Patricia J. Giardina

Effectiveness and safety of ICL670 in iron-loaded patients with thalassaemia: a randomised, double-blind, placebo-controlled, dose-escalation trial

BACKGROUND Transfusional iron overload is a potentially fatal complication of the treatment of thalassaemia. We aimed to investigate short-term efficacy, pharmacokinetic/pharma- codynamic (PK/PD) relations, and safety of ICL670, a novel, tridentate, orally active iron chelator. METHODS We enrolled 24 patients and divided them into three cohorts consisting of a minimum of seven individuals. Patients were admitted to a metabolic unit and consumed a diet with a defined content of iron. Two patients in each cohort were randomly allocated placebo. Five or more patients received one daily dose of ICL670 at 10, 20, or 40 mg x kg(-1) x day(-1), from day 1 to 12. Net iron excretion (NIE) was measured between days 1 and 12. Primary objectives included assessment of safety and tolerability (measured by adverse events and clinical laboratory monitoring), pharmacokinetics (measured as drug and drug-iron complex), and cumulative net iron excretion (measured by faecal and urine output minus food input). Analysis was for efficacy. FINDINGS ICL670 was absorbed promptly and was detectable in the blood for 24 h. Exposure (area under the curve of plasma concentration) to ICL670 at pharmacokinetic steady state was proportional to dose. All three doses resulted in positive NIE. The NIE achieved at 20mg x kg(-1) day(-1) would prevent net iron accumulation in most patients transfused with 12-15 mL packed red-blood-cells kg(-1) month(-1), equivalent to 0.3-0.5 mg iron kg(-1) x day(-1). A linear relation (PK/PD) was recorded between exposure to ICL670 and total iron excretion, by contrast with placebo (r2=0.54, p<0.0001). Skin rashes were noted in four patients treated at 20 and 40 mg x kg(-1) x day(-1), and one patient also developed grade 2 transaminitis. INTERPRETATION ICL670 given once daily at 20 mg/kg seems to be an effective orally active iron chelator and is reasonably well tolerated. Long-term studies are now necessary to establish the practical contribution of this drug.

Relative response of patients with myelodysplastic syndromes and other transfusion-dependent anaemias to deferasirox (ICL670): a 1-yr prospective study

Objectives/methods:  This 1‐yr prospective phase II trial evaluated the efficacy of deferasirox in regularly transfused patients aged 3–81 yrs with myelodysplastic syndromes (MDS; n = 47), Diamond–Blackfan anaemia (DBA; n = 30), other rare anaemias (n = 22) or β‐thalassaemia (n = 85). Dosage was determined by baseline liver iron concentration (LIC).

How I treat thalassemia

The purpose of this article is to set forth our approach to diagnosing and managing the thalassemias, including β-thalassemia intermedia and β-thalassemia major. The article begins by briefly describing recent advances in our understanding of the pathophysiology of thalassemia. In the discussion on diagnosing the condition, we cover the development of improved diagnostic tools, including the use of very small fetal DNA samples to detect single point mutations with great reliability for prenatal diagnosis of homozygous thalassemia. In our description of treatment strategies, we focus on how we deal with clinical manifestations and long-term complications using the most effective current treatment methods for β-thalassemia. The discussion of disease management focuses on our use of transfusion therapy and the newly developed oral iron chelators, deferiprone and deferasirox. We also deal with splenectomy and how we manage endocrinopathies and cardiac complications. In addition, we describe our use of hematopoietic stem cell transplantation, which has produced cure rates as high as 97%, and the use of cord blood transplantation. Finally, we briefly touch on therapies that might be effective in the near future, including new fetal hemoglobin inducers and gene therapy.

Hepcidin as a therapeutic tool to limit iron overload and improve anemia in β-thalassemic mice

Excessive iron absorption is one of the main features of β-thalassemia and can lead to severe morbidity and mortality. Serial analyses of β-thalassemic mice indicate that while hemoglobin levels decrease over time, the concentration of iron in the liver, spleen, and kidneys markedly increases. Iron overload is associated with low levels of hepcidin, a peptide that regulates iron metabolism by triggering degradation of ferroportin, an iron-transport protein localized on absorptive enterocytes as well as hepatocytes and macrophages. Patients with β-thalassemia also have low hepcidin levels. These observations led us to hypothesize that more iron is absorbed in β-thalassemia than is required for erythropoiesis and that increasing the concentration of hepcidin in the body of such patients might be therapeutic, limiting iron overload. Here we demonstrate that a moderate increase in expression of hepcidin in β-thalassemic mice limits iron overload, decreases formation of insoluble membrane-bound globins and reactive oxygen species, and improves anemia. Mice with increased hepcidin expression also demonstrated an increase in the lifespan of their red cells, reversal of ineffective erythropoiesis and splenomegaly, and an increase in total hemoglobin levels. These data led us to suggest that therapeutics that could increase hepcidin levels or act as hepcidin agonists might help treat the abnormal iron absorption in individuals with β-thalassemia and related disorders.

Bone loss caused by iron overload in a murine model: importance of oxidative stress.

Osteoporosis is a frequent problem in disorders characterized by iron overload, such as the thalassemias and hereditary hemochromatosis. The exact role of iron in the development of osteoporosis in these disorders is not established. To define the effect of iron excess in bone, we generated an iron-overloaded mouse by injecting iron dextran at 2 doses into C57/BL6 mice for 2 months. Compared with the placebo group, iron-overloaded mice exhibited dose-dependent increased tissue iron content, changes in bone composition, and trabecular and cortical thinning of bone accompanied by increased bone resorption. Iron-overloaded mice had increased reactive oxygen species and elevated serum tumor necrosis factor-α and interleukin-6 concentrations that correlated with severity of iron overload. Treatment of iron-overloaded mice with the antioxidant N-acetyl-L-cysteine prevented the development of trabecular but not cortical bone abnormalities. This is the first study to demonstrate that iron overload in mice results in increased bone resorption and oxidative stress, leading to changes in bone microarchitecture and material properties and thus bone loss.

Bone Disease in Thalassemia: A Frequent and Still Unresolved Problem

Adults with β thalassemia major frequently have low BMD, fractures, and bone pain. The purpose of this study was to determine the prevalence of low BMD, fractures, and bone pain in all thalassemia syndromes in childhood, adolescence, and adulthood, associations of BMD with fractures and bone pain, and etiology of bone disease in thalassemia. Patients of all thalassemia syndromes in the Thalassemia Clinical Research Network, ≥6 yr of age, with no preexisting medical condition affecting bone mass or requiring steroids, participated. We measured spine and femur BMD and whole body BMC by DXA and assessed vertebral abnormalities by morphometric X‐ray absorptiometry (MXA). Medical history by interview and review of medical records, physical examinations, and blood and urine collections were performed. Three hundred sixty‐one subjects, 49% male, with a mean age of 23.2 yr (range, 6.1–75 yr), were studied. Spine and femur BMD Z‐scores < −2 occurred in 46% and 25% of participants, respectively. Greater age, lower weight, hypogonadism, and increased bone turnover were strong independent predictors of low bone mass regardless of thalassemia syndrome. Peak bone mass was suboptimal. Thirty‐six percent of patients had a history of fractures, and 34% reported bone pain. BMD was negatively associated with fractures but not with bone pain. Nine percent of participants had uniformly decreased height of several vertebrae by MXA, which was associated with the use of iron chelator deferoxamine before 6 yr of age. In patients with thalassemia, low BMD and fractures occur frequently and independently of the particular syndrome. Peak bone mass is suboptimal. Low BMD is associated with hypogonadism, increased bone turnover, and an increased risk for fractures.

The effect of deferasirox on cardiac iron in thalassemia major: impact of total body iron stores.

We present results from a prospective, multicenter, open-label, single-arm study evaluating response of cardiac and liver iron to deferasirox therapy for 18 months. Twenty-eight patients with abnormal T2* and normal left ventricular ejection fraction were enrolled from 4 US centers. All patients initially received deferasirox doses of 30 to 40 mg/kg per day. Patients were severely iron overloaded: mean liver iron concentration (LIC) 20.3 mg Fe/g dry weight, serum ferritin 4417 ng/mL, and cardiac T2* 8.6 ms. In the intent-to-treat population, 48% reached the primary endpoint (cardiac T2* improvement at 18 months, P = not significant). There were 2 deaths: 1 from congestive heart failure and 1 from sepsis. In the 22 patients completing the trial, LIC and cardiac T2* improvements were 16% (P = .06) and 14% (P = .07), respectively. Cardiac T2* improvement (13 patients) was predicted by initial LIC, final LIC, and percentage LIC change, but not initial cardiac T2*. Cardiac iron improved 24% in patients having LIC in the lower 2 quartiles and worsened 8.7% in patients having LIC in the upper 2 quartiles. Left ventricular ejection fraction was unchanged at all time points. Monotherapy with deferasirox was effective in patients with mild to moderate iron stores but failed to remove cardiac iron in patients with severe hepatic iron burdens. This study was registered at www.clinicaltrials.gov as #NCT00447694.

Decreased differentiation of erythroid cells exacerbates ineffective erythropoiesis in β-thalassemia

In beta-thalassemia, the mechanism driving ineffective erythropoiesis (IE) is insufficiently understood. We analyzed mice affected by beta-thalassemia and observed, unexpectedly, a relatively small increase in apoptosis of their erythroid cells compared with healthy mice. Therefore, we sought to determine whether IE could also be characterized by limited erythroid cell differentiation. In thalassemic mice, we observed that a greater than normal percentage of erythroid cells was in S-phase, exhibiting an erythroblast-like morphology. Thalassemic cells were associated with expression of cell cycle-promoting genes such as EpoR, Jak2, Cyclin-A, Cdk2, and Ki-67 and the antiapoptotic protein Bcl-X(L). The cells also differentiated less than normal erythroid ones in vitro. To investigate whether Jak2 could be responsible for the limited cell differentiation, we administered a Jak2 inhibitor, TG101209, to healthy and thalassemic mice. Exposure to TG101209 dramatically decreased the spleen size but also affected anemia. Although our data do not exclude a role for apoptosis in IE, we propose that expansion of the erythroid pool followed by limited cell differentiation exacerbates IE in thalassemia. In addition, these results suggest that use of Jak2 inhibitors has the potential to profoundly change the management of this disorder.

Prolonged survival in patients with beta-thalassemia major treated with deferoxamine

To determine whether survival of patients with beta-thalassemia major has been prolonged by management that utilizes hypertransfusion and chelation with deferoxamine, we analyzed longevity by the Kaplan-Meier product-limit method. Group 1 patients (n = 71) followed between 1960 and 1976 with a low-transfusion regimen (pretransfusion hemoglobin level 7 to 8 gm/dl) and no chelation had an estimated median age of survival of 17.4 years, whereas it was 31.0 years for group 2 subjects (n = 80), who began hypertransfusion between 1976 and 1978 (pretransfusion hemoglobin level 10.5 to 11.5 gm/dl) and chelation with deferoxamine (20 to 60 mg/kg per day) (p less than 0.0001). For 70 patients who were treated with hypertransfusion and deferoxamine, we had data to calculate the ratio of total milligrams of transfusional iron to cumulative grams of deferoxamine. The 24 patients who died had a total iron burden of greater than 1.05 gm/kg; the ratio for them exceeded 31. These patients were characterized by poor compliance with chelation or by late start of therapy, with inability to receive enough deferoxamine before death. Death was preceded by arrhythmia requiring therapy in all but one, and by cardiac failure in all. Of 41 similarly iron-loaded survivors, 33 had a ratio of less than 31; only three had an arrhythmia, and five had cardiac failure. We conclude that treatment with deferoxamine, when used in amounts proportional to iron burden, delayed cardiac complications and improved longevity.

Differences in the prevalence of growth, endocrine and vitamin D abnormalities among the various thalassaemia syndromes in North America.

This study aimed to determine differences in the rates of growth, endocrine‐ and calcium‐related abnormalities in the various thalassemia syndromes in North America treated with current therapies. Medical history, physical examinations and blood and urine collections were obtained from patients with all thalassemia syndromes age 6 years and older in the Thalassemia Clinical Research Network. 361 subjects, 49% male, mean age 23·2 years (range 6·1–75 years) were studied. Approximately 25% of children and adults, regardless of the thalassemia syndrome, had short stature. Overall growth in children was mildly affected. Final height was close to midparental height (z = −0·73 ± 1·24). Patients with beta thalassemia major (TM) had higher rates of hypogonadism, multiple endocrinopathies, worse hyperglycaemia, subclinical hypoparathyroidism and hypercalciuria. Hypogonadism remained the most frequent endocrinopathy and was frequently under‐treated. 12·8% of the subjects had 25 vitamin D concentrations less than 27 nmol/l and 82% less than 75 nmol/l, regardless of the thalassemia syndrome. Adolescents had lower 25 vitamin D levels than children and adults. Compared to patients with other thalassemia syndromes, those with beta TM suffered from higher rates of multiple endocrinopathies, abnormal calcium metabolism and hypercalciuria. Vitamin D abnormalities were high among adolescents.