A modified, longer-acting form of insulin-like growth factor 1, used mainly as a research reagent.
Key takeaway
IGF-1 LR3 is an 83-amino-acid variant of insulin-like growth factor 1 with an extended chain and one amino-acid change that reduce binding to its carrier proteins.
At a glance
| FDA status | Not FDA-approved |
|---|---|
| 503A compounding | No 503A pathway: not approved and not on FDA’s bulks lists |
| Body areas | Muscle, joints & recovery, Hormones & pituitary |
| Through ScriptMates | Information only |
| Open questions | 1 noted below |
What is IGF-1 LR3?
IGF-1 LR3 is an 83-amino-acid variant of insulin-like growth factor 1 with an extended chain and one amino-acid change that reduce binding to its carrier proteins.
It is not the same molecule as mecasermin, the FDA-approved form of IGF-1. It has no approval and no 503A pathway.
Dosage forms
No FDA-approved dosage form. A standardized dosage form for human use was not confirmed from the sources below.
Is IGF-1 LR3 FDA-approved?
Not FDA-approved. It does not appear on FDA’s 503A bulks list or in any 503A category.
Can it be prescribed through ScriptMates?
No 503A pathway: not approved and not on FDA’s bulks lists. A partner pharmacy lists it, but it has no lawful 503A pathway today (not approved and not on FDA’s bulks lists).
What we could not confirm
- At over 40 amino acids it may also meet FDA’s definition of a protein (biological product). FDA has not addressed it directly.
Sources
- FDA: Bulk drug substances nominated under 503A, Categories 1–3 (May 14, 2026)
- FDA: Notice to compounders on the March 23, 2020 biologics transition
Checked October 27, 2026. FDA updates these pages, so confirm before relying on them.