IGF-1 LR3

In simple words

IGF-1 LR3 is a modified man-made form of IGF-1 that stays active in the blood longer. It is studied in animals as a strong stimulator of tissue growth and a protector of nerve cells, but there have been no human trials.

What this molecule is

83 aa. Modifications: deletion of aa 1-3 + Glu3→Arg3 substitution + 13-aa N-terminal extension. ~10× less binding to IGFBP. T½ ~20-30 h. ~9111 Da.

Why it is studied

Modified IGF-1 with ↑bioavailability (↓IGFBP binding) and prolonged action. Preclinical: potent anabolic agent, neuroprotector (AD models), glucose regulator. Has NO regulatory approval.

How it works

Same IGF-1R, but ↓binding to IGFBP-1-6 → ↑free fraction. T½ 20-30 h vs 12-15 h for the native form. In the GI tract: the most pronounced mitogenic effect. In neurons: ↓amyloid plaques (intranasal, 2025).

Doses used in studies

There are NO clinical data. In practice, 20-50 mcg/day SC was used, an extrapolation from animal studies that has not been validated.

Combined with in studies

• Mod-GRF + Ipamorelin — stimulating the GH axis → ↑endogenous IGF-1, preferable
• Insulin — DO NOT combine without monitoring

Level of evidence

Level C Animal studies. Effects have been shown in animals. Whether they carry over to humans has not been proven. Animals and in vitro only. No clinical data.

Important to know

⚠️ Has NOT undergone clinical trials. WADA S2. Severe hypoglycemia + cancer risk (potent mitogen, c-Met oncogene). DO NOT confuse with Increlex® (FDA). Research only.

Studies in PubMed

1. Des(1-3)IGF-I: a truncated form of insulin-like growth factor-I. (Int J Biochem Cell Biol, 1996)
2. Increased weight gain, nitrogen retention and muscle protein synthesis following treatment of diabetic rats with insulin-like growth factor (IGF)-I and des(1-3)IGF-I. (Biochem J, 1991)
3. Intranasal long R3 insulin-like growth factor-1 treatment promotes amyloid plaque remodeling in cerebral cortex but fails to preserve cognitive function in male 5XFAD mice. (J Alzheimers Dis, 2025)
4. Attenuated glucose-stimulated insulin secretion during an acute IGF-1 LR3 infusion into fetal sheep does not persist in isolated islets. (J Dev Orig Health Dis, 2023)
5. Des(1-3)IGF-1 treatment normalizes type 1 IGF receptor and phospho-Akt (Thr 308) immunoreactivity in predegenerative retina of diabetic rats. (Int J Exp Diabesity Res, 2003)
6. Effectiveness and safety of rhIGF1 therapy in patients with or without Laron syndrome. (Eur J Endocrinol, 2021)