Side-by-side · Research reference

IGF-1 LR3vsP21

Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.

AAnimal-StrongHUMAN-REVIEWED10/58 cited

BAnimal-MechanisticHUMAN-REVIEWED8/36 cited

IGF-1 LR3

IGF-1 Analogue · Research

3–10×Potency vs IGF-I

Low IGFBPBinding affinity

ResearchStatus

Research only · SQ typical in animal models

P21

CNTF-Derived Neuropeptide · Animal Model Evidence

CNTFR/gp130Primary receptorGuo 2022

Animal onlyEvidence level

NeurogenesisPrimary effectJia 2020 Mottolese 2024

SQ · Site unspecified · Frequency unknown

01Mechanism of Action

Parameter

IGF-1 LR3

P21

Primary target

IGF-1 receptor (IGF-1R)McTavish 2009

CNTF receptor alpha (CNTFRα) / LIF receptor (LIFR) / gp130 complex on neural stem cells

Pathway

IGF-1R → IRS-1 → PI3K/Akt → Cell proliferation, protein synthesis, anti-apoptosisMuhlbradt 2009

CNTF mimetic → CNTFRα/LIFR/gp130 heterotrimer → JAK/STAT3 signaling → neurogenesis, stem cell proliferation, neuroprotection

Downstream effect

Enhanced cell proliferation, muscle anabolism, inhibition of apoptosis, increased telomerase activity

Increased neural stem cell self-renewal, globose basal cell activation (Mash1+ cells), olfactory sensory neuron regeneration, hippocampal neurogenesis, neuroprotection in developmental disorders

Feedback intact?

No — exogenous IGF analogue bypasses GH-mediated regulation

—

Origin

Synthetic 83-AA analogue: 13-AA N-terminal extension + Arg substitution at position 3

Small-molecule peptide mimetic derived from full-length ciliary neurotrophic factor (CNTF), designed to retain receptor activation with improved pharmacokineticsMottolese 2024

Antibody development

—

02Dosage Protocols

Parameter

IGF-1 LR3

P21

Research dose (animal models)

Variable by protocol and species

In vivo murine atherosclerosis studies used sustained delivery.

—

In vitro typical concentration

10–1000 ng/mLThomas 2007

Dose-dependent effects on follicle growth and estradiol production.

—

Half-maximal stimulation

0.6 nM LR3 vs 1.5 nM native IGF-1Price 2004

2.5-fold greater potency in lung fibroblast proliferation.

—

Evidence basis

Animal / in vitro only

Animal models only

CDKL5 KO mice, methimazole-induced olfactory injury, CNTF-/- knockout models.Mottolese 2024 Cox 2026 Jia 2020

Human use

Not FDA-approved; no published human trials

—

Human dosing

—

No established protocol

No clinical trial data available.

Animal models (mice)

—

Dose and route not specified in abstractsMottolese 2024 Jia 2020

In vitro and in vivo studies demonstrate efficacy; precise dosing protocols not disclosed.

Duration

—

Not specified

Route

—

Presumed subcutaneous or intraperitoneal (animal studies)

03Metabolic / Fat Loss Evidence

Parameter

IGF-1 LR3

P21

Mechanism

IGF-1R activation → lipolytic signaling; secondary to anabolic effects

—

Direct lipolytic evidence

Minimal — primarily anabolic/anti-apoptotic in literature

—

Atherosclerotic plaque effects

Reduced stenosis and core size in ApoE-KO micevon 2011

Plaque stabilization via vSMC phenotype modulation, not direct fat loss.

—

Human data

None published

—

04Side Effects & Safety

Parameter

IGF-1 LR3

P21

Hypoglycemia risk

Theoretical — IGF-1 analogues can lower blood glucose

—

Excessive cell proliferation

Mitogenic signaling; theoretical tumor promotion risk

—

Telomerase activation

2–10-fold increase in prostate cancer cells (PC-3, DU-145, LAPC-4)Wetterau 2003

Critically involved in cancer cell immortalization.

—

Oocyte degeneration

Increased oocyte degeneration at high doses (≥1000 ng/mL) in bovine folliclesThomas 2007

—

Unregulated anabolism

Bypasses physiological GH/IGF-1 feedback; no pulsatility control

—

Unknown human safety profile

No published human trials; safety data absent

—

Human safety data

—

None available

No clinical trials in humans.

Animal tolerability

—

Well-tolerated in mouse models; no toxicity reported in available abstracts

Theoretical risks

—

Uncontrolled stem cell proliferation, immune response to peptide, unknown long-term CNS effects

Absolute Contraindications

IGF-1 LR3

·Active malignancy or history of cancer
·Not approved for human use

P21

·Use in humans not validated

Relative Contraindications

IGF-1 LR3

·Diabetes or glucose intolerance
·Family history of cancer

P21

·Active malignancy (theoretical — neurotrophic signaling may affect tumour growth)
·Pregnancy or lactation (no safety data)

05Administration Protocol

Parameter

IGF-1 LR3

P21

1. Research use only

IGF-1 LR3 is not FDA-approved for human use. All administration data derives from animal or in vitro studies.

Not established. No FDA approval, no clinical trial data.

2. Typical research route

Subcutaneous or intraperitoneal injection in animal models. In vitro: added directly to culture medium at concentrations of 10–1000 ng/mL.Thomas 2007

In vivo studies used systemic administration (route not specified in abstracts) in mouse models of neurodegeneration, olfactory injury, and CDKL5 deficiency disorder. In vitro studies used primary cell cultures.

3. Reconstitution (research)

Lyophilised powder reconstituted in sterile water or buffered saline per manufacturer protocol. Store at 2–8 °C after reconstitution.

—

4. Stability

Enhanced stability vs native IGF-1 due to reduced IGFBP binding; exact half-life in vivo not fully characterized in humans.

—

06Stack Synergy

IGF-1 LR3

+ GHRP-6

Multi-pathway

View GHRP-6 →

GHRP-6 stimulates endogenous GH release, which drives hepatic IGF-1 synthesis. IGF-1 LR3 provides exogenous, IGFBP-resistant IGF signaling. Combining upstream GH stimulation with downstream IGF receptor activation creates a dual-pathway anabolic effect. However, this bypasses natural feedback and carries compounded mitogenic risk.

GHRP-6: 100–200 mcg SQ · 2–3× daily
IGF-1 LR3: Research doses variable · post-workout typical in animal models
Note: Research context only — no human protocols exist
Primary benefit: Theoretical maximal anabolic signaling (GH + IGF axes)

+ Ipamorelin

Multi-pathway

View Ipamorelin →

Ipamorelin (selective GHRP) stimulates pulsatile GH release without cortisol/prolactin elevation. IGF-1 LR3 directly activates IGF-1R independent of GH. This stack targets both upstream (GH secretion) and downstream (IGF receptor) nodes but eliminates physiological feedback, raising safety concerns around unchecked proliferation.

Ipamorelin: 200–300 mcg SQ · evening
IGF-1 LR3: Research doses only · timing variable
Caution: No human data; animal/in vitro only
Primary benefit: Dual-axis anabolic signaling (theoretical)

P21

— no documented stacks