What Is Mecasermin? Definition and What Research Reports

Definition

Mecasermin is the international nonproprietary (generic) name for recombinant human insulin-like growth factor I, usually abbreviated rhIGF-1, and a 2009 review in Advances in Therapy used the name specifically to denote recombinant human insulin-like growth factor I rather than any modified analogue (PMID 19198769). In plain terms, mecasermin is a laboratory-manufactured copy of a growth factor the human body already makes: IGF-1 is a single-chain polypeptide hormone, structurally related to proinsulin, that is secreted largely by the liver under growth hormone stimulation and that acts on the IGF-1 receptor in many tissues. Because the recombinant molecule is intended to match the natural sequence, the word “mecasermin” in a paper title normally signals the unmodified human growth factor itself, not a peptide fragment, a secretagogue, or a growth-hormone analogue.

This page is for educational purposes only and is not medical advice; consult a licensed physician for any question about diagnosis, treatment, or a specific medicine.

What Class of Molecule It Is

Mecasermin sits in the class of recombinant protein and polypeptide hormones — the same broad family as recombinant insulin or recombinant growth hormone — rather than in the class of short synthetic research peptides. That distinction matters for how the literature is organised:

• It is a full growth factor, not a fragment. Reviews refer to mecasermin as recombinant human IGF-I in its entirety (PMID 19198769).
• It acts through an endocrine receptor system. IGF-1 signalling overlaps partially with insulin signalling, which is why a case report and literature review examined mecasermin in the setting of insulin receptor-related severe insulin resistance syndromes (PMID 29695048).
• It exists in more than one formulation. A pharmacology review described mecasermin rinfabate as a complex of rhIGF-I with recombinant human IGF binding protein 3 (rhIGFBP-3), marketed under the name iPLEX (PMID 18363546).

Where It Comes From

Mecasermin is not extracted from human or animal tissue. It is produced by recombinant DNA technology, in which the human IGF-1 gene sequence is inserted into a host cell line that then expresses the protein for purification. A methods paper in Research in Pharmaceutical Sciences described recombinant production of mecasermin in an Escherichia coli expression system, illustrating the bacterial-expression route used for this class of molecule (PMID 26339260). Papers of this kind are process-development work: researchers reported on expression, folding and purification strategy rather than on clinical outcomes.

Mecasermin compared with mecasermin rinfabate

How the Term Is Used in Research

In the published record, “mecasermin” is used in three fairly distinct ways.

1. As a named prescription biologic. Mecasermin is the generic name behind an approved recombinant IGF-1 product indicated for severe primary IGF-1 deficiency; regulatory and pharmacology reviews therefore treat it as a licensed medicine rather than a research-only compound (PMID 19198769).
2. As an investigational agent in metabolic disease. Because IGF-1 can signal when insulin receptor function is impaired, a case report and review discussed mecasermin in insulin receptor-related severe insulin resistance syndromes (PMID 29695048).
3. As an investigational agent in neurodevelopmental disorders. The largest recent cluster of mecasermin papers concerns Rett syndrome, including a 2025 systematic review in Neurogenetics that evaluated mecasermin for the treatment of Rett syndrome (PMID 41174329).

A note on vocabulary: mecasermin is sometimes discussed alongside unrelated compounds simply because both involve the growth-hormone/IGF-1 axis. Growth hormone secretagogues and GH-releasing peptides act upstream to stimulate endogenous hormone release, whereas mecasermin is the downstream growth factor supplied directly. Papers that use the word “mecasermin” are referring to the recombinant protein.

What the Published Literature Reports

IGF-1 deficiency and insulin resistance syndromes

The pharmacology literature frames mecasermin around IGF-1 replacement. The 2009 Advances in Therapy review summarised mecasermin as recombinant human insulin-like growth factor I and situated it within IGF-1 deficiency states (PMID 19198769). A separate review in Expert Opinion on Drug Metabolism & Toxicology addressed the binding-protein complex mecasermin rinfabate (iPLEX), reflecting interest in how IGFBP-3 co-administration alters the disposition of recombinant IGF-1 (PMID 18363546). On the metabolic side, a 2018 paper in the International Journal of Molecular Sciences combined a case report with a review of the literature on mecasermin in insulin receptor-related severe insulin resistance syndromes, a group of rare conditions in which insulin signalling is genetically impaired (PMID 29695048).

Rett syndrome

Rett syndrome is the most heavily represented clinical context in the mecasermin literature indexed here. A 2016 report in Autism Research and Treatment described ten patients with Rett syndrome treated with recombinant human IGF-1 and examined illness severity, social and cognitive ability, and EEG analysis (PMID 26925263). A 2022 paper in Frontiers in Neuroscience took a biomarker approach, examining molecular signatures of response to mecasermin in children with Rett syndrome (PMID 35712450). Most recently, researchers published a systematic review in Neurogenetics in 2025 that pooled and appraised the available evidence on mecasermin for the treatment of Rett syndrome (PMID 41174329). Readers looking for outcome magnitudes should consult the study reports themselves, since sample sizes in this area have been small and endpoints have differed between papers.

Safety and Tolerability: What Studies Report

Safety information for mecasermin in the indexed literature sits mainly inside review articles and single-case reports rather than large dedicated safety studies. The mecasermin rinfabate review was published in a drug metabolism and toxicology journal and therefore covered disposition and safety considerations for the rhIGF-I/rhIGFBP-3 complex (PMID 18363546), while the 2009 review covered mecasermin as a recombinant IGF-1 product in clinical use (PMID 19198769). In the insulin resistance setting, the 2018 case report and literature review documented an individual patient course alongside previously published experience (PMID 29695048). Because mecasermin is a prescription biologic, adverse-event data are also captured in product labelling and pharmacovigilance systems that sit outside the scope of this glossary entry. No doses, schedules or event rates are listed here, because they are not within the title-and-abstract scope of the sources cited on this page.

Limits of the Evidence

• Rare-disease sample sizes. The Rett syndrome report described ten patients (PMID 26925263), and the insulin resistance paper was a single case report with a review attached (PMID 29695048).
• Mixed study types. The indexed sources include process-development work (PMID 26339260), narrative pharmacology reviews (PMID 18363546) and a systematic review (PMID 41174329), which are not interchangeable forms of evidence.
• Formulation matters. Findings described for mecasermin rinfabate do not automatically transfer to mecasermin alone, since the two differ by the presence of IGFBP-3 (PMID 18363546).
• Biomarker work is early. The molecular-signature analysis was exploratory in design and focused on response markers in children with Rett syndrome (PMID 35712450).

Related Glossary Concepts

• IGF-1 — the endogenous growth factor that mecasermin replicates in recombinant form (PMID 19198769).
• IGFBP-3 — the principal circulating IGF binding protein, co-formulated in mecasermin rinfabate (PMID 18363546).
• Recombinant expression — the manufacturing route by which the protein is generated in host cells such as E. coli (PMID 26339260).

References

• Mecasermin (recombinant human insulin-like growth factor I) (Advances in Therapy, 2009)
• Mecasermin rinfabate: rhIGF-I/rhIGFBP-3 complex: iPLEX (Expert Opinion on Drug Metabolism & Toxicology, 2008)
• Mecasermin in Insulin Receptor-Related Severe Insulin Resistance Syndromes: Case Report and Review of the Literature (International Journal of Molecular Sciences, 2018)
• Mecasermin for the treatment of Rett Syndrome: a systematic review (Neurogenetics, 2025)
• Molecular Signatures of Response to Mecasermin in Children With Rett Syndrome (Frontiers in Neuroscience, 2022)
• Illness Severity, Social and Cognitive Ability, and EEG Analysis of Ten Patients with Rett Syndrome Treated with Mecasermin (Recombinant Human IGF-1) (Autism Research and Treatment, 2016)
• Recombinant production of mecasermin in E. coli expression system (Research in Pharmaceutical Sciences, 2014)