British Journal of Haematology, 1990. 76, 5 50-553

L 1 (1,2-dimethyl-3-hydroxypyrid-4-one) for oral iron chelation in patients with beta-thalassaemia major

PETRIN TONDURY, GEORGE J. KONTOGHIORGHES,* ANNETTE RIDOLFI-LUTHY, ANDREAS HIRT, A. VICTOR HOFFBRAND,* ANNE MARIE LOTTENBACH, THEO SONDEREGGER? A N D HANS P. WAGNER Department of Pediatrics and TCentraf Pharmacy, University Hospitals. Inselspital, Bern, Switzerland, and *Department of Haematology, Royal Free Hospital School of Medicine, London

Received 23 April 1990; acceptedfor publication 28 August 1990

Summary. L1 was given to eight patients with beta-thalas- saemia major who had previously been treated with deferox- amine (DF) for 4-10 years. The patients’ ages ranged from 11 to 2 7 years. Serum ferritin values ranged from 1 . 3 to 11.5 x l o3 pg/L L1 was given twice daily at a daily dose of 55-80 mg/kg body weight and was continued for 10 months in two patients, 9 months in three, 7 months in two patients and 4 months in one patient. As previously observed with DF, each patient’s urinary iron excretion (UIE) varied greatly from day to day. The mean UIE of the eight patients ranged from 11 to 49 mg/d (0.2-0.87 mmol/d) on subcutaneous DF

and from 16 to 5 3 mg/d (0.28-0.95 mmol/d) on L1. Two patients excreted significantly more and one patient signifi- cantly less iron while on L1. If the UIE was calculated as mmol Fe/mmol creatinine there was no statistically signifi- cant difference. Serum ferritin values fluctuated widely in all, with a consistent downward trend in three, no change in four and an increase in one of two non-splenectomized patients. This patient’s splenomegaly and need for transfusions con- tinued to increase while on L1. No toxicities attributable to the drug were detected during the period of study and tolerance of the drug was excellent.

The treatment of transfusional iron overload is hampered by the lack of a cheap, safe and orally active iron chelator. Deferoxamine JDF) is the only well-established and widely used iron chelator. but DF is orally inactive and expensive (Pippard, 1989: Hoffbrand & Wonke, 1989). In children and adolescents with thalassaemia major DF chelation is cumber- some and compliance often unsatisfactory (Cohen, 1987). Attempts to develop orally active chelators have been frustrating.

The most promising agents are the alpha-ketohydroxy- pyridines (Kontoghiorghes & Hoffbrand. 1988: Porter et 01, 1989a. b). 1,2-dialkyl-3-hydroxypyrid-4-ones can be syn- thesized in a cheap, one-step reaction from the natural plant product maltol or its ethyl homologue and the related alkylamine (Kontoghiorghes & Sheppard. 198 7).

One of the best tolerated orally active iron chelators is 1.2-dimethyl-3-hydroxypyrid-4-one (L1) (Kontoghiorghes, 1986: Kontoghiorghes et al, 1989b). This compound was first administered to three patients with myelodysplasia (Kontoghiorghes et al, 1987b). Within 1 2 h increased urinary iron excretion (UIE) was observed while urinary

Correspondence: Professor Hans P. Wagner, Department of Pedia- trics, University Hospitals, Inselspital, 3010 Bern, Switzerland.

excretion of zinc, calcium and magnesium was unaffected. More extensive studies on six patients with beta-thalassaemia major (Kontoghiorghes et al, 1987a. 1988a, b, 1989a) revealed that: (i) doses of L 1 >2 g daily were needed to produce effective UIE: (ii) the level of IJIE increased with the dose of L l and with the degree of iron load of the patient: (iii) coadministration of ascorbic acid might further increase UIE in some but not all patients; (iv) doses of > 50 mg/kg body weight induced UIE of > 2 5 mg/d in some cases suggesting that a negative iron balance could be achieved despite regular blood transfusions: (v) overall UIE after comparable doses of DF and L 1 was equivalent: (vi) fecal iron excretion after administration of L1 and DF to patients with similar iron loads and maintained at comparable haemoglobin levels needed further study: and (vii) no acute toxicity was observed after single doses of 4 g and divided doses of up to 16 g daily and no major longer-term toxicity was registered in patients treated up to a maximum of 15 months (Kontoghiorghes et ai, 1989b), except agranulocytosis and thrombocytopenia in a patient with Blackfan-Diamond anaemia receiving L1, although there was no direct evidence that the drug caused this problem (Hoffbrand et al, 1989).

In view of the limited experience with long-term oral administration of L1 to human subjects, we performed a pilot

5 50

L1 in ~-Thalassaemia Major 551

Table I. Clinical details of patients

Patient

7 1 I 3 4 5 6 7 8

Year of birth Sex

Splenectomy

Weight (kg)

Onset DF (s.c.) Dose DF DF/year (nights)

Other drugs

Months on L l (January 1990) Dosage L 1

Serum ferritin (pg/l) Onset of L 1 Last on L 1

1975 F

-

46

1982 2 g 240

FA

70 2 x 2 g

3 700 3530

1978 M

-

31

1984 I g 240

FA

10 2 x l g

4400 5790

1977 F

1988

30

1983 1 g 240

FA/P

9 2 x 1 g

2500 2710

1978 M

I986

24

1985

180

FA/P

9

l g

L x l g

5 500 2520

1971 M

1976

5 0

1981 2.g 60 + FA

7 2 x 2 g

1 1 500 6380

1971 1968 1962 M M F

1984 1987 1967

43 70 52

1982 1979 1979

80 240 120

FA FA/P FA

9 4 7 2 x 2 g 2 x L g 2 x L g

2 g 2 g 2 g

2150 1380 2350 1112 1180 2180

DF = deferoxamine; FA = folic acid; P = penicillin prophylaxis.

study of L 1 therapy in eight patients with beta-thalassaemia major. in seven patients for 7-10 months.

PATIENTS AND METHODS

The Institutional Review Board of the Universitaets-Kinder- klinik in Berne approved this clinical trial. Written informed consent was obtained from all patients. Thirteen children and adolescents with beta-thalassaemia major were initially considered for L1 treatment. Five were excluded for different reasons: age below 10 years (three patients), cardiac compli- cations (one patient) and lymphadenopathy syndrome (one HIV positive patient). The remaining eight patients had received subcutaneous DF for 4-10 years with regular clinical assessment and tests of their haematological, bio- chemical and endocrinological status, UIE and serum ferritin levels. In all patients haemoglobin levels were maintained above 9-10 g/dl. Clinical details are listed in Table I.

Prior to the first dose of L1, the following baseline studies were performed: full blood count, plasma or serum sodium, potassium, calcium, phosphorus, iron, iron binding capacity, ferritin, uric acid, creatinine, bilirubin, GOT, GPT, ganima- GT. fructosamine, IgE. LH, FSH. growth hormone levels. A glucose tolerance test, ECG and echocardiograni, computer- ized tomographic scan of the liver with determination of the hepatic density were also carried out.

L1 was initially administered in gelatine capsules contain- ing 0.2 5 g each, later in tablets containing the same amount of L1, at least 1 h before breakfast and 1 h before or after supper. The individual daily dosage of L 1 varied between 57 and 87 mg/kg body weight (Table I). L 1 was supplied by G.J.K. L 1 had been synthesized and its purity confirmed as previously described (Kontoghiorghes & Sheppard. 1987). UIE was determined by 24 h urine collection, daily in the first

week, then twice weekly for 1 month, and weekly thereafter. Urine iron was assessed by atomic absorption spectroscopy. Before L1 therapy, DF induced UIE had been monitored at 1- 2 months intervals. Urinary creatinine was measured in order to rule out incomplete sampling and to reduce the bias of sequential rather than alternate assessment of DF- and L1-induced UIE. UIE on L 1 and DF were compared by comparing all values obtained during L1 therapy with all values obtained during the last 1-3 years of DF treatment preceeding L1 therapy. The interval between DF and L1 therapy was short, less than 2 weeks in all, less than 1 week in the majority of the patients. Haematological and chemical parameters were monitored weekly during the first month of L1 therapy and every fortnight during the following months. Three patients first received L 1 alone for 2 or 3 months, then had L1 and 200 mg of vitamin C daily for 5 or 6 months and finally continued on L 1 alone.

Statistical analysis was performed using the t-test.

RESULTS

UIE after comparable doses of L1 varied considerably from patient to patient. The daily UIE varied between 11 and 49 mg/d (0.2-0.87 mmol/d) and was similar in 5/8. higher in 218 and lower in 1/8 patients than after subcutaneous DF (Table 11). If the mean daily UIE was calculated in mmol per mmoI creatinine no statistically significant differences were observed. No significant increase of UIE was noted, when the patients took 200 mg of ascorbic acid daily with the first dose of L1 (Table 111).

No subjective symptoms were noted. There were no significant changes in haematological and biochemical para- meters. Transaminases were increased above the normal range (30-3 10 U/I) in all patients before L1 was started and

552 Petrin Tondury et a1 Table 11. Mean iron excretion in mmol per day (absolute or per mmol creatinine)

Patient

I 2 3 4 5 6 7 8

Fe/24 h (mmol) Creatinine/24 h (mrnol) (mean& 1 SD) ( n ) DF 0.089f0.042 0.087f0.046 0,045f0.027 0.062zk0.039 0.0'7310.052 0.068zk0002 0.056f0.015 N.D.

(20) (22, (32) (9) (11) ( 8 ) (19)

P n.s. n.s. n.s. n.s. n.s. ns. n.s.

L l 0.078 10,018 0.062 f0.031 0.052 f0.019 0.06k0.02 0.076f0.038 0.087zk0.025 0.04if0.015 N.D. (20) (22) (41) (45) (29) (25) (21)

DF = deferoxamine; L 1 = 1,2-dimethyl-3-hydroxypyrid-4-one: P = significance of t-test; n.s. =not statistically significant: N.D. =not done.

Table HI. Comparison of urinary iron excretion after L1 to f vitamin C administration

Patient

1 2 4

Fe/24 h (mmol) (mean & 1 SD)) in) L 1 0.92f0.31 0.51f0.34 0.23f0.02

(11) (11) (9)

P n.s. n.s. n.s

Ll+vitamin C 0.98f0.33 0.49f0.39 0.29f0.09 19) (11) (36)

Fe/24 h (mmol) Creatinine/24 h (mmol) (mean zk 1 SD) 01) L 1 0.072 +0.018 0.064zk00.032 0.05 fO.005

(11) (11) (9 1 P n.s. n.s ns .

(9) (11) (36) L 1 +vitamin C 0.085+0.016 0.06f0.031 0.06k0.02

L 1 = 1.2-dimethyl-3-hydroxypyrid-4-one: ns. =not statistically significant; P=significance of t-test.

remained stable in seven patients or decreased to borderline normal values in one patient. Hypercholesterolaemia was not observed. In one 11-year-old male patient (no. 2), the size of the spleen continued to increase during L 1 treatment and concomitantly more transfusions were required to maintain a haemoglobin level above 9 g/dl. Two years before L 1 this patient required 2 70 ml; 1 year before L 1 3 10 ml; and while

on L1 410 ml packed red cells/kg body weight/year. Splenectomy was therefore performed and, while still on L1, the need for packed red cells after splenectomy could be calculated as 195 ml/kg body weight/year. No evidence of autoimmune haemolysis was found.

Serum ferritin levels were monitored monthly. They continued to oscillate in the range observed before L 1 in four patients and showed a consistent trend downwards in three patients (Table I, nos. 4, 5 and 6). In patient 2 , who required more transfusions while on L1, an increase rather than a decrease was observed.

DISCUSSION

These preliminary results confirm earlier reports (Konto- ghiorghes et al, 1987a. 1988a. b, 1989a) that at least with regard to UIE L 1 is as effective an iron chelator as DF. UIE was maintained during L1 therapy. There appeared to be no cyclical UIE variations related to blood transfusions. For many patients receiving DF, compliance is a problem. In our experience patients with the best compliance infused DF on about 240 d/year, those with the poorest compliance only on about 60 d/year. Since compliance is not a problem with L1, iron chelation should be significantly improved with L 1 therapy, particularly in patients failing to comply with DF.

In the seven patients receiving L1 for 7-10 months no untoward reactions, in particular no transient arthralgia (Hoffbrand et al, 1989) or blood count abnormalities have been detected, despite the fact that in some of the rodent toxicity studies hypersalivation (Kontoghiorghes et al, 198 7c). anaemia, leucopenia and, in non-iron overloaded animals, unconfirmed interactions with barbiturates and retinal toxicity have been reported (Porter et ai, 1989a. b; Kontoghiorghes et al, 1 9 8 7 ~ . 1989b). In toxicity studies in

L l in P-Thalassaemia Major 5 5 3 normal rats given 1.2-dimethyl-3-hydroxypyrid-4-one (CP 94). 300 mg/kg daily by mouth for 30 d, hyperplasia of the adrenals and ovaries was found (Hider et al, 1990). Neither ophthalmic or auditory nor adrenal steroid monitoring was done in our patients.

The recognition of toxic side effects of chronically admini- stered drugs such as DF and L 1 may, however, take many years (Porter & Huehns, 1989). Therefore, large numbers of patients will have to be treated for prolonged periods of time, before the exact safety of any oral iron chelator can be fully assessed.

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