Mecasermin

What it is

Mecasermin is recombinant human IGF-1: a 70-amino-acid protein with the same sequence as the body's IGF-1, made in genetically modified Escherichia coli. The INCRELEX label also records three internal disulfide bridges. This is a defined manufactured drug, not IGF-1 LR3.

The approved record is for the labeled sterile subcutaneous INCRELEX product. Mecasermin is not IGF-1 LR3, a modified longer-acting research analog. The words IGF-1 or mecasermin alone do not establish formulation, excipients, concentration, sterility, stability, storage history, or approval.

Why people care

Mecasermin is the approved IGF-1 comparator that makes identity errors around IGF-1 LR3 especially consequential. Its human evidence concerns linear growth in rare pediatric deficiency, while circulating claims often move that record to adult physique or recovery questions without evidence.

What humans actually show

Mecasermin is sequence-identical recombinant human IGF-1 and the active ingredient in the FDA-approved INCRELEX product. Its United States approval is limited to growth failure in defined pediatric severe-primary-IGF-1-deficiency populations. It is not IGF-1 LR3, and the pediatric growth record does not establish adult muscle, performance, recovery, or anti-aging effects.

• approved label — 71 pediatric participants with severe primary IGF-1 deficiency in five pooled clinical studies; Route: Subcutaneous INCRELEX in four open-label studies and one double-blind placebo-controlled study; Outcome: Annual height velocity and height standard-deviation score: Among 58 participants with paired pretreatment data, mean height velocity increased from 2.8 cm per year before treatment to 8.0 cm per year in year one, then declined over later years. The seam: Most evidence was open label; The population had extreme short stature and biochemically defined severe primary deficiency; Participant numbers decreased with each additional follow-up year; A pediatric height-velocity result does not establish adult muscle, performance, recovery, or anti-aging benefit.
• other human — 21 children with severe IGF-1 deficiency treated until adult or near-adult height; Route: Subcutaneous recombinant human IGF-1 in a predominantly open-label long-term study; Outcome: Height velocity and adult or near-adult height: Mean height velocity increased from 3.1 cm per year before treatment to 7.4 cm per year in year one. After a mean ten years of treatment, the observed mean height gain was 13.4 cm more than the investigators' untreated projection; most participants did not reach the normal adult-height range. The seam: Only 21 participants were included; The study lacked a concurrent untreated long-term control; Nine participants also received a gonadotropin-releasing-hormone analog; Projected untreated height is not a randomized comparator.
• randomized human — 136 short prepubertal children with low IGF-1 and normal stimulated growth hormone; Route: Subcutaneous recombinant human IGF-1 or observation in a one-year randomized open-label study; Outcome: First-year height velocity: Among completers, the two higher studied groups had mean height velocities of 7.0 and 7.9 cm per year versus 5.2 cm per year in the untreated group. The seam: The study was open label; Its entry thresholds were broader than the current label's severe-primary-deficiency definition; It does not broaden the approved indication; It did not study adult muscle, recovery, performance, or anti-aging outcomes.

Mechanistic and nonhuman evidence

• mechanistic — Labeled pharmacology record; Route: Type 1 IGF-1 receptor activation; Outcome: Growth-plate, cellular, organ-growth, and glucose-utilization pathways: The label describes IGF-1 as a hormonal mediator of statural growth and describes effects on growth-plate chondrocytes and glucose utilization. The seam: Mechanism does not establish an adult performance or recovery outcome; Cell and organ growth pathways also inform safety concerns; Mechanism does not make mecasermin interchangeable with IGF-1 LR3.
• animal — Rats in a two-year carcinogenicity study summarized in the label; Route: Subcutaneous mecasermin exposure; Outcome: Tumor findings and mortality related to hypoglycemia: The label reports increased incidences of several tumor types at studied exposures and excess mortality at doses above the maximum tolerated dose due to IGF-1-induced hypoglycemia. The seam: Animal findings do not quantify an individual human risk; Exposure comparisons varied by tumor type; The animal record does not establish human efficacy.

FDA and U.S. status

The July 2025 INCRELEX label is FDA approved for growth failure in pediatric patients aged two years and older with severe primary IGF-1 deficiency or growth-hormone gene deletion with neutralizing antibodies to growth hormone. The label defines severe primary deficiency and excludes secondary IGF-1 deficiency from growth-hormone deficiency, malnutrition, hypothyroidism, or chronic pharmacologic corticosteroid treatment. It is not a substitute for growth hormone in approved growth-hormone indications. The openFDA record updated July 28, 2026 lists BLA021839 INCRELEX with Prescription marketing status.

Risks and warning limits

• approved label: The label warns that severe hypoglycemia, including seizures and loss of consciousness, has occurred. In the 71-participant clinical program, 42% had at least one reported hypoglycemia event.
• approved label: Labeled warnings include hypersensitivity and anaphylaxis, intracranial hypertension, tonsillar and adenoidal hypertrophy, slipped capital femoral epiphysis, progression of preexisting scoliosis, malignant neoplasia, and serious benzyl-alcohol reactions in neonates and infants.
• approved label: The label contraindicates INCRELEX in known hypersensitivity, closed epiphyses, and pediatric malignant neoplasia or a history of malignancy.

What remains unknown

• The cited evidence does not establish benefit for adult muscle gain, recovery, performance, anti-aging, or people outside the exact pediatric growth-failure populations.
• The evidence base is small and predominantly open label, leaving uncertainty about long-term benefit and harm beyond the studied populations and follow-up.
• The cited sources do not provide general clinical interaction clearance with glucose-lowering medicines, growth hormone, or other substances.
• The identity, potency, sterility, stability, and excipient profile of a compounded or unidentified product cannot be inferred from the words IGF-1 or mecasermin.

Product identity and quality limits

• Mecasermin is sequence-identical recombinant human IGF-1 and is not the modified research analog IGF-1 LR3.
• INCRELEX is a specific approved formulation. FDA states that compounded drugs are not FDA approved, and the INCRELEX label cannot be transferred to another material carrying an IGF-1 name.

What has been studied together

• Mecasermin with glucose-lowering medicines or substances — theoretical mechanism overlap: The label establishes that mecasermin has insulin-like hypoglycemic effects but provides no general clinical interaction result for every glucose-lowering combination. Mechanistic overlap does not quantify an individual interaction.
• Mecasermin with growth hormone — no direct evidence: The label says INCRELEX is not a substitute for growth hormone in approved growth-hormone indications. That indication boundary is not evidence that a combination is beneficial, safe, or appropriate.

What people are hearing

These are claims this profile checks, not established conclusions.

• Claim under review: “Mecasermin and IGF-1 LR3 are the same substance.”
• Claim under review: “Pediatric height-velocity evidence proves adult muscle, recovery, performance, or anti-aging benefit.”
• Claim under review: “Any product described as IGF-1 inherits the INCRELEX approval and safety record.”

Questions readers raise

• No reproducible community sample was collected for this profile.

The community-signal layer is not efficacy or safety evidence. Its current limits are:

• No reproducible community sample has been collected for this profile.
• Self-reports would be subject to selection and reporting bias.
• The identity of a product described in a self-report could not be verified.
• Concurrent medicines, health conditions, diet, and behavior could confound an anecdote.
• Reported outcomes could not be independently verified.
• Anecdotes cannot establish efficacy, safety, approval, product identity, or interaction compatibility.

What would change this answer

• A revised FDA label or approval action would change the exact pediatric indication, contraindication, or warning boundary.
• Controlled human studies in a clearly defined adult population with patient-important muscle, function, or recovery outcomes would be needed before considering those separate claims.
• Product-specific analytical and manufacturing evidence would be required to assess an unidentified material; a shared IGF-1 name is insufficient.

Sources and records

• WADA — 2026 Prohibited List

• INCRELEX (mecasermin) prescribing information, revised July 2025 — U.S. Food and Drug Administration
• Drugs@FDA API exact active-ingredient search for mecasermin — U.S. Food and Drug Administration
• Compounding and the FDA: Questions and Answers — U.S. Food and Drug Administration
• ClinicalTrials.gov intervention search for mecasermin — ClinicalTrials.gov
• PubMed search for mecasermin in human records — National Library of Medicine
• Long-term recombinant human IGF-1 study in severe primary IGF-1 deficiency — ClinicalTrials.gov
• Adult and near-adult height in severe IGF-1 deficiency after long-term recombinant human IGF-1 — PubMed
• Randomized recombinant human IGF-1 trial in prepubertal children with low IGF-1 — ClinicalTrials.gov
• Recombinant IGF-1 treatment in short children with low IGF-1: first-year randomized results — PubMed