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Published: December 2025
Category: Clinical Research Update
Compound: Retatrutide (LY3437943)
Eli Lilly has released the first topline Phase 3 clinical results for retatrutide, marking a significant milestone in late-stage obesity research. The data come from the TRIUMPH-4 trial, a 68-week randomized study evaluating retatrutide in adults with obesity and knee osteoarthritis.
This is the first Phase 3 readout in Lilly’s broader retatrutide program, which includes multiple ongoing trials across obesity, type 2 diabetes, sleep apnea, and cardiometabolic conditions through 2026.
Sources:
https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-weight-loss
https://www.pharmacytimes.com/view/once-weekly-retatrutide-reduces-weight-and-knee-pain-in-patients-with-obesity-and-osteoarthritis
Retatrutide is an investigational triple hormone receptor agonist designed to simultaneously activate:
GLP-1 receptors
GIP receptors
Glucagon receptors
This multi-pathway mechanism is intended to influence appetite regulation, energy balance, and metabolic signaling more broadly than single- or dual-agonist therapies.
Retatrutide is not FDA-approved and remains under active clinical investigation.
Source:
https://en.wikipedia.org/wiki/Retatrutide
Study name: TRIUMPH-4
Phase: Phase 3
Duration: 68 weeks
Population: Adults with obesity and knee osteoarthritis
Dosing: Once-weekly retatrutide vs placebo
Primary endpoints:
Percent change in body weight
Improvement in knee osteoarthritis pain and function scores
According to Lilly’s topline release and secondary reporting:
Participants receiving retatrutide achieved an average body weight reduction of approximately 28.7% at 68 weeks among treatment-adherent subjects.
This corresponded to up to ~71 pounds (32.3 kg) of average weight loss in the highest-dose group.
All primary and key secondary endpoints were met, including statistically significant reductions in knee osteoarthritis pain and improved physical function scores.
Secondary cardiometabolic markers showed favorable trends, including reductions in:
Non-HDL cholesterol
Triglycerides
Systolic blood pressure
Sources:
https://www.pharmacytimes.com/view/once-weekly-retatrutide-reduces-weight-and-knee-pain-in-patients-with-obesity-and-osteoarthritis
https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-weight-loss
As expected for incretin-based therapies, reported adverse events were primarily gastrointestinal in nature.
Most commonly reported events included:
Nausea
Diarrhea
Vomiting
Constipation
Reduced appetite
Some participants discontinued treatment due to adverse events or rapid weight reduction. Overall safety findings were described as consistent with prior Phase 2 data for retatrutide and with the broader GLP-1 class.
The magnitude of weight reduction reported in TRIUMPH-4 places retatrutide among the most potent investigational obesity therapies studied to date in late-stage trials.
Key implications include:
Validation of triple-agonist metabolic targeting at Phase 3 scale
Potential expansion beyond weight loss into joint health and mobility outcomes
Strong momentum heading into remaining Phase 3 trials
However, these data remain preliminary topline results. Full peer-reviewed publications and regulatory evaluations are still pending.
Eli Lilly has confirmed additional Phase 3 readouts are expected through 2026, including studies focused on:
Obesity without osteoarthritis
Type 2 diabetes
Obstructive sleep apnea
Cardiometabolic risk markers
Regulatory submissions have not yet been announced.
This page is provided for educational and research discussion purposes only. Retatrutide is an investigational compound and is not approved for medical use. Clinical outcomes described above are derived from controlled trials conducted by the sponsor and should not be interpreted as medical guidance.
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Retatrutide is a first-in-class “Triple G” agonist, targeting three distinct metabolic pathways: GLP-1, GIP, and Glucagon. While dual agonists like Tirzepatide focus on insulin and satiety, the addition of the Glucagon receptor increases energy expenditure and targets liver fat directly. This 2026 research indicates that this triple-action approach allows for metabolic flexibility that dual-agonists cannot achieve, essentially “reprogramming” the body’s fat-burning potential.
The TRIUMPH-4 results (December 2025) were unprecedented. At the highest 12 mg dose, researchers observed an average weight loss of 28.7% (71.2 lbs) over 68 weeks. For comparison, previous gold-standard dual agonists averaged 22–23%. Notably, nearly 24% of participants achieved a staggering 35% weight loss, reaching a threshold previously only attainable through invasive bariatric surgery.
Beyond weight, Retatrutide demonstrated massive systemic benefits. In patients with knee osteoarthritis, researchers recorded a 75.8% reduction in WOMAC pain scores. Furthermore, the highest dose reduced systolic blood pressure by 14.0 mmHg and significantly lowered non-HDL cholesterol and triglycerides. This confirms that the triple-agonist model is as much a cardiovascular and anti-inflammatory intervention as it is a weight-management tool.
While gastrointestinal side effects (nausea at 43%, vomiting at 21%) remain consistent with the class, a new safety signal emerged in Phase 3: Dysesthesia (abnormal skin sensitivity), reported in up to 20.9% of participants at high doses. Additionally, the 18.2% discontinuation rate was notably higher than previous incretins, often due to “perceived excessive weight loss” in participants with lower baseline BMIs. This has led researchers to favor more cautious titration protocols in 2026.
With a molecule as powerful as Retatrutide, synthesis precision is non-negotiable to avoid metabolic over-activation. Luxara Labs ensures every batch of Retatrutide undergoes 3rd-party HPLC and MS testing to verify 99% purity. We provide expedited, temperature-stable shipping across Canada and the USA, ensuring that your research materials arrive with their triple-signaling integrity fully intact for high-precision laboratory application.
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