● pepmg Research Desk · Peer-reviewed evidence review
What the research says about IGF-1 LR3
A neutral summary of the peer-reviewed literature on IGF-1 LR3 (Long R3 IGF-1), an insulin-like growth factor-1 analog used mainly as a laboratory research reagent and studied only in animal and cell models. No controlled human trials of the analog exist. Research use only.
Preclinical only — Animal or in-vitro studies only — no controlled human trials. This describes the state of the published literature, not a claim that this compound works, is safe, or is for human use. Research use only.
The short version
- IGF-1 LR3 (Long R3 IGF-1) is a modified insulin-like growth factor-1 analog with reduced binding to the IGF-binding proteins, used chiefly as a laboratory research reagent [3][6].
- The published work on IGF-1 LR3 itself is animal and cell-based (fetal-sheep infusions, cardiac and insulin studies, and in-vitro cell work), not human trials [1][4].
- There are no controlled human trials of IGF-1 LR3; broader IGF-1 biology in humans does not transfer to a safety or efficacy claim for this analog [2][7].
- This page reports what the studies measured. It is not medical advice, an efficacy or safety claim, or dosing guidance. Research use only.
What IGF-1 LR3 is
IGF-1 LR3, also called Long R3 IGF-1, is described in the literature as an analog of insulin-like growth factor-1 (IGF-1) engineered to have low affinity for the IGF-binding proteins and high affinity for the IGF-1 receptor, which increases the fraction of unbound, active peptide relative to native IGF-1 [3]. It is produced recombinantly and is used mainly as a research reagent, including as a cell-culture growth supplement [6]. It is sold by third-party research-chemical vendors and is offered for laboratory and research use only.
Essentially all of the published research on IGF-1 LR3 specifically is preclinical, carried out in animals and in cultured cells rather than in controlled human trials [1][4]. Broader IGF-1 biology has been studied in humans, but findings about native IGF-1 do not transfer to a safety or efficacy claim for this analog.
What the preclinical research has measured
Preclinical onlyMuch of the direct IGF-1 LR3 literature comes from infusion studies in fetal sheep. A one-week infusion of LR3 IGF-1 into late-gestation fetal sheep was reported to increase the weight of some fetal organs, such as the heart, adrenal gland, and spleen, and to raise skeletal-muscle myoblast proliferation, without increasing overall fetal weight [1]. In a companion study using a growth-restricted fetal-sheep model, a one-week IGF-1 LR3 infusion did not improve fetal growth [2].
A related fetal-sheep study reported that IGF-1-stimulated cardiac growth was accompanied by matched growth of the coronary vasculature [4]. Other fetal-sheep work examined effects on insulin: a one-week IGF-1 LR3 infusion was reported to lower plasma insulin and to reduce glucose-stimulated insulin secretion, which the authors attributed to an intrinsic islet effect [3].
In cell and tissue systems, the stable analog Long R3 IGF-1 has been used to probe IGF-1 signaling: in an atherosclerosis model combining cultured vascular smooth muscle cells with an apolipoprotein-E-knockout mouse model, Long R3 IGF-1 was reported to alter smooth-muscle-cell phenotype and plaque composition [5]. Manufacturing-oriented work recombinantly expressed IGF-1 and LR3 IGF-1 and reported that the purified analog retained cell-proliferation bioactivity comparable to a standard IGF-1 reference [6]. All of this is animal, cell, or protein-production research.
What the trials report on safety and adverse events
Preclinical onlyThere is no controlled human-trial safety data for IGF-1 LR3 to report. The direct literature is confined to animal infusion studies and cell experiments, which are not designed to establish human safety, tolerability, or adverse-event rates [1][3][4]. Some of the animal findings, such as lowered fetal insulin secretion, illustrate that manipulating the IGF-1 axis has systemic effects that these study designs cannot translate into a human safety profile [3].
A recent review of growth-hormone/IGF-1-axis peptides used outside medical supervision places IGF-1 Long R3 among analogs with a near-absence of human studies and notes reported adverse effects across this broader class, while stressing the lack of regulatory approval and the uncertainty of unregulated product composition [7]. Because human data on the analog are absent, nothing here should be read as evidence that IGF-1 LR3 is safe for people. This is not medical advice; consult a qualified professional and read the studies directly.
How strong is the evidence
Because the IGF-1 LR3 evidence base is entirely preclinical (animal infusion studies, cell and tissue experiments, and protein-production work, with no controlled human trials), it is characterized as preclinical only [1][6][7]. IGF-1 is well studied in human physiology, but that general biology does not establish that this specific analog works or is safe in people, and animal results frequently fail to translate.
Nothing here is dosing, medical, or safety guidance. Read the studies themselves and consult a qualified professional. This page is a map to the evidence, not a recommendation.
Sources · 7
- IGF-1 infusion to fetal sheep increases organ growth but not by stimulating nutrient transfer to the fetus.
- IGF-1 LR3 does not promote growth in late-gestation growth-restricted fetal sheep.
- Reduced glucose-stimulated insulin secretion following a 1-wk IGF-1 infusion in late gestation fetal sheep is due to an intrinsic islet defect.
- Coronary vascular growth matches IGF-1-stimulated cardiac growth in fetal sheep.
- IGF-1 has plaque-stabilizing effects in atherosclerosis by altering vascular smooth muscle cell phenotype.
- Recombinant expression of IGF-1 and LR3 IGF-1 fused with xylanase in Pichia pastoris.
- The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration.
pepmg summarizes the peer-reviewed literature and links to every source — it sells nothing, ships nothing, and gives no medical, dosing, or human-use guidance. Don't just trust this summary: follow any citation to its source and read it yourself. Research use only.