Hydroxyurea as Treatment for Sickle Cell Anemia

A pilot clinical phase II trial MemSID: Acute and durable changes of red blood cells of sickle cell disease patients on memantine treatment

An increase in abundance and activity of N‐methyl D‐aspartate receptors (NMDAR) was previously reported for red blood cells (RBCs) of sickle cell disease (SCD) patients. Increased Ca²⁺ uptake through the receptor supported dehydration and RBC damage. In a pilot phase IIa‐b clinical trial MemSID, memantine, a blocker of NMDAR, was used for treatment of four patients for 12 months. Two more patients that have enrolled into the study did not finish it. One of them had psychotic event following the involuntary overdose of the drug, whereas the other had vertigo and could not comply to the trial visits schedule. Acute and durable responses of RBCs of SCD patients to daily oral administration of memantine were monitored. Markers of RBC turnover, changes in cell density, and alterations in ion handling and RBC morphology were assessed. Acute transient shifts in intracellular Ca²⁺, volume and density, and reduction in plasma lactate dehydrogenate activity were observed already within the first month of treatment. Durable effects of memantine included (a) decrease in reticulocyte counts, (b) reduction in reticulocyte hemoglobinization, (c) advanced membrane maturation and its stabilization as follows from reduction in the number of NMDAR per cell and reduction in hemolysis, and (iv) rehydration and decrease in K⁺ leakage from patients’ RBC. Memantine therapy resulted in reduction in number of cells with sickle morphology that was sustained at least over 2 months after therapy was stopped indicating an improvement in RBC longevity.

Burden of Sickle Cell Disease in Ghana: The Korle-Bu Experience

In Africa, sickle cell disease (SCD) is a major public health problem with over 200,000 babies born per year. In Ghana, approximately 15,000 (2%) of Ghanaian newborns are diagnosed with SCD annually. A retrospective review of medical records of all SCD patients aged 13 years and above, who presented to the sickle cell clinic at Ghana Institute of Clinical Genetics (GICG), Korle-Bu, from 1st January 2013 to 31st December 2014, was carried out, using a data abstraction instrument to document their phenotypes, demographics, attendance/clinic visits, pattern of attendance, and common complications seen. During the period under review 5,451 patients were seen at the GICG, with 20,788 clinic visits. The phenotypes were HbSS (55.7%) and HbSC (39.6%) with other sickle cell phenotypes (4.7%). Out of the 20,788 clinic visits, outpatient visits were 15,802 (76%), and urgent care visits were 4,986 (24%), out of which 128 (2.6%) patients were admitted to the Teaching Hospital for further management of their acute complications. There were 904 patient referrals (out of 5,451 patients) for specialist care; the 3 specialties that had the most referrals were Obstetrics and Gynaecology (168 patients), Orthopaedics (150 patients), and Ophthalmology (143 patients). In 2014, complications seen at KBTH included 53 patients with avascular necrosis (AVN) and 61 patients with chronic leg ulcers. Our centre has a large number of patients living with sickle cell disease. From our experience, early recognition and referral of sickle cell related complications can reduce morbidity and mortality associated with this disease. A multidisciplinary approach to care of SCD patients is therefore important.

Current sickle cell disease management practices in Nigeria

BACKGROUND

Although Nigeria has the highest burden of sickle cell disease (SCD) worldwide, there is still variable and poor utilisation of standard-of-care practices for SCD patients in the country.

METHODS

This was a questionnaire survey of doctors in some dedicated SCD clinics in Nigeria in order to document the facilities available and common management practices.

RESULTS

There were responses from 18 clinics based in 11 institutions. The number of patients being followed in each centre ranged from 15 to approximately 11 000. All clinics provided malaria prophylaxis and folic acid routinely to their patients. Only eight clinics prescribe penicillin prophylaxis. Eight prescribe hydroxyurea to patients who can afford it when indicated. All of the centres except three have electronic cell counters, but all had access to haemoglobin electrophoresis. Three had high-performance liquid chromatography machines installed but none was being routinely used. One institution had a functioning molecular biology laboratory. There is no official newborn screening programme in the country. All had access to microbiology and chemistry laboratories. Nine institutions had CT, six had MRI and three had transcranial Doppler facilities.

CONCLUSION

The care available for SCD in Nigeria is still suboptimal and there is an urgent need for concerted effort to tackle the problem, but to make a significant impact on the burden of the disease would require more focus at the primary care level. Some steps to achieving this are outlined.

Hydroxyurea enhances SMN2 gene expression through nitric oxide release

Small molecules that increase full-length survivor motor neuron (SMN) gene transcript are promising therapeutic candidates for spinal muscular atrophy (SMA). Hydroxyurea (HU) has recently been shown to increase full-length SMN transcript in cultured lymphocytes from patients with SMA. We investigate the mechanism by which HU enhances full-length SMN2 gene expression in SMA lymphocytes. Nitric oxide (NO) is a major intracellular metabolite of HU. We test whether NO donors can themselves enhance full-length SMN2 expression. Eighteen cell lines (five type I, five type II, six type III SMA, and two non-SMA controls) were treated with or without NO donors for 48 h. SMA cells treated with HU and three NO donors: two long-acting donors, Deta-NONOate and S-nitrosoglutathione, and one short-acting donor, 3-ethyl-3-(ethylaminoethyl)-1-hydroxy-2-oxo-1-triazene, resulted in significant increase in full-length SMN2 mRNA. These effects were abolished by co-treatment with an NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide. One short-acting NO donor, S-nitroso-N-acetyl-DL-penicillamine, failed to show significant effect on full-length SMN2 expression, possibly due to high degree of cytotoxicity. These results were observed using both densitometry and quantitative PCR methods. We conclude that HU enhances SMN2 expression through the release of NO. NO donors may themselves be considered as new therapeutic candidates for SMA.

The role of hydroxyurea in the management of sickle cell disease

Sickle cell disease (SCD) is one of the most common genetic diseases with some 250,000 new births each year. Most patients suffer intermittent pain crises and life-threatening events while life expectancy is considerably reduced. Until the last decade management was purely preventative or supportive aimed at symptom control. Apart from stem cell transplant, there is no cure but the oral chemotherapeutic drug hydroxyurea (HU) has now established a role in ameliorating the disease and improving life expectancy for most patients. There are side effects and risks of HU treatment in SCD but for moderate and severely affected patients, the benefits can be significant.

Hydroxyurea for sickle cell disease

BACKGROUND

Sickle cell disease is one of the most common inherited diseases world wide. It is associated with life long morbidity and a reduced life expectancy. Hydroxyurea, a chemotherapeutic drug taken by mouth, raises fetal haemoglobin and, as such, is expected to ameliorate some of the clinical problems of sickle cell disease.

OBJECTIVES

To assess the effects of hydroxyurea therapy in sickle cell disease patients of all types, of any age, regardless of setting.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group specialised register of controlled trials for haemoglobinopathies, which comprises references identified from comprehensive electronic database searches, hand-searching relevant journals, and hand-searching abstract books of conference proceedings. Date of the most recent search(es): November 2000.

SELECTION CRITERIA

All randomised or quasi-randomised controlled trials comparing the use of oral hydroxyurea for one month or longer with placebo, standard therapy or other interventions for the treatment of patients with sickle cell disease.

DATA COLLECTION AND ANALYSIS

Both reviewers independently assessed trial quality and extracted data from the two studies included.

MAIN RESULTS

Twenty trials were found of which two trials, which reported results from a total of 324 adults and children were suitable for inclusion in the review. From the data provided in the published reports only one study (the MSH study to the United States of America) could be analysed. This study showed marked differences in favour of hydroxyurea treatment as compared with placebo in terms of annual crisis rate, use of transfusions, and life-threatening complications (in particular, the acute sickle chest syndrome). No serious adverse effects were reported from either study.

REVIEWER'S CONCLUSIONS

While hydroxyurea appears both effective and safe in the severely affected SS adults over a two year period; further studies are required to elucidate its role in other patient groups and for other conditions.

Mechanism for fetal hemoglobin induction by hydroxyurea in sickle cell erythroid progenitors

Hydroxyurea (HU) is a widely used cytotoxic agent that is known to induce fetal hemoglobin (HbF) production and is presently used to ameliorate the severity of pain episodes in patients with sickle cell anemia (HbSS). Previously we have shown that HU inhibits growth of burst forming unit-erythroid (BFU-E) colonies in a dose-dependent manner, while fetal hemoglobin levels were increased. In the present report, we extended our analysis demonstrating the number of S phase cells is significantly higher for HbSS patients that respond to HU therapy. Studies were completed in vitro using erythroid progenitors derived from umbilical cord samples or peripheral blood from patients with HbS-hereditary persistence of fetal hemoglobin (HbS-HPFH) or HbSS disease. The effect of HU on (a) S phase erythroid progenitors, (b) BFU-E colony growth, (c) HbF levels in BFU-E colonies, and (d) total cellular RNA synthesis was analyzed in vitro for the three groups. The level of S phase erythroid progenitors was similar for all three groups and BFU-E colony growth was inhibited 92-94% for all samples in a dose-dependent manner. The HbF levels were increased in BFU-E colonies from HbSS patients (control, 4.0% +/- 1.15% vs. +HU, 22.67% +/- 2.03%) whereas HbF levels were decreased in BFU-E colonies derived from umbilical cord samples (control, 80% +/- 9.07% vs. +HU, 35.7% +/- 4.81%) or HbS-HPFH patients (control, 49.67% +/- 3.84% vs. +HU, 23.3% +/- 0.88%). Total RNA synthesis measured by 3H-uridine incorporation increased with increasing concentrations of HU; however, actinomycin D inhibited HU-induced RNA synthesis. These results suggest that HU can inhibit an active globin gene without preference and that newly synthesized RNA is under transcriptional control mechanisms.

Effect of hydroxyurea in sickle cell anemia: a clinical trial in children and teenagers with severe sickle cell anemia and sickle cell beta-thalassemia

This study evaluated the efficacy of hydroxyurea treatment in the prevention of vaso-occlusive crises among children and teenagers with severe sickle cell anemia and sickle cell beta-thalassemia. Nineteen children and young adults with severe sickle cell disease were enrolled to the hydroxyurea treatment trial. The incidence of vaso-occlusive crises, acute chest syndrome, hemolytic crises, splenic sequestration episodes, blood transfusions, and hospital days in the 2 years before hydroxyurea (HU) treatment were compared with the same parameters in the first 2 years of treatment. The patients received a mean dose of 21.3 mg/kg/day daily and were treated during a mean period of 40.3 +/- 14 months (range 20 to 68 months). Significant increases were observed after 1 month in the Hgb, MCV, MCH, and MCHC levels and were more notable after 3 months. The increase in the Hgb F level became important after 3 months of HU therapy and was highly significant (p < .001) beyond 6 months. No differences were observed in the RDW, reticulocyte count, Hgb S, and Hgb A2. Severe neutropenia was observed in one case. A decrease in the frequency of vaso-occlusive crises, acute chest syndrome, hemolytic crises, blood transfusions, and days spent in the hospital was demonstrated during the HU treatment period compared to the same period before. The clinical and laboratory response to HU was dramatic in severely affected sickle cell anemia (SCA) patients. The response to HU in children and teenagers with severe sickle cell anemia is similar to the response in adults, and no severe adverse effects were observed.

Hydroxyurea in children with sickle cell disease: impact on splenic function and compliance with therapy

PURPOSE

Hydroxyurea therapy reduces clinical complications in sickle cell disease. While evaluating the clinical and laboratory responses to hydroxyurea in children with sickle cell disease, we concurrently objectively monitored, for the first time during such treatment, compliance with therapy. Because most deaths in affected children are related to infection, we also evaluated the impact of hydroxyurea on splenic function, estimated by the percentage of red cells containing endocytic vacuoles ("pitted" cells) over 1 year of therapy.

PATIENTS AND METHODS

Seventeen children with a history of > or = 3 hospital admissions in the previous year, aged (mean +/- standard error of mean) 12.3 +/- 1.2 years, were treated with hydroxyurea. Clinical and laboratory assessments monitored efficacy and toxicity. Compliance was monitored using computerized pill bottles containing cap microprocessors which monitor the frequency of bottle openings.

RESULTS

Over 18.5 +/- 2.1 months, compliance with hydroxyurea (as determined by percent of the prescribed drug actually taken) was 96 +/- 2%, resulting in increases in mean fetal hemoglobin from 7.7 +/- 1.6% to 16.7 +/- 1.8% (p < 0.005). In 11 patients who reached maximum tolerated doses, an increase to 18.8 +/- 2.5% (p = 0.0001) was observed. Pitted red cell counts did not change. Annual rates of vaso-occlusive crisis (p = 0.0105), acute chest syndrome (p = 0.0417), transfusions administered (p = 0.0168), and days in hospital (p = 0.0017) all decreased significantly.

CONCLUSIONS

Hydroxyurea in children is associated with sustained excellent compliance and monitoring this compliance is uncomplicated. Splenic function in most hydroxyurea-treated children did not change over 1 year of therapy.

BFU-E colony growth in response to hydroxyurea: correlation between in vitro and in vivo fetal hemoglobin induction

Patients with sickle-cell anemia treated with hydroxyurea may have significant reduction in frequency and severity of pain episodes. However, previous clinical trials show a variable response to hydroxyurea. Criteria which can be used to select patients who are likely to respond to hydroxyurea treatment would be useful. Our laboratory has previously demonstrated an inverse linear relationship between the total number of burst-forming unit-erythroid (BFU-E) colonies and fetal hemoglobin levels in sickle-cell patients treated with hydroxyurea. In the present report, an in vitro cell culture system was established to evaluate the effects of hydroxyurea on BFU-E colony growth and induction of fetal hemoglobin production. Five Hb SS patients who were not previously treated with hydroxyurea and three Hb SS patients who failed to respond to hydroxyurea treatment were included in the study. The results show that the number of BFU-E colonies is decreased from 153.7 to 7.2 per 3 x 10(5) mononuclear cells, whereas fetal hemoglobin levels were increased from 5.1 to 19.4% in the presence of hydroxyurea in vitro in cultured erythroid progenitors, which were derived from 5 patients before treatment. The number of BFU-E colonies decreased from 153.7 to 2.0 per 3 x 10(5) mononuclear cells in the in vitro cultures obtained from serial peripheral blood samples over a 9- to 20-week period of oral hydroxyurea therapy. A simultaneous rise in fetal hemoglobin level from 10.2 to 28.6% in the peripheral blood over the same period of hydroxyurea therapy was also observed. Our results demonstrate that the increase in fetal hemoglobin levels in cells treated with hydroxyurea in vitro is comparable to the rise of fetal hemoglobin production following hydroxyurea therapy in these patients. On the contrary, these findings were not observed in three previously non-responsive sickle-cell patients. These results suggest that the changes in number of BFU-E colonies and fetal hemoglobin levels after in vitro exposure to hydroxyurea may be a useful approach to select sickle-cell patients who will respond to hydroxyurea therapy.

[Sickle cell anemia in children: value of hydroxyurea in severe forms]

BACKGROUND

Sickling of red cells in patients with sickle cell anemia causes painful vaso-occlusive crises (VOC). Hydroxyurea (HU) has been shown to increase HbF production and therefore has the potential to prevent these crises in adult patients. This work aimed to confirm its clinical efficiency in children.

PATIENTS AND METHODS

Since 1993, eight children and adolescents (5-16 years old) with hemoglobinopathy (HbS > 65%) were given HU (14 to 27 mg/kg/day) for a mean duration of 10 months. We did a retrospective study about different data, especially inpatient days for VOC, pain intensity during these crises, individual transfusion requirements and HbF level.

RESULTS

As the HbF levels increased, we observed a reduction of the inpatient days for VOC, of the pain intensity during these crises and of the mean number of units transfused per month.

CONCLUSION

HU is the first clinically acceptable drug shown to prevent painful crises in adults but also in children with sickle cell anemia. However, its effects and potential toxicity are still unknown and the other therapeutic possibilities have to be considered before starting a long-term treatment with HU.

Hydroxyurea-induced denaturation of normal and sickle cell hemoglobins in vitro

Use of hydroxyurea (HU) to treat sickle cell disease is usually associated with increments in fetal hemoglobin (Hb F) production; however, in vitro studies show that HU may also induce hemoglobin denaturation. Whole blood samples from Hb AA, Hb AS, and Hb SS patients were treated in vitro with 100, 150, 200, 250, and 300 micrograms/mL HU, incubated at 30 degrees C for up to 12 days, and analyzed by high-performance liquid chromatography (HPLC). Hb AA levels show decrements of 91 to 14% with 100 micrograms/mL and 89 to 4% with 150 micrograms/mL after 12 days; 86 to 2% with 200 micrograms/mL after 10 days; 86 to 8% with 250 and 300 micrograms/mL after 8 days. Similar treatment and incubation times for Hb AS whole blood demonstrate that HU equally degrades the A and S components of Hb AS. A comparable approach for Hb SS whole blood samples, using a 300 micrograms/mL HU treatment, showed a hemoglobin denaturing pattern that went from 93% to 1% after 12 days. Globin chain analysis of these samples by reverse-phase HPLC showed that the denaturing effects occur mostly on the beta-globin chain.

Hydroxyurea therapy in children severely affected with sickle cell disease

HYPOTHESIS

The major clinical manifestations of sickle cell disease (SCD) are hemolytic anemia, predisposition to infection, and recurrent vaso-occlusive episodes resulting in pain, organ dysfunction, or both. There has been no satisfactory treatment for children with recurrent severe painful episodes caused by SCD. Hydroxyurea is an antimetabolite drug shown in adults with SCD to increase fetal hemoglobin levels and reduce the symptoms of SCD. We hypothesized that hydroxyurea therapy in children with severe (defined as > or = 3 vaso-occlusive events per year) SCD could improve hematologic parameters and reduce vaso-occlusive events.

OBJECTIVE

To assess the safety and efficacy of hydroxyurea for the treatment of severe SCD in children.

STUDY DESIGN

After obtaining informed consent, we initiated hydroxyurea therapy at a dosage of 10 to 20 mg/kg per day in 15 patients with severe SCD (hemoglobin SS, hemoglobin SS-alpha thalassemia, or hemoglobin S-beta0-thalassemia). Doses were escalated as tolerated. Patients were monitored with bimonthly physical examinations and monthly laboratory measures. To assess the impact of hydroxyurea on clinical symptoms, we recorded the number of inpatient days for each patient during the period of treatment and compared it with the number of inpatient days for the 12- to 24-month period before institution of hydroxyurea therapy, using the subject as his or her own control subject.

RESULTS

Thirteen patients received hydroxyurea for a median of 24 months (range, 6 to 39 months). The mean dose of hydroxyurea was 21.4 +/- 5.2 mg/kg. Treatment with hydroxyurea induced statistically significant increases in the total hemoglobin concentration, mean corpuscular volume, and percentage of hemoglobin F, and a decrease in the serum concentration of bilirubin. Toxic effects included three episodes of a reversible myelotoxic reaction, two of which required transfusion of packed erythrocytes. For the entire group, hospitalization decreased from a prehydroxyurea median of 3.9 +/- 2.0 days per month to 1.1 +/- 2.1 days per month of therapy (p = 0.09). For those subjects (n = 10) completing at least 1 year of treatment, the decrease in hospitalization from 4.1 +/- 2.2 to 1.0 +/- 1.7 days per month was significant (p = 0.03).

CONCLUSIONS

In this pilot trial, hydroxyurea treatment of severe SCD in children was associated with improved hematologic parameters, acceptable toxic effects, and a trend to reduced hospitalization. Hydroxyurea appears to be a safe and potentially effective agent for the treatment of severe SCD in children. A prospective, controlled trial to investigate the efficacy of hydroxyurea in children is therefore warranted.

Nursing management of children with sickle cell disease: an update

This article reviews current trends in managing children with sickle cell disease (SCD). The pathophysiology, medical and nursing management, and complications of SCD are discussed. Current trends and research findings related to improving the prognosis of children with SCD are offered. The importance of the nurse's role in educating the family about the disease process and clinical interventions to prevent or manage complications are stressed. Lastly, a nursing care plan is offered which focuses on pertinent nursing diagnosis.

Hydroxyurea as an inhibitor of human immunodeficiency virus-type 1 replication

Hydroxyurea, a drug widely used in therapy of several human diseases, inhibits deoxynucleotide synthesis--and, consequently, DNA synthesis--by blocking the cellular enzyme ribonucleotide reductase. Hydroxyurea inhibits human immunodeficiency virus-type 1 (HIV-1) DNA synthesis in activated peripheral blood lymphocytes by decreasing the amount of intracellular deoxynucleotides, thus suggesting that this drug has an antiviral effect. Hydroxyurea has now been shown to block HIV-1 replication in acutely infected primary human lymphocytes (quiescent and activated) and macrophages, as well as in blood cells infected in vivo obtained from individuals with acquired immunodeficiency syndrome (AIDS). The antiviral effect was achieved at nontoxic doses of hydroxyurea, lower than those currently used in human therapy. Combination of hydroxyurea with the nucleoside analog didanosine (2',3'-dideoxyinosine, or ddl) generated a synergistic inhibitory effect without increasing toxicity. In some instances, inhibition of HIV-1 by hydroxyurea was irreversible, even several weeks after suspension of drug treatment. The indirect inhibition of HIV-1 by hydroxyurea is not expected to generate high rates of escape mutants. Hydroxyurea therefore appears to be a possible candidate for AIDS therapy.

Sickle cell anemia and fetal hemoglobin

Fetal hemoglobin, the predominant hemoglobin of the fetus, is good for sickle cell anemia. This hemoglobin inhibits the polymerization of sickle hemoglobin. Clinical studies have shown that at any level of fetal hemoglobin, the more that is present, the better off is the patient. We are now able to increase fetal hemoglobin levels by pharmacologic means. We should know shortly if this is associated with clinical benefit.

[A sickle cell homozygote with transfusion deadlock. Favorable outcome with hydroxyurea treatment]

Alloimmunization following multiple transfusions, a frequently observed complication in sickle cell anemia patients, may make subsequent transfusion attempts extremely hazardous. The case of a young woman with sickle-cell anemia is reported; she was hospitalized for the treatment of extensive invalidating leg ulcers. The transfusion program that was initiated as a prerequisite to skin allografts had to be stopped, due to rapid occurrence of multiple alloimmunization. Broad spectrum alloantibodies precluded further selection of compatible blood units. In an attempt to get round this impossibility, a treatment with Hydroxyurea was initiated in order to boost synthesis of F-hemoglobin. After one year under this treatment, the patient's clinical status has clearly improved without requiring any new blood transfusion.