Mecasermin (IGF-1)

Mecasermin is a manufactured form of human insulin-like growth factor 1 (IGF-1). It is approved only to treat poor growth in children with severe primary IGF-1 deficiency, a rare condition.

What it is

Mecasermin is recombinant human insulin-like growth factor 1 (IGF-1), sold as Increlex ^[1]. IGF-1 is the hormone that carries out many of the effects of growth hormone. Mecasermin is a specialist medicine for a small number of children whose bodies do not make enough IGF-1 even though they make normal amounts of growth hormone ^{[1, 2]}. In the EU it was authorised under "exceptional circumstances" because the condition is so rare that full information could not be collected ^[3].

How it works

Mecasermin binds to and activates the type 1 IGF receptor on cells. This stimulates growth of bone and other tissues ^[1]. IGF-1 also has insulin-like actions: it increases the uptake of glucose into tissues and reduces glucose release from the liver, which is why low blood sugar is its main side effect ^{[1, 2]}. After injection under the skin, its half-life in children is about 5.8 hours ^[1].

Approved medical uses

Mecasermin is approved for growth failure in children and adolescents with severe primary IGF-1 deficiency ^{[1, 2, 4]}. In the US it is also approved for children with growth hormone gene deletion who have developed neutralising antibodies to growth hormone ^[1]. It is not a substitute for growth hormone and is not approved for secondary IGF-1 deficiency, where low IGF-1 is caused by another condition ^[1]. It should only be used under specialist medical supervision.

What the research shows

• Approval evidence: the US approval was based on five studies (four open-label and one placebo-controlled) in 71 children with severe primary IGF-1 deficiency, who were treated for an average of 3.9 years ^[1]. Because the condition is rare, these studies are small.
• Low blood sugar: in these studies, hypoglycaemia was reported in 42% of children, severe hypoglycaemia in 7% and seizures in 6% ^[1].
• Tumours: after approval, cases of benign and malignant tumours were reported in children treated with mecasermin. EU and UK product information now states there is an increased risk, because IGF-1 plays a role in starting and growing tumours ^{[1, 2, 4]}.
• There are no approved uses in adults, and the product information does not support use outside the licensed indication ^{[1, 2]}.

Known risks and side effects

• Hypoglycaemia (low blood sugar), which can be severe and cause seizures. The product information says it should be given close to a meal ^{[1, 2]}.
• Enlarged tonsils and adenoids (about 15% of children in US studies), with snoring, sleep apnoea and middle-ear fluid ^{[1, 2]}.
• Raised pressure in the skull (intracranial hypertension), with headache, vision changes, nausea or vomiting ^{[1, 2]}.
• Benign and malignant tumours. It must not be used with active or suspected cancer, or conditions that increase cancer risk ^{[2, 4]}.
• Slipped upper femoral epiphysis (a hip problem) and worsening scoliosis ^[1].
• Severe allergic reactions, including anaphylaxis ^[1].
• Other common effects in EU/UK product information include headache, vomiting, injection-site changes, ear infections, heart murmurs, fast heart rate and joint pain ^[4].
• IGF-1 (mecasermin) is prohibited at all times in sport under the WADA Prohibited List ^[5].

Blood tests commonly monitored

• Blood glucose before meals, at the start of treatment and until a stable, well-tolerated dose is reached ^{[1, 2]}.
• An echocardiogram before treatment is recommended in EU product information ^[2].
• Regular eye examination (fundoscopy) for intracranial hypertension and ear, nose and throat checks for tonsil and adenoid enlargement ^{[1, 2]}.
• Watch for signs of tumours, hip problems and scoliosis ^[1].

Sources

1. US Food and Drug Administration. Increlex (mecasermin) injection: prescribing information. Revised 2025. FDA label (PDF)
2. European Medicines Agency. Increlex: EPAR product information (Summary of Product Characteristics). EMA product information (PDF)
3. European Medicines Agency. Increlex: European public assessment report (EPAR) overview page. EMA
4. Esteve Pharmaceuticals. Increlex solution for injection: Summary of Product Characteristics. Electronic Medicines Compendium, updated 2025. eMC SmPC
5. World Anti-Doping Agency. Prohibited List 2026, class S2: peptide hormones, growth factors, related substances and mimetics (English text as reproduced by the German Sport University Cologne). DSHS Cologne

Related

Last reviewed 7 October 2026. General information, not medical advice. Found a mistake? Email [email protected].