Discontinued Growth Hormone Axis

Mecasermin rinfabate

also known as: iPlex, rhIGF-1/rhIGFBP-3, IGF-1/IGFBP-3 complex

Insmed's IGF-1 / IGFBP-3 complex (iPlex) — briefly FDA-approved in 2005 for severe primary IGF-1 deficiency; discontinued in 2008 after a labeling/patent injunction that resolved the competitive dispute between Tercica's Increlex and Insmed's iPlex in favor of Increlex.

A recombinant 1:1 molar binary complex of human IGF-1 and IGFBP-3 (its principal circulating binding protein), developed by Insmed as an alternative to free rhIGF-1 that was intended to provide IGF-1 replacement with a longer effective half-life and a lower hypoglycemia risk. FDA-approved December 2005 as iPlex for severe primary IGF-1 deficiency. A 2007–2008 patent litigation and FDA/court-imposed labeling restrictions effectively removed iPlex from the growth indication market in favor of Increlex; Insmed divested the program in 2008 and the product was discontinued. Included here for reference because it remains a cited archetype of IGF-1/IGFBP complex therapy.

Mechanism of action

Same IGF-1R agonism as free rhIGF-1, but delivered as a preformed IGF-1 / IGFBP-3 binary complex. The complex slows renal clearance, buffers the acute post-dose insulin-receptor-mediated hypoglycemia effect, and resembles the physiological circulating form of IGF-1 (which is almost entirely bound to IGFBP-3 and acid-labile subunit in a ternary complex).

Primary uses

Severe primary IGF-1 deficiency (historical, 2005–2008)
Investigated in ALS and myotonic dystrophy (not approved)

Typical dosing

0.5–2.0 mg/kg/day once or twice daily (subcutaneous)

Historical dosing; not currently available for clinical use.

Regulatory status

FDA-approved December 2005 as iPlex (Insmed) for severe primary IGF-1 deficiency. Patent litigation with Tercica (Increlex) 2006–2008 led to an injunction and labeling restrictions limiting iPlex marketing for the growth indication. Insmed divested the program to Ipsen in 2009; commercial distribution for growth indications ended. Small-scale off-label use in ALS and myotonic dystrophy was later explored without reaching approval.

References

[pubmed] Kemp SF, et al. "Efficacy and safety results of long-term therapy with recombinant human insulin-like growth factor-1/recombinant human insulin-like growth factor binding protein-3 complex in children with severe primary IGF-1 deficiency." Horm Res Paediatr, 2013;80:275-281.
[manufacturer] Insmed Incorporated. SEC filings and press releases regarding iPlex, 2005–2009.

Related peptides

Mecasermin

Ipsen's recombinant human IGF-1 (Increlex) — FDA-approved in 2005 for severe primary IGF-1 deficiency; the direct replacement for IGF-1 in patients whose own IGF-1 production is inadequate despite normal GH levels.

Somatropin (HGH)

FDA-approved recombinant human growth hormone — the direct hormone replacement, with multiple clinical indications, prescription-only status, and specific federal criminal provisions against off-label distribution.

IGF-1 LR3

A 13-amino-acid N-terminal extension plus Arg3 substitution gives IGF-1 LR3 roughly 2–3× the potency of native IGF-1 in bioassays — a research-reagent favorite that became a bodybuilding staple despite no human approval.

Guides & tools

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Disclaimer

This entry is for educational purposes only and does not constitute medical advice. Dosing information reflects published regulatory or research data and is not a recommendation. Many compounds described here are not approved for human use in the United States. Consult a licensed medical professional before considering any peptide therapy.