Mecasermin Rinfabate: Insulin-Like Growth Factor-I/Insulin-Like Growth Factor Binding Protein-3, Mecaserimin Rinfibate, rhIGF-I/rhIGFBP-3

Insulin growth factor binding proteins as therapeutic targets in type 2 diabetes

INTRODUCTION

The signaling pathways of the insulin-like growth factors (IGFs) have been implicated in the aetiology of type 2 diabetes (T2D) and a number of therapeutic modalities aiming at the IGF-axis have been considered. Administration of IGF-I has been reported to improve insulin sensitivity in healthy subjects and patients with T2D. In recent years, the IGF binding proteins (IGFBPs) have also been associated with metabolic disorders, prompting the idea that IGFBPs play important roles in the pathogenesis of T2D. Thus, by virtue of their role in the regulation of IGF effects, the IGFBPs have emerged as potential biomarkers and therapeutic targets in metabolic syndromes and T2D.

AREAS COVERED

The article provides an overview on recent findings in clinical and experimental IGFBP-research and addresses the studies that have investigated the potentials of the IGFBPs as therapeutic targets in T2D.

EXPERT OPINION

There is plenty of therapeutic promise within the IGF system, but further understanding of the IGFs in T2D is necessary to avoid off-target effects. Strong evidence supports the use of IGFBPs as therapeutic targets in the treatment of T2D, and it is not difficult to foresee the use of IGFBPs as part of a combination therapy alongside other anti-diabetic drugs.

Anaphylactic reaction to recombinant insulin-like growth factor-I

Mecasermin [rDNA] (Increlex; Tercica, Inc.) is recombinant insulin-like growth factor-I (IGF-I) that has been approved to treat growth failure in children with severe primary IGF-I deficiency. Serious allergic reactions related to Increlex therapy have not been reported. We report a 13 year-old male who developed life-threatening anaphylaxis early in the course of Increlex therapy.

Efficacy and safety of mecasermin rinfabate

There has been interest in using recombinant human (rh) insulin-like growth factor (IGF)-I (rhIGF-I) to treat short stature, either alone or in combination with its binding protein (insulin-like growth factor binding protein [IGFBP]-3). IGF-I has been shown to increase growth velocity in children with IGF deficiency, either as a result of growth hormone insensitivity syndrome (GHIS) or IGF gene deletion. However, there have been adverse events, particularly hypoglycaemia, reported with administration of unbound rhIGF-I. In addition, the serum half-life of unbound rhIGF-I is shorter when administered to patients with GHIS, who have low serum concentrations of its binding proteins IGFBP-3 and acid-labile subunit (ALS), than when administered to normal volunteers or to the patient with an IGF-I gene deletion (who had normal levels of IGFBP-3). iPlex (mecasermin rinfabate), an equimolar mixture of IGF-I and its binding protein IGFBP-3, was developed to prolong the half-life and to counteract acute adverse events (particularly hypoglycaemia) associated with administration of IGF-I. Although there are no published data on the efficacy of mecasermin rinfabate in treating growth disorders, it does appear that mecasermin rinfabate has a longer half-life in patients with GHIS than unbound IGF-I, and fewer reports of adverse events (including hypoglycaemia) when administered to patients with diabetes.

Investigational agents for the treatment of growth hormone-insensitivity syndrome

Growth hormone-insensitivity syndrome (GHIS) is usually caused by mutations in the growth hormone receptor. Recombinant IGF-I has been used to treat GHIS either alone (mecasermin) or in combination with IGF-binding protein (IGFBP)-3 (mecasermin rinfabate). IGF-I increases the growth velocity of children with IGF deficiency, which is either as a result of GHIS or an IGF-I gene deletion. Hypoglycaemia has been reported with administration of unbound IGF-I and, in addition, the serum half-life of unbound IGF-I is shorter when administered to patients with GHIS (who have low serum concentrations of its binding protein IGFBP-3) than when administered to normal volunteers or to patients with an IGF-I gene deletion (but normal IGFBP-3 levels). The IGF-I-IGFBP-3 combination was developed to prolong the half-life and counteract the acute adverse events (particularly hypoglycaemia) that are associated with administration of IGF-I. It seems that the IGF-I-IGFBP-3 combination has a longer half-life in patients with GHIS than unbound IGF-I, with fewer reports of adverse events (including hypoglycaemia) when administered to patients with diabetes. There are no studies comparing the efficacy of mecasermin with mecasermin rinfabate; both drugs have been shown to be effective but cannot be differentiated in terms of efficacy.