B. Wonke

Effective chelation of iron in beta thalassaemia with the oral chelator 1,2-dimethyl-3-hydroxypyrid-4-one.

The main iron chelator used for transfusional iron overload is desferrioxamine, which is expensive, has toxic side effects, and has to be given subcutaneously. An orally active iron chelator is therefore required. The effects of oral 1,2-dimethyl-3-hydroxypyrid-4-one on urinary iron excretion were studied in eight patients who had received multiple transfusions: four had myelodysplasia and four beta thalassaemia major. Different daily doses of the drug up to 100 mg/kg/day, alone or in combination with ascorbic acid, were used. In three patients with thalassaemia the effect of the drug was compared with that of subcutaneous desferrioxamine at the same daily dose. In all eight patients a single dose of oral 1,2-dimethyl-3-hydroxypyrid-4-one resulted in substantial urinary iron excretion, mainly in the first 12 hours. Urinary iron excretion increased with the dose and with the degree of iron loading of the patient. Giving two or three divided doses over 24 hours resulted in higher urinary iron excretion than a single dose of the same amount over the same time. In most patients coadministration of oral ascorbic acid further increased urinary iron excretion. 1,2-Dimethyl-3-hydroxypyrid-4-one caused similar iron excretion to that achieved with subcutaneous desferrioxamine at a comparable dose. In some cases the iron excretion was sufficiently high (maximum 99 mg/day) to suggest that a negative iron balance could be easily achieved with these protocols in patients receiving regular transfusions. No evidence of toxicity was observed on thorough clinical examination or haematological and biochemical testing in any of the patients. None of the patients had any symptoms that could be ascribed to the drug. These results suggest that the oral chelator 1,2-dimethyl-3-hydroxypyrid-4-one is as effective as subcutaneous desferrioxamine in increasing urinary iron excretion in patients loaded with iron. Its cheap synthesis, oral activity, and lack of obvious toxicity at effective doses suggest that it should be developed quickly and thoroughly tested for the management of transfusional iron overload.

Terminal Deoxynucleotidyl Transferase Expression in Acute Non-lymphoid Leukaemia: an Analysis by Immunofluorescence

Summary. Indirect immunofluorescence for terminal transferase enzyme (TdT) was used to study the blasts of 64 patients with acute non‐lymphoid leukaemia (ANLL). In 32 patients no TdT positive cells were seen. In 19 cases a small subpopulation of cells expressing TdT was detected; these constituted up to 5% of total nucleated cells, and it was not clear whether these TdT positive cells were part of the leukaemic process or represented residual normal bone marrow lymphoid cells.

Serum non‐transferrin‐bound iron in beta‐thalassaemia major patients treated with desferrioxamine and L1

Summary. Non‐transferrin‐bound iron (NTBI) in plasma is toxic due to its ability to participate in free radical formation with resultant peroxidation and damage to cell membranes and other biomolecules. NTBI concentration was determined in serum in 12 normal volunteers and in 52 patients with β‐thalassaemia major by a modification of the method described by Singh et al (1990). There was no detectable NTBI in normal individuals. In the patients NTBI values ranged from −1.5 to 9.0 μmol/l (mean ± SD: 3.6 ± 2.3). The patients’serum ferritin concentrations ranged from 207 to 11400 μg/l (2674±2538), total serum iron from 20 to 61 μmol/l (39.5 ± 9.6) and transferrin saturation from 44 to 110% (84.5 ± 13.8). The NTBI correlated significantly with serum ferritin (r=0.467, P < 0.001), total serum iron (r=0.608, P<0.001) and transferrin saturation (r=0.481, P<0.005). When patients were grouped according to their compliance with desferrioxamine (DFX) therapy, the good compliers had significantly lower NTBI concentrations compared to the poor compliers (poor: 5.4±1.8 μmol/l v good: 2.7±1.7 μmol/l, P<0.001). There was also a significant difference between the level of NTBI and whether or not the patients had complications of iron overload (5.2±1.7 μmol/l v 2.9±1.6 μmol/l, P <0.001). During this study 10 patients were entered into a trial of the oral iron chelator 1,2‐dimethy 1–3‐hydroxypyrid‐4‐one (L1). Their NTBI values were observed during the first 6 months of the trial and showed a significant fall (paired t‐test: P= 0.007). These results suggest that the level of NTBI may prove helpful in assessing the efficiency of chelation in patients with transfusion dependent anaemia and help to predict organ damage.

Deferiprone‐associated myelotoxicity

Abstract:  Agranulocytosis developed in a 63‐year‐old patient with myelodysplasia 6 weeks after commencing treatment with the oral iron chelator deferiprone (L1, 1,2‐dimethyl‐3‐hydroxypyrid‐4‐one, CP20) at a daily dose of 79 mg/kg. This was the 3rd case of agranulocytosis (neutrophils 0 times 109/***1) in clinical trials of L1 at the Royal Free Hospital. The neutrophil count recovered 7 days after stopping and commencing G‐CSF at a dose of 300 μg daily. Three other patients with milder degrees of neutropenia (neutrophils <1.5 times 109/1) have also been observed in our trials. The case histories of these 4 patients are described here; other reported cases of neutropenia or agranulocytosis are reviewed. Based on worldwide long‐term clinical trials the incidence of agranulocytosis is about 1.6% and of neutropenia 2%.

A novel delivery system for continuous desferrioxamine infusion in transfusional iron overload

Fifteen iron‐overloaded thalassaemia major (TM) patients and two homozygous sickle cell patients (SCD) were treated continuously for 7d each week with the novel 48h continuous subcutaneous (s.c.) desferrioxamine (DFX) delivery device (code C1083, Baxter) and 10 TM patients received the 24h continuous intravenous (i.v.) DFX delivery device (code C1071). The 27 patients had previously received conventional s.c. DFX for 8–10h on 5 or more days each week. The serum non‐transferrin bound iron (NTBI) levels fell significantly in both groups within 12h of commencing the continuous infusion. In the s.c. group the mean level fell from 4.2 to 2.0μmol/l (P=0.001), whereas in the i.v. group the mean level fell from 3.6 to 0.1μmol/l (P=0.006) the initial levels being measured 12h after stopping conventional s.c. DFX. After 4 weeks there was a significant fall in serum ferritin in both groups (P=0.009). The new DFX delivery device is effective at removing toxic‐free iron from plasma and reducing body iron. Moreover, it is preferred by patients with much improved compliance compared to the conventional s.c. DFX pump.

Agranulocytosis in a patient with thalassaemia major during treatment with the oral iron chelator, 1,2-dimethyl-3-hydroxypyrid-4-one

Agranulocytosis developed in a 20-year-old Greek patient with beta-thalassaemia major, 11 weeks after commencing chelation with the oral iron chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1) and 6 weeks after receiving the drug at a total daily dose of 105 mg/kg. The patient presented with generalised weakness, low-grade fever and sore throat. The total white cell count was 2.0 x 10(9)/l with 0.1 x 10(9)/l neutrophils. The patient was admitted to hospital and successfully treated with intravenous broad-spectrum antibiotics. Neutrophil count recovered 7 weeks later. A number of immunological tests were performed in an attempt to elucidate the cause of agranulocytosis. These investigations gave inconclusive evidence for the presence of a weak IgM antibody to myeloid cells exposed to L1 in this patient. Further studies are required, however, to evaluate the mechanism in any other patient who develops agranulocytosis in association with L1 therapy.

The effect of deferiprone (L1) and desferrioxamine on myelopoiesis using a liquid culture system

Summary. Agranulocytosis was observed in a 63‐year‐old patient with myelodysplasia 6 weeks after commencing chelation with the oral iron chelator deferiprone (1,2‐dimethyl‐3‐hydroxypyrid‐4‐one, L1) at a daily dose of 79 mg/kg. Using a liquid culture system no difference was observed when L1 toxicity to normal and patient myelopoiesis was compared (IC50: 150 v 172 μM respectively). L1 was found to be less toxic than desferrioxamine (DFX) (IC50: 150 u 9 μM respectively) to normal myelopoiesis. Delayed addition of iron to myeloid cultures containing an inhibitory concentration of L1 or DFX was associated with reversal of chelator‐induced inhibition of myelopoiesis up to 6 h but not after 24 h. Further studies are needed to determine the incidence and elucidate the pathogenesis of agranulocytosis associated with L1 therapy.

Management of Beta Thalasseamia Major

Homozygous /?-thalasseamia (implying defective fi globin production from both alleles) is a disorder which results from the defective synthesis of /Ihaemoglobin chains. It is one of the commonest inherited genetic disorders; 100 000 infants are born annually throughout the world. The condition is inherited in a Mendelian recessive manner. /?thalasseamia has arisen as a result of mutations or rarely deletions in and around the /? globin gene on chromosome 11. These have persisted within particular ethnic groups because of the selective advantage of relative protection against plasmodium falciparum malaria. Therefore the /I-thalasseamia gene is encountered in ethnic groups originating from the malaria belt - Mediterranean, Chinese, Arabic, and AfroCaribbean populations. /I-thalasseamia is rarely found in Northern Europeans, but the disease is found in Europe and North America because of population migrations. The UK Thalasseamia Register shows that at the end of 1992, 535 patients with /Sthalasseamia were alive and well. As a result of the basic genetic defect the P-thalasseamic red cells do not survive long in the circulation - this leads to severe aneamia which if not treated results in early death. In this article the emphasis will be on the treatment of the anaemia with blood transfusions and the management of the consequences of this treatment modality.