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    IGF-1 LR3 Peptide: A Provider's Guide to Structure, Supply Format, and Access

    Short answer: IGF-1 LR3 (also written IGF1 LR3, or Long R3 IGF-I) is a recombinant, 83-amino-acid analogue of human insulin-like growth factor I. It keeps the complete 70-residue human IGF-I sequence, substitutes arginine for glutamic acid at position 3 (the "R3"), and adds a 13-amino-acid N-terminal extension (the "Long") (Sigma-Aldrich datasheet; Francis et al., 1992). Its molecular weight is about 9.1 kDa (Sigma-Aldrich). Biomed Peptides lists IGF-1 LR3 as a 1 mg lyophilized vial for verified, licensed providers only.

    This guide sticks to identity, supply format, storage, documentation, and provider access. Clinical decisions stay with the prescribing clinician.

    What is the IGF-1 LR3 peptide?

    Native IGF-I as the reference point

    The human IGF-1 gene codes for a longer precursor, but the mature IGF-I protein is 70 amino acids long (Sigma-Aldrich technical note). IGF-1 LR3 starts from that 70-residue sequence and changes it in two places.

    The two changes: "R3" and "Long"

    1. R3 substitution. Glutamic acid at position 3 of the IGF-I sequence is replaced with arginine (Glu3 → Arg3).
    2. N-terminal extension. Thirteen amino acids, MFPAMPLSSLFVN, are added ahead of the normal IGF-I N-terminus. Sigma-Aldrich notes that these 13 residues "are quite different from" the residues that come before mature IGF-I in the natural precursor (Sigma-Aldrich technical note).

    The construct was described by Francis and colleagues at CSIRO in Adelaide in 1992. Their analogues joined an IGF-I sequence to "the first 11 amino acids of methionyl porcine growth hormone" plus a Val-Asn linker. They called the Arg3 version "Long [Arg3]-IGF-I" (Francis et al., 1992). The paper also notes that the hydrophobic N-terminal extension "appears to facilitate the correct folding" of the analogues during recombinant production.

    Identity at a glance

    Attribute Value
    Common names IGF-1 LR3, IGF1 LR3, Long R3 IGF-I, LR3 IGF-1
    Type Recombinant protein analogue of human IGF-I (expressed in E. coli)
    Length 83 amino acids (70 IGF-I + 13 N-terminal)
    Key substitution Arg for Glu at IGF-I position 3
    N-terminal extension MFPAMPLSSLFVN
    Empirical formula (Sigma-Aldrich) C400H619N111O115S9
    Molecular weight (Sigma-Aldrich) ≈9111 Da
    CAS (Sigma-Aldrich) 143045-27-6

    Sources: Sigma-Aldrich substance record; Sigma-Aldrich technical note.

    Full 83-residue sequence, as published by Sigma-Aldrich:

    MFPAMPLSSLFVNGPRTLCGAELVDALQFVCGDRGFYFNKPTGYGSSSRRAPQTGIVDECCFRSCDLRRLEMYCAPLKPAKSA

    How it's made

    IGF-1 LR3 is recombinant, not built residue by residue on a peptide synthesizer. Sigma-Aldrich describes producing it in E. coli. The protein is recovered from inclusion bodies, folded under oxidizing conditions, purified by several liquid chromatography steps, and then lyophilized (Sigma-Aldrich datasheet). That's why identity testing for IGF-1 LR3 looks a little different from testing a short synthetic peptide. More on that below.

    IGF-1 LR3 is not ipamorelin

    IGF-1 LR3 and ipamorelin are unrelated molecules. Ipamorelin is a short synthetic pentapeptide, while IGF-1 LR3 is an ≈9 kDa recombinant protein analogue. See our ipamorelin peptide guide for ipamorelin's identity. Keep separate records, COAs, and storage locations for each.

    How IGF-1 LR3 is supplied to clinics

    Lyophilized vial format

    IGF-1 LR3 is supplied as a lyophilized powder in a sealed vial. Sigma-Aldrich's reagent-grade product is lyophilized from dilute acetic acid (Sigma-Aldrich datasheet). The Biomed Peptides lyophilized catalog lists IGF-1 LR3 in a 1 mg vial. Pricing appears only after a provider account is approved.

    Storage and handling pointers

    • Follow the product label first. The labeled storage condition and expiration for your lot are the ones that count.
    • Keep vials sealed, dry, and protected from light.
    • Bachem notes that peptides containing Asn, Gln, Met, Cys, and/or Trp have limited shelf lives (Bachem). IGF-1 LR3 contains Met, Cys, Gln, and Asn, so labeled conditions and expiration dates matter here.
    • Peptides are hygroscopic. Let a cold vial reach room temperature before opening (Bachem).
    • Avoid repeated freeze-thaw cycles. Sigma-Aldrich gives the same advice for its stock solutions (Sigma-Aldrich datasheet).
    • Sigma-Aldrich's handling notes warn that the peptide can adsorb to plastic or glass surfaces in dilute buffer solutions (Sigma-Aldrich datasheet). That's one more reason to use only the diluent the labeling specifies.

    Our lyophilized peptides storage guide walks through receiving, cold storage, and inventory rotation step by step.

    Documentation to request for IGF-1 LR3

    IGF-1 LR3 is a recombinant protein with six cysteine residues in its sequence, and it's folded under oxidizing conditions during manufacture. A good COA should cover more than an HPLC purity number:

    • Identity by mass spectrometry, matching the ≈9111 Da expected mass for the 83-residue analogue (not ≈7.6 kDa, which would point to the 70-residue R3 IGF-I without the extension)
    • Purity by HPLC, with the method stated
    • Peptide/protein content where reported
    • Endotoxin results where applicable. This matters for any material produced in E. coli.
    • Lot number, manufacture date, and labeled storage conditions

    For comparison, Sigma-Aldrich lists the 70-residue R3 IGF-I (no extension) at 7,676 Da (Sigma-Aldrich). That makes the two forms easy to tell apart by mass. Our peptide COA guide explains how to read these sections.

    Regulatory context

    Questions about compounding pathways belong with your compounding pharmacist. Section 503A requires bulk drug substances to meet a USP/NF monograph, be a component of an FDA-approved drug, or appear on FDA's 503A bulks list, and to come with a valid COA from an FDA-registered establishment (FDA). We didn't find IGF-1 LR3 named on FDA's 503A nominations list (updated May 14, 2026) (FDA). For more on the pathway, see what a 503A pharmacy is.

    How providers get access to IGF-1 LR3

    Biomed Peptides supplies physician-use product only to licensed healthcare providers and GPOs. We don't sell to patients or consumers.

    1. Submit the provider application.
    2. Our team verifies your credentials, usually within 24–48 hours.
    3. Approved accounts can view pricing, the full catalog, and lot documentation.
    4. Order for office use or patient-specific fulfillment, with shipping to all 50 states.

    Prescribing authority depends on your license and your state. See who can prescribe peptides.

    Source IGF-1 LR3 for your practice

    Licensed practices can apply for provider access to view IGF-1 LR3 pricing and lot COAs, or browse the lyophilized catalog.

    FAQ

    What is the IGF-1 LR3 peptide?

    IGF-1 LR3 (Long R3 IGF-I) is an 83-amino-acid recombinant analogue of human IGF-I. It has an arginine in place of glutamic acid at position 3 and a 13-amino-acid N-terminal extension. Its molecular weight is about 9.1 kDa.

    What do "LR3" and "Long R3" mean?

    "R3" refers to the arginine (R) substitution at position 3 of the IGF-I sequence. "Long" refers to the added 13-amino-acid N-terminal extension, MFPAMPLSSLFVN.

    Is IGF1 LR3 the same as IGF-1 LR3?

    Yes. IGF1 LR3, IGF-1 LR3, LR3 IGF-1, and Long R3 IGF-I are spelling variants of the same molecule.

    How is IGF-1 LR3 supplied?

    As a lyophilized powder in a sealed vial. Biomed Peptides lists IGF-1 LR3 in a 1 mg vial for approved providers.

    What should an IGF-1 LR3 COA show?

    Mass spectrometry identity matching about 9111 Da, HPLC purity with the method stated, endotoxin results where applicable, and the lot number, manufacture date, and storage conditions.

    Sources

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