Modified IGF-1 analog peptide (research-stage anabolic agent)
Long R3 IGF-1
A potent IGF-1 analog discussed for muscle and tissue anabolism with significant theoretical risk profile and no approved use.
- Evidence:
- Preclinical evidence primarily
- Status:
- Not FDA-approved
- Reviewed:
- 2026-08-03
Also known as: Long R3 IGF-1, Insulin-like growth factor-1 LR3
What is Long R3 IGF-1?
A potent IGF-1 analog discussed for muscle and tissue anabolism with significant theoretical risk profile and no approved use.
This profile is educational. It organizes publicly discussed research context for Long R3 IGF-1 and related naming aliases — it is not a treatment guide.
Proposed mechanism
IGF-1 receptor activation with reduced IGF binding protein affinity and extended half-life, promoting cell proliferation and anabolism.
Mechanism language on PepGuide describes how researchers discuss pathways. Proposed mechanisms can change as evidence evolves.
Current research notes
Human evidence grade: Preclinical evidence primarily
Preclinical evidence grade: Early-stage human research
IGF-1 LR3 is significantly more potent than endogenous IGF-1 in vitro. No approved human therapeutic use. WADA strictly prohibits. Researchers note theoretical risks including hypoglycemia, organomegaly, and mitogenic concerns. Human clinical evidence for safe use is absent.
Key uncertainties
- Any safe human research context outside controlled trials
Research areas being studied
- Muscle anabolism research
- Tissue repair research
Being studied for a topic is not the same as proven benefit in that topic. Prefer primary literature for study design, endpoints, and limitations.
Safety & side-effect notes
Reported or discussed adverse effects
- Hypoglycemia in animal models
- Human AE profile unknown
Additional risks & considerations
- Hypoglycemia
- Mitogenic/cancer theoretical concerns
- Organ growth
- WADA prohibited
Regulatory status
Not FDA-approved
Prohibited in sport; not approved for any indication.
Regulatory framing here is educational and can lag policy changes. Check official sources for current status.
Frequently asked questions
What is Long R3 IGF-1?
A potent IGF-1 analog discussed for muscle and tissue anabolism with significant theoretical risk profile and no approved use.
How does Long R3 IGF-1 work (proposed mechanism)?
IGF-1 receptor activation with reduced IGF binding protein affinity and extended half-life, promoting cell proliferation and anabolism.
What is Long R3 IGF-1 being researched for?
Long R3 IGF-1 has been discussed in research contexts including: Muscle anabolism research, Tissue repair research.
What does current evidence say about Long R3 IGF-1?
Preclinical evidence primarily. IGF-1 LR3 is significantly more potent than endogenous IGF-1 in vitro. No approved human therapeutic use. WADA strictly prohibits. Researchers note theoretical risks including hypoglycemia, organomegaly, and mitogenic concerns. Human clinical evidence for safe use is absent.
What safety considerations are noted for Long R3 IGF-1?
Reported or discussed considerations include: Hypoglycemia in animal models; Human AE profile unknown; Hypoglycemia; Mitogenic/cancer theoretical concerns; Organ growth; WADA prohibited. This is educational information, not medical advice.
Is Long R3 IGF-1 FDA approved?
Not FDA-approved. Prohibited in sport; not approved for any indication.
References & sources
- Adams GR (2010). IGF-1 and analogs in muscle biology — Pediatr Nephrol. Evidence type: review.
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Educational and research information only. PepGuide does not sell or prescribe peptides, diagnose conditions, or provide personalized medical advice. Evidence summaries may include early-stage, animal, or limited human research — none of that is a substitute for primary literature or clinician guidance.