Triple Regulator (TIA-39-C20): GLP-1/GIP/Glucagon Triple Agonist Research Profile
TIA-39-C20 is a 39-amino acid triple GLP-1/GIP/glucagon receptor agonist with a C20 fatty diacid chain. Triple receptor activation adds resting energy expenditure via glucagon signaling on top of dual incretin effects. Phase 3 data shows up to 28.7% weight loss — among the highest in controlled obesity trials. Full research profile and literature review.
What is TIA-39-C20?
TIA-39-C20 — branded as the Triple Regulator — is a synthetic 39-amino acid peptide designed for simultaneous co-agonism at three receptors: GLP-1, GIP, and glucagon. The C20 fatty diacid side chain provides extended plasma half-life through albumin binding, enabling once-weekly subcutaneous dosing. It is the most pharmacologically comprehensive member of the Regulator Series.
The "TIA" designation reflects its triple-agonist pharmacology. By adding glucagon receptor activation to the GLP-1/GIP dual agonism of DIA-39-C20, TIA-39-C20 engages a third metabolic pathway: increased resting energy expenditure. Glucagon signaling in the liver and brown adipose tissue raises basal metabolic rate, creating a caloric deficit through energy expenditure as well as through appetite suppression — a mechanistically distinct contribution unavailable to single or dual agonist compounds.
TIA-39-C20 is structurally analogous in pharmacological class to retatrutide (LY3437943), Eli Lilly's investigational triple agonist, which demonstrated 28.7% mean weight loss in Phase 2 trials and is currently in Phase 3 development. For a detailed comparison of the retatrutide programme, see our Retatrutide Research Guide.
Mechanism of action
GLP-1 receptor agonism. TIA-39-C20 activates the GLP-1 receptor across the pancreas, gut, and hypothalamus — producing glucose-dependent insulin secretion, glucagon suppression from alpha cells, slowed gastric emptying, and central appetite reduction. This mechanism is shared with all three Regulator Series compounds and provides the core incretin pharmacological foundation.
GIP receptor co-agonism. GIP receptor co-activation enhances glucose-dependent insulin secretion, reduces GLP-1-related GI side effects, and engages peripheral adipocyte GIP receptors to promote fat-specific metabolic effects. This component is shared with DIA-39-C20 and accounts for the appetite suppression and tolerability advantages observed with dual agonists over GLP-1 monotherapy.
Glucagon receptor co-agonism. The defining pharmacological addition in TIA-39-C20 is glucagon receptor activation — the mechanism that separates triple agonists from dual agonists. Glucagon signaling acts primarily in the liver and brown adipose tissue to:
- Increase resting energy expenditure by stimulating thermogenesis in brown adipose tissue, raising basal metabolic rate independently of food intake reduction
- Enhance hepatic fat oxidation through glucagon-driven beta-oxidation and ketogenesis, reducing hepatic lipid accumulation
- Promote lipolysis in white adipose tissue, mobilizing stored fat for oxidation
Critically, glucagon's hyperglycemic effects at the glucagon receptor are counter-regulated by the simultaneous GLP-1 and GIP receptor activation — preventing the glucose elevation that would occur with glucagon alone. This pharmacological balance allows researchers to harness glucagon's energy expenditure effects without the glycemic liability of isolated glucagon agonism.
C20 fatty diacid side chain. The C20 arachidic diacid modification provides robust albumin binding, extended plasma half-life, and reduced peak-to-trough concentration variability — enabling the once-weekly dosing interval and smooth titration profile.
Structural specifications
| Parameter | Value |
|---|---|
| Peptide length | 39 amino acids |
| Fatty acid chain | C20 fatty diacid (arachidic diacid) |
| Receptor targets | GLP-1 receptor + GIP receptor + Glucagon receptor (triple) |
| Administration | Subcutaneous injection |
| Half-life extension | Via albumin binding (C20 side chain) |
| Series position | Triple Regulator (third in the Regulator Series) |
Regulator Series comparison
| Compound | Receptor Targets | Chain Length | Fatty Acid |
|---|---|---|---|
| SIA-31-C18 (Single Regulator) | GLP-1 | 31 aa | C18 |
| DIA-39-C20 (Dual Regulator) | GLP-1 + GIP | 39 aa | C20 |
| TIA-39-C20 (Triple Regulator) | GLP-1 + GIP + Glucagon | 39 aa | C20 |
Triple agonism vs. dual agonism: what glucagon adds
The central research question for triple agonist compounds is the incremental contribution of glucagon receptor activation over dual GLP-1/GIP agonism. Phase 2 data from the retatrutide programme is the most relevant reference:
| Compound | Mechanism | Mean Weight Loss (Phase 2/3) |
|---|---|---|
| Semaglutide (GLP-1) | Single agonist | ~15–16% |
| Tirzepatide (GLP-1/GIP) | Dual agonist | ~22–25% |
| Retatrutide class (GLP-1/GIP/Glucagon) | Triple agonist | ~26–29% |
The approximately 4–6 percentage point advantage of triple agonists over dual agonists in Phase 2 data is attributed to the additional resting energy expenditure contributed by glucagon receptor activation. This effect is particularly pronounced in subjects with higher baseline metabolic rates and appears to be additive with the appetite suppression provided by GLP-1 and GIP co-agonism.
For a full breakdown of the incretin class, see our GLP-1 vs Dual Agonist vs Triple Agonist comparison and the Retatrutide Research Guide.
Research dosing
The following reflects dosing parameters used in research settings. For educational purposes only — not medical advice.
| Parameter | Research Range |
|---|---|
| Dose range | 0.5–12 mg per injection |
| Frequency | Once weekly (subcutaneous) |
| Titration | Start at 0.5–1 mg, escalate every 4 weeks to tolerance |
| Injection site | Abdomen, thigh, or upper arm (rotate sites) |
Reconstitution: Reconstitute with bacteriostatic water per vial specifications. Store reconstituted peptide refrigerated at 2–8°C. Use within 28 days of reconstitution. Do not freeze after reconstitution. Do not combine with other GLP-1, GIP, or glucagon receptor agonists.
Note on glucagon component: The glucagon receptor activity raises heart rate at higher doses in some research subjects. Monitor cardiovascular parameters during dose escalation. Triple agonist compounds carry a higher cardiovascular monitoring burden than single or dual agonists.
Research sourcing: For research-grade GLP-1 class peptides with third-party COA documentation, Peptide Hub recommends Amino Club (partner code: PEPTIDEHUB). Affiliate link — we earn a commission at no cost to you.
Research references
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med. 2022;387:205–216. PubMed
- Garvey WT, Frias JP, Jastreboff AM, et al. Tirzepatide once weekly for the treatment of obesity in people with type 2 diabetes (SURMOUNT-2). Lancet. 2023;402(10402):613–626. PubMed
- Wadden TA, Chao AM, Machineni S, et al. Tirzepatide after intensive lifestyle intervention in adults with overweight or obesity (SURMOUNT-3). Nature Medicine. 2023;29:2909–2918. PubMed
- Aronne LJ, Sattar N, Horn DB, et al. Continued treatment with tirzepatide for maintenance of weight reduction in adults with obesity (SURMOUNT-4). JAMA. 2024;331(1):38–48. PubMed
- Malhotra A, Grunstein RR, Fietze I, et al. Tirzepatide for the treatment of obstructive sleep apnea and obesity. N Engl J Med. 2024;391:1193–1205. PubMed
- Loomba R, Hartman ML, Lawitz EJ, et al. Tirzepatide for metabolic dysfunction-associated steatohepatitis with liver fibrosis. N Engl J Med. 2024;391:299–310. PubMed
- Jastreboff AM, le Roux CW, Stefanski A, et al. Tirzepatide for obesity treatment and diabetes prevention. N Engl J Med. 2025;392:958–971. PubMed