IGF-1 LR3
also known as Long R3 IGF-1, LR3-IGF-I, Long Arg3 IGF-1
Synthetic IGF-1 analogue with arginine substitution at position 3 and a 13-amino-acid N-terminal extension. Exhibits markedly reduced binding to IGF-binding proteins (IGFBPs), producing prolonged half-life and enhanced bioavailability compared to native IGF-1. Primarily studied in research contexts for anabolic, anti-apoptotic, and cell proliferation effects.
- Class
- IGF-1 Analogue
- Evidence level
- Strong animal evidence
- Regulatory status
- Not FDA-approved (US) — research use only
At a glance
Research only · SQ typical in animal models
Primary target — IGF-1 receptor (IGF-1R) [mctavish-2009].
Pathway — IGF-1R → IRS-1 → PI3K/Akt → Cell proliferation, protein synthesis, anti-apoptosis [muhlbradt-2009].
Downstream effect — Enhanced cell proliferation, muscle anabolism, inhibition of apoptosis, increased telomerase activity.
Origin — Synthetic 83-AA analogue: 13-AA N-terminal extension + Arg substitution at position 3.
Feedback intact — No — exogenous IGF analogue bypasses GH-mediated regulation.
| Parameter | Value |
|---|---|
| Research dose (animal models) | Variable by protocol and speciesIn vivo murine atherosclerosis studies used sustained delivery. |
| In vitro typical concentration | 10–1000 ng/mL [thomas-2007]Dose-dependent effects on follicle growth and estradiol production. |
| Half-maximal stimulation | 0.6 nM LR3 vs 1.5 nM native IGF-1 [price-2004]2.5-fold greater potency in lung fibroblast proliferation. |
| Evidence basis | Animal / in vitro only |
| Human use | Not FDA-approved; no published human trials |
Reconstitution
A pure mass-to-volume utility. Enter what you have in the vial; the atlas computes the volume per dose. No prescription information.
Animal models only · No controlled human trials
| Outcome | Finding |
|---|---|
| Mechanism | IGF-1R activation → lipolytic signaling; secondary to anabolic effects |
| Direct lipolytic evidence | Minimal — primarily anabolic/anti-apoptotic in literature |
| Atherosclerotic plaque effects | Reduced stenosis and core size in ApoE-KO mice [von-2011]Plaque stabilization via vSMC phenotype modulation, not direct fat loss. |
| Human data | None published |
- — Active malignancy or history of cancer
- — Not approved for human use
- — Diabetes or glucose intolerance
- — Family history of cancer
- 01Research use only
IGF-1 LR3 is not FDA-approved for human use. All administration data derives from animal or in vitro studies.
- 02Typical research route
Subcutaneous or intraperitoneal injection in animal models. In vitro: added directly to culture medium at concentrations of 10–1000 ng/mL. [thomas-2007]
- 03Reconstitution (research)
Lyophilised powder reconstituted in sterile water or buffered saline per manufacturer protocol. Store at 2–8 °C after reconstitution.
- 04Stability
Enhanced stability vs native IGF-1 due to reduced IGFBP binding; exact half-life in vivo not fully characterized in humans.
GHRP-6 stimulates endogenous GH release, which drives hepatic IGF-1 synthesis. IGF-1 LR3 provides exogenous, IGFBP-resistant IGF signaling. Combining upstream GH stimulation with downstream IGF receptor activation creates a dual-pathway anabolic effect. However, this bypasses natural feedback and carries compounded mitogenic risk.
Ipamorelin (selective GHRP) stimulates pulsatile GH release without cortisol/prolactin elevation. IGF-1 LR3 directly activates IGF-1R independent of GH. This stack targets both upstream (GH secretion) and downstream (IGF receptor) nodes but eliminates physiological feedback, raising safety concerns around unchecked proliferation.
Frequently asked
How does IGF-1 LR3 work?
IGF-1 LR3 acts on IGF-1 receptor (IGF-1R), signalling via IGF-1R → IRS-1 → PI3K/Akt → Cell proliferation, protein synthesis, anti-apoptosis. [mctavish-2009][muhlbradt-2009]
Is IGF-1 LR3 FDA-approved?
IGF-1 LR3 is not FDA-approved in the United States and is handled as a research compound (research use only). Regulatory status may differ in other jurisdictions.
Sources
of 58 rendered claims carry a resolvable citation.
- [mctavish-2009]McTavish 2009 — Novel insulin-like growth factor-methotrexate covalent conjugate inhibits tumor growth in vivo at lower dosage than methotrexate alone.
journal, 2009 - [muhlbradt-2009]Muhlbradt 2009 — NKX3.1 activates expression of insulin-like growth factor binding protein-3 to mediate insulin-like growth factor-I signaling and cell proliferation.
journal, 2009 - [price-2004]Price 2004 — Regulation of insulin-like growth factor (IGF)-binding protein expression by growth factors and cytokines alters IGF-mediated proliferation of postnatal lung fibroblasts.
journal, 2004 - [thomas-2007]Thomas 2007 — Effects of IGF-I bioavailability on bovine preantral follicular development in vitro.
journal, 2007 - [von-2011]von 2011 — IGF-1 has plaque-stabilizing effects in atherosclerosis by altering vascular smooth muscle cell phenotype.
journal, 2011 - [wetterau-2003]Wetterau 2003 — Insulin-like growth factor I stimulates telomerase activity in prostate cancer cells.
journal, 2003