Hydroxyurea therapy of a murine model of sickle cell anemia inhibits the progression of pneumococcal disease by down-modulating E-selectin

Abstract Sickle cell anemia is characterized by chronic hemolysis coupled with extensive vascular inflammation. This inflammatory state also mechanistically promotes a high risk of lethal, invasive pneumococcal infection. Current treatments to reduce vaso-occlusive complications include chronic hydroxyurea therapy to induce fetal hemoglobin. Because hydroxyurea also reduces leukocytosis, an understanding of the impact of this treatment on pneumococcal pathogenesis is needed. Using a sickle cell mouse model of pneumococcal pneumonia and sepsis, administration of hydroxyurea was found to significantly improve survival. Hydroxyurea treatment decreased neutrophil extravasation into the infected lung coincident with significantly reduced levels of E-selectin in serum and on pulmonary epithelia. The protective effect of hydroxyurea was abrogated in mice deficient in E-selectin. The decrease in E-selectin levels was also evident in human sickle cell patients receiving hydroxyurea therapy. These data indicate that in addition to induction of fetal hemoglobin, hydroxyurea attenuates leukocyte–endothelial interactions in sickle cell anemia, resulting in protection against lethal pneumococcal sepsis.

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Optimizing hydroxyurea therapy for sickle cell anemia

Hematology ◽

10.1182/asheducation-2015.1.436 ◽

2015 ◽

Vol 2015 (1) ◽

pp. 436-443 ◽

Cited By ~ 19

Author(s):

Russell E. Ware

Keyword(s):

Sickle Cell ◽

Sickle Cell Anemia ◽

Fetal Hemoglobin ◽

Maximum Tolerated Dose ◽

Sub Saharan Africa ◽

Future Research ◽

Published Evidence ◽

Treatment Indications ◽

Hydroxyurea Treatment ◽

Hydroxyurea Therapy

Abstract Hydroxyurea has proven efficacy in numerous clinical trials as a disease-modifying treatment for patients with sickle cell anemia (SCA) but is currently under-used in clinical practice. To improve the effectiveness of hydroxyurea therapy, efforts should be directed toward broadening the clinical treatment indications, optimizing the daily dosage, and emphasizing the benefits of early and extended treatment. Here, various issues related to hydroxyurea treatment are discussed, focusing on both published evidence and clinical experience. Specific guidance is provided regarding important but potentially unfamiliar aspects of hydroxyurea treatment for SCA, such as escalating to maximum tolerated dose, treating in the setting of cerebrovascular disease, switching from chronic transfusions to hydroxyurea, and using serial phlebotomy to alleviate iron overload. Future research directions to optimize hydroxyurea therapy are also discussed, including personalized dosing based on pharmacokinetic modeling, prediction of fetal hemoglobin responses based on pharmacogenomics, and the risks and benefits of hydroxyurea for non-SCA genotypes and during pregnancy/lactation. Another critical initiative is the introduction of hydroxyurea safely and effectively into global regions that have a high disease burden of SCA but limited resources, such as sub-Saharan Africa, the Caribbean, and India. Final considerations emphasize the long-term goal of optimizing hydroxyurea therapy, which is to help treatment become accepted as standard of care for all patients with SCA.

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Optimizing hydroxyurea therapy for sickle cell anemia

Hematology ◽

10.1182/asheducation.v2015.1.436.3917688 ◽

2015 ◽

Vol 2015 (1) ◽

pp. 436-443 ◽

Cited By ~ 8

Author(s):

Russell E. Ware

Keyword(s):

Sickle Cell ◽

Sickle Cell Anemia ◽

Fetal Hemoglobin ◽

Maximum Tolerated Dose ◽

Sub Saharan Africa ◽

Future Research ◽

Published Evidence ◽

Treatment Indications ◽

Hydroxyurea Treatment ◽

Hydroxyurea Therapy

Hydroxyurea has proven efficacy in numerous clinical trials as a disease-modifying treatment for patients with sickle cell anemia (SCA) but is currently under-used in clinical practice. To improve the effectiveness of hydroxyurea therapy, efforts should be directed toward broadening the clinical treatment indications, optimizing the daily dosage, and emphasizing the benefits of early and extended treatment. Here, various issues related to hydroxyurea treatment are discussed, focusing on both published evidence and clinical experience. Specific guidance is provided regarding important but potentially unfamiliar aspects of hydroxyurea treatment for SCA, such as escalating to maximum tolerated dose, treating in the setting of cerebrovascular disease, switching from chronic transfusions to hydroxyurea, and using serial phlebotomy to alleviate iron overload. Future research directions to optimize hydroxyurea therapy are also discussed, including personalized dosing based on pharmacokinetic modeling, prediction of fetal hemoglobin responses based on pharmacogenomics, and the risks and benefits of hydroxyurea for non-SCA genotypes and during pregnancy/lactation. Another critical initiative is the introduction of hydroxyurea safely and effectively into global regions that have a high disease burden of SCA but limited resources, such as sub-Saharan Africa, the Caribbean, and India. Final considerations emphasize the long-term goal of optimizing hydroxyurea therapy, which is to help treatment become accepted as standard of care for all patients with SCA.

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Pharmacokinetics, pharmacodynamics, and pharmacogenetics of hydroxyurea treatment for children with sickle cell anemia

Blood ◽

10.1182/blood-2011-07-364190 ◽

2011 ◽

Vol 118 (18) ◽

pp. 4985-4991 ◽

Cited By ~ 89

Author(s):

Russell E. Ware ◽

Jenny M. Despotovic ◽

Nicole A. Mortier ◽

Jonathan M. Flanagan ◽

Jin He ◽

...

Keyword(s):

Sickle Cell ◽

Sickle Cell Anemia ◽

Oral Absorption ◽

Fetal Hemoglobin ◽

Maximum Tolerated Dose ◽

Interpatient Variability ◽

Nucleotide Polymorphisms ◽

Hydroxyurea Treatment ◽

Treatment Responses ◽

Hydroxyurea Therapy

Abstract Hydroxyurea therapy has proven laboratory and clinical efficacies for children with sickle cell anemia (SCA). When administered at maximum tolerated dose (MTD), hydroxyurea increases fetal hemoglobin (HbF) to levels ranging from 10% to 40%. However, interpatient variability of percentage of HbF (%HbF) response is high, MTD itself is variable, and accurate predictors of hydroxyurea responses do not currently exist. HUSTLE (NCT00305175) was designed to provide first-dose pharmacokinetics (PK) data for children with SCA initiating hydroxyurea therapy, to investigate pharmacodynamics (PD) parameters, including HbF response and MTD after standardized dose escalation, and to evaluate pharmacogenetics influences on PK and PD parameters. For 87 children with first-dose PK studies, substantial interpatient variability was observed, plus a novel oral absorption phenotype (rapid or slow) that influenced serum hydroxyurea levels and total hydroxyurea exposure. PD responses in 174 subjects were robust and similar to previous cohorts; %HbF at MTD was best predicted by 5 variables, including baseline %HbF, whereas MTD was best predicted by 5 variables, including serum creatinine. Pharmacogenetics analysis showed single nucleotide polymorphisms influencing baseline %HbF, including 5 within BCL11A, but none influencing MTD %HbF or dose. Accurate prediction of hydroxyurea treatment responses for SCA remains a worthy but elusive goal.

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Influence of Globin Gene Modifiers on Baseline and Hydroxyurea-Induced Fetal Hemoglobin Levels in Children with Sickle Cell Anemia.

Blood ◽

10.1182/blood.v106.11.3171.3171 ◽

2005 ◽

Vol 106 (11) ◽

pp. 3171-3171

Author(s):

Russell E. Ware ◽

Barry Eggleston ◽

Tatiana Abramova ◽

Sherri A. Zimmerman ◽

Alice Lail ◽

...

Keyword(s):

Sickle Cell ◽

Sickle Cell Anemia ◽

Globin Gene ◽

Fetal Hemoglobin ◽

Globin Genes ◽

Beta Globin ◽

Gene Number ◽

Gamma Globin ◽

Alpha Globin ◽

Hydroxyurea Therapy

Abstract Fetal hemoglobin (HbF) is recognized as a major determinant of clinical disease severity in children and adults with sickle cell anemia (SCA). Patients with elevated HbF levels have a milder disease course, and many current therapeutic protocols for SCA include pharmacological induction of HbF. However, baseline and treatment HbF levels vary widely due to presumed genetic and environmental factors. Recognized globin gene modifiers of HbF include the beta globin haplotype and a potential contribution from concomitant alpha thalassemia. To characterize more fully the influence of globin gene modifiers on both baseline and treatment HbF levels, we retrospectively determined the beta globin haplotype (Benin, CAR, Senegal, Cameroon, or Arab-Indian) by selective gamma globin gene nucleotide sequencing and the alpha globin gene number (2, 3, or 4) by PCR for 67 African-American children with SCA receiving hydroxyurea therapy at stable maximal tolerated dose (MTD). The four beta globin haplotypes and frequencies identified in our cohort of children include Benin (0.61), CAR (0.17), Senegal (0.12), and Cameroon (0.10). The number of alpha globin genes and frequencies identified were 4 genes (0.72), 3 genes (0.25) and 2 genes (0.03). Baseline and MTD HbF levels were analyzed according to each variable. The average baseline HbF value for the entire cohort of children was 7.7 ± 4.4% (median 7.6%, range 1.3 – 19.3%), while the average treatment HbF value was 23.9 ± 7.2 % (median 22.9%, range 10.2 – 40.7%). All 67 children increased their HbF in response to hydroxyurea therapy (median 16.7%, range 5.0 – 28.8%). There was a modest but statistically significant correlation between the baseline and treatment HbF (r=0.66, p<.0001). The estimated effect of one unit change in baseline HbF on treatment HbF was 1.11 (95% CI of 0.78, 1.43). When baseline %HbF was analyzed according to the beta globin haplotype, the overall ANOVA had a p-value of 0.02, indicating a statistically significant influence. Further analysis confirmed associations previously identified in adults with SCA, i.e. children with at least one copy of the CAR haplotype had a lower baseline HbF (5.9% vs 8.4%, p=.05), while those with at least one copy of the Senegal haplotype had a higher baseline HbF (11.1% vs 6.7%, p<.001). When hydroxyurea MTD (treatment) HbF values were analyzed according to beta globin haplotype while adjusting for baseline HbF, however, the effect of beta globin haplotype was not statistically significant (p=.13). Analyses of HbF according to alpha globin gene number revealed no statistically significant effects on either baseline or treatment HbF values. Taken together, these data support the hypothesis that beta globin haplotype significant influences baseline HbF values for children with SCA, but has no significant effects on hydroxyurea MTD HbF values. Accordingly, children with SCA should be offered hydroxyurea based solely on clinical indications, without consideration of baseline HbF or beta globin haplotype. Even children with low baseline HbF values or the CAR beta globin haplotype can respond to hydroxyurea therapy with an elevated %HbF. Future studies designed to identify genetic modifiers of treatment HbF values should focus on sequence polymorphisms in non-globin genes that have trans-acting effects on gamma globin gene expression.

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Expression Levels of CD11b, CD18, CD32, CD62L (L-Selectin) and CD62P (P-Selectin) and Its Role in Sickle Cell Anemia Inflammatory State

Blood ◽

10.1182/blood.v112.11.2504.2504 ◽

2008 ◽

Vol 112 (11) ◽

pp. 2504-2504

Author(s):

Bruno Antônio Veloso Cerqueira ◽

Wendell Vilas Boas ◽

Magda Oliveira Seixas ◽

Elder Trindade Damasceno ◽

Cyntia Cajado Souza ◽

...

Keyword(s):

Cell Surface ◽

Sickle Cell ◽

Sickle Cell Anemia ◽

Fetal Hemoglobin ◽

Surface Antigens ◽

Control Group ◽

Leukocyte Activation ◽

Cell Surface Antigens ◽

Expression Levels ◽

Inflammatory State

Abstract Vascular occlusions (VOC) underlie most of the acute and chronic sickle cell anemia (SCA) clinical complications and have been correlated to soluble adhesion molecules up regulation and leukocyte activation. A sequential process involving adhesion through selectins and integrins governs leukocyte recruitment to activated endothelium and to sickle red blood cells (RBC), resulting in heterotypic aggregation and VOC. The chronic hemolysis is the major cause of oxidative stress and it can induce transcriptions factors involved in the recruitment of adherent leukocytes in venules. In this work, we assessed the inflammatory potential of leukocytes in venous blood samples by examining cell surface antigens expression by flow cytometry, activation state and its association with hemolytic state in SCA patients group. The study was approved by the FIOCRUZ ethical committee and informed consents were signed by patients or official responsible. Leukocytes were obtained from 22 SCA patients and 22 healthy controls after RBC lyses and labeled with monoclonal anti-CD11b, anti-CD18, anti-CD32, anti-CD62L (L-Selectin) and anti-CD62P (P-Selectin). Leukocyte activation was stimulated by LPS. Statistical analyses were performed using SPSS version 9.0. The basal expression levels on leukocytes cell surface antigens from patients were not different from the control group. However, the CD62L expression levels were associated to C-reactive protein (CRP) higher levels and decrease of fetal hemoglobin in SCA patients (p=0.012). The SCA patients had higher CRP levels when compared to reference levels. Moreover, the data showed a co-expression of CD11b with CD18 (p<0.0001) and CD62P (p=0.011).The platelet count was positively correlated to CD11b expression (p=0.016) and the alanine transaminase high levels with the CD62P expression (p=0.012). Our results demonstrate a leukocyte chronic activation state by expression of CD62L related to CRP higher levels. Interestingly, the platelets could be activated by the indirect activation of CD62P by CD11b, participating of the inflammation state presents at vaso-occlusive events. It seems that the stress oxidative generated by the hemolytic state can contribute to endothelial dysfunction and vaso-occlusive events by CD62L activation in SCA. Fetal hemoglobin is a prognostic factor for several sickle cell complications and we showed that it can ameliorate the CD62L expression on leukocytes, decreasing the chronic inflammatory state of this disease. CD62L serves to as a homing receptor for naïve T lymphocytes and dendritic cells to lymph nodes, mediating the biding of T cells to high endothelial venules, in this view, this can be important marker to inflammatory state and vascular complications in SCA.

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Serum Cystatin-C Levels in Infants with Sickle Cell Anemia: Baseline Data from the BABY HUG Trial

Blood ◽

10.1182/blood.v112.11.4791.4791 ◽

2008 ◽

Vol 112 (11) ◽

pp. 4791-4791 ◽

Cited By ~ 2

Author(s):

Scott T. Miller ◽

Russell E. Ware ◽

Abdullah Kutlar ◽

Ofelia A. Alvarez ◽

Rathi V. Iyer ◽

...

Keyword(s):

Sickle Cell ◽

Cystatin C ◽

Sickle Cell Anemia ◽

Serum Levels ◽

Cysteine Protease Inhibitor ◽

P Value ◽

Renal Tubules ◽

Schwartz Formula ◽

The Impact ◽

Hydroxyurea Therapy

Abstract Background: BABY HUG is an NHLBI/NICHD sponsored double-blind placebo-controlled trial (NCT00006400) testing the hypothesis that hydroxyurea therapy (HU), if started early in life, will prevent or postpone organ damage to the spleen and kidney in infants with sickle cell anemia (SCA). All BABY HUG subjects at entry have GFR measured by 99mTc-DTPA radioisotope clearance (DTPA) and estimated using the Schwartz formula, a calculation based on serum creatinine (Cr) and height of the patient (GFR = κ (height)/Cr); κ=0.55 for children age >1 to 13 yr or 0.45 for term infants to age 1 yr. Measurement of GFR in infants is problematic due to difficulties in obtaining urine specimens and venous access. While Cr is a well-established marker for GFR it is not independent of body mass and may be secreted by renal tubules, leading to an overestimate of GFR. Cystatin C (CysC) is a cysteine protease inhibitor produced by all human nucleated cells and freely filtered by the kidney. Serum levels are not affected by muscle mass or gender and stable from age 18 mo to 50 yr, with higher levels in newborns reflecting a lower GFR. CysC offers a more practical and perhaps more accurate measure of GFR than Cr, especially in children with SCA. Normal non-SCA values are 0.5 to 1.4 mg/L. Formulas are published to translate serum levels of CysC to GFR as conventionally reported. Our aim was to determine usual and mean CysC levels in infants with SCA and compare CysC to DTPA and Cr-based assessments of GFR. Methods: Sera obtained and frozen during the eligibility screening phase of BABY HUG were used to determine CysC levels by particle enhanced immune nephelometry. Results: A total of 152 sera from infants age 9–17 mo (mean 13.5) were available. CysC levels ranged from 0.532 to 1.369 mg/L (mean 0.92; median 0.907), approximating the normal range. CysC was strongly and inversely associated with GFR estimated by DTPA (R2=0.086; p=0.001). CysC was also significantly associated with age (inversely, p=0.02), Schwartz GFR (using κ=0.55) (inversely, p=0.007) and Cr (p=0.01), but not with Hb, HbF or WBC count. GFR determined using two CysC-based formulae and the Schwartz formula were compared to GFR by DTPA. GFR Formula GFR* R-square P-value Regression slope *(mean ± SD in ml/min/1.73m2);99mTc-DTPA GFR=123.67±33.72 ml/min/1.73 m2 GFR in non-SS infants age 1–1.5 yr by 51Cr-EDTA clearance: 91.5±17.8 ml/min/1.73 m2 (Piepsz A et al. Eur J Nucl Med Imag2006;33:1477) Schwartz, κ=0.55 191.11±57.85 0.062 0.036 0.141 Schwartz, κ=0.45 154.80 ± 54.06 0.052 0.0123 0.172 CysC (1) 84.45±19.11 0.18 0.0026 0.149 CysC (2) 102.78±25.09 0.16 0.0029 0.196 GFR determined using CysC-based formula 2: GFR = antilog {1.92 + [1.123 × log (1/CysC)]} gave mean values closest to DTPA and similar to published estimates of GFR in non-SCA infants. The Schwartz formula overestimated GFR, especially when the higher κ was used. While correlations are low due to high GFR variability, the four GFR determinations all have a significant association with DTPA. However, because the slopes of the regression lines are not close to 1 (line of equality), measurement agreement with DTPA is poor. Conclusion: The Schwartz formula overestimated GFR in BABY HUG subjects. CysC-based GFR formulae underestimate GFR compared to concurrent DTPA values, but results are similar to published norms. Reports of hyperfiltration, based on creatinine-based determination of GFR, may be exaggerated. The impact of hydroxyurea therapy on CysC levels, if any, will be apparent at completion of the trial in late 2009.

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Long-term hydroxyurea therapy for infants with sickle cell anemia: the HUSOFT extension study

Blood ◽

10.1182/blood-2004-12-4973 ◽

2005 ◽

Vol 106 (7) ◽

pp. 2269-2275 ◽

Cited By ~ 161

Author(s):

Jane S. Hankins ◽

Russell E. Ware ◽

Zora R. Rogers ◽

Lynn W. Wynn ◽

Peter A. Lane ◽

...

Keyword(s):

Sickle Cell ◽

Sickle Cell Anemia ◽

White Blood Cells ◽

Fetal Hemoglobin ◽

Hemoglobin Concentration ◽

Extension Study ◽

Acute Chest Syndrome ◽

Event Rates ◽

Hydroxyurea Therapy

AbstractThe long-term efficacy and toxicity of hydroxyurea for infants are undefined, and its role in preventing organ dysfunction is unknown. Short-term feasibility of hydroxyurea administration, toxicities, hematologic effects, and effect on spleen function in infants with sickle cell anemia (SCA) were reported (Hydroxyurea Safety and Organ Toxicity [HUSOFT] trial). These infants completing 2 years of hydroxyurea therapy (20 mg/kg/d) were offered study extension with dose escalation to 30 mg/kg/d. Patients were monitored with laboratory tests and biannual imaging studies. Hematologic indices were compared with predicted age-specific values and event rates compared with historic rates. All 21 subjects completing the original trial enrolled in the extension study: median age, 3.4 years old (range, 2.6 to 4.4 years); 12 females; 20 with Hb SS, 1 with Hb S/β0-thalassemia. Seventeen patients completed 4 years of hydroxyurea, and 11 completed 6 years. After 4 years, hydroxyurea was associated with increased hemoglobin concentration, percentage of fetal hemoglobin (Hb F), and mean corpuscular volume (MCV) and decreased reticulocytes, white blood cells (WBCs), and platelets (P < .01). Patients experienced 7.5 acute chest syndrome (ACS) events per 100 person-years, compared with 24.5 events per 100 person-years among historic controls (P = .001). Treated patients had better spleen function than expected and improved growth rates. Infants with SCA tolerate prolonged hydroxyurea therapy with sustained hematologic benefits, fewer ACS events, improved growth, and possibly preserved organ function.

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Higher Fetal Hemoglobin Following Escalation of Hydroxyurea to Maximum Tolerated Dose Provides Clinical Benefit to Children with Sickle Cell Anemia

Blood ◽

10.1182/blood.v124.21.85.85 ◽

2014 ◽

Vol 124 (21) ◽

pp. 85-85 ◽

Cited By ~ 2

Author(s):

Jeremie H. Estepp ◽

Matthew P. Smeltzer ◽

Guolian Kang ◽

Banu Aygun ◽

Russell E. Ware ◽

...

Keyword(s):

Sickle Cell ◽

Clinical Data ◽

Sickle Cell Anemia ◽

Clinical Benefit ◽

Research Funding ◽

Fetal Hemoglobin ◽

Long Term Effects ◽

Clinical Benefits ◽

Hydroxyurea Therapy

Abstract Background. Hydroxyurea has proven laboratory and clinical benefits for children with sickle cell anemia (SCA); however, the benefits of escalation to a maximum tolerated dosage (MTD) over a fixed or low-dose approach to therapy, remains controversial. Clinical trials utilizing hydroxyurea at MTD reported higher fetal hemoglobin (HbF) levels (~20% versus ~15%) compared to those with a fixed lower-dose (Ware, Blood 2010). The clinical benefits gained, if any, from increasing HbF levels from 15% to 20% has not been described. The Hydroxyurea Study of Long-Term Effects (HUSTLE) provides the opportunity to examine the relationship between the magnitude and duration of pharmacologically induced HbF and clinical outcomes, specifically the number of hospitalizations for vaso-occlusive complications such as acute chest syndrome (ACS) and vaso-occlusive events (VOE). Methods. The Hydroxyurea Study of Long-Term Effects (HUSTLE) is a prospective observational study (NCT00305175) with a primary goal of describing the long-term effects of HU therapy in children with SCA, using serial and longitudinal collection of laboratory and clinical data. All children (≤18 years of age) who enrolled in HUSTLE and did not receive chronic blood transfusions are included in this analysis. All participants received hydroxyurea therapy escalated to a stable MTD, which was defined by moderate myelosuppression (typically ANC of 2,000-4,000 x 106/L) and no dose-limiting toxicities. Children were initially evaluated monthly but then every 2-3 months after achieving MTD. Neutropenia was defined as an ANC of <1,000 x 106/L. For this analysis, laboratory and clinical data were abstracted over twenty-seven months following enrollment onto HUSTLE, which constituted nine consecutive three month intervals. Hospitalizations for VOE and ACS were evaluated categorically for each three month time period, and %HbF levels at the beginning of each interval were used as the representative value for that period. To account for the correlated nature of the data, with potentially multiple hospitalizations per patient and time, a generalized estimating equation model was utilized. Results. A total of 162 children with SCA (148 HbSS, 14 HbSβ0thalassemia) at a mean (SD) age of 10.7 (4.3) years were analyzed. Children were hospitalized a total of 253 (52 ACS, 201 VOE) times during the first twenty-seven months following enrollment. The Figure illustrates the number of individuals hospitalized (yes versus no), stratified by HbF category, for each consecutive 3-month interval following HUSTLE enrollment. Compared to intervals when HbF levels were >20%, those with HbF levels of ≤20% had 2.2 (95% CI: 1.2-4.0; p=0.013) higher chance of hospitalization, and intervals with HbF levels <15% had 2.6 (95% CI: 1.3-5.1; p=0.021) times higher odds of hospitalization. For every 5% decrease in HbF, the odds of hospitalization due to VOE/ACS increased by 1.3 (95% CI: 1.1-1.5; p=0.014), correlating to a 30% increase. There was no statistically significant association between hydroxyurea dose (mg/kg) and hospitalization over time. Neutropenia occurred 39 times in 22 (13.6%) children; no episodes were associated with an invasive bacterial infection. Figure Children hospitalized versus not during three month intervals following HUSTLE enrollment, stratified by fetal hemoglobin percentage. Figure. Children hospitalized versus not during three month intervals following HUSTLE enrollment, stratified by fetal hemoglobin percentage. Discussion. In this pediatric cohort receiving hydroxyurea therapy escalated to MTD, higher %HbF levels conferred greater protection against hospitalization for severe vaso-occlusive pain or ACS. Escalation of hydroxyurea to MTD was rarely associated with neutropenia and had no clinical implications. These prospectively collected data from HUSTLE suggest that hydroxyurea dose escalation to MTD, designed to maximize %HbF levels, provides additional clinical benefit by reducing vaso-occlusive complications in children with SCA. Disclosures Estepp: Ely Lily: Research Funding; NIH: Research Funding. Off Label Use: Hydroxyurea in children with sickle cell anemia.

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Assessment of Genotoxicity Associated with Hydroxyurea Therapy in Children with Sickle Cell Anemia.

Blood ◽

10.1182/blood.v114.22.2554.2554 ◽

2009 ◽

Vol 114 (22) ◽

pp. 2554-2554

Author(s):

Jonathan M Flanagan ◽

Thad A. Howard ◽

Nicole Mortier ◽

Svetlana Avlasevich ◽

Matthew Smeltzer ◽

...

Keyword(s):

Sickle Cell ◽

Sickle Cell Anemia ◽

Drug Exposure ◽

Fold Increase ◽

Cross Sectional ◽

Flow Cytometric ◽

Hydroxyurea Treatment ◽

Serial Measurements ◽

Hydroxyurea Therapy

Abstract Abstract 2554 Poster Board II-531 Introduction: Hydroxyurea induces fetal hemoglobin (HbF), improves laboratory parameters, and reduces acute clinical complications of sickle cell anemia (SCA), but its long-term efficacy and safety remain incompletely defined. One long-term safety concern is that hydroxyurea may elicit DNA alterations via genotoxic damage. During normal erythropoiesis, red blood cells (RBC) extrude their nucleus as they develop into functional reticulocytes. Occasionally, membrane bound DNA remains in the cell after erythrocyte maturation and these inclusion bodies are known as micronuclei (MN) or Howell-Jolly Bodies. MN-containing reticulocytes are formed at higher frequency upon exposure to genotoxic agents. Patients with SCA have increased basal MN production while also having decreased MN clearance due to diminished splenic filtrative function. In a previous small cross sectional study, we showed that hydroxyurea exposure further increases MN production in SCA patients. To better address this long-term safety issue of hydroxyurea, we evaluated MN production and clearance both in a large cross-sectional and prospective study of children with SCA on hydroxyurea therapy. Patients and Methods: A high-throughput flow cytometric technique was used to detect and quantitate MN within circulating erythrocyte subpopulations. After written informed consent, venous blood samples were collected from children with SCA enrolled in the Hydroxyurea Study of Long-term Effects (HUSTLE, ClinicalTrials.gov NCT00305175). A total of 105 subjects had at least 1 MN measurement, including 37 subjects with serial measurements at baseline and at follow-up time points up to 24 months of hydroxyurea exposure. MN were quantified in both reticulocytes (MN-CD71(+)) and mature RBC (MN-RBC), and then tested for associations with individual subject laboratory and clinical data. Results: In cross-sectional analysis of 293 samples from 105 children with SCA and a median of 2 years hydroxyurea exposure (range 3 months – 12 years), hydroxyurea therapy significantly lowered %CD71(+) reticulocytes (mean fold reduction 0.53 ± 0.44, p < 0.001). Compared to baseline values, hydroxyurea treatment increased levels of MN in both reticulocytes (%MN-CD71(+), mean fold increase 1.80 ± 0.91, p < 0.05) and mature RBC (%MN-RBC, mean fold increase 1.89 ± 1.39, p<0.01). The increase in MN-CD71(+) was evident by 6 months of hydroxyurea treatment, but did not significantly escalate further with up to 12 years of continued drug exposure (Fig. 1). To prospectively determine the genotoxic effect of hydroxyurea, serial measurements over 2 years were performed on 37 patients. After 9 months on hydroxyurea therapy all subjects were on a stable maximum tolerated dose (MTD, average 25.1 mg/kg/day); 15 of 37 children had > 3.0 fold increase in %MN-CD71(+) while 22 of 37 had < 3.0 fold increase (Mean 3.68 ± 0.65 vs. 1.52 ± 0.52, p < 0.001). The observed inter-individual variation was associated with the predicted laboratory effects of hydroxyurea; increases in %MN-CD71(+) were positively correlated with MTD values of HbF (r2=0.22, p=0.005), mean corpuscular volume (r2=0.35, p=0.002), and mean corpuscular hemoglobin (r2=0.29, p=0.006) but negatively correlated with absolute neutrophil count (r2=0.14, p=0.02) and bilirubin levels (r2=0.20, p=0.008). There were no significant associations between %MN-CD71(+) and gender, age, or hydroxyurea dosage although %MN-RBC clearance decreased with age. Conclusions: A highly sensitive and quantitative flow cytometric technique can detect circulating MN-containing erythrocytes and this technique may be used to assess the in vivo genotoxic effect of any drug. Children with SCA have high basal MN production that is probably related to the degree of erythropoiesis in these patients. Hydroxyurea therapy was associated with genotoxicity but with substantial inter-patient variability in hydroxyurea induced %MN-CD71(+) levels. The increases in %MN-CD71(+) are observed within 6 months of starting hydroxyurea therapy but persist at the same level in patients with up to 12 years of continued drug exposure. Correlations between increased %MN-CD71(+) and predicted hydroxyurea effects on other laboratory parameters suggest that hydroxyurea induces measurable genotoxicity that may be related to individual patient sensitivity and efficacy of hydroxyurea within the bone marrow. These patients will be monitored further to confirm that hydroxyurea does not pose any long term safety issues. Disclosures: Off Label Use: Off label use of hydroxyurea in children with sickle cell anemia. Avlasevich:Litron Laboratories: Employment. Dertinger:Litron Laboratories: Employment.

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Hydroxyurea Treatment of Young Children with Sickle Cell Anemia: Safety and Efficacy of Continued Treatment – the BABY HUG Follow-up Study

Blood ◽

10.1182/blood.v118.21.7.7 ◽

2011 ◽

Vol 118 (21) ◽

pp. 7-7 ◽

Cited By ~ 1

Author(s):

Zora R. Rogers ◽

Billie Fish ◽

Zhaoyu Luo ◽

Rathi V. Iyer ◽

Courtney D. Thornburg ◽

...

Keyword(s):

Sickle Cell ◽

Sickle Cell Anemia ◽

Hospital Admissions ◽

Controlled Trial ◽

Laboratory Data ◽

Acute Chest Syndrome ◽

Follow Up Study ◽

Hydroxyurea Treatment ◽

The Impact

Abstract Abstract 7 BABY HUG [Clinical Trials #NCT00006400], an NIH-NICHD sponsored randomized placebo-controlled trial showed that hydroxyurea (HU) administered to 9–18 month old children with sickle cell anemia (SCA) provides substantial clinical benefit. Benefits include a decrease in pain crises, acute chest syndrome events, need for transfusion and hospital admission; hematologic improvement include higher total and fetal hemoglobin concentration, larger red cell size, and lower WBC counts with toxicity limited to transient reduction in absolute neutrophil count (ANC) [Lancet 2011; 377:1663–72]. The parent or guardian of all 176 children who completed at least 18 months of randomized treatment were offered participation in an initial observational BABY HUG Follow-Up Study and 163 (93%) consented to participate. Clinical and laboratory data were collected every 6 months by structured abstraction of the medical record regarding use of clinically prescribed HU (dose escalation recommended), blood counts, clinical imaging, and sickle cell-related events. At the time of enrollment the family did not know their child's randomized study treatment assignment; 133 (82%) initially chose clinical prescription of open-label HU. Acceptance of HU has remained high through 36 months of follow-up; during each 6 month data collection period 68–75% of participants reported having taken HU. Only 2 patients have left the study (due to relocation) and more than 93% of expected data have been collected. Preliminary analyses as of May 2011, including 417 patient years (pt-yrs) of follow up, demonstrate that in comparison to participants not taking HU, children who continue to take HU have statistically lower rates of pain crises requiring emergency department (ED) visits, episodic transfusions, and hospital admissions for any reason, including acute chest syndrome or febrile illness (see table). The substantial decrease in acute chest syndrome episodes is similar to the effect demonstrated with HU use in the randomized BABY HUG trial in younger infants and consistent with published trials detailing the benefit of HU therapy in older children and adults. The decrease in the rate of admission for febrile events in HU-treated patients is also comparable to that in the randomized trial, but the reason for this benefit is uncertain. There was no difference in hospitalization rates for painful events including dactylitis. Two patients in the non-HU group had a stroke. There were no differences between groups in the frequency of a palpable spleen or rate of acute splenic sequestration crises. Through 36 months of follow up children taking HU had persistently higher hemoglobin and MCV, and lower WBC and ANC than those not taking HU. Results of these analyses including growth and development assessments will enhance our understanding of the impact of HU use in children with SCA starting at a very young age. The accruing data from the BABY HUG Follow-Up Study demonstrate a continuation of the substantial benefits of early HU therapy with no discernable additional toxicities. Ongoing follow up of this cohort is essential to fully define these benefits as children grow, and to observe for late toxicity.Event Rate per 100 pt-yrsHUNo HUp valueED visit for Pain Crisis28.853.60.004Episodic Transfusion18.334.00.010Hospital Admission (any cause)74.9133.20.001Acute Chest Syndrome (admission)9.522.30.0001Febrile Illness (admission)30.764.3<.001Pain Crisis (admission)18.630.40.102 Disclosures: Off Label Use: Hydroxyurea is not indicated for treatment of children with sickle cell disease. Use of this medication was for clinical indications and not mandated by this observational study.

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