Is mecasermin FDA-approved, and what does the research show?

What is mecasermin?

Mecasermin is human IGF-1 made by recombinant DNA technology ¹. In that method, bacteria that have been given the gene for human IGF-1 produce the protein ¹. It is a single chain of 70 amino acids, the building blocks of proteins ¹. The label says its sequence "is identical to that of endogenous human IGF-1," meaning the IGF-1 the body makes itself ¹.

Mecasermin is a prescription medicine for children with a severe growth disorder ¹. Its label lists one use, growth failure in two groups of pediatric patients, and none for wellness, weight loss or performance ¹. It is sold as Increlex, a solution injected under the skin, which the label calls subcutaneous injection ¹. The label says treatment "should be supervised by a physician who is experienced in the diagnosis and management of pediatric patients with short stature associated with severe primary IGF-1 deficiency or with growth hormone gene deletion and who have developed neutralizing antibodies to growth hormone" ¹.

Is mecasermin FDA-approved?

Yes for Increlex (mecasermin), a prescription drug approved for one use in children; a second product, Iplex (mecasermin rinfabate), is listed as "Discontinued" ¹, ², ³. FDA approved Increlex on August 30, 2005 ². Drugs@FDA, the agency's database of approved drugs, lists it under the application number BLA 021839, a biologics license application ². Its marketing status is "Prescription" as of November 9, 2026, the date of the Drugs@FDA record's data ².

The label gives one indication: "the treatment of growth failure in pediatric patients 2 years of age and older with severe primary IGF-1 deficiency or with growth hormone (GH) gene deletion who have developed neutralizing antibodies to GH" ¹. Growth hormone is the hormone that normally prompts the liver and other tissues to make IGF-1 ¹.

The label defines severe primary IGF-1 deficiency by three findings together ¹. They are a height standard deviation score of -3.0 or lower, a basal (baseline) IGF-1 standard deviation score of -3.0 or lower, and "normal or elevated growth hormone" ¹. A standard deviation score says how far a child's measurement sits from the average for age and sex. These children are very short and have very little IGF-1, though their growth hormone is not low ¹. The second group is children with a deletion of the growth hormone gene who "have developed neutralizing antibodies to GH," antibodies that block the hormone ¹.

The label also says who the drug is not for ¹. It "is not a substitute to GH for approved GH indications" ¹. It "is not indicated for use in patients with secondary forms of IGF-1 deficiency, such as GH deficiency, malnutrition, hypothyroidism, or chronic treatment with pharmacologic doses of anti-inflammatory corticosteroids" ¹. Secondary means the low IGF-1 follows from another condition, such as the ones the label lists ¹.

Drugs@FDA holds one other application whose ingredient name includes mecasermin ³. Iplex, whose ingredient the record names "MECASERMIN RINFABATE RECOMBINANT," was approved December 12, 2005, and is listed as "Discontinued" ³. Drugs@FDA calls its application, BLA 021884, a former NDA "Deemed To Be a BLA on March 23, 2020" ³. "Discontinued" is the record's marketing status: the record does not say the approval was withdrawn, and it gives no reason ³.

The Iplex label calls mecasermin rinfabate a "binary protein complex" of IGF-1 and IGF-binding protein-3, for growth failure in the same two groups of children ⁴. The label and the warnings cited elsewhere on this page are Increlex's ¹.

See the FDA status of every peptide, updated weekly.

How does mecasermin work?

The Increlex label calls the body's own IGF-1 "a key hormonal mediator on statural growth," meaning growth in height ¹. IGF-1 activates its own receptor in target tissues, and that signal drives the processes that produce growth ¹.

In severe primary IGF-1 deficiency, growth hormone is normal or high, yet IGF-1 stays very low ¹. A long-term study of 76 children says severe IGF-1 deficiency from "defects in GH action" leaves children with "short stature that cannot be remedied by GH treatment" ⁵. Mecasermin is IGF-1 itself, given by injection ¹.

Bones lengthen at the cartilage growth plates of the epiphyses, where new cartilage cells form and harden into bone ¹. The epiphyses are the ends of the bones. Growth goes on "until the cartilage growth plates fuse at the end of puberty" ¹. The label's contraindication for "closed epiphyses" refers to that fusion ¹.

IGF-1 also acts on blood sugar. The label says it "suppresses hepatic glucose production and stimulates peripheral glucose utilization and therefore has a hypoglycemic potential" ¹. The liver releases less sugar and the tissues take up more, so blood sugar can fall ¹. The label notes that the IGF-1 receptor is "homologous to the insulin receptor" ¹. Homologous means similar in structure.

What does the research show?

Increlex (mecasermin) is approved by FDA for growth failure in children with the labeled conditions, on five clinical studies in 71 pediatric subjects with severe primary IGF-1 deficiency ¹. Four were open-label ¹. Open-label means everyone knew what was given. One was double-blind and placebo-controlled ¹. That means neither doctors nor families knew who received the drug and who received a dummy injection.

Children were enrolled "on the basis of extreme short stature, slow growth rates, low IGF-1 serum concentrations, and normal growth hormone secretion" ¹. The label pools the five studies and reports no separate result for the placebo-controlled one ¹.

At the start, the patients in the label's efficacy analyses had a mean age of 6.7 years and a mean height score of -6.7 ¹. Sixty-one had at least one year of treatment ¹. Of those, 53 had Laron syndrome, 7 had a growth hormone gene deletion and 1 had neutralizing antibodies to growth hormone ¹. Laron syndrome is an inherited condition in which the body does not respond to growth hormone.

The main measure was height velocity, the rate of growth in centimeters a year ¹. Each year's rate was compared with the same children's own rate before treatment, not with an untreated group ¹. Among the 58 children with a pre-treatment measurement, the mean rose from 2.8 centimeters a year to 8.0 in the first year ¹. It was 5.8 in the second year among 48 children and 5.5 in the third among 38 ¹.

The gain over the pre-treatment rate was statistically significant, meaning unlikely to be chance, through year six, when 20 children remained ¹. It was not significant in year seven (16 children, P = 0.0897) or year eight (13 children, P = 0.3059) ¹. P is the probability of seeing a gain at least that large if the treatment made no difference.

The mean height score rose with treatment and was still below -5 after eight years ¹. Among 61 children, the mean height score moved from -6.7 before treatment to -5.9 after one year ¹. Among the 13 treated for eight years it was -5.2, a mean gain of 1.5 over their own starting scores ¹. In 49 children, bone age, a measure of skeletal maturation, advanced by a mean of 5.3 years while the children aged a mean of 4.9 years ¹.

Studied in people: that long-term study, published online December 27, 2006, gave its 76 children recombinant IGF-1 for up to 12 years "under a predominantly open-label design" ⁵. They had IGF-1 deficiency due to growth hormone insensitivity ⁵. Entry required an age over 2 years, height and IGF-1 scores below -2 for age and sex, and evidence of resistance to growth hormone ⁵. Height velocity rose from 2.8 centimeters a year on average at baseline to 8.0 in the first year, and it "was dependent on the dose administered" ⁵. In later years it was lower but "remained above baseline for up to 8 yr" ⁵.

The Increlex label gives the same baseline and first-year averages as the paper ⁵, ¹. Each growth result comes from children with IGF-1 deficiency, and the paper's entry scores (below -2) were wider than the label's condition (-3.0 or lower) ⁵, ¹. The label's clinical studies section holds no trial in adults, and no trial for weight, muscle, aging or athletic performance ¹. The label states that safety and effectiveness have not been established in children under 2 or in patients aged 65 and over ¹.

What are the side effects?

The Increlex label's side-effect figures come from the same 71 children, treated for a mean of 3.9 years, and it gives no placebo figures beside them ¹. No child withdrew from a study because of an adverse reaction ¹.

Hypoglycemia, the medical word for low blood sugar, was reported at least once by 30 of the 71 children, or 42 percent ¹. Most cases were mild or moderate ¹. Five children had severe episodes "requiring assistance and treatment," and four had "hypoglycemic seizures/loss of consciousness" ¹. Fourteen of the 30 had a history of hypoglycemia before treatment ¹. Episodes were most frequent in the first month and in younger children ¹.

The label's first warning reads: "Severe hypoglycemia leading to hypoglycemic seizures has been observed with INCRELEX treatment" ¹. Because the drug "has insulin-like hypoglycemic effects," the label says it "should not be administered when the meal or snack is omitted" ¹. It adds that patients "should avoid engaging in any high-risk activities (e.g., driving, exercise, etc.) within 2 to 3 hours after dosing," above all early in treatment ¹.

Tonsillar hypertrophy, or enlarged tonsils, was noted in 11 children (15 percent), and 7 had their tonsils, or tonsils and adenoids, removed ¹. Intracranial hypertension, raised pressure inside the skull, occurred in three, with visual changes, headache, nausea or vomiting among its signs ¹. Besides enlarged tonsils, reactions seen in 5 percent or more included lipohypertrophy, a buildup of fatty tissue where injections are given ¹. Others included snoring, middle-ear infections and fluid, reduced hearing, headache, dizziness, convulsions, vomiting and joint pain ¹. The label adds that "thickening of the soft tissues of the face was observed in several patients" ¹.

In the 76-child study of recombinant IGF-1, hypoglycemia was reported by 49 percent of treated children and "was observed both before and during therapy" ⁵. Lipohypertrophy followed at 32 percent, and enlarged tonsils or adenoids at 22 percent ⁵. The authors wrote that adverse events "are common but are rarely of sufficient severity to interrupt or modify treatment" ⁵.

The Increlex label has three contraindications, conditions in which the drug must not be used ¹. They are known hypersensitivity, or allergy, to mecasermin; closed epiphyses; and malignant neoplasia, the label's term for cancer ¹. On the last, the drug "is contraindicated in pediatric patients with malignant neoplasia or a history of malignancy" ¹.

Allergic reactions have been reported since approval ¹. The label says they "range from localized (injection site) reactions to systemic reactions, including anaphylaxis requiring hospitalization," anaphylaxis being a severe whole-body allergic reaction ¹. It estimates the frequency of cases indicative of anaphylaxis at 0.3 percent ¹.

On cancer, the label says: "There have been postmarketing reports of malignant neoplasms in pediatric patients who have received treatment with INCRELEX" ¹. It continues: "It is unknown whether there is any relationship between INCRELEX therapy and new occurrence of neoplasia" ¹. Most reports were in patients with rare genetic short-stature conditions that raise cancer risk, or with other predisposing conditions ¹. Tumors were also seen "more frequently in patients who received INCRELEX at higher than recommended doses, or at doses that produced serum IGF-1 levels above the normal reference ranges for age and sex" ¹.

Slipped capital femoral epiphysis, a slip at the growth plate of the hip, "can occur in patients who experience rapid growth" ¹. It "may lead to osteonecrosis," the death of bone tissue ¹. The label says a child with "the onset of a limp or complaints of hip or knee pain" should be evaluated for it ¹. Existing scoliosis, a curve of the spine, may progress with rapid growth ¹. Enlarged tonsils and adenoids have been "associated with complications, such as snoring, sleep apnea, and chronic middle-ear effusions" ¹.

The product contains benzyl alcohol as a preservative ¹. The label warns that "serious and fatal adverse reactions including 'gasping syndrome' can occur in neonates and infants treated with benzyl alcohol-preserved drugs" ¹. It says use in infants "is not recommended" ¹. The label also has "no available data" on use in pregnant women ¹.

On overdose, the label says treatment "should be directed at reversing hypoglycemia" ¹. It adds that long-term overdosage "may result in signs and symptoms of acromegaly" ¹. Acromegaly is a condition in which bones and soft tissues grow larger than normal.

Studied in animals for cancer risk: in a rat study of up to two years, the drug "was tumorigenic" ¹. The label reports increases in "adrenal medullary hyperplasia and pheochromocytoma," an overgrowth and a tumor of the adrenal gland's inner part ¹. They came at exposures below the human exposure at the maximum recommended dose ¹.

In sport

Mecasermin is named on WADA's 2026 Prohibited List ⁶. WADA, the World Anti-Doping Agency, places it in section S2, peptide hormones, growth factors, related substances, and mimetics ⁶. Within S2 it sits under S2.3, growth factors and growth factor modulators ⁶. The entry reads "Insulin-like growth factor 1 (IGF-1, mecasermin) and its analogues" ⁶. The list marks the substances of section S2 as prohibited at all times, in and out of competition ⁶.

What JumpstartMD offers

JumpstartMD does not prescribe mecasermin. Our peptide library covers it so you have the facts on its FDA status and the evidence, current as of November 10, 2026.

Ready to talk?

Book FREE Consultation

Share your details and a JumpstartMD team member will reach out shortly. Or call 408.478.3496 for your free, no-obligation consultation.

Share your details and a JumpstartMD team member will reach out when we open.

Disclaimer

Compounded medications are not FDA-approved, and FDA does not review their safety, effectiveness, or quality before they are marketed. A licensed clinician decides after an evaluation whether a peptide is appropriate for you, and not every patient will qualify.