Is IGF-1 LR3 FDA approved?

No. IGF-1 LR3 has no FDA application of any kind. Searching Drugs@FDA for an IGF-1 active ingredient returns exactly two applications, and both are different molecules: BLA 021839 (INCRELEX, mecasermin recombinant, Ipsen, marketing status Prescription) and BLA 021884 (IPLEX, mecasermin rinfabate recombinant, Insmed, marketing status Discontinued). Queries against the generic-name, substance-name and brand-name fields return only those same approved mecasermin products, and every query for the LR3 analogue returns no matches on any field. IGF-1 LR3 is also not in clinical development: ClinicalTrials.gov returned zero registered studies for 'IGF-1 LR3', 'Long R3 IGF-1' and 'LR3 IGF-1' when queried on 2 August 2026, so there is no sponsor and no registered trial to point at. Being unapproved says nothing about whether it is sold — it is.

Is IGF-1 LR3 the same thing as Increlex or mecasermin?

No — they are different molecules, and the FDA-approved label says so on its face. INCRELEX (mecasermin) labeling states that 'IGF-1 consists of 70 amino acids in a single chain with three intramolecular disulfide bridges and a molecular weight of 7649 Da' and that 'The amino acid sequence of the product is identical to that of endogenous human IGF-1.' IGF-1 LR3 is defined by not being identical: it carries an arginine substituted for glutamic acid at position 3 plus an additional N-terminal extension, engineered to reduce binding to the IGF-1 binding proteins that regulate the native hormone. Because they are different molecules, mecasermin's approval, its prescribing information and the clinical trials behind it describe mecasermin and do not describe IGF-1 LR3. The approved indication is also far narrower than the market implies: INCRELEX is indicated 'for 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', and the label states it 'is not indicated for use in patients with secondary forms of IGF-1 deficiency'.

Are there any human studies on IGF-1 LR3?

No peer-reviewed human studies of IGF-1 LR3 have been identified. A 2026 narrative review in Frontiers in Endocrinology, which ran its own literature search to January 2026, assigns IGF-1 LR3 to the lowest of its four evidentiary tiers and states that IGF-1 LR3, PEG-MGF and CJC-1295 without DAC 'have no peer-reviewed human studies and are supported only by preclinical extrapolation and grey-literature user narratives', adding that 'Mechanistic plausibility for tier-D compounds does not constitute clinical evidence and should not be interpreted as such.' An independent search on 2 August 2026 reached the same result: across five name variants, every interventional study retrieved from PubMed administered IGF-1 LR3 to animals — fetal sheep, mice, rats, guinea pigs, cattle — or to cells in culture, the same searches restricted to clinical-trial and randomised-controlled-trial publication types returned zero records, and ClinicalTrials.gov returned zero registered studies. The absence of human studies is not the same as evidence of safety, and it is not the same as evidence of harm.

Is IGF-1 LR3 banned in sport?

Yes. The World Anti-Doping Agency's 2026 Prohibited List, effective 1 January 2026, prohibits 'Insulin-like growth factor 1 (IGF-1, mecasermin) and its analogues' under S2.3, Growth Factors and Growth Factor Modulators. IGF-1 LR3 is an IGF-1 analogue and falls inside that wording; the List is also written to catch substances it does not name, stating that 'The following substances, and other substances with similar chemical structure or similar biological effect(s), are prohibited.' Class S2 is prohibited at all times, both in and out of competition, and the List records that 'All prohibited substances in this class are non-Specified Substances', which is the category carrying the least scope for a reduced sanction. Anti-doping laboratories have published a validated method that distinguishes LongR3-IGF-I from the related analogues Des(1-3)-IGF-I and R3-IGF-I, so a detection method for this specific molecule exists in the literature — which is not the same as a statement about how often it is applied.

Can a compounding pharmacy legally make IGF-1 LR3?

Not under section 503A. IGF-1 LR3 does not appear anywhere in FDA's list of bulk drug substances nominated for use in compounding under section 503A, updated 14 May 2026 — not in Category 1, not in Category 2, not in Category 3. A bulk drug substance that is neither the subject of an applicable USP or NF monograph nor a component of an FDA-approved drug must appear on the 503A bulks list to be used in 503A compounding, and IGF-1 LR3 appears on it in no category. Read the absence precisely: it is not a legalisation, it is not a safety finding, and it does not tell you whether IGF-1 LR3 was ever nominated and withdrawn or was simply never nominated at all — which is why this record carries no 503A category rather than guessing one. Note that a nearby entry is routinely confused with this compound: 'Mechano growth factor (MGF)' does appear in the list, and it is an IGF-1 splice variant, not IGF-1 LR3.

What is actually in a vial sold as IGF-1 LR3?

Not necessarily IGF-1 LR3, and not necessarily only IGF-1 LR3. In a 2010 case report, an anti-doping laboratory analysed a confiscated injection vial and identified the contents by mass spectrometry as 'Long-R³-IGF-I with a His₆-tag attached to the C-terminus by the linker amino acids Leu-Glu' — a purification construct of the kind added during recombinant protein production for laboratory work and normally removed. The authors wrote that 'The effects of His-tagged Long-R³-IGF-I in humans have not been elucidated or described and the product may rather be a by-product from biochemical studies than synthesized for injection purposes.' Separately, a 2021 anti-doping method paper reported that 'Abundant signs of lower quality, oxidized peptide forms were found in black market products', and a 2009 laboratory survey reported unpurified long-R(3)-IGF-1 among confiscated items. The point is narrower than 'fakes exist': even when the core sequence matches, the molecule in the vial may carry modifications with no described human effects at all.

Does IGF-1 LR3 build muscle?

No study in humans has tested that question. The most recent interventional study of IGF-1 LR3 is in fetal sheep and is negative on its growth endpoint: researchers reported in the American Journal of Physiology — Endocrinology and Metabolism in 2025 that 'a 1-wk IGF-1 LR3 treatment did not improve growth in FGR fetuses' after treating growth-restricted fetal sheep, and that 'IGF-1 LR3 treatment administered directly into growth-restricted fetal sheep circulation did not improve fetal growth'. They also reported that circulating amino acids, notably branched-chain amino acids, decreased with treatment. That finding is about growth-restricted fetal sheep and cannot be carried across to adults, in either direction — but it is the opposite of a supportive result, and it is the highest-quality interventional evidence that exists for this compound. The mechanistic case for IGF-1 LR3 rests on IGF-1 receptor signalling being well characterised in cell and oncology models, which a 2026 review in Frontiers in Endocrinology — cited separately on this record, not in the study quoted here — describes as plausibility rather than clinical evidence.

IGF-1 LR3

Also sold as: Long R3 IGF-1, LongR3-IGF-I, Long-R³-IGF-I, IGF-1 Long R3, long-(Arg3)insulin-like growth factor-I

IGF-1 LR3 (Long R3 IGF-1) is not an FDA-approved drug and is not the FDA-approved IGF-1 medicine. Drugs@FDA contains exactly two applications for an IGF-1 active ingredient, both for different molecules: mecasermin (INCRELEX, BLA 021839), whose FDA labeling states 'The amino acid sequence of the product is identical to that of endogenous human IGF-1' and which is approved only for growth failure in paediatric patients 2 years and older with severe primary IGF-1 deficiency or GH gene deletion with neutralizing antibodies to GH; and mecasermin rinfabate (IPLEX, BLA 021884), recorded as discontinued. IGF-1 LR3 is instead an engineered analogue carrying an arginine-for-glutamic-acid substitution at position 3 and an N-terminal extension, and a 2026 review in Frontiers in Endocrinology places it in the lowest of its four evidence tiers, stating that IGF-1 LR3 and two other compounds 'have no peer-reviewed human studies and are supported only by preclinical extrapolation and grey-literature user narratives'. IGF-1 LR3 also appears in none of Categories 1, 2 or 3 of FDA's 503A bulk drug substances list updated 14 May 2026, and the World Anti-Doping Agency's 2026 Prohibited List prohibits 'Insulin-like growth factor 1 (IGF-1, mecasermin) and its analogues' at all times, in and out of competition.

Which molecule this is. IGF-1 LR3 is an engineered ANALOGUE of insulin-like growth factor 1 — it is not insulin-like growth factor 1, and it is not the FDA-approved IGF-1 medicine. A 2026 review in Frontiers in Endocrinology describes it as 'an engineered analogue of IGF-1 characterised by the substitution of glutamic acid with arginine at position 3 and the presence of an additional N-terminal amino acid extension', modifications the authors report as markedly reducing affinity for IGF-1 binding proteins relative to native IGF-1. The approved drug is mecasermin (INCRELEX, BLA 021839), and its FDA labeling states that 'The amino acid sequence of the product is identical to that of endogenous human IGF-1' and that 'IGF-1 consists of 70 amino acids'. Sequence-identical and engineered-analogue are not the same molecule, so mecasermin's approval, its label, and the trials behind it do not describe IGF-1 LR3. A second approved application exists and is also a different molecule: mecasermin rinfabate (IPLEX, BLA 021884), recorded in Drugs@FDA as discontinued. Adjacent research analogues sold under similar names — Des(1-3)-IGF-I and R3-IGF-I — are again distinct substances; anti-doping laboratories treat all three as separate analytes.

FDA status

Not FDA-approved

FDA has not approved this and it is not in active development toward approval. That says nothing about whether it is being sold — most substances in this category are.

Not an FDA-approved drug for any indication, and not in active development toward approval. Drugs@FDA contains exactly two applications for an IGF-1 active ingredient and neither is this molecule: BLA 021839 (INCRELEX, mecasermin recombinant, Ipsen, marketing status Prescription) and BLA 021884 (IPLEX, mecasermin rinfabate recombinant, Insmed, marketing status Discontinued). 'Not-approved' rather than 'investigational' is a determination, not a default. The investigational tier requires active development by an identifiable sponsor with registered trials, and there is no sponsor and no registration: the ClinicalTrials.gov API v2 was queried on 2026-08-02 for 'IGF-1 LR3', 'Long R3 IGF-1' and 'LR3 IGF-1' and returned totalCount 0 for all three. There is no programme here that stopped; there was never one. This says nothing about whether IGF-1 LR3 is sold — it is, and the anti-doping literature cited on this record documents confiscated vials of it.

Drugs@FDA (openFDA drug/drugsfda) — applications with an active ingredient named mecasermin — FDA, 31 July 2026Checked against the source on 2 August 2026.

Evidence

Animal or in-vitro only

No randomised controlled trials in humans. Read the notes — the details matter more than the label.

Administration check RUN, not assumed — and it produced the INVERSE of the MOTS-c trap. The studies here are not endogenous-biomarker studies: they really did administer IGF-1 LR3. They administered it to animals. The search, so it can be repeated: PubMed on 2026-08-02 across five name variants — 'long r3 igf-1', 'IGF-1 LR3', 'LR3 IGF-1', 'Long-R3-IGF-1' and 'LongR3' — with every retrieved record opened. The interventional work is in fetal sheep (Am J Physiol Endocrinol Metab 2021 and 2025; J Dev Orig Health Dis 2023), mice (J Alzheimers Dis 2025), rats (Drug Test Anal 2021; Int J Biol Macromol 2025), guinea pigs, beef heifers and cell culture. The same searches restricted to publication types 'Clinical Trial' or 'Randomized Controlled Trial' returned ZERO records. ClinicalTrials.gov API v2 returned totalCount 0 for all three LR3 name variants, so there is no registration to check sponsor, status or results against — and per this site's policy a registration would not have been evidence anyway. Two independent lines therefore agree: our own search, and a 2026 peer-reviewed review that ran its own literature search to January 2026 and placed IGF-1 LR3 in its lowest evidentiary tier. READ THE LABEL NARROWLY. 'Animal-or-in-vitro-only' means no human administration was found at any level of quality. It does NOT mean the animal work supports the marketing: the most recent interventional study is negative on the growth endpoint, and is recorded under faqs. SCOPE: none of this transfers from, or to, mecasermin. Mecasermin has human trials because it is a different, sequence-identical molecule with an approved label; those trials are evidence about mecasermin.

The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration — Frontiers in Endocrinology, 18 June 2026

“At the opposite end, CJC-1295 without DAC, PEG-MGF, and IGF-1 LR3 (tier D) have no peer-reviewed human studies and are supported only by preclinical extrapolation and grey-literature user narratives.”

Checked against the source on 2 August 2026.

What FDA found

FDA’s own words. These are the most citable thing on this site, and the least likely to appear anywhere funded by someone selling the compound.

Drugs@FDA contains no application for IGF-1 LR3. Searching Drugs@FDA for an IGF-1 active ingredient returns exactly two applications, both for different molecules: BLA 021839 (INCRELEX, mecasermin recombinant, Ipsen Inc, marketing status Prescription) and BLA 021884 (IPLEX, mecasermin rinfabate recombinant, Insmed, marketing status Discontinued).
The URL is the query itself, so this negative is checkable rather than asserted. It was cross-run against `openfda.generic_name`, `openfda.substance_name` and `products.brand_name`, each of which returns only these same approved mecasermin products, and against LR3-specific terms, which return NOT_FOUND on every field. Both directions matter: an openFDA record's `openfda` block is sometimes EMPTY, so a query touching only that block can fail for reasons having nothing to do with the substance. A NOT_FOUND from a single badly-shaped query is an artifact of the query — that exact mistake produced a false 'sermorelin is not in Drugs@FDA' claim in this library — so the positive hits above are load-bearing: they prove the query shape finds IGF-1 substances when they exist. Per Drugs@FDA, INCRELEX was originally approved 2005-08-30 as a Type 1 New Molecular Entity with priority review and orphan designation, and the submission records carry the note 'This Former NDA Was Deemed To Be a BLA on March 23, 2020.' IPLEX was originally approved 2005-12-12 and is recorded as discontinued; this record does not state why, because we have not opened a document that says.
Drugs@FDA (openFDA drug/drugsfda) — applications with an active ingredient named mecasermin — FDA, 31 July 2026Checked against the source on 2 August 2026.
The FDA-approved IGF-1 product is a different molecule. INCRELEX (mecasermin) labeling states: 'Mecasermin is a human insulin-like growth factor-1 (rhIGF-1) produced by recombinant DNA technology. IGF-1 consists of 70 amino acids in a single chain with three intramolecular disulfide bridges and a molecular weight of 7649 Da. The amino acid sequence of the product is identical to that of endogenous human IGF-1.'
Recorded verbatim because it is the sentence that settles the disambiguation, and it comes from FDA-approved labeling rather than from us. The approved molecule is defined by being IDENTICAL to endogenous human IGF-1. IGF-1 LR3 is defined by NOT being identical to it — an arginine-for-glutamic-acid substitution at position 3 plus an N-terminal extension, engineered specifically to escape the binding proteins that regulate native IGF-1. Whatever one thinks of that design, it is the opposite of the property this label describes.
INCRELEX (mecasermin) injection — Highlights of Prescribing Information (SPL) — FDA, 18 May 2026
“Mecasermin is a human insulin-like growth factor-1 (rhIGF-1) produced by recombinant DNA technology. IGF-1 consists of 70 amino acids in a single chain with three intramolecular disulfide bridges and a molecular weight of 7649 Da. The amino acid sequence of the product is identical to that of endogenous human IGF-1.”
Checked against the source on 2 August 2026.
The approved indication for INCRELEX is narrow and paediatric: 'INCRELEX (mecasermin) injection is indicated for 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.' The label adds a limitation of use — 'INCRELEX is not a substitute to GH for approved GH indications' — and states 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.'
This is the gap that makes 'IGF-1 is FDA-approved' misleading even when it is true. The approval is for growth failure in children with a rare, defined deficiency confirmed by a height standard deviation score at or below -3.0 AND a basal IGF-1 standard deviation score at or below -3.0 with normal or elevated growth hormone. It is not an approval for muscle gain, recovery, or anti-aging in adults, and the label expressly excludes SECONDARY IGF-1 deficiency — which is the category most adults with a low IGF-1 reading would fall into. This finding is about mecasermin. It is recorded on the IGF-1 LR3 record because the halo it generates is the thing IGF-1 LR3 is sold under.
INCRELEX (mecasermin) injection — Highlights of Prescribing Information (SPL) — FDA, 18 May 2026
“INCRELEX (mecasermin) injection is indicated for 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. … INCRELEX 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.”
Checked against the source on 2 August 2026.
IGF-1 LR3 appears in none of Categories 1, 2 or 3 of FDA's 503A bulk drug substances list updated 2026-05-14. The document returns no hit for 'IGF', 'insulin-like', 'mecasermin', 'LR3' or 'long R3' anywhere.
Recorded to close a misreading, not to assert a status. Verified by fetching the document with a browser user-agent and text-extracting it: zero hits for 'IGF', 'insulin-like', 'mecasermin', 'LR3' or 'long R3' anywhere in the seven pages. The extraction was validated rather than trusted — the six known Category 2 substances (cesium chloride, domperidone, germanium sesquioxide, ibutamoren mesylate, kisspeptin-10 and quinacrine hydrochloride) are all present in the extracted text, so the absence is an absence and not a broken parse. WHAT THIS DOES AND DOES NOT ESTABLISH. It establishes that IGF-1 LR3 is in none of the three categories, which is why this record carries no compoundingStatus: absence alone cannot tell 'nominated then withdrawn' apart from 'never nominated', and no docket entry or briefing document exists for this substance to settle it. It is not permission and it is not a safety finding. Note also what IS in the list, one line away in Category 3 and frequently confused with this compound: 'Mechano growth factor (MGF)', an IGF-1 splice variant and a different substance again. FDA's companion safety-risks page separately publishes a concern for pegylated MGF; it publishes nothing about IGF-1 LR3.
Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the Federal Food, Drug, and Cosmetic Act — FDA, 14 May 2026Checked against the source on 2 August 2026.

Documented safety signals

In a 2023 study, researchers infusing IGF-1 LR3 into late-gestation fetal sheep reported that fetal plasma insulin concentrations decreased and that insulin concentrations during a hyperglycemic clamp were 66% lower with IGF-1 LR3 infusion than with control.
Attributed to the study, and the species is not a footnote — these are fetal sheep, infused directly into the fetal circulation, and nothing about the finding can be carried to an adult human. It is recorded because it runs against the market's mental model of IGF-1 LR3 as a purely anabolic agent: the measured effect here is on insulin secretion. The same group reported in 2021 that a one-week infusion produced reduced glucose-stimulated insulin secretion attributable to an intrinsic islet defect, and in 2023 that isolated islets recovered after an acute infusion. Read as a signal worth knowing about, not as a human safety finding — there is no human safety data to weigh it against.
Attenuated glucose-stimulated insulin secretion during an acute IGF-1 LR3 infusion into fetal sheep does not persist in isolated islets — Journal of Developmental Origins of Health and Disease, 1 June 2023
“Fetal plasma insulin concentrations decreased with IGF-1 LR3 infusion (P < 0.05), and insulin concentrations during the hyperglycemic clamp were 66% lower with IGF-1 LR3 infusion compared to CON (P < 0.0001).”
Checked against the source on 2 August 2026.
An anti-doping laboratory analysing a confiscated injection vial identified its contents as His-tagged Long-R³-IGF-I — a purification construct, not the substance a purchaser would expect — and reported that the effects of that molecule in humans have not been described.
The cleanest product-identity finding on this record, and it cuts deeper than 'underdosed or fake'. A His₆-tag is added during recombinant production to allow purification and is normally cleaved off; the authors' reading is that this vial held material made for biochemical laboratory work and diverted into an injection vial. So the question is not only whether a vial labelled IGF-1 LR3 contains IGF-1 LR3 — it is that even when the core sequence matches, the molecule in the vial may carry an appendage with no described human effects at all. The same laboratory's 2009 survey of confiscated products separately reported unpurified long-R(3)-IGF-1 among its findings.
Detection of His-tagged Long-R³-IGF-I in a black market product — Growth Hormone & IGF Research, 1 October 2010
“(Tandem) mass spectra characterized the protein as Long-R³-IGF-I with a His₆-tag attached to the C-terminus by the linker amino acids Leu-Glu. … The effects of His-tagged Long-R³-IGF-I in humans have not been elucidated or described and the product may rather be a by-product from biochemical studies than synthesized for injection purposes.”
Checked against the source on 2 August 2026.
In a 2021 anti-doping method paper, the authors state that IGF-I and its analogs LongR3-IGF-I, Des(1-3)-IGF-I and R3-IGF-I 'were never approved for use in humans' while being 'readily available as black market products for bodybuilding', and report that 'Abundant signs of lower quality, oxidized peptide forms were found in black market products'.
A quality finding, not a pharmacology finding — and the reason it belongs here is that oxidation is invisible to the checks purchasers actually run. The authors did not go looking for degraded product; they had to add mono-oxidized forms to their detection method because the black-market material contained them. Note also what the paper's own animal work found about persistence: after a single intramuscular administration in rats, unchanged LongR3-IGF-I 'disappeared rapidly after 4 h', while several N-terminal degradation products persisted longer. The 'never approved for use in humans' clause is the authors' statement; this record verifies the same point independently against Drugs@FDA above rather than resting on it.
Detection of LongR3-IGF-I, Des(1-3)-IGF-I, and R3-IGF-I using immunopurification and high resolution mass spectrometry for antidoping purposes — Drug Testing and Analysis, 1 July 2021
“Insulin-like growth factor-I (IGF-I) and its analogs LongR3-IGF-I, Des(1-3)-IGF-I, and R3-IGF-I are prohibited substances in sport. Although they were never approved for use in humans, they are readily available as black market products for bodybuilding and can be used to enhance physical performance. … Abundant signs of lower quality, oxidized peptide forms were found in black market products, justifying the need to monitor at least both the native and mono-oxidized forms.”
Checked against the source on 2 August 2026.
A 2026 review states that claims about IGF-1 analogues including IGF-1 LR3 'rest on extrapolation rather than direct human data', that clinicians 'should treat exposure to these compounds as evidence-poor', and that concern about long-term cancer risk from exogenous IGF-1 analogues 'should be presented as theoretical but clinically relevant, especially in the absence of long-term safety data for off-label IGF-1 analogue use'.
Reproduced with its hedges intact, because the hedges are the finding. The authors do NOT claim IGF-1 LR3 causes cancer; they describe a theoretical concern drawn from epidemiologic associations between higher circulating IGF-1 and several cancers, and from IGF-1 receptor signalling being a well-characterised proliferative pathway in oncology models. Stripping the hedge in either direction misreports them: 'IGF-1 LR3 causes cancer' overstates it, and 'no evidence of harm' misreads an absence of studies as a negative result. Their own summary table records 'No peer-reviewed human studies' in the adverse-effects column for IGF-1 LR3 — there is no human safety profile to report, which is a different statement from a clean one.
The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration — Frontiers in Endocrinology, 18 June 2026
“claims about IGF-1 analogues (PEG-MGF, IGF-1 LR3) and CJC-1295 without DAC rest on extrapolation rather than direct human data; clinicians should treat exposure to these compounds as evidence-poor and frame counselling accordingly. … This risk framing should be presented as theoretical but clinically relevant, especially in the absence of long-term safety data for off-label IGF-1 analogue use.”
Checked against the source on 2 August 2026.
The FDA-approved IGF-1 product mecasermin (INCRELEX) — a different molecule from IGF-1 LR3, recorded here for contrast — carries contraindications for closed epiphyses and for malignant neoplasia or a history of malignancy, and its labeling lists hypoglycemia, hypersensitivity including anaphylaxis, intracranial hypertension, tonsillar and adenoidal hypertrophy, slipped capital femoral epiphysis and progression of preexisting scoliosis among serious adverse reactions.
Recorded on this record for one reason: IGF-1 is marketed as a benign endogenous molecule, and the one IGF-1 product FDA has actually reviewed is contraindicated in malignancy and reports hypoglycemia at high frequency in its trials. SCOPE, and it runs in both directions: these are mecasermin's labeled risks in a paediatric deficiency population, and they cannot be transferred to IGF-1 LR3 in adults as if they were its safety profile. What they establish is narrower and still worth stating — that FDA's own review of an IGF-1 drug did not conclude it was risk-free, and that a purchaser of an unapproved analogue is never asked the screening questions this label requires, because there is no label to ask them.
INCRELEX (mecasermin) injection — Highlights of Prescribing Information (SPL) — FDA, 18 May 2026
“Known Hypersensitivity to mecasermin (4) Closed Epiphyses (4) Malignant Neoplasia (4) … INCRELEX is contraindicated in pediatric patients with malignant neoplasia or a history of malignancy”
Checked against the source on 2 August 2026.

Questions people actually ask

Every answer cites the document behind it. Where the honest answer is “nobody knows”, that is the answer you will get.

Is IGF-1 LR3 FDA approved?: No. IGF-1 LR3 has no FDA application of any kind. Searching Drugs@FDA for an IGF-1 active ingredient returns exactly two applications, and both are different molecules: BLA 021839 (INCRELEX, mecasermin recombinant, Ipsen, marketing status Prescription) and BLA 021884 (IPLEX, mecasermin rinfabate recombinant, Insmed, marketing status Discontinued). Queries against the generic-name, substance-name and brand-name fields return only those same approved mecasermin products, and every query for the LR3 analogue returns no matches on any field. IGF-1 LR3 is also not in clinical development: ClinicalTrials.gov returned zero registered studies for 'IGF-1 LR3', 'Long R3 IGF-1' and 'LR3 IGF-1' when queried on 2 August 2026, so there is no sponsor and no registered trial to point at. Being unapproved says nothing about whether it is sold — it is.
Drugs@FDA (openFDA drug/drugsfda) — applications with an active ingredient named mecasermin — FDA, 31 July 2026Checked against the source on 2 August 2026.
Is IGF-1 LR3 the same thing as Increlex or mecasermin?: No — they are different molecules, and the FDA-approved label says so on its face. INCRELEX (mecasermin) labeling states that 'IGF-1 consists of 70 amino acids in a single chain with three intramolecular disulfide bridges and a molecular weight of 7649 Da' and that 'The amino acid sequence of the product is identical to that of endogenous human IGF-1.' IGF-1 LR3 is defined by not being identical: it carries an arginine substituted for glutamic acid at position 3 plus an additional N-terminal extension, engineered to reduce binding to the IGF-1 binding proteins that regulate the native hormone. Because they are different molecules, mecasermin's approval, its prescribing information and the clinical trials behind it describe mecasermin and do not describe IGF-1 LR3. The approved indication is also far narrower than the market implies: INCRELEX is indicated 'for 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', and the label states it 'is not indicated for use in patients with secondary forms of IGF-1 deficiency'.
INCRELEX (mecasermin) injection — Highlights of Prescribing Information (SPL) — FDA, 18 May 2026
“The amino acid sequence of the product is identical to that of endogenous human IGF-1. … INCRELEX (mecasermin) injection is indicated for 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.”
Checked against the source on 2 August 2026.
Are there any human studies on IGF-1 LR3?: No peer-reviewed human studies of IGF-1 LR3 have been identified. A 2026 narrative review in Frontiers in Endocrinology, which ran its own literature search to January 2026, assigns IGF-1 LR3 to the lowest of its four evidentiary tiers and states that IGF-1 LR3, PEG-MGF and CJC-1295 without DAC 'have no peer-reviewed human studies and are supported only by preclinical extrapolation and grey-literature user narratives', adding that 'Mechanistic plausibility for tier-D compounds does not constitute clinical evidence and should not be interpreted as such.' An independent search on 2 August 2026 reached the same result: across five name variants, every interventional study retrieved from PubMed administered IGF-1 LR3 to animals — fetal sheep, mice, rats, guinea pigs, cattle — or to cells in culture, the same searches restricted to clinical-trial and randomised-controlled-trial publication types returned zero records, and ClinicalTrials.gov returned zero registered studies. The absence of human studies is not the same as evidence of safety, and it is not the same as evidence of harm.
The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration — Frontiers in Endocrinology, 18 June 2026
“IGF-1 LR3 is an engineered analogue of IGF-1 characterised by the substitution of glutamic acid with arginine at position 3 and the presence of an additional N-terminal amino acid extension. … CJC-1295 without DAC, PEG-MGF, and IGF-1 LR3 (tier D) have no peer-reviewed human studies and are supported only by preclinical extrapolation and grey-literature user narratives.”
Checked against the source on 2 August 2026.
Is IGF-1 LR3 banned in sport?: Yes. The World Anti-Doping Agency's 2026 Prohibited List, effective 1 January 2026, prohibits 'Insulin-like growth factor 1 (IGF-1, mecasermin) and its analogues' under S2.3, Growth Factors and Growth Factor Modulators. IGF-1 LR3 is an IGF-1 analogue and falls inside that wording; the List is also written to catch substances it does not name, stating that 'The following substances, and other substances with similar chemical structure or similar biological effect(s), are prohibited.' Class S2 is prohibited at all times, both in and out of competition, and the List records that 'All prohibited substances in this class are non-Specified Substances', which is the category carrying the least scope for a reduced sanction. Anti-doping laboratories have published a validated method that distinguishes LongR3-IGF-I from the related analogues Des(1-3)-IGF-I and R3-IGF-I, so a detection method for this specific molecule exists in the literature — which is not the same as a statement about how often it is applied.
The 2026 Prohibited List — World Anti-Doping Code International Standard — World Anti-Doping Agency, 1 January 2026
“Insulin-like growth factor 1 (IGF-1, mecasermin) and its analogues … and other growth factors or growth factor modulators affecting muscle, tendon or ligament protein synthesis/degradation, vascularisation, energy utilization, regenerative capacity or fibre type switching.”
Checked against the source on 2 August 2026.
Can a compounding pharmacy legally make IGF-1 LR3?: Not under section 503A. IGF-1 LR3 does not appear anywhere in FDA's list of bulk drug substances nominated for use in compounding under section 503A, updated 14 May 2026 — not in Category 1, not in Category 2, not in Category 3. A bulk drug substance that is neither the subject of an applicable USP or NF monograph nor a component of an FDA-approved drug must appear on the 503A bulks list to be used in 503A compounding, and IGF-1 LR3 appears on it in no category. Read the absence precisely: it is not a legalisation, it is not a safety finding, and it does not tell you whether IGF-1 LR3 was ever nominated and withdrawn or was simply never nominated at all — which is why this record carries no 503A category rather than guessing one. Note that a nearby entry is routinely confused with this compound: 'Mechano growth factor (MGF)' does appear in the list, and it is an IGF-1 splice variant, not IGF-1 LR3.
Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the Federal Food, Drug, and Cosmetic Act — FDA, 14 May 2026Checked against the source on 2 August 2026.
What is actually in a vial sold as IGF-1 LR3?: Not necessarily IGF-1 LR3, and not necessarily only IGF-1 LR3. In a 2010 case report, an anti-doping laboratory analysed a confiscated injection vial and identified the contents by mass spectrometry as 'Long-R³-IGF-I with a His₆-tag attached to the C-terminus by the linker amino acids Leu-Glu' — a purification construct of the kind added during recombinant protein production for laboratory work and normally removed. The authors wrote that 'The effects of His-tagged Long-R³-IGF-I in humans have not been elucidated or described and the product may rather be a by-product from biochemical studies than synthesized for injection purposes.' Separately, a 2021 anti-doping method paper reported that 'Abundant signs of lower quality, oxidized peptide forms were found in black market products', and a 2009 laboratory survey reported unpurified long-R(3)-IGF-1 among confiscated items. The point is narrower than 'fakes exist': even when the core sequence matches, the molecule in the vial may carry modifications with no described human effects at all.
Detection of His-tagged Long-R³-IGF-I in a black market product — Growth Hormone & IGF Research, 1 October 2010
“(Tandem) mass spectra characterized the protein as Long-R³-IGF-I with a His₆-tag attached to the C-terminus by the linker amino acids Leu-Glu. … The effects of His-tagged Long-R³-IGF-I in humans have not been elucidated or described and the product may rather be a by-product from biochemical studies than synthesized for injection purposes.”
Checked against the source on 2 August 2026.
Does IGF-1 LR3 build muscle?: No study in humans has tested that question. The most recent interventional study of IGF-1 LR3 is in fetal sheep and is negative on its growth endpoint: researchers reported in the American Journal of Physiology — Endocrinology and Metabolism in 2025 that 'a 1-wk IGF-1 LR3 treatment did not improve growth in FGR fetuses' after treating growth-restricted fetal sheep, and that 'IGF-1 LR3 treatment administered directly into growth-restricted fetal sheep circulation did not improve fetal growth'. They also reported that circulating amino acids, notably branched-chain amino acids, decreased with treatment. That finding is about growth-restricted fetal sheep and cannot be carried across to adults, in either direction — but it is the opposite of a supportive result, and it is the highest-quality interventional evidence that exists for this compound. The mechanistic case for IGF-1 LR3 rests on IGF-1 receptor signalling being well characterised in cell and oncology models, which a 2026 review in Frontiers in Endocrinology — cited separately on this record, not in the study quoted here — describes as plausibility rather than clinical evidence.
IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetal sheep — American Journal of Physiology — Endocrinology and Metabolism, 1 January 2025
“In summary, a 1-wk IGF-1 LR3 treatment did not improve growth in FGR fetuses. … IGF-1 LR3 treatment administered directly into growth-restricted fetal sheep circulation did not improve fetal growth or attenuate circulating insulin or fetal GSIS.”
Checked against the source on 2 August 2026.