search shows that the minority of African-American adults have potential alternative donors, 10% and 50% MUD and UCB, respectively. These numbers will likely be reduced when major ABO mismatches are excluded. Further, unlike pediatric patients, one cord blood unit may not provide sufficient cells to overcome the barrier of graft rejection in most adults. Given these limitations, the feasibility of haplo-identical family donor allo-HSCT should be investigated.

Improvement in Hemolytic Parameters and Tricuspid Regurgitant Jet Velocity (TRV) Following Non-Myeloablative Allogeneic Stem Cell Transplantation (allo-SCT) in Adults with Severe Sickle Cell Disease (SCD).

Although SCD has a variable clinical course, many individuals develop end-organ complications that are associated with significant morbidity and early mortality. SCD-related pulmonary hypertension is a frequently recognized complication (up to 30%), is associated with significant mortality, and is resistant to hydroxyurea or chronic exchange transfusions. Currently myeloablative allo-SCT in children under age 16 is curative in the majority, preventing or ameliorating many of the complications of the disease. However, it is unclear whether reduced intensity allo-SCT in adults that allows mixed hematopoietic chimerism could offer the same benefit. Furthermore, reversal of pulmonary hypertension has not been previously demonstrated in either setting. Beginning in 2003, we initiated an IRB approved clinical trial testing a nonmyeloablative approach in adults with severe SCD. Protocol entry criteria include end-organ complications, (stroke, pulmonary hypertension TRV≥ 2.5 m/s, or frequent vaso-occlusive crises or acute chest syndrome not ameliorated by hydroxyurea. Conditioning was achieved with low dose radiation, alemtuzumab, and sirolimus (rapamycin). All patients receive unmanipulated G-CSF mobilized peripheral blood progenitors obtained from an HLA-matched sibling. Assessment of donor chimerism is measured by microsatellite PCR of CD3 and CD14/15 positive white cells. Hemolysis is monitored by serial measurements of total bilirubin, lactate dehydrogenase, hemoglobin and absolute reticulocyte counts. Transthoracic echocardiography is performed in all patients, and serially in those with TRV ≥ 2.5 m/s. Transmitral flow, Doppler determinations of valvular regurgitant velocity, and left ventricular stroke volume are assessed and graded. A total of 8 patients have accrued. 4 of 8 patients met criteria for pulmonary hypertension. Post transplant follow-up for these 4 patients ranged from 7 to 36 months and stable donor lymphoid (13–39%) and myeloid (53–100%) chimerism was observed in all 4. This pattern of mixed chimerism was sufficient for full donor erythroid engraftment as all demonstrated normal hemoglobin, allowing for therapeutic phlebotomy to correct transfusional iron overload. Improvement in TRV and hemolytic parameters were observed (see table) as early as 3 months post transplant. The average pre- and post allo-SCT values were: TRV 3.1 → 2.5 m/s (p=0.13, Wilcoxon rank sum), total bilirubin 4.0 → 0.6 (p=0.1), lactate dehydrogenase 487 →178 units/L (p=0.2), hemoglobin (hgb) 8.6 → 12.6 g/dL (p=0.002), and reticulocyte (retic) count 326 → 68 k/uL (p=0.01). Our results indicate that reduced intensity allo-SCT in adults patients with SCD allows for full donor erythroid engraftment, normalization of blood counts, reversal of hemolysis, and improvement in TRV.TRV and hemolytic parametersPatient 1Patient 2Patient 3Patient 4AverageTRVPre3.72.63.42.63.08(m/s)BMT2.62.42.52.32.45T biliPre8.34.01.91.94.0(0.1–1.1 mg/dL)BMT0.80.50.50.40.6LDHPre1065330338215487113–226 units/L)BMT23417820990178HgbPre8.18.58.88.98.6(g/dL)BMT12.913.911.911.612.6ReticPre344213417331326(31–105 k/uL)BMT7632768768