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IGF-LR3

Long R3 IGF-1 · LR3-IGF-1 · IGF-1 LR3

C
Animal replicated
Research chemicalIGF-1 AnalogGrowth Factor PeptidePeptide Hormone Analog
RouteInjectableGray-market only
C
Evidence grade: Animal replicated

Effect demonstrated in multiple animal studies; human data sparse or extrapolated. Grades summarize evidence quality, not whether a compound is appropriate, legal, or risk-free.

At a glance
What it is
Long Arg3 IGF-1 / Long-R3 Insulin-Like Growth Factor-1 / LR3-IGF-1 — IGF-1 Analog, Growth Factor Peptide, Peptide Hormone Analog.
Why people use it
Used primarily for tissue repair and healing and muscle and performance.
What the evidence supports
IGF-LR3 dosing protocols are based entirely on community practice — there are no clinically validated dose ranges for the body composition application. All numbers below are observational community data, not clinical guidance.
If you only read one thing

IGF-LR3 was designed to remove a regulatory constraint — IGFBP binding — so scientists could study clean IGF-1R pharmacology. The IGFBP system it bypasses exists in the body for a reason. It regulates how much free IGF-1R stimulation occurs in each tissue, including tissues where IGF-1R activation promotes cell survival and proliferation — that is, tumor tissue. IGF-1R is one of the most heavily targeted receptors in oncology drug development: pharmaceutical companies build antibodies to block it. The community uses IGF-LR3 to activate it continuously for 4-6 weeks. The compound has no controlled human evidence for body composition benefit, no approved indication, no regulatory oversight of the doses used, and a theoretical cancer risk whose real magnitude in the doses and cycles actually employed is genuinely unknown. The anabolic pathways are real. The risks are not fabricated. Whether the benefit-risk calculation is favorable for any individual user depends on variables — including undetected pre-malignant cell populations — that no current test can reliably assess.

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Published literature
0human trials0human studies0animal0in vitro
Evidence reality check
Human evidence
No human studies
0 observational; RCT evidence not present in corpus.
Preclinical base
0 lab signals
0 animal; 0 in-vitro/mechanistic.
Evidence snapshot
IGF-LR3 dosing protocols are based entirely on community practice — there are no clinically validated dose ranges for the body composition application. All numbers below are observational community data, not clinical guidance.
From the chapter quick-reference block.
Categories
Healing & RecoveryMuscle & PerformanceHormonal & HPTA
Properties
Active malignancy: hard stopWADA S2Not injectable
Half-life
the 20-30 hour half-life meant once-daily dosing
Evidence
CAnimal replicated
Why the IGFBP System Matters
In human physiology, approximately 99% of circulating IGF-1 is bound to one of six IGF binding proteins (IGFBPs). Only the 1% that is 'free' can bind IGF-1 receptors on target cells. IGFBPs serve as a sophisticated delivery and regulation system — controlling when, where, and how much IGF-1 reaches receptors in any given tissue. This regulation is not just a pharmacokinetic inconvenience; it is a biological control system that limits mitogenic and anti-apoptotic IGF-1R signaling to appropriate levels in appropriate contexts. IGF-LR3 bypasses this entire system, circulating almost entirely as free, receptor-accessible analog. At equal total concentrations, this means ~100x more receptor-accessible ligand compared to native IGF-1.
The Pharmacological Consequence
Because IGF-LR3 circulates as nearly 100% free ligand: it delivers sustained, continuous IGF-1R stimulation across all tissues that express IGF-1R for the duration of its 20-30 hour half-life. There is no tissue selectivity — muscle cells, liver cells, adipocytes, and tumor cells all express IGF-1R and all receive IGF-LR3 signal. The compound does not preferentially stimulate muscle over other tissues. Any oncogenic cell population with elevated IGF-1R expression will be stimulated equivalently.
Cancer Risk — The Central Safety Concern
IGF-1R is one of the most actively studied drug targets in oncology. Pharmaceutical companies are developing anti-IGF-1R monoclonal antibodies and small-molecule inhibitors specifically because IGF-1R activation promotes tumor cell survival, proliferation, and metastasis. Elevated circulating IGF-1 is epidemiologically associated with increased risk of breast, prostate, and colorectal cancer. IGF-LR3, which delivers sustained unregulated IGF-1R stimulation, has no human safety data for the body composition doses and durations used by the community. The cancer risk is theoretical — no controlled human study has established it — but the mechanistic basis is one of the most well-documented in cancer biology.
Human Evidence for Body Composition
There are no controlled human clinical trials of IGF-LR3 for body composition, muscle hypertrophy, or fat loss in healthy adults. All body composition evidence is: (1) preclinical — animal models and cell culture; (2) mechanistic — inferred from the well-established downstream pathways (PI3K/Akt/mTOR, satellite cell activation); (3) community consensus — observational reports from users. Grade E for body composition claims. The anabolic mechanisms are real; the human outcome evidence is absent.
Regulatory and WADA Status
Not FDA-approved for any indication. Not approved for human use by any regulatory authority. Native IGF-1 (mecasermin, Increlex) is FDA-approved for severe primary IGF-1 deficiency (Laron syndrome) — IGF-LR3 is not the same compound and does not share this approval. WADA S2 — Peptide Hormones, Growth Factors, Related Substances and Mimetics — banned at all times. Available only as a research chemical for in vitro and preclinical research use.
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