Modified insulin-like growth factor protein · Fact sheet
IGF-1 LR3
Also known as Long R3 IGF-I · Long arginine 3 IGF-1
IGF-1 LR3 is a modified IGF-1 research protein with reduced binding to IGF-binding proteins. Cell and animal findings do not establish safe human muscle growth, recovery or cognitive benefits.
What is IGF-1 LR3?
The analog extends and changes the IGF-1 sequence. Reduced binding to carrier proteins changes its biological exposure.
It is not the same molecule as approved mecasermin, and mecasermin labeling cannot supply an LR3 regimen.
Benefits & claims
Interest comes from IGF-1 growth signaling and cell-culture use. More tissue growth is not automatically better health or improved athletic function.
What the evidence supports
- Guinea-pig infusion increased some organ weights without improving overall growth.
- A cachexia mouse study limited muscle loss but accelerated tumor growth with LR3.
- A prolonged Alzheimer-model mouse study altered plaque biology without preserving cognition.
Research areas
- IGF-1 receptor signaling
- Cell growth
- Preclinical body composition
Dosage & frequency
No established human regimenThe reviewed sources do not establish a human treatment amount or frequency for IGF-1 LR3. Animal and laboratory exposures are not human regimens.
How to read these amounts
An approved regimen belongs to a specific product, indication, and population. A study regimen describes what researchers tested; it does not establish a prescription or a safe self-use protocol. Products, routes, and formulations are not interchangeable. A prescriber uses the full label and individual clinical circumstances.
Personal accounts may describe amounts, schedules and outcomes beyond clinical research. They do not establish a regimen. Read the reported experiences
Formulations, interactions & practical context
- Identity and pharmacology
- The analog extends and changes the IGF-1 sequence. Reduced binding to carrier proteins changes its biological exposure.
Formulation differences
- It is not the same molecule as approved mecasermin, and mecasermin labeling cannot supply an LR3 regimen.
Interactions & precautions
- The reviewed sources do not establish a comprehensive human interaction profile for this exact substance or combination.
What is still unresolved
- Human safety and pharmacokinetics
- Whether muscle changes improve function
- Tumor and metabolic effects over time
Side effects & risks
- Tumor acceleration in a cancer-bearing mouse model is a preclinical hazard signal, not a quantified human cancer risk.
- Effects on organ growth and metabolic signaling warrant concern; human incidence and repeated-exposure safety remain unknown.
This is a summary of the cited evidence, not a complete product label. A lack of human safety data does not establish safety.
Clinical research
Mostly animal or lab researchThe cited studies involve cell culture, guinea pigs and mice. They include unfavorable or absent functional results as well as biological activity.
Studies
Seven-day infusion study; organ effects without greater overall growth.
Muscle preservation accompanied by accelerated tumor growth.
No preservation of behavior or memory despite plaque changes.
Personal experiences
Reports describe what someone noticed. They cannot establish cause, typical results, or how often a side effect happens. Amounts and schedules describe the individual account, not an effective or safe dose. Product identity and strength may be unverified, and missing details are left explicit.
No attributable personal accounts were found in the sources reviewed.
Approval status
No FDA-approved IGF-1 LR3 product is established. Research use and approved uses of other IGF-1 products are separate matters.
Preclinical evidence; no FDA-approved product
Approval covers the labeled product, use and population. A trial phase does not establish success; a stopped program is not ongoing research.
Open questions
- Human safety and pharmacokinetics
- Whether muscle changes improve function
- Tumor and metabolic effects over time
Summary
A prolonged Alzheimer-model mouse study altered plaque biology without preserving cognition.
Sources
Medical evidence and regulatory sources are listed here. Personal reports are linked separately in the experiences section.
- pubmedLR3 organ growth in guinea pigs
Seven-day infusion study; organ effects without greater overall growth.
- pubmedLR3 in a cancer-cachexia mouse model
Muscle preservation accompanied by accelerated tumor growth.