What Is Mecasermin Rinfabate? Definition and What Research Reports

Definition

Mecasermin rinfabate is the international non-proprietary name for a 1:1 molar complex of recombinant human insulin-like growth factor-I (rhIGF-I) and recombinant human insulin-like growth factor binding protein-3 (rhIGFBP-3), developed under the trade name iPLEX and referred to in the literature as the rhIGF-I/rhIGFBP-3 complex; a 2005 profile in Drugs in R&D catalogued the compound under this name alongside the variant spellings "mecaserimin rinfibate" that appeared in early records (PMID 15777106). In plain terms, the name describes one hormone-like protein packaged together with the carrier protein that normally transports it in human circulation, produced by recombinant DNA technology rather than extracted from tissue.

What Class of Molecule It Is

Mecasermin rinfabate is not a small synthetic peptide of the kind assembled on a solid-phase synthesiser. It is a two-component recombinant protein complex. The first component, IGF-I, is a single-chain polypeptide of 70 amino acids with structural homology to proinsulin. The second component, IGFBP-3, is a much larger glycoprotein that in the body binds the large majority of circulating IGF-I and, together with an acid-labile subunit, forms the ternary complex that acts as the body's IGF reservoir.

Where the molecule comes from

Both halves are recombinant: the human gene sequences are expressed in engineered host cells, purified, and then combined so that the IGF-I is presented already bound to its carrier. The stated pharmacological rationale, as summarised in a 2008 review of the complex in Expert Opinion on Drug Metabolism & Toxicology, was that pairing IGF-I with IGFBP-3 changes how the growth factor is handled after administration compared with free rhIGF-I given alone (PMID 18363546). The single-agent, unbound form of recombinant IGF-I carries its own separate non-proprietary name, mecasermin, which is why the two terms are frequently confused.

How the Term Is Used in Peptide Research

Within the growth-factor literature, "mecasermin rinfabate" is used in three fairly narrow ways:

• As a product name. Papers use it interchangeably with "rhIGF-I/rhIGFBP-3" and "iPLEX" when describing the specific manufactured complex rather than IGF-I biology in general.
• As a pharmacological contrast term. Authors invoke it when contrasting bound IGF-I delivery with free IGF-I delivery, because the binding protein is the variable under discussion (PMID 18363546).
• As an indication marker. The term appears in reviews of severe primary IGF-I deficiency and growth hormone insensitivity, and in reviews surveying investigational metabolic applications (PMID 16610982).

Because the complex is a licensed biologic in some jurisdictions rather than a research-only material, literature about it sits in clinical pharmacology journals rather than in the preclinical peptide-chemistry literature where many other entries in this glossary live. This page is for educational purposes only and is not medical advice; consult a licensed physician for any question about a medical condition or a medication.

What the Published Literature Reports

Three reference-level publications form the core of the accessible literature summarised here. A 2005 Drugs in R&D adis profile described mecasermin rinfabate as the rhIGF-I/rhIGFBP-3 complex under development for growth failure associated with growth hormone insensitivity and for several additional metabolic indications (PMID 15777106). A 2006 review in Expert Opinion on Biological Therapy examined the efficacy and safety record assembled to that point, and researchers framed the complex as an approach intended to deliver IGF-I while limiting the tolerability problems associated with unbound recombinant IGF-I (PMID 16610982). A 2008 review in Expert Opinion on Drug Metabolism & Toxicology focused specifically on the metabolism and toxicology of the complex marketed as iPLEX (PMID 18363546).

The recurring theme across these sources is pharmacokinetic modification. Free IGF-I is cleared rapidly and, because of its structural similarity to insulin, can act at the insulin receptor. The reviews reported that binding IGF-I to IGFBP-3 before administration was intended to extend circulating exposure and to moderate the acute, insulin-like effects of a free growth factor bolus (PMID 18363546). Reported clinical interest centred on growth failure in children whose bodies produce growth hormone but cannot respond to it normally, a setting in which IGF-I replacement rather than growth hormone is the physiological target (PMID 16610982).

Tolerability and Safety Signals: What Studies Report

Safety discussion in this literature is dominated by the insulin-like activity of IGF-I. The 2006 efficacy-and-safety review examined hypoglycaemia as the characteristic class concern for recombinant IGF-I therapy and discussed the binding-protein complex in that context (PMID 16610982). The 2008 toxicology-oriented review likewise addressed the toxicological profile of the rhIGF-I/rhIGFBP-3 complex rather than treating it as pharmacologically identical to free IGF-I (PMID 18363546). Neither review is reproduced here in numerical detail, and no dosing figures are stated on this page because dose selection for a growth-factor biologic is a clinical decision made under medical supervision, not a reference-entry fact.

Regulatory and Naming Context

Two practical points help readers interpret older sources:

1. Mecasermin and mecasermin rinfabate are different entries. Mecasermin is recombinant IGF-I alone; mecasermin rinfabate is IGF-I complexed with IGFBP-3 (PMID 15777106). Literature searches that conflate the two will return mismatched safety and pharmacokinetic material.
2. Trade names travel with the term. The complex appears in the literature as iPLEX, which is the label used in the 2008 pharmacology review (PMID 18363546). Commercial availability of biologics changes over time and by jurisdiction, and regulatory status is not addressed on this page.

Mecasermin rinfabate is not a research chemical distributed for laboratory use in the way many investigational peptides are; it is a manufactured biologic whose literature sits in the clinical-pharmacology domain. Nothing here describes how the compound is administered, in what quantity, or for how long.

Summary of the Entry

Mecasermin rinfabate names a recombinant IGF-I/IGFBP-3 complex, developed as iPLEX, whose defining feature is that the growth factor is supplied already bound to its natural carrier protein. Published reviews described this pairing as an attempt to alter the pharmacokinetic and tolerability profile of IGF-I therapy and surveyed its investigation in growth failure related to growth hormone insensitivity and in metabolic settings (PMID 16610982, PMID 18363546). Readers comparing sources should confirm whether a given paper refers to the complex or to unbound mecasermin, because the two names describe different products.

References

• Mecasermin rinfabate: rhIGF-I/rhIGFBP-3 complex: iPLEX (Expert Opinion on Drug Metabolism & Toxicology, 2008)
• Efficacy and safety of mecasermin rinfabate (Expert Opinion on Biological Therapy, 2006)
• Mecasermin rinfabate: insulin-like growth factor-I/insulin-like growth factor binding protein-3, mecaserimin rinfibate, rhIGF-I/rhIGFBP-3 (Drugs in R&D, 2005)