K4 Elite
K4 Elite
Metabolic & Weight
This vial contains two acylated incretin-class peptides co-lyophilised in a 1:1 mass ratio — 30 mg of GLP-3 (retatrutide, Eli Lilly code LY3437943) and 30 mg of tirzepatide (LY3298176) — for a nominal 60 mg total. GLP-3 is a 39-residue single peptide engineered to activate three receptors at once: the glucose-dependent insulinotropic polypeptide (GIP) receptor, the GLP-1 receptor and the glucagon receptor [1][2]. Tirzepatide is a 39-residue GIP-based sequence with a C20 fatty diacid that activates the GIP and GLP-1 receptors but not the glucagon receptor [4]. Both carry fatty-diacid side chains that bind albumin and extend circulating half-life to the once-weekly range. The blend is supplied as a laboratory reference material for in-vitro pharmacology of overlapping receptor systems.
The two molecules share GIP and GLP-1 receptor activity and differ in one respect: GLP-3 adds glucagon-receptor agonism. In rodent and human work, GLP-1 receptor activation lowers food intake and slows gastric emptying, GIP receptor activation appears to improve tolerability of GLP-1 agonism and may act on adipose and central pathways, and glucagon receptor activation raises hepatic energy expenditure and lipid oxidation [2][4]. Placing the dual and triple agonist in one experimental system lets researchers isolate the contribution of the glucagon-receptor arm by comparing the two against matched GIP/GLP-1 activity. The published pharmacology of GLP-3 describes deliberately imbalanced potency — near-native activity at the GIP receptor with attenuated activity at the GLP-1 and glucagon receptors relative to the endogenous ligands — which is itself a design question for receptor-signalling studies [2].
Coskun and colleagues characterised LY3437943 in cell-based assays, rodents and a first-in-human study, reporting glucose lowering and weight reduction consistent with contributions from all three receptors [2]. A phase 2 obesity trial (n = 338; 48 weeks) reported mean body-weight changes of −17.5% at 4 mg, −22.8% at 8 mg and −24.2% at 12 mg weekly versus −2.1% with placebo [1]. A separate phase 2 in type 2 diabetes (n = 281; 36 weeks) reported HbA1c reductions of up to 2.02 percentage points, with gastrointestinal events the most common adverse effect and transient increases in heart rate noted [3]. Phase 3 (TRIUMPH) results were pending at the time of writing.
Tirzepatide is the active compound in the approved medicines Mounjaro and Zepbound. Its discovery paper reports a GIP-sequence backbone with a C20 diacid at lysine 20 and a half-life of roughly five days in humans [4]. SURMOUNT-1 (n = 2,539; 72 weeks) reported mean weight changes of −15.0%, −19.5% and −20.9% at 5, 10 and 15 mg versus −3.1% with placebo, with nausea, diarrhoea and constipation the most common adverse events [5].
The 1:1 mass ratio is a manufacturing convenience, not a ratio drawn from any study. The molecules have different molecular weights (approximately 4,731 g/mol for GLP-3 and 4,813 g/mol for tirzepatide) and different receptor potencies, so equal mass does not mean equal molar or equal pharmacological input. Researchers requiring a specific molar ratio should source the two peptides separately.
No published clinical or preclinical trial has studied retatrutide and tirzepatide co-administered together. Each molecule was developed as a stand-alone agent; the trial data cited above describe each compound alone, in GMP form, under medical supervision. Nothing is known from the peer-reviewed record about the safety, tolerability, pharmacokinetics or receptor interactions of the combination, and the two agents share the same class-level cautions (gastrointestinal effects, rodent thyroid C-cell findings, pancreatitis, gallbladder events). GLP-3 remains an investigational compound not approved anywhere. This blend has not been evaluated by the FDA, and no statement here describes a benefit or use in a person or animal.
View COA — Retatrutide + Tirzepatide →
Format. Co-lyophilised powder containing 30 mg GLP-3 (retatrutide) and 30 mg tirzepatide in a single sealed glass vial (60 mg nominal). The certificate of analysis reports each component separately.
Reconstitution. Reconstitute with bacteriostatic water or sterile water for injection-grade solvent, adding the liquid slowly against the vial wall and swirling until clear. Both peptides are acylated and can foam if agitated. The reconstitution calculator gives the concentration of each component from the total vial mass and diluent volume.
Storage. Lyophilised: −20°C long-term, 2–8°C for short periods, protected from light. Reconstituted: 2–8°C, do not freeze, use within the laboratory’s validated period.
Handling. Gloves and eye protection; treat as a bioactive peptide mixture. For in-vitro laboratory research only — not for human or veterinary use.