ALBERT

Description: Background: Nephropathy in sickle cell anemia (SCA) begins in childhood and portends chronic kidney disease, renal failure, and early mortality among affected adults. Individuals of African descent have disproportionately higher rates of developing non-diabetic renal disease. Several candidate genetic variants have been identified, including some specific to African Americans, which are associated with the development of albuminuria and renal disease. The influence of genetic polymorphisms on albuminuria and elevated glomerular filtration rate (GFR) in children with SCA, both early signs of sickle nephropathy, has not been investigated. Objectives: To determine the influence of selected single nucleotide polymorphisms (SNPs) on the development of albuminuria and elevated GFR in children with SCA; to identify novel genetic variants influencing albuminuria and GFR by whole exome sequencing (WES). Design/Methods: Genomic DNA was collected on children with SCA enrolled in two prospective studies with pre-hydroxyurea renal assessments (n=185): (1) Hydroxyurea Study of Long-Term Effects (HUSTLE, NCT00305175, n=79) with no prior disease-modifying therapy; and (2) Transcranial Doppler (TCD) With Transfusions Changing to Hydroxyurea (TWiTCH, NCT 01425307, n=106) on chronic transfusions for abnormal TCD velocities. Albuminuria was defined as ≥30mg albumin/gm creatinine on the pre-hydroxyurea urine specimen. GFR was measured in HUSTLE using plasma DTPA (technetium 99m-labeled diethylenetriaminepentaacetic acid) clearance, and estimated GFR (eGFR) in TWiTCH based on serum creatinine. DNA samples were genotyped for 8 candidate SNPs previously associated with renal disease, using PCR-based allelic discrimination, bidirectional Sanger sequencing, and analysis of variable number tandem repeats (VNTR). Associations between albuminuria and genetic polymorphisms were tested using an additive model and correlation trend test. Linked WES data from the same patients were analyzed to identify other variants associated with albuminuria and GFR. Results: Albuminuria was present in 13.1% of patients, including 16.3% in HUSTLE and 11.0% in TWiTCH. APOL1 genetic variants were common (G1 allele frequency = 21.9%, G2 allele = 16.0%, Table) and similar to published cohorts. Children with two APOL1 G1 alleles had an increased risk of albuminuria that approached statistical significance (p=0.053). Conversely, the presence of the DARC SNP that confers Duffy antigen expression had a protective effect (p=.038). WES analysis did not identify additional non-synonymous APOL1 variants linked with albuminuria. However, 93 non-synonymous variants were associated with DTPA GFR (p

Description: Transcranial Doppler (TCD) screening in children with sickle cell anemia (SCA) identifies abnormally elevated cerebral artery flow velocities that confer an elevated risk for primary stroke. Chronic transfusions offer effective stroke prophylaxis in this setting, but must be continued indefinitely and lead to transfusional iron overload. An alternative treatment strategy that offers similar effective protection against primary stroke, and provides control of iron overload, is needed. TCD With Transfusions Changing to Hydroxyurea (TWiTCH, NCT01425307) was an NHLBI-funded Phase III multicenter randomized clinical trial comparing 24-months of standard treatment (transfusions) to alternative treatment (hydroxyurea) in children with SCA and abnormal TCD velocities. All eligible children had received at least 12 months of transfusions. TWiTCH had a non-inferiority trial design; the primary study endpoint was the 24-month TCD velocity obtained from a linear mixed model, controlling for baseline (enrollment) values, with a non-inferiority margin of 15 cm/sec. The transfusion arm maintained children at HbS

Description: Introduction: Transcranial Doppler ultrasonography (TCD) is an established screening modality used to predict stroke in children with sickle cell anemia (SCA). Children with abnormal TCD velocities are at high risk for primary stroke. Based on STOP and STOP 2 data, indefinite chronic red cell transfusion therapy is recommended for children with SCA and abnormal TCD velocity, defined as a maximum time-averaged mean velocity (TAMV) ≥200 cm/sec. The aim of the current analysis was to evaluate the long term effects of transfusion therapy on TCD velocities, in a large cohort of children with SCA who received chronic red cell transfusion therapy for primary stroke prophylaxis. Methods: The TCD With Transfusions Changing to Hydroxyurea (TWiTCH) study is a phase III, randomized, controlled, multicenter non-inferiority trial comparing hydroxyurea to transfusions for primary stroke prevention in children with SCA and abnormal TCD velocities (ClinicalTrials.gov NCT01425307). Children with SCA and a history of abnormal TCD who received at least 12 months of transfusion therapy were eligible to participate. All subjects’ index TCD velocities (the TCD examination that prompted the start of chronic transfusion therapy) were reviewed centrally to confirm study eligibility. At enrollment, study TCD velocities were obtained using the SONARA/tek TCD Module by trained examiners and reviewed centrally. In addition, all children were evaluated with brain magnetic resonance angiography (MRA) scans, which were also reviewed centrally. Associations between demographic, clinical, radiological, and laboratory findings and index/enrollment TCD velocities were examined. Results: One hundred and thirty eight children with complete data were included in this analysis. Mean age for the entire cohort at enrollment was 9.8±2.8 years; 40% were male and 98.8% had HbSS. Mean age at the diagnosis of index TCD was 5.5±2 years. The mean duration of transfusion therapy was 4.3±2.4 years with 63% receiving simple transfusions, 30% receiving partial exchange transfusions, and 7% undergoing erythrocytapheresis. The mean pre-transfusion hemoglobin at study entry was 9.1±0.8 gm/dL and the mean pre-transfusion %HbS for the last 6 months prior to study entry was 29.5±8.3%. The average index TCD TAMV was 217±22 cm/sec (range 147-325). At study entry, the average TAMV was lower at 150±27cm/sec overall (142±27 cm/sec on the left and 140±29 cm/sec on the right). In 77% of the subjects, the TCD velocities had decreased to normal levels (

Description: Background: Elevated total white blood cell (WBC) count is associated with increased morbidity and mortality in sickle cell anemia (SCA), and is a biomarker for disease severity. In addition, a higher WBC and absolute neutrophil count (ANC) have been associated with a higher maximum tolerated dose (MTD) for hydroxyurea in treated patients. Several single nucleotide polymorphisms (SNPs), especially variants in the Duffy Antigen Receptor for Chemokine (DARC) gene, influence WBC and ANC in the general population; however, their effects on children with SCA have not been reported. Objectives: To determine the effects of candidate SNPs on the baseline WBC and ANC in children with SCA; to identify novel genetic variants affecting WBC and ANC; and to investigate their effects on hydroxyurea MTD. Design/Method: Genomic DNA was analyzed from children with SCA enrolled in prospective trials involving hydroxyurea treatment, including: (1) Hydroxyurea Study of Long-Term Effects (HUSTLE, NCT 00305175); (2) Stroke With Transfusions Changing to Hydroxyurea (SWiTCH, NCT 00122980); and (3) Transcranial Doppler With Transfusions Changing to Hydroxyurea (TWiTCH, NCT 01425307). DNA samples were genotyped for 6 candidate SNPs that were previously reported to have a significant effect on the WBC and ANC in the general population, using a combination of PCR-based allelic discrimination and Sanger sequencing (Table). WBC and ANC phenotypes (n=429) were obtained at study enrollment, as well as hydroxyurea MTD values (n=224) for children receiving the drug. An additive model and correlation trend test was used to perform statistical testing. Whole exome sequencing (WES) analysis was performed after randomizing the entire cohort into a discovery (n=256) and validation group (n=127), to identify novel associations with WBC and ANC. Results: The average age (mean ± SD) of the entire cohort was 10.7 ± 4.1 years, with WBC = 13.8 ± 4.4 x 109/L and ANC = 7.6 ± 3.2 x 109/L. The DARC SNP rs2814778 regulating Duffy antigen expression had a minor allele frequency (MAF) of 15.1%, similar to published reports in African-American populations. After adjusting for age, children either homozygous or heterozygous for the A allele had significantly higher WBC and ANC, compared to G homozygotes known as "Duffy null" (14.6 vs. 13.5 x 109/L and 8.5 vs. 7.2 x 109/L, p=0.015 and p=0.001, respectively). For DARC rs12075, which distinguishes the major Duffy alleles, the G allele that results in Fya expression was associated with higher ANC than Fyb, 8.8 vs. 7.4 x 109/L, p=0.017. The hydroxyurea MTD was 25.6 ± 4.5 mg/kg/day for the treated cohort, which was associated with pre-treated WBC (p=0.009) and ANC (0.002), but with none of the DARC polymorphisms. An unbiased search using WES identified a total of 45,228 non-synonymous variants with allele frequency 〉1%, including 2,238 variants associated with WBC and ANC in the discovery group (p

Description: Introduction: The multicenter phase 3 randomized clinical trial TCD With Transfusions Changing to Hydroxyurea (TWiTCH, NCT01425307) investigated whether hydroxyurea could maintain TCD velocities and prevent stroke in children with sickle cell anemia and abnormal TCD velocities. The trial was stopped early after reaching the primary endpoint, when the average TCD velocity in the alternative (hydroxyurea) arm was found to be non-inferior and even slightly better (138 versus 143 cm/sec) than the standard (transfusion) arm. A planned secondary analysis was to determine the variation in serial TCD velocity measurements for individual study participants, to document the normal TCD velocity fluctuations that occur and to inform the need for frequent TCD evaluations in this clinical setting. Methods: All TCD examinations collected in TWiTCH were analyzed for the maximum time-averaged mean velocity (TAMV) measured in the main intracranial arteries. TCD studies were performed by certified examiners using identical non-imaging instruments, no more than one week before a scheduled transfusion or phlebotomy procedure. Measurements on the index side, defined as the cerebral hemisphere with the higher mean arterial velocity at baseline assessment, were used for these statistical analyses. TCD values were analyzed according to four phases of the trial: (1) screening with three monthly TCD examinations performed at Weeks -8, -4, and 0 before randomization; (2) initial treatment period (hydroxyurea dose escalation with overlap transfusions or transfusions only) with three quarterly TCD measurements at Weeks 12, 24, and 36; (3) steady-state treatment period (hydroxyurea only or transfusions only) with four quarterly TCD measurements at Weeks 48, 60, 72, and 84; and (4) study exit with three monthly TCD examinations performed at Weeks 96, 100, and 104 or during the accelerated close-out period. The within-patient variance and standard deviation of the TAMV values were found using a linear mixed model, which was calculated using SAS Version 9.3. Results: TAMV measurements on the index side from 1458 TCD examinations on 121 randomized patients formed the overall dataset. TAMV values ≥170 cm/sec were identified in 140 measurements on 40 children (9.6% of TCD values) and exceeded 200 cm/sec in 1.8% of examinations (26 values, 8 children) during the study treatment phase. The within-patient TCD variation, representing fluctuation of repeated TCD measurements in the same study participant, was 12.0 cm/sec for the entire cohort during the initial screening phase (363 TCD measurements). In the initial treatment phase, TCD variation in the hydroxyurea arm (180 values, 60 children) was 10.5 cm/sec, similar to 10.2 cm/sec on the transfusion arm (183 values, 61 children). In the steady-state treatment phase, the TCD variation in the hydroxyurea arm was 10.2 cm/sec (207 values, 57 children), compared to 12.3 cm/sec on the transfusion arm (212 values, 58 children). In the final exit phase, TCD variation in the hydroxyurea arm was 9.8 cm/sec (155 values, 58 children), similar to 10.2 cm/sec on the standard arm (155 values, 57 children). TCD variation was greater with higher baseline TCD velocity and shorter transfusion duration, but was not affected by age or gender. For example, participants with baseline TCD velocity of

Description: Introduction Chronic transfusion therapy represents the standard of care for sickle cell anemia (SCA) patients with abnormal transcranial Doppler (TCD) ultrasound or prior stroke. While effective, monthly transfusions produce iron overload and toxicity if not controlled with chelation therapies. Liver iron concentration (LIC) is a powerful surrogate for total body iron stores. Unfortunately, liver biopsy is not suited for longitudinal analysis because it is invasive, expensive, and prone to sampling variability. MRI transverse relaxation rates, R2 and R2*, are highly correlated with LIC and have mostly supplanted liver biopsy for iron quantification in clinical practice and clinical trials. Since R2 and R2* have different sensitivity to the size and scale of tissue iron distribution, we compared the agreement of LIC values predicted by R2 and R2* in children with SCA and transfusional iron overload from the prospective multicenter TCD with Transfusions Changing to Hydroxyurea (TWiTCH) trial (ClinicalTrials.gov; NCT01425307). Methods 133 patients underwent LIC assessment using both R2 and R2* techniques at 22 MRI sites. All sites used 1.5 Tesla magnets and torso phased array coils. Images for R2 measurements were collected on validated scanners and analyzed centrally according to the FerriScan” protocol (Resonance Health, Western Australia, see St Pierre, T.G., et al. Blood,105, 855-861, 2005). Images for R2* assessment were collected using multiple-echo gradient echo sequences (see Wood, J.C., et al. Blood,106, 1460-1465, 2005). Images were analyzed centrally at Children's Hospital Los Angeles, using an exponential-plus-constant fit to the signal decay. Bland-Altman analysis on log-transformed LIC values was used to test agreement between LICR2 and LICR2*; the residuals of this relationship were probed for association with transfusion/chelation history, markers of inflammation, and markers of hemolysis. Results Figure 1A illustrates the scattergram between LICR2* and LICR2. The variance of the disagreement between the two techniques increases with LIC, so log-transformation was performed prior to Bland Altman analysis. LICR2* was systematically higher than LICR2 below about 5 mg Fe/g dw and systematically lower above 5 mg Fe/g dw. Bland Altman comparison of the log-transformed data (Figure 1B) reveals a downward trend (r2 of 0.203, p

Description: Introduction Chronic transfusion therapy is the standard of care for children with sickle cell anemia (SCA) and abnormal transcranial Doppler velocities. Although effective, monthly transfusions are costly, inconvenient, and produce iron overload in the liver and extrahepatic organs. The TWiTCH study (ClinicalTrials.gov NCT01425307) is a randomized clinical trial to determine whether hydroxyurea therapy leads to comparable time averaged TCD velocities as conventional transfusion therapy, while reducing somatic iron stores. We report baseline data on iron burden in the spleen, pancreas, and kidneys from the TWiTCH cohort. Methods Pediatric patients from 22 centers underwent screening R2* assessment of the liver, spleen, pancreas, and kidneys. All sites used a 1.5 Tesla magnet, torso phased array coils, and a multiple echo gradient echo sequence with a minimum echo time ≤1.3 ms. Images were analyzed centrally at Children’s Hospital Los Angeles; core laboratory staff were blinded to patient, site, and visit data. Raw R2* values were used as iron surrogates for spleen, pancreas, and kidney. All statistics were performed by the TWiTCH Data Coordinating Center. Results A total of 113/159 enrolled patients (mean age 8.8 ± 6.3 years) successfully completed baseline abdominal R2* assessment (Table 1). Patients had received chronic transfusions for 4.2 ± 2.4 years and iron chelation for 3.2 ± 2.2 years. Serum ferritin values ranged from 191 to 10593 ng/ml (2655.6 ± 1668.1 ng/ml). All subjects had liver iron detectable by R2*, with 51.3% having liver iron concentration (LIC) 〉7 mg/g, and 13.3% 〉15 mg/g of dry weight. Splenic R2* could be assessed in 80/113 (71%) subjects, with the remainder having surgical splenectomy or autoinfarction. Splenic R2* revealed splenic tissue was comparable to liver tissue containing on average 13.1 mg Fe/g of dry weight. Pancreas R2* was greater than the upper limits of normal in 39.3% but no values exceeded 100 Hz (the level associated with pancreas dysfunction, pituitary iron accumulation, and cardiac iron deposition in thalassemia patients). LIC was the only significant predictor of pancreas R2* (r2 = 0.06, p=0.001). Kidney R2* was above the upper limits of normal in 79.5% of the patients and demonstrated preferential cortical distribution. Kidney R2* positively correlated with lactate dehydrogenase levels (p 〈 0.001), positive correlated with LIC R2* (p=0.005) and negatively correlated with hemoglobin level(p = 0.01) with a combined r2 of 0.29. No association was found with total bilirubin or reticulocyte count. Discussion This represents the first multicenter study documenting the prevalence and extent of extrahepatic iron deposition in children with SCA receiving chronic transfusions. Splenic iron deposition was common but uncorrelated with LIC,, suggesting different kinetics of iron loading transport. Clinically-significant pancreatic iron deposition was not observed. Renal R2* tracked with intravascular hemolysis markers, rather than LIC or ferritin, consistent with tubular uptake of filtered cell-free hemoglobin. Overall, chronically transfused children with SCA have greater splenic and renal iron deposition, but much milder pancreatic iron overload, than that observed in transfused thalassemia patients. Disclosures: Wood: Novartis: Honoraria; Apopharma: Honoraria, Patents & Royalties; Shire: Consultancy, Research Funding. Off Label Use: Hydroxyurea is FDA-approved for use in adults but not children. Thompson:Amgen: Research Funding; Eli Lilly: Research Funding; Glaxo Smith Kline: Research Funding; ApoPharma: Consultancy, Honoraria; Novartis: Consultancy, Research Funding; bluebird bio: Research Funding.

Description: Introduction : Stroke is a major cause of morbidity and mortality in children with sickle cell anemia (SCA), and current efforts seek to prevent primary stroke in this high-risk population through transcranial Doppler (TCD) screening programs and prophylactic blood transfusions for children with abnormally high intracranial TCD velocities. During the SWITCH trial (ClinicalTrials.gov NCT00122980), a novel MRA vasculopathy grading (VOG) scale was developed, which documented baseline bilateral vessel stenosis and parenchymal injury in children receiving transfusions for secondary stroke prophylaxis, and provided a severity scale suitable for future clinical trials. We now describe the baseline brain magnetic resonance imaging/angiography (MRI/MRA) results and vasculopathy grading scores in children with SCA on primary stroke prophylaxis, and report correlations with intracranial TCD velocities and duration of transfusion. Methods: TCD With Transfusions Changing to Hydroxyurea (TWiTCH) is a Phase three randomized, controlled, multicenter clinical trial (ClinicalTrials.gov NCT01425307), comparing transfusions versus hydroxyurea for children with abnormal TCD velocities. Children were eligible for TWiTCH enrollment if they currently receive monthly transfusions for primary stroke prophylaxis, and had no known history of stroke, transient ischemic attack, or severe vasculopathy. All TWiTCH participants underwent baseline MRI/MRA examinations with central review after study enrollment. Baseline TCD examinations were also centrally reviewed and Time-Averaged Mean Velocities (TAMV) were recorded for the distal internal carotid artery (dICA), internal carotid bifurcation (BIF), first segment middle cerebral artery (MCA) = M1, mid MCA (MCA), and posterior cerebral artery (PCA). MRA vasculopathy grades were recorded bilaterally and compared to the TCD velocities and duration of transfusion. Results: Of 159 enrolled subjects, 143 had complete baseline MRI/MRA data. The mean age at study enrollment was 9.8 years, with a 2:3 male:female ratio, and mean age at the original abnormal (Index) TCD exam was 5.4 years. A total of 62 children had parenchymal abnormalities identified on baseline brain MRI, including 2 with infarcts, 54 with leukoencephalopathy, 5 with encephalomalacia, and 20 with lacunae lesions (not mutually exclusive). A total of 124 children had baseline MRA vasculopathy scores ≤3, while 19 had grades 4-6 (severe vasculopathy) that required removal from the study. There were significant positive associations between the baseline hemisphere vasculopathy grades and the corresponding TAMV velocities in the Left dICA (p=0.02), Left BIF (p˂.0001), Left MCA (p=.0002), Right BIF (p=.0003) and Right MCA (p=.0002). Likewise, when TCD velocities were categorized as low (