Retatrutide vs P21
Side-by-side comparison of key properties, dosing, and research.
GLP-1 / Weight Loss Agonists
RetatrutideCognitive EnhancementAnti-Aging & Longevity
P21- Summary
- Retatrutide is an investigational triple receptor agonist targeting GLP-1, GIP, and glucagon receptors simultaneously. Phase 2 trials showed an unprecedented average 24% body weight reduction at 48 weeks — exceeding any approved medication to date. It is in Phase 3 trials as of 2024.
- P21 is a synthetic peptide derived from CNTF (ciliary neurotrophic factor) that promotes hippocampal neurogenesis, enhances memory and spatial learning, and may reduce amyloid-beta pathology. It is used as a neurogenic and cognitive enhancer with potential anti-Alzheimer's applications.
- Half-Life
- ~10–12 days
- Not well characterized; likely short, but neurogenic effects persist long after administration
- Admin Route
- SubQ
- SubQ, Intranasal
- Research
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- Typical Dose
- 0.5 mg → 1 mg → 2 mg → 4 mg → 8 mg → 12 mg
- 100–500 mcg
- Frequency
- Once weekly
- Once daily
- Key Benefits
- ~24% body weight reduction at 48 weeks in Phase 2 (highest dose)
- Superior to both semaglutide and tirzepatide in early trial comparisons
- Triple receptor mechanism addresses multiple obesity pathways
- Significant reduction in liver fat (MASH/NAFLD indication being studied)
- Improved cardiovascular and metabolic markers
- Once-weekly dosing
- Potential for greatest weight loss of any currently investigated compound
- Promotes hippocampal neurogenesis
- Enhances spatial memory and learning
- Increases BDNF expression
- Reduces amyloid-beta plaque formation (animal models)
- Anti-tau pathology potential
- Cognitive enhancement without stimulant effects
- Potential therapeutic for Alzheimer's and cognitive aging
- Side Effects
- Nausea and vomiting (common during titration, similar to semaglutide/tirzepatide)
- Diarrhea
- Constipation
- Heart rate increase (from glucagon receptor agonism)
- +2 more
- Generally well tolerated in animal studies
- Limited human clinical data
- Injection site reactions
- Potential mild fatigue at initiation
- Stacks With
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