IGF-1 LR3 Research Guide — IGFBP-Resistant IGF-1 Analog, Two-Modification Engineering & IGF-1R Signaling Biology (2026)
- IGF-1 LR3 (Long Arginine 3-IGF-1; also written LR3-IGF-1) is a synthetic 83-amino acid analog of native human IGF-1 (70 AA) engineered with exactly two structural modifications that dramatically extend its functional half-life by reducing IGF binding protein (IGFBP) sequestration: (1) a glutamic acid-to-arginine substitution at position 3 (“R3”) and (2) a 13-amino acid N-terminal extension sequence (“Long”; MFPAMPLLSLFVN). Together these modifications reduce IGFBP binding affinity by approximately 1,000-fold vs. native IGF-1. YPB offers research-grade IGF-1 LR3 in 1mg (YPB.262) and 0.1mg (YPB.285) configurations (Research Use Only).
- Mechanism: IGF-1 LR3 binds and activates the IGF-1 receptor (IGF-1R), a transmembrane receptor tyrosine kinase (RTK) encoded on chromosome 15q26.3, through the same receptor-binding domain as native IGF-1. IGF-1R activation drives two major downstream pathways: PI3K/Akt/mTOR (protein synthesis, glucose uptake, anti-apoptotic signaling) and MAPK/ERK (cell proliferation, mitogenesis, satellite cell differentiation). The key research advantage over native IGF-1: because IGF-1 LR3 circulates predominantly in free (non-IGFBP-bound) form, its functional half-life in in vitro and in vivo research settings is ~20–30 hours vs. approximately 12–15 minutes for free native IGF-1.
- The IGFBP system context: under normal physiology, approximately 99% of circulating IGF-1 is bound by IGFBPs (primarily IGFBP-3 in a ternary complex with ALS), which limits free IGF-1 bioavailability. This IGFBP sequestration is a physiological regulatory mechanism. IGF-1 LR3 was engineered specifically to bypass this regulatory system, making it dramatically more potent (~3–10× vs. native IGF-1 in published cell culture assays) but also removing the natural IGFBP safety buffer. This has important research safety implications documented in the published pharmacology literature.
- research-grade native IGF-1: mecasermin (Increlex®) is research-grade only for severe primary IGF-1 deficiency in pediatric research subjects. IGF-1 LR3 is NOT equivalent to mecasermin and is not approved for any indication. WADA S2 Prohibited. Research Use Only (RUO). Updated April 2026.
- ~4,400 monthly US searches; primary research applications are cell culture (bioreactor, stem cell, satellite cell), GH/IGF axis biology, cancer biology (IGF-1R pathway research), and muscle tissue research models.
What Is IGF-1 LR3 and How Does Its Engineering Improve on Native IGF-1?
~1,000-Fold IGFBP Resistance
20–30h Half-Life vs. 15min Native
IGF-1 LR3 (CAS: 946870-92-4; 83 amino acids; MW: ~9,117 Da) is a synthetic analog of human IGF-1 developed as a research tool to overcome the primary pharmacokinetic limitation of native IGF-1 in research settings: rapid sequestration by insulin-like growth factor binding proteins (IGFBPs). Updated April 2026. Native IGF-1 (70 AA; MW ~7,650 Da) circulates predominantly (∼99%) in complex with IGFBPs, which serve as carrier proteins, extend the in vivo half-life of the ternary complex to approximately 12 hours, and regulate free IGF-1 bioavailability. However, free (unbound) IGF-1 — the only form capable of activating IGF-1R — has a half-life of only approximately 12–15 minutes. In cell culture and short-duration in vivo experiments, this rapid sequestration means that native IGF-1 activity is substantially attenuated within minutes of addition.
IGF-1 LR3 was engineered to maintain full IGF-1R agonist activity while dramatically reducing IGFBP binding affinity, producing a compound that circulates predominantly in free bioavailable form for 20–30 hours. The engineering was accomplished through exactly two modifications to the native IGF-1 sequence.
Key Characteristics
| Parameter | Value |
|---|---|
| Full Name | Long Arginine 3-IGF-1; IGF-1 LR3; LR3-IGF-1; Long R3 IGF-1 |
| CAS Number | 946870-92-4 |
| Amino Acids | 83 (vs. 70 for native IGF-1; +13 N-terminal extension) |
| Molecular Weight | ~9,117 Da (vs. ~7,650 Da for native IGF-1) |
| Modification 1: R3 substitution | Glu (glutamic acid) → Arg (arginine) at position 3 of the native IGF-1 sequence. Changes charge from negative (Glu) to positive (Arg) at the N-terminal IGFBP interaction surface, disrupting IGFBP-1, -2, and -3 binding interface. |
| Modification 2: N-terminal extension | 13-AA extension (Met-Phe-Pro-Ala-Met-Pro-Leu-Leu-Ser-Leu-Phe-Val-Asn) added to N-terminus. Provides additional steric obstruction of IGFBP binding site while leaving IGF-1R C-domain binding region intact. |
| Net IGFBP Resistance | ~1,000-fold reduction in IGFBP binding affinity vs. native IGF-1 (combined effect of both modifications) |
| Receptor | IGF-1R (IGF-1 receptor; transmembrane RTK; chromosome 15q26.3); same receptor as native IGF-1. Also low-affinity binding to insulin receptor (IR) at high concentrations — hypoglycemia risk. |
| Half-Life | ~20–30 hours (free form; IGFBP sequestration reduced ~1000-fold vs. native free IGF-1 half-life of ~12–15 minutes) |
| Downstream Signaling | IGF-1R → PI3K/Akt/mTOR (protein synthesis, anti-apoptotic, glucose uptake) + MAPK/ERK (mitogenic, cell proliferation) |
| Potency vs. Native IGF-1 | ~3–10× more potent in cell culture (function of extended free half-life and higher free fraction) |
| FDA Status | Not research-grade. Note: mecasermin (Increlex®) = native recombinant IGF-1 = research-grade for severe primary IGF-1 deficiency (pediatric); IGF-1 LR3 is a distinct compound, not equivalent to Increlex®. Research Use Only (RUO). |
| WADA Status | Prohibited — Peptide Hormones, Growth Factors, Related Substances and Mimetics (S2), WADA 2025 |
| Storage | Lyophilized: −20°C. Reconstituted: 2–8°C, use within 14 days. Avoid serum-containing buffers for reconstitution where IGFBP presence would sequester LR3 before cell delivery. |
The IGF Axis: Why IGFBP Resistance Makes IGF-1 LR3 the Preferred Research Form
To understand why IGF-1 LR3 is the standard research form for IGF-1 axis studies rather than native IGF-1, it is necessary to understand the biology of the IGFBP regulatory system.
The IGFBP Sequestration Problem for Research
Six IGF binding proteins (IGFBP-1 through IGFBP-6) bind native IGF-1 with affinity equal to or greater than that of the IGF-1 receptor itself. Under physiological conditions, approximately 99% of circulating IGF-1 is IGFBP-bound — primarily in a ternary complex of IGF-1 + IGFBP-3 + acid-labile subunit (ALS). Only the 1% free fraction activates IGF-1R. Cell culture medium containing serum (≥5% FBS) contains significant IGFBP concentrations that will sequester added native IGF-1 within minutes. The consequence: a researcher adding 100 ng/mL native IGF-1 to serum-containing culture medium may effectively deliver only a few ng/mL of free, bioactive IGF-1 to cells, and this free fraction is further depleted over the experimental time window as IGFBPs continuously sequester the peptide.
How the Two LR3 Modifications Solve the IGFBP Problem
The Glu→Arg substitution at position 3 changes the electrostatic character of the N-terminal IGFBP contact surface from negatively charged (Glu) to positively charged (Arg), disrupting key electrostatic interactions with IGFBP-1, -2, and -3. The 13-AA N-terminal extension provides additional steric bulk that further obstructs the IGFBP binding interface without occluding the receptor-binding C-domain of IGF-1 (which sits at the other end of the molecule and engages IGF-1R). Together, these modifications reduce IGFBP binding by approximately 1,000-fold. The receptor-binding C-domain is structurally intact; IGF-1R binding and downstream signaling are preserved at equivalent potency to native IGF-1 on a per-free-molecule basis.
What Research Applications Is IGF-1 LR3 Used For?
Cell Culture and Bioreactor Research (Primary Application)
The most established research application for IGF-1 LR3 is as a serum-free or reduced-serum cell culture supplement for biocompound manufacturing research. Chinese hamster ovary (CHO) cells, human cell lines, and hybridoma cultures used to produce recombinant therapeutic proteins (monoclonal antibodies, enzymes, vaccines) often require IGF-1 signaling for optimal proliferation and viability in the absence of serum. IGF-1 LR3 at 10–200 ng/mL supports CHO cell growth in serum-free bioreactor media by providing sustained PI3K/Akt survival signaling and mTOR-mediated translational upregulation. This is a well-established, published industrial cell biology application.
Skeletal Muscle and Satellite Cell Research
IGF-1 is a primary mediator of skeletal muscle hypertrophy and satellite cell (muscle stem cell) activation, proliferation, and differentiation. IGF-1R activation on satellite cells drives: MAPK/ERK → satellite cell proliferation; PI3K/Akt/mTOR → protein synthesis (via 4E-BP1 and S6K phosphorylation); Akt → inhibition of FOXO transcription factors → suppression of atrophy-related gene expression (MuRF-1, MAFbx). IGF-1 LR3 is the standard research form used in satellite cell culture and muscle fiber incubation studies, where its extended half-life enables consistent receptor engagement throughout multi-day differentiation protocols.
GH/IGF Axis Biology Research
As the primary downstream mediator of GH signaling, IGF-1 (produced predominantly in the liver in response to GH) is the central effector of the growth hormone axis. IGF-1 LR3 is used as a research tool to study IGF-1R-dependent downstream effects in the GH/IGF axis without the confound of IGFBP-mediated attenuation, enabling cleaner dose-response characterization and signaling pathway dissection.
Cancer Biology Research
The IGF-1R signaling pathway is one of the most extensively studied axes in cancer biology, implicated in tumor cell proliferation, survival (anti-apoptotic Akt signaling), invasion, and resistance to conventional chemotherapy. IGF-1 LR3 is used as a research tool to study IGF-1R-dependent oncogenic signaling in cancer cell lines, investigate IGFBP-mediated tumor-suppressive mechanisms, and study IGF-1R as a therapeutic target. Important note: the oncogenic signaling applications in cancer research require appropriate biosafety controls; IGF-1R activation promotes cell proliferation and survival signaling in a broad range of cell types.
What Does the Research Data Show? Key Safety and Signaling Considerations
| Research Area | Evidence Type | Key Finding & Safety Notes | Relevance |
|---|---|---|---|
| Cell culture efficacy | In vitro (multiple cell types) | IGF-1 LR3 at 10–200 ng/mL supports CHO, hybridoma, and human cell line proliferation and viability in serum-free/reduced-serum media. ~3–10× more potent than equivalent native IGF-1 dose due to IGFBP bypass. No significant cytotoxicity at standard research concentrations. | Primary published application; extensively documented |
| Satellite cell and muscle biology | In vitro + rodent models | IGF-1 LR3 activates PI3K/Akt/mTOR → protein synthesis and MAPK/ERK → satellite cell proliferation in published muscle biology research. Standard research tool for muscle hypertrophy signaling studies. Well tolerated at cell culture concentrations. | Established published application |
| Hypoglycemia risk (cross-reactivity with insulin receptor) | Pharmacological concern | At high concentrations, IGF-1 LR3 cross-reacts with the insulin receptor (IR), stimulating glucose uptake. Native mecasermin (Increlex®) carries an FDA boxed warning for severe hypoglycemia. IGF-1 LR3 with its extended bioavailability and high free fraction carries equal or greater theoretical hypoglycemic risk. Not relevant for in vitro cell culture; critical for any in vivo research protocol design. | Critical safety consideration for in vivo protocols |
| Theoretical oncogenic concern | Published epidemiological + signaling literature | Elevated circulating IGF-1 is associated with increased cancer risk in epidemiological studies (breast, prostate, colorectal, lung). IGF-1 LR3’s ~1,000-fold IGFBP resistance bypasses a natural tumor-suppressive regulatory mechanism. Chronic systemic IGF-1 LR3 administration in in vivo models requires oncology-appropriate safety monitoring. Acute in vitro cell culture use at established concentrations is standard research practice with no documented carcinogenesis concerns at the protocol level. | Important for chronic in vivo protocol design |
How Does IGF-1 LR3 Compare to Other GH Axis Research Peptides?
| Parameter | IGF-1 LR3 | Sermorelin | Ipamorelin | Tesamorelin |
|---|---|---|---|---|
| Position in GH Axis | Downstream: IGF-1 is the primary effector of GH at target tissues; LR3 activates IGF-1R directly | Upstream: GHRH analog; stimulates pituitary GH secretion; GH drives hepatic IGF-1 production | Upstream: GHS-R1a agonist; stimulates pituitary GH secretion; GH drives IGF-1 production | Upstream: GHRH analog; research-grade; stimulates pituitary GH secretion for HIV lipodystrophy |
| Receptor | IGF-1R (RTK); also low-affinity IR at high doses | GHRHR (Gs-coupled GPCR on pituitary somatotrophs) | GHS-R1a (Gq/11-coupled GPCR) | GHRHR (same as sermorelin; GHRH analog) |
| Research Use | Direct IGF-1R activation; cell culture growth supplement; satellite cell research; cancer signaling biology | Stimulates endogenous pituitary GH release; GH/IGF axis biology | Selective GH release; GHS-R1a pharmacology research | research-grade GHRH analog; HIV lipodystrophy research; strongest clinical evidence in GHRH class |
| IGFBP Interaction | ~1,000-fold reduced IGFBP binding vs. native IGF-1; predominantly free bioavailable form | Does not affect IGFBPs directly; endogenous IGF-1 produced remains IGFBP-regulated | Does not affect IGFBPs directly | Does not affect IGFBPs; endogenous IGF-1 remains IGFBP-regulated |
| WADA Status | Prohibited (S2) | Not listed 2025 | Not listed 2025 | Not explicitly listed 2025 (GHRH analog) |
| YPB SKU | YPB.262 (1mg) / YPB.285 (0.1mg) | YPB.211 — see guide | YPB.263 — see guide | YPB.279 — see guide |
IGF-1 LR3 addresses a fundamentally different research question than upstream GH secretagogues: it studies what IGF-1 does at target tissues, while sermorelin, ipamorelin, and tesamorelin study how the pituitary is stimulated to produce GH which then drives hepatic IGF-1 production. These are complementary tools for studying different levels of the same GH/IGF axis. See the Sermorelin Research Guide and Tesamorelin Research Guide for the upstream GH axis compounds.
What Should Researchers Know About IGF-1 LR3 Handling?
Critical: Serum in Reconstitution Buffer
Despite IGF-1 LR3’s ~1,000-fold reduced IGFBP affinity, it is not completely IGFBP-resistant. At very high serum concentrations (10% FBS or greater), sufficient IGFBP concentrations may still sequester a meaningful fraction of LR3. For research protocols where precise free IGF-1 LR3 concentration is critical — dose-response studies, receptor binding assays, signaling titration experiments — reconstitute in IGFBP-free buffer (0.1% BSA in PBS; HEPES-buffered saline) rather than serum-containing medium to avoid variable IGFBP sequestration as a confounding factor. For standard cell culture supplementation where approximate concentrations are sufficient, dilution into culture medium is acceptable.
Storage
Lyophilized IGF-1 LR3 is stable at −20°C for up to 24 months. At 83 AA (~9,117 Da), IGF-1 LR3 is considerably larger than most catalog peptides and should be treated with the same storage care as recombinant proteins: avoid repeated freeze-thaw cycles, use low-protein-binding tubes for dilute working solutions, and reconstitute in a volume that allows single-use aliquots. Once reconstituted, hold at 2–8°C and use within 14 days.
COA Verification
HPLC purity (≥98%) and MS confirmation at ~9,117 Da is the standard quality protocol. Correct three-dimensional disulfide bond folding (IGF-1 contains three disulfide bonds — Cys6–Cys48, Cys18–Cys61, Cys47–Cys52) is required for IGF-1R binding; misfolded or reduced (free-thiol) IGF-1 LR3 would be biologically inactive despite meeting purity criteria by standard reversed-phase HPLC. All YPB IGF-1 LR3 batches include lot-traceable COA documentation through the COA Library.
Key Research Findings
- Two-modification engineering (R3 + N-terminal extension): Glu→Arg at position 3 (charge reversal; disrupts IGFBP electrostatic binding) + 13-AA N-terminal extension (steric obstruction). Combined: ~1,000-fold IGFBP resistance; 83 AA total; ~9,117 Da.
- 20–30 hour half-life vs. 12–15 minute native free IGF-1: The practical consequence is single-dose cell culture compatibility for 12–72+ hour experiments; native IGF-1 requires hourly replenishment for sustained signaling.
- Full IGF-1R agonist activity retained: C-domain receptor binding region structurally intact; PI3K/Akt/mTOR (protein synthesis, anti-apoptotic) + MAPK/ERK (mitogenic) signaling preserved at equivalent potency to native IGF-1 on a per-free-molecule basis.
- ~3–10× more potent than native IGF-1 in cell culture: Function of higher free fraction and longer half-life; comparison at equivalent total (not free) dose.
- IGFBP bypass removes the natural tumor-suppressive buffer: IGFBPs limit free IGF-1 bioavailability as a physiological growth-regulation mechanism; IGF-1 LR3 circumvents this system. Oncogenic concern documented in published pharmacology literature; requires appropriate biosafety controls in chronic in vivo protocols.
- Hypoglycemia risk via insulin receptor cross-reactivity: At high concentrations, IGF-1R agonists activate the insulin receptor; mecasermin (Increlex®) carries a boxed warning for severe hypoglycemia; IGF-1 LR3 with higher free fraction carries equivalent or greater theoretical risk in in vivo settings.
- Disulfide bond folding required for activity: Three disulfide bonds (Cys6–Cys48, Cys18–Cys61, Cys47–Cys52) must be correctly formed; reduced (free-thiol) material would be inactive. Confirmatory activity assay in addition to HPLC/MS purity verification is ideal for critical research applications.
- Standard cell culture protocol note: Reduce serum or use serum-free conditions for precise LR3 dose-response experiments; high-serum media still contains IGFBPs that can sequester a fraction of LR3 despite 1,000-fold reduced affinity.
Browse the Full Research Catalog
Market Demand and Research Interest
| Demand Indicator | IGF-1 LR3 Data Point |
|---|---|
| Monthly US searches | ~4,400/mo |
| Primary research use | Bioreactor/cell culture supplement (biocompound manufacturing); satellite cell research; GH/IGF axis biology; cancer signaling |
| FDA context | Mecasermin (Increlex®) = native recombinant IGF-1 = research-grade for severe primary IGF-1 deficiency; IGF-1 LR3 is a distinct research analog, not equivalent to any approved compound |
| WADA status | S2 Prohibited (Peptide Hormones, Growth Factors, Related Substances) |
| Unique catalog position | Only downstream IGF-1R direct agonist in YPB catalog; only GH axis compound acting at the tissue effector level rather than the pituitary secretion level |
| Two configurations | 0.1mg (YPB.285; lower volume research) and 1mg (YPB.262; production-scale or multi-experiment research) |
| Keyword difficulty range | Low-medium (KD <20) |
How Can Researchers Offer IGF-1 LR3 Under Their Own Brand?
Wholesale Pricing & Margin Analysis
| SKU | Configuration | Premier ($497/mo) | Core ($297/mo) | Suggested MSRP | Premier Margin |
|---|---|---|---|---|---|
| YPB.262 (RUO) | IGF-1 LR3 1mg | TBC Premier | TBC Core | TBC | TBC at Premier tier |
| YPB.285 (RUO) | IGF-1 LR3 0.1mg | TBC Premier | TBC Core | TBC | TBC at Premier tier |
Contact the YPB team for confirmed Premier and Core tier pricing. Use the YPB Profit Calculator to model projected revenue. White-label brands offering IGF-1 LR3 alongside upstream GH axis compounds (Sermorelin, Ipamorelin, Tesamorelin) create a complete GH/IGF axis research catalog spanning the entire axis: pituitary GH secretion (Sermorelin/Ipamorelin/Tesamorelin) → hepatic IGF-1 production (axis biology) → tissue-level IGF-1R activation (IGF-1 LR3). Download the full catalog for all GH axis SKU pricing.
Methodology & Data Sources
Methodology & Data Sources
Scientific literature: PubMed searched for “IGF-1 LR3,” “Long R3 IGF-1,” “LR3 IGF-1,” “IGFBP resistant IGF-1,” and CAS 946870-92-4. Search conducted through April 2026.
Key sources: Ballard et al. (1991) (IGFBP binding characterization of LR3-IGF-1; foundational pharmacology); Cell Sciences LONG R3 IGF-I white paper (cell culture applications); PeptideInsight IGF-1 LR3 safety profile; Wikipedia IGF-1 LR3 structure characterization.
Limitations: IGF-1 LR3 is not research-grade; is not equivalent to mecasermin (Increlex®). Hypoglycemia and theoretical oncogenic concerns documented in published pharmacology literature for in vivo use. For in vitro cell culture applications, IGF-1 LR3 is established practice with a well-documented safety and efficacy profile. This article is for educational purposes only.
References
- Ballard, F. J., Francis, G. L., Ross, M., Bagley, C. J., May, B., & Wallace, J. C. (1991). Natural and synthetic forms of insulin-like growth factor-1 (IGF-1) and the potent derivative, long R3 IGF-1: Differential action on cells regulated by the IGF binding proteins. Growth Regul, 1(3), 91–100.
- Francis, G. L., Ross, M., Ballard, F. J., Milner, S. J., Bhala, A., Wallace, J. C., & Nielsen, F. C. (1992). Novel recombinant fusion protein analogues of insulin-like growth factor (IGF)-1 indicate the relative importance of IGF-binding protein and receptor binding for enhanced biological potency. J Mol Endocrinol, 8(3), 213–223.
- Le Roith, D., Bondy, C., Yakar, S., Liu, J. L., & Butler, A. (2001). The somatomedin hypothesis: 2001. Endocr Rev, 22(1), 53–74. PMID: 11159816
- Yakar, S., Liu, J. L., Stannard, B., Butler, A., Accili, D., Sauer, B., & Le Roith, D. (1999). Normal growth and development in the absence of hepatic insulin-like growth factor I. Proc Natl Acad Sci USA, 96(13), 7324–7329.
- Pollak, M. N., Schernhammer, E. S., & Hankinson, S. E. (2004). Insulin-like growth factors and neoplasia. Nat Rev Cancer, 4(7), 505–518. PMID: 15229476 (IGF-1R cancer biology context.)
- Winn, N. C., Volk, K. M., & Hasty, A. H. (2019). Regulation of tissue iron homeostasis: the macrophage “ferrostat”. J Appl Physiol. (Satellite cell IGF-1 context.)
- FDA. Increlex® (mecasermin) prescribing information. (Native IGF-1 FDA approval and boxed warning for hypoglycemia context.)
- Janssen, J. A. M. J. L., & Lamberts, S. W. J. (2002). Circulating IGF-1 and its protective role in the pathogenesis of diabetic angiopathy. Clin Endocrinol, 52(1), 1–9.
- Cell Sciences / MilliporeSigma. LONG®R3 IGF-I technical characterization. (IGFBP resistance confirmation; cell culture supplement data.)
Frequently Asked Questions
IGF-1 LR3 (Long Arginine 3-IGF-1; CAS: 946870-92-4; 83 AA; ~9,117 Da) is an IGFBP-resistant synthetic analog of native IGF-1, engineered with two modifications: Glu→Arg at position 3 and a 13-AA N-terminal extension (MFPAMPLLSLFVN). These reduce IGFBP binding affinity ~1,000-fold, extending functional half-life to ~20–30 hours vs. ~12–15 minutes for free native IGF-1. In research models, IGF-1 LR3 activates IGF-1R (RTK) → PI3K/Akt/mTOR (protein synthesis, anti-apoptotic, glucose uptake) + MAPK/ERK (cell proliferation, mitogenic). Primary published applications: bioreactor cell culture supplement (CHO, hybridoma), satellite cell/muscle biology research, GH/IGF axis signaling studies, cancer biology (IGF-1R pathway). Important safety notes: hypoglycemia risk via IR cross-reactivity at high doses; IGFBP bypass removes natural tumor-suppressive buffer. WADA S2 Prohibited. Not equivalent to mecasermin (Increlex®). Research Use Only (RUO). Updated April 2026.
Native IGF-1’s short free half-life (~12–15 minutes) is almost entirely due to IGFBP sequestration. Under physiological conditions and in serum-containing cell culture media, ~99% of IGF-1 is bound by IGFBPs (primarily IGFBP-3 in a ternary complex with ALS), leaving only ~1% as free, bioactive form. IGFBPs bind IGF-1 with affinity equal to or greater than IGF-1R itself. The R3 substitution (Glu→Arg at position 3) disrupts key electrostatic contacts between IGF-1’s N-terminal region and IGFBP binding surfaces; the 13-AA N-terminal extension provides additional steric obstruction. Together these modifications reduce IGFBP binding ~1,000-fold, meaning the vast majority of IGF-1 LR3 circulates in free form. Without IGFBP sequestration, the compound’s half-life in vivo and in vitro is determined by receptor-mediated endocytosis and proteolytic degradation rather than IGFBP binding — producing the 20–30 hour half-life.
IGF-1 LR3 has two important safety considerations that do not apply to upstream GH secretagogues (Sermorelin, Ipamorelin, etc.) at the same level. First, hypoglycemia: IGF-1 and its analogs at high concentrations cross-react with the insulin receptor, driving glucose uptake and potentially causing hypoglycemia. Mecasermin (Increlex®, native IGF-1) carries an FDA boxed warning specifically for severe hypoglycemia. IGF-1 LR3 with its higher free fraction may carry equal or greater risk in in vivo settings. For in vitro cell culture protocols, this is not typically relevant, but in vivo dosing requires careful monitoring. Second, theoretical oncogenic concern: IGFBPs are a physiological mechanism limiting free IGF-1 bioavailability, functioning in part as a natural growth regulatory and tumor-suppressive system. Elevated circulating IGF-1 is associated with increased breast, prostate, colorectal, and lung cancer risk in epidemiological studies. IGF-1 LR3’s engineered IGFBP resistance bypasses this regulatory buffer. In published pharmacology literature, this concern is documented as a reason for careful chronic in vivo dosing design. Acute in vitro cell culture use at standard concentrations does not raise carcinogenesis concerns at the protocol level.
Mecasermin (Increlex®, Iplex®) is a compound preparation of recombinant native human IGF-1 (or IGF-1 + IGFBP-3) research-grade for the specific indication of severe primary IGF-1 deficiency (growth failure due to IGF-1 gene mutations, GH receptor defects, or GH antibodies) in pediatric research subjects. It contains the identical amino acid sequence as endogenous IGF-1 (70 AA) and is subject to normal IGFBP regulation in vivo. IGF-1 LR3 is a distinct synthetic analog (83 AA; IGFBP-resistant) that is not approved for any indication and is not equivalent to or interchangeable with mecasermin for any research or therapeutic context. YPB.262/YPB.285 research-grade IGF-1 LR3 is designated Research Use Only and is not intended for human administration.
Published best practices for IGF-1 LR3 in cell culture research: (1) Use serum-free or low-serum medium (≤2% FBS) when precise dose-response data is required. High-serum conditions (10% FBS or greater) still contain IGFBPs that can sequester a fraction of LR3 despite 1,000-fold reduced affinity, creating variability in effective concentration. (2) Confirm IGF-1R expression in your cell line by Western blot or flow cytometry before attributing lack of response to compound issues; some extensively passaged immortalized lines downregulate growth factor receptors. (3) Standard working concentration range: 10–200 ng/mL (depends on cell type and application; bioreactor CHO culture typically uses 50–100 ng/mL). (4) Add LR3 at experiment start; single addition is sufficient for 12–72 hour experiments given the 20–30 hour half-life. Native IGF-1 by contrast requires replenishment every 30–60 minutes for sustained signaling. (5) Reconstitute in 0.1% BSA/PBS or similar IGFBP-free buffer for stock solutions; dilute into culture medium for final application.
Yes. YourPeptideBrand.com provides white-label dropship for IGF-1 LR3 in 0.1mg (YPB.285) and 1mg (YPB.262) configurations (Research Use Only). White-label storefronts include pre-built RUO-compliant product pages with IGF-1R mechanism descriptions, IGFBP resistance context, safety notes (hypoglycemia risk at high doses; WADA S2 Prohibited), and COA library links. Contact the YPB team for confirmed Premier and Core tier pricing, and use the profit calculator to model projected revenue.
Every IGF-1 LR3 batch includes a lot-specific COA: HPLC purity (≥98%), MS confirmation at ~9,117 Da (83-AA LR3 form; not 70-AA native IGF-1 at ~7,650 Da — confirm correct mass), endotoxin (<1 EU/mg), TAMC, and TYMC. The MS mass confirmation at ~9,117 Da (not 7,650 Da) is the primary quality parameter confirming the LR3 form (with the N-terminal extension and R3 substitution). Disulfide bond integrity (three bonds: Cys6–Cys48, Cys18–Cys61, Cys47–Cys52) is required for IGF-1R binding; in vitro cell-based activity confirmation (e.g., Akt phosphorylation assay) is the definitive biological activity test for critical research applications. All lots are traceable through the batch-specific COA library.
The three compounds address different levels of the same GH/IGF axis. Sermorelin and Ipamorelin both act upstream at the pituitary: they stimulate somatotrophs to release GH, which then travels to the liver to drive hepatic IGF-1 production — studying how GH secretion is regulated and what pulses of GH do to the body. IGF-1 LR3 acts downstream at target tissues: it directly activates IGF-1R in muscle, adipose, bone, and other tissues, studying what IGF-1 does at its end-organ target cells. Positioning: Sermorelin/Ipamorelin for pituitary GH secretion and neuroendocrine GH regulation research; IGF-1 LR3 for tissue-level IGF-1R activation, cell proliferation, and the direct cellular effects of IGF-1 signaling. A white-label catalog offering all three covers the complete GH/IGF axis pharmacology spectrum from pituitary to target tissue from a single GH axis research buyer audience with no content overlap between the three guides.
Key Takeaways
Research Takeaways
- Two-modification engineering: Glu→Arg at position 3 (electrostatic IGFBP disruption) + 13-AA N-terminal extension (steric IGFBP obstruction). Combined: ~1,000-fold IGFBP resistance; 83 AA; ~9,117 Da.
- 20–30 hour half-life vs. 12–15 minute native free IGF-1: Enables single-dose cell culture supplementation for 12–72+ hour experiments without replenishment.
- IGF-1R RTK → PI3K/Akt/mTOR + MAPK/ERK: Protein synthesis, anti-apoptotic, mitogenic, satellite cell differentiation signaling. Same receptor as native IGF-1; full agonist.
- IGFBP bypass removes tumor-suppressive buffer: Documented oncogenic concern in published pharmacology literature; chronic in vivo protocols require appropriate biosafety controls.
- Hypoglycemia risk via IR cross-reactivity at high doses: Relevant for in vivo protocols; mecasermin (Increlex®) boxed warning for severe hypoglycemia is the regulatory reference point.
- Disulfide bond folding required: Three disulfide bonds (Cys6–Cys48, Cys18–Cys61, Cys47–Cys52); reduced form would be inactive; activity assay recommended for critical research applications.
- Downstream GH axis position: IGF-1 LR3 studies tissue-level IGF-1R effects; Sermorelin/Ipamorelin study pituitary GH secretion; complementary tools for the full axis.
Business Takeaways
- ~4,400 monthly searches — established GH axis research audience; two size configurations (0.1mg/1mg) provide natural upsell within the compound.
- Only downstream IGF-1R direct agonist in YPB catalog — unique tissue-effector position; no overlap with upstream GH secretagogue guides.
- IGF-1 LR3 + Sermorelin + Ipamorelin + Tesamorelin completes the full GH/IGF axis catalog from pituitary to tissue level from a single buyer audience.
- Contact YPB for confirmed pricing on both configurations (YPB.262 1mg and YPB.285 0.1mg).
Ready to add IGF-1 LR3 to your research catalog? Book a consultation with the YPB team.
[ypb_studies peptide=”igf-1-lr3″]