IGF-1 LR3 has a ~20–30 hour half-life from resistance to IGF-binding proteins; DES(1-3) IGF-1 has a short half-life (~20 min) but ~10× greater potency at the IGF-1 receptor — the two analogues are optimised for different research protocols.
Research reference only — all information on this page summarises peer-reviewed scientific literature and does not constitute medical advice. View full compound profiles: IGF-1 LR3 · DES(1-3) IGF-1
Mechanism Comparison
Both compounds are synthetic analogues of human insulin-like growth factor 1 (IGF-1) engineered to overcome the limitations of native IGF-1 in research settings. Native IGF-1 has a very short free half-life (~10 minutes) because it is tightly bound by six IGF-binding proteins (IGFBPs), particularly IGFBP-3. IGF-1 LR3 (Long R3 IGF-1) addresses this by an N-terminal 13-amino-acid extension and an Arg³ → Arg substitution that dramatically reduces IGFBP binding affinity, extending the half-life to ~20–30 hours. DES(1-3) IGF-1 achieves a different pharmacological goal: by truncating the first 3 N-terminal amino acids, it loses IGFBP-3 binding (short half-life) but gains ~10-fold greater intrinsic potency at the IGF-1 receptor. Each analogue is optimised for a different research question: sustained IGF-1R exposure (LR3) versus high-potency, acute receptor activation (DES).
Side-by-Side Attributes
| Attribute | IGF-1 LR3 | DES(1-3) IGF-1 |
|---|---|---|
| Structural modification | 13-AA N-terminal extension + Arg³ substitution | N-terminal truncation (remove first 3 amino acids) |
| Amino acid count | 83 amino acids (83 AA vs 70 AA for native IGF-1) | 67 amino acids |
| Molecular weight | ~9,117 Da | ~7,371 Da |
| CAS number | 946590-37-0 | 112603-37-9 |
| IGFBP binding | Very low (key feature — resists IGFBP-3/5) | Low — IGFBP-3 binding eliminated by truncation |
| Half-life (approx.) | ~20–30 hours (IGFBP resistance) | ~20 minutes (no IGFBP, but short intrinsic half-life) |
| IGF-1R potency vs native IGF-1 | Similar to native at receptor level | ~10× greater (truncation exposes binding domain) |
| Research use case | Sustained IGF-1R activation; systemic IGF-1 axis studies | High-potency acute activation; local tissue protocols |
| Regulatory status | Investigational; 503A restricted | Investigational; 503A restricted |
Key Research Points
- 1The pharmacological tradeoff between the two analogues is fundamental: IGF-1 LR3 sacrifices receptor potency to gain sustained systemic exposure; DES(1-3) IGF-1 sacrifices duration to gain acute potency at the receptor. Neither is "better" — the choice depends entirely on the research question.
- 2DES(1-3) IGF-1's 10-fold greater IGF-1R potency vs native IGF-1 has been attributed to the loss of the first three amino acids, which in native IGF-1 partially occlude the receptor-binding B-domain. This conformational change exposes the receptor-binding domain more fully.
- 3IGF-1 LR3 is particularly useful in protocols studying systemic IGF-1 axis effects (GH/IGF-1 axis signalling, anabolic signalling, anti-catabolic effects) over extended time windows, where the 20–30 hour half-life allows once-daily or every-other-day dosing.
- 4Both compounds activate the IGF-1R and insulin receptor (with lower affinity) — researchers studying insulin signalling contamination of IGF-1R data must account for this cross-reactivity in experimental design.
- 5Native IGF-1 (not these analogues) is FDA-approved as mecasermin (Increlex) for severe primary IGF-1 deficiency. Both LR3 and DES analogues are investigational.
Frequently Asked Questions
What is the difference between IGF-1 LR3 and DES(1-3) IGF-1?
IGF-1 LR3 (Long R3 IGF-1) is an 83-amino-acid analogue with an N-terminal 13-AA extension and an Arg substitution that reduces IGF-binding protein (IGFBP) affinity, extending the half-life to ~20–30 hours. This makes it suitable for protocols requiring sustained IGF-1R exposure. DES(1-3) IGF-1 is a 67-amino-acid truncated form lacking the first three N-terminal amino acids; this truncation eliminates IGFBP-3 binding (short half-life ~20 min) but increases intrinsic IGF-1R potency ~10-fold compared to native IGF-1. The choice between them depends on the research question: sustained systemic exposure (LR3) versus high-potency acute receptor activation (DES).
Which IGF-1 analogue is more potent — LR3 or DES?
DES(1-3) IGF-1 is approximately 10-fold more potent at the IGF-1 receptor than native IGF-1 and IGF-1 LR3 at equivalent doses. The truncation of the first three amino acids exposes the receptor-binding B-domain more fully, increasing intrinsic receptor affinity. However, DES(1-3) IGF-1's very short half-life (~20 minutes) means this potency advantage is brief; LR3's 20–30 hour half-life produces greater total receptor activation over time despite lower per-molecule receptor affinity.
Why does IGF-1 LR3 have a longer half-life than native IGF-1?
Native IGF-1 circulates almost entirely bound to IGF-binding proteins (primarily IGFBP-3 in a ternary complex with ALS), which dramatically limits its free fraction and biological activity. IGF-1 LR3's N-terminal 13-amino-acid extension and the Arg³ → Arg substitution structurally interfere with IGFBP binding, leaving a much larger free fraction available for IGF-1 receptor binding. Because the free fraction is not sequestered by IGFBPs, it has a longer half-life (~20–30 hours vs ~10 minutes free for native IGF-1) and produces sustained systemic IGF-1R activation unsuitable without IGFBP resistance.
Deep Dive
For extended mechanism analysis, trial data, and regulatory context, see the full research article:
IGF-1 LR3 vs DES(1-3) IGF-1: IGF Analogue Research Comparison →Full compound profile
IGF-1 LR3
Full compound profile
DES(1-3) IGF-1