83AA Preclinical
IGF-1 LR3
A 83-amino-acid IGF-1 analogue with ~1,000-fold reduced binding-protein affinity, conferring 20–30 h half-life and ~3× greater potency than native IGF-1 in preclinical models.
In Plain English:
Your body naturally makes insulin-like growth factor 1 (IGF-1) to build muscle, burn fat, and repair tissue — but it gets mopped up by binding proteins within minutes. IGF-1 LR3 is a lab-engineered version with a 13-amino-acid tail added to one end and a single amino-acid swap (glutamate → arginine at position 3). Those two changes mean binding proteins barely grab it, so it stays free and active in the bloodstream for up to 30 hours instead of 15 minutes. Researchers study it for muscle hypertrophy and hyperplasia (growing existing fibres and creating new ones), faster tissue repair, fat metabolism, and — more recently — Alzheimer's amyloid remodelling.
Research Maturity
Preclinical (120+ PubMed-indexed publications on IGF-1 LR3 / LongR3; largely preclinical+ Studies)
Focus
Cell Growth & Repair
Metabolic Signaling
Muscle & Strength Research
Origin
Fully synthetic recombinant protein; engineered by GroPep Ltd (Australia) in the early 1990s as a serum-free cell-culture supplement. The sequence is identical to human IGF-1 except for an N-terminal 13-aa extension (MFPAMPLSLFVNG) and Glu3→Arg3 substitution. Never progressed to FDA or EMA regulatory approval for any human therapeutic indication.
Mechanism
Binds the IGF-1 receptor (IGF-1R) with 2–3× higher affinity than native IGF-1, triggering the IGF-1R/IRS-1/PI3K/Akt and MAPK/ERK1–2 cascades. PI3K/Akt activation (EC50 2–5 nM, peak at 5–15 min) drives mTOR-dependent protein synthesis, GLUT4 translocation, and anti-apoptotic signalling. ERK activation drives mitogenesis (new myofibre nuclei). The Glu3→Arg3 substitution reduces IGFBP-1–6 affinity by ~1,000-fold, keeping >90 % of the molecule free and bioactive for 48 h in serum-containing media vs <20 % for native IGF-1. Bioactivity remains >90% after 48 h at 37 °C in serum-containing media.
Outcome
Preclinical endpoints: lean muscle mass, myofibre cross-sectional area, adipose lipolysis (fat loss), organ weight (adrenal, kidney, spleen, gut), tissue repair rate, amyloid plaque morphology (Alzheimer's models), and glucose/amino-acid flux.
