Mecasermin: new drug. Insufficient improvement in statural growth

(1) Human insulin-like growth factor type 1 (IGF-1) is the main effector of growth hormone action. Primary IGF-1 deficiency is a rare disease, mainly resulting in very short stature; (2) Mecasermin is a recombinant IGF-1 marketed for this indication as a twice daily subcutaneous injection; (3) Clinical evaluation is mainly based on a non-comparative follow-up study of 76 children with an average age of 7 years, some of whom were treated for 8 years. The mean height at treatment initiation was 6.7 standard deviations below normal. Eight years later, it was 5.2 standard deviations below normal, i.e. their growth failure remained very severe; (4) The main short-term adverse effects of mecasermin are hypoglycaemia, headache and intracranial hypertension. Nearly one in 5 children developed tonsillar hypertrophy, resulting in otitis and hypoacusis; (5) Animal studies showed hypertrophy of other organs (kidneys, spleen and heart) as well as carcinogenic effects. The risk in humans is unknown; (6) The mecasermin packaging is not well-adapted (a multidose vial designed to be punctured several times), and is a potential source of contamination and errors. Prefilled pens or syringes would be easier to use; (7) In practice, the limited clinical benefits of mecasermin do not justify exposure to its potential risks.