recombinant IGF-1 analogue / growth-factor receptor agonist

IGF-1 LR3

aka Long [Arg3]-IGF-I · Long R3 IGF-I · LR3IGF-I · long-(Arg3)insulin-like growth factor-I

Evidence grade
Grade D: Preclinical only
for muscle growth and recovery
User score too few reports (6) needs ≥ 10 reports
US FDA Not approved checked 2026-11-13
WADA 2026 Prohibited (S2.3) at all times · checked 2026-11-13
EU LR3-specific EMA authorization not found; the EMA authorization for mecasermin concerns a different active substance. · checked 2026-11-13

Goals: Recovery & injury · Fat loss · Muscle & strength Compare with another peptide →

User reports

approximate — combined from two independent Reddit reads

Men 45–60

0 men aged 45–60

No reports in this group yet.

All men

0 men

No reports in this group yet.

Everyone

6 people

small sample · n = 6

Outcome mixed 3 of 6 · positive 3 of 6

Benefits muscle 5 of 6 · fat loss 2 of 6 · strength 2 of 6 · endurance 1 of 6 · energy 1 of 6 · joints / tendons 1 of 6 · recovery 1 of 6

Side effects joint pain 1 of 6 · other 1 of 6 · tingling / numbness 1 of 6 · water retention 1 of 6

Stopped 0 of 6 Used with other compounds 4 of 6

User reports are anecdata, not evidence: self-selected, unverified, often combined with other compounds.

In their words

  • “Week 3-4 is where this stuff kicked in for me. I felt an amazing endurance benefit.”

  • “I’ve never had a more potent driver for just straight lean mass.”

  • “Definitely put on muscle, but I decided to run anavar with the IGF.”

  • “I don’t really get a ton out of it so I wouldn’t say it’s worth much more than that.”

Read summaries and method notes

Read 1. No readable thread (one seed was on excluded r/BodyHackGuide, five were unavailable), so n=0 everywhere.

Read 2. No explicitly male reporter. Six users: 3 positive, 3 mixed — muscle fullness/growth, strength, endurance, occasionally fat loss; one had less chronic biceps/shoulder pain. The most detailed six-week log had water retention, sore joints, hand tingling and a cholesterol change. Several glowing reports were stacked with testosterone, Anavar or trenbolone. Pumps/endurance within three weeks; cycles about four to six weeks.

Note 1. One seed excluded (r/BodyHackGuide); five unavailable.

Note 2. No qualifying male age data. Anabolic-steroid stacking was common and weakens attribution.

Each read counted people independently. Overlap between the two reads is estimated from shared threads and removed; counts are approximate. How we count.

Summary

Engineered IGF-I analogue investigated in laboratory and animal models. Human trials supporting muscle growth, recovery or anti-aging were not found. FDA records its chemical identity, which does not imply approval. It differs from the approved medicine mecasermin. (FDA identity, mecasermin label)

Proposed mechanism

The molecule adds an N-terminal extension and substitutes arginine at IGF-I position 3. Reduced interaction with IGF-binding proteins alters activity in cell assays. This is mechanistic evidence, not a demonstrated human enhancement benefit. (Original characterization)

Safety

  • Human LR3 adverse-event frequencies and long-term safety not found
  • Hypoglycemia is a pharmacologic concern; severe events are established for mecasermin, not quantified for LR3
  • Growth and neoplasia concerns cannot be quantified from LR3 human trials
  • Human half-life and a clinically validated dosing range not found

From labels, regulators and trials. No signal in small studies ≠ safe.

Evidence D muscle growth and recovery

D stands. Cell and animal data only; no human administration trial found.

Human trials · 0

No human trials found for the marketed use.

Dose ranges

Reported ranges from labels and studies, with context. Not a recommendation.

No data.

Editorial ratings EDITORIAL

Editors’ judgement, 0–5. Opinion, not data; separate from grade and user score.

Not rated yet.

Sources

  1. precision.fda.gov/uniisearch/srs/unii/M9L22Y19H9
  2. wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf
  3. ema.europa.eu/en/medicines/human/EPAR/increlex
  4. pubmed.ncbi.nlm.nih.gov/1378742/
  5. pubmed.ncbi.nlm.nih.gov/7693845/
  6. pubmed.ncbi.nlm.nih.gov/7683526/
  7. accessdata.fda.gov/drugsatfda_docs/label/2025/021839s033lbl.pdf
  8. fda.gov/advisory-committees/pharmacy-compounding-advisory-committee/2026-meeting-materials
  9. clinicaltrials.gov/search?term=%22IGF-1%20LR3%22
  10. pubmed.ncbi.nlm.nih.gov/?term=%28%22IGF-1+LR3%22+OR+%22Long+R3%22+OR+%22LR3IGF-I%22%29+AND
  11. fda.gov/media/94155/download

Reddit threads read · 4

1 further source on commercial or non-primary hosts not listed.

Research checked 2026-11-13.