The Pharmaceutical Journal Vol 267 No 7176 p767-773
1 December 2001

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Growth hormone receptor antagonist effective treatment for acromegaly

Pegvisomant, a new growth hormone receptor antagonist produced by Sensus Drug Development Corp, is effective in the long-term treatment of acromegaly, a new study has shown.

The study is an extension of a previously published 12-week trial of pegvisomant, which showed improvement in the clinical symptoms of acromegaly and normalisation of insulin-like growth factor-1 (IGF-1) (see PJ, 13 May 2000, p718). The increase in the production of IGF-1 in patients with acromegaly is caused by excessive production of growth hormone.

Dr Aart Jan van der Lely, Erasmus Medical Centre, Rotterdam, the Netherlands, and colleagues assessed the effects of pegvisomant in 160 patients treated with daily subcutaneous injections of the drug for up to 18 months. Daily doses of pegvisomant began at 10mg per day and were titrated up or down, in increments of 5mg, until the patient's serum IGF-1 concentration was normal or a maximum dose of 40mg had been reached.

The researchers say that mean serum IGF-1 concentrations fell by at least 50 per cent in patients treated for six, 12 and 18 months. Normal serum IGF-1 concentrations were achieved in 97 per cent of patients (87 out of 90) treated for 12 months or more, and this response rate is high compared with the response rate of approximately 65 per cent obtained with existing medical treatments such as dopamine agonists and somatostatin analogues, they say. Increases in mean serum growth hormone concentrations were seen which mirrored falls in serum IGF-1 concentrations.

The researchers also say that long-term efficacy of pegvisomant is thought to be compromised by the development of antibodies to growth hormone or to pegvisomant. In the study 16.9 per cent of patients tested positive for antibodies to pegvisomant. They add that patients with acromegaly are insulin-resistant and that up to 30 per cent of untreated patients with acromegaly have been previously reported to develop type 2 diabetes. They say that in their study, fasting serum insulin and glucose concentrations fell significantly in patients treated with pegvisomant for up to 18 months, even though none of these patients were overtly diabetic at baseline (Lancet 2001;358:1754).

In an accompanying editorial, Dr Ken K. Y. Ho, Garvan Institute of Medical Research, St Vincent's Hospital, Sydney, says: "Despite being the most effective of all available treatments, it is unlikely to claim a place as primary treatment because it exerts control by blocking hormone action rather than acting on the tumour. Surgery remains first-line treatment for most patients with acromegaly." (Ibid, p1743.)

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