Mecasermin: what has been measured about safety

Mecasermin has the safety documentation almost nothing else in this catalogue has. It went through a regulatory review, it carries an approved label under biologics licence application BLA021839, and two long-running registries have followed the licensed population since it was approved: one enrolling 1,378 participants and one enrolling 500 [1] [5] [6].

That documentation belongs to a prescriber and to a patient with a diagnosis, and this page reproduces none of it. The label's warnings, its monitoring requirements and the circumstances it rules out are directions for use, they are used alongside laboratory monitoring a reference site cannot supply, and this site's editorial standards do not permit publishing them. What this page reports is that the document exists, who holds it, and what kind of thing it covers.

The other half of the page is the population. Every trial in the registered programme enrolled children with a severe deficiency of this protein, and the licence is written the same way [2] [3]. Nothing in that record describes an adult with normal levels, and nothing in it describes the engineered analog sold to adults under a different name.

What this page reports, and what it does not

We report what has been documented. We do not prescribe what should be done.

Every sentence below reports what a named source measured, recorded or stated, in what population, and what it found. Where the answer is that this page will not reproduce something, it says so and gives the reason.

This page publishes no dose, no schedule, no route instruction and no list of people who should avoid anything. That rule holds here even though an approved label supplies all four, and the reason it holds harder rather than more weakly is that a real document exists: a monitoring requirement lifted out of a prescribing document and put on a reference page has lost the thing that made it usable, and what remains reads as instruction.

One distinction runs through everything here. IGF-1 LR3 is an engineered version of this protein carrying a substitution and a thirteen amino acid extension so that it evades the binding proteins. It is a different molecule with no registered trial of its own, and nothing on this page is a statement about it.

What has been measured

What a regulatory review produced, and what this page will not reproduce

The label for this compound exists because a regulator reviewed the programme behind it and wrote down the conditions under which the drug may be given. That document carries the warnings, the monitoring requirements and the circumstances in which the drug is not to be used, and it is supplied to prescribers and dispensed with the product [1].

None of it appears on this page, and the reason is a rule rather than an oversight. A list of circumstances in which a compound is not to be given is a directions-for-use document: it only makes sense to a reader who is going to use the thing, and publishing one here would make this page part of the instructions rather than part of the record. The same rule keeps the dosing off the protocols page, where the figures are equally real and equally available.

What is on the record and reportable is the shape of the file. It is a biologics licence application, BLA021839, held by a named manufacturer, for a product given by subcutaneous injection, with an indication and a limitation of use written into it [1]. Those are agency facts with a date on them, and the main review sets them out in full in its regulatory section.

Two registries, and what a registry establishes

Two long-running registries follow the licensed population after approval. One enrolled 1,378 participants before being terminated [5], and a global registry monitoring long-term safety was still recruiting when this page was reviewed [6].

A registry observes rather than tests, so it does not establish that a drug does anything and it does not produce a controlled comparison. What it does is watch a real treated population over years and capture what happens to them, which is the one thing a fixed-length trial cannot do.

This site did not read the registry outputs and states no findings from them. The reportable fact is structural rather than numerical: post-marketing surveillance exists here because the drug is approved, and none of the research chemicals in this catalogue is followed by anything at all. That is a category difference rather than a result.

The population the whole record covers

The registered programme studied children. The largest Phase 3 enrolled 137 prepubertal children with growth failure associated with IGF-1 deficiency [2], and a Phase 2/3 studied long-term recombinant IGF-1 in 92 participants with growth hormone insensitivity syndrome [3]. The licence follows the evidence: growth failure in pediatric patients two years of age and older with severe primary IGF-1 deficiency, or with growth hormone gene deletion who have developed neutralizing antibodies to growth hormone [1].

Read that as a boundary on the safety record rather than only on the indication. Everything known about what this protein does to a body under supervision was learned in children whose own production of it is severely deficient, and who were monitored throughout. A safety observation made in that population is a safety observation about that population.

Nothing in the record enrolled an adult with normal IGF-1 taking the protein for growth or performance. That use is outside every part of the file, and anyone asking about it is asking about a population the evidence does not include.

What none of this covers

The approval on this page is routinely offered as evidence for IGF-1 LR3, which is an engineered version of the same protein sold to adults as a research chemical. That reading does not hold, and the reason is the analog's own design.

The analog carries a substitution and a thirteen amino acid extension built specifically to give it low affinity for the binding proteins that regulate how much free hormone reaches tissue [9]. That is the whole point of the molecule, and it means the two behave differently in circulation by construction. Safety documentation about a protein under normal binding-protein control is not documentation about a version made to escape it.

The analog also has no registered trial of any kind, in any species, under its own name. What its record does hold, which is animal infusion work in fetal sheep and cattle, is set out on the IGF-1 LR3 safety record, linked under Safety records this page refers to at the foot of this page.

What has not been characterised

Set out plainly, so the shape of the gap is visible rather than implied. Nothing in this record describes an adult with normal IGF-1 taking the protein, for growth, for performance or for anything else. The registered programme enrolled children with a severe deficiency [2] [3] and the licence is written for that population [1], so the question most readers arrive with is outside the evidence rather than answered unfavourably by it.

This site has not established whether any of the 29 registered records has posted results, and did not read the outputs of either registry [7]. It also read the label through the openFDA drug label API rather than from the label document itself [1]. Those are limits on this page rather than on the record, and they are recorded here as open items rather than glossed.

And nothing here covers a product obtained outside a pharmacy. The licensed material is manufactured under a biologics licence and dispensed against a prescription. Anything offered for sale under this name through another channel is not that product, whatever the label says, and none of the documentation on this page describes it.

Our takeThis is what a finished safety file looks like, and the useful thing about it is how narrow it is. A protein with a full development programme, a regulatory review, a label and two post-marketing registries behind it is documented for children with a severe deficiency of it, given under monitoring. That is the whole of what was established, after all of that work. Every other use of this protein, and every use of the analog sold beside it, sits outside a file this complete.

Talk to a licensed clinician about anything concerning your health.

Frequently asked questions

References

1. US Food and Drug Administration. INCRELEX (mecasermin) injection prescribing information. Biologics licence application BLA021839, Ipsen Biopharmaceuticals, Inc., subcutaneous route. Read through the openFDA drug label API on 23 August 2026. Carries the approved indication and the limitation of use quoted on this page. The label document itself was not read, which is recorded as an open item. openFDA drug label. 2026. Increlex label
2. Ipsen. Prepubertal Children With Growth Failure Associated With IGF-1 Deficiency. Phase 3, 137 participants, completed. Read through the ClinicalTrials.gov v2 API on 23 August 2026. ClinicalTrials.gov. 2005. NCT00125164
3. Ipsen. Long-Term Treatment With rhIGF-1 in Growth Hormone Insensitivity Syndrome. Phase 2/3, 92 participants, completed. ClinicalTrials.gov. 2007. NCT00571727
4. Massachusetts General Hospital. IGF-1 and Bone Loss in Women With Anorexia Nervosa, 148 participants, completed; and Effects of Anorexia Nervosa on Peak Bone Mass, Phase 3, 75 participants, completed. Investigator-led work outside the licensed indication. Registry records read; no publication was read. ClinicalTrials.gov. 2011. NCT01406444
5. Ipsen. IGFD Registry: A Patient Registry for Monitoring the approved population after licensing. 1,378 participants, terminated. ClinicalTrials.gov. 2008. NCT00747604
6. Esteve Pharmaceuticals. Global Patient Registry to Monitor Long-term Safety. 500 participants, recruiting as of 23 August 2026. ClinicalTrials.gov. 2009. NCT00903110
7. ClinicalTrials.gov. Registry sweep for mecasermin, Increlex, mecasermin rinfabate, iPlex, rhIGF-1, IGF-1 LR3 and Long R3 IGF-1, run through the v2 API on 23 August 2026 and filtered to records whose interventions name one of those drugs. Twenty-nine records survive the filter. An unfiltered query returns 135, because IGF-1 is a widely measured biomarker. ClinicalTrials.gov. 2026. ClinicalTrials.gov
8. World Anti-Doping Agency. The 2026 Prohibited List. Section S2.3, Growth Factors and Growth Factor Modulators, carries the entry: Insulin-like growth factor 1 (IGF-1, mecasermin) and its analogues. The S2 class heading states that the class is prohibited at all times, in and out of competition, and that all substances in it are non-Specified. Read in full on 23 August 2026. World Anti-Doping Agency. 2026. WADA 2026 Prohibited List
9. White A, Stremming J, Wesolowski SR, Al-Juboori SI, Dobrinskikh E, Limesand SW, Brown LD, Rozance PJ. IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetal sheep. Am J Physiol Endocrinol Metab. 2025. PMID 39679943 DOI 10.1152/ajpendo.00259.2024 Cited here for its description of the analog's engineering, which is what separates that molecule from this one.
10. Stremming J, White A, Donthi A, Batt DG, Hetrick B, Chang EI, Wesolowski SR, Seefeldt MB, McCurdy CE, Rozance PJ, Brown LD. Sheep recombinant IGF-1 promotes organ-specific growth in fetal sheep. Front Physiol. 2022. PMID 36091374 Cited for what unmodified IGF-1 does in the preparation the analog was also tested in.