Peptide Schedule
Cyclic Glycine-Proline (cGP)2 residuesGPEach bubble = one amino acid. Size = residue mass. Color = chemical class.Cyclic Glycine-Proline (cGP) Dosage Calculator
Cyclic Glycine-Proline (cGP) is a naturally occurring cyclic dipeptide derived from the enzymatic cleavage of insulin-like growth factor-1 (IGF-1).
0.04mcg · Daily
Summary: Add 0mL BAC water to your 5mg vial. Draw to < 0.1 units on a U-100 syringe for a 0.04mcg dose. This vial will last 0 doses.
Cycle Planner
Cyclic Glycine-Proline (cGP) Pharmacokinetics
Pharmacokinetics — Active Dose Over Time
t½ = ~4-6 hours (estimated; enzymatically stable cyclic dipeptide)Disclaimer: This curve is a simplified first-order exponential decay model. Actual pharmacokinetics vary based on injection site, individual metabolism, body composition, and other factors. Half-life values are approximate and based on available preclinical and clinical literature. Many research peptides lack formal human pharmacokinetic studies. This is for educational purposes only — not medical advice.
Cyclic Glycine-Proline (cGP) Dosing Protocol
| Level | Dose / Injection | Frequency |
|---|---|---|
| Beginner | 0.04mg | Daily |
| Moderate | 0.04mg | 2x Daily |
| Aggressive | 0.08mg | Daily |
Note: cGP is an endogenous cyclic dipeptide metabolite of IGF-1, belonging to the 2,5-diketopiperazine class. It's found naturally in human plasma, cerebrospinal fluid, and breast milk. Unlike its precursor GPE (half-life <4 min), cGP is enzymatically stable due to its rigid cyclic structure. It's orally bioavailable, crosses the blood-brain barrier efficiently, and is commercially available as the supplement cGPMAX at 40 mcg/day. NNZ-2591, a synthetic cGP analog, is in Phase 2 clinical trials for neurodevelopmental disorders at doses of 4-12 mg/kg twice daily.
About Cyclic Glycine-Proline (cGP)
Cyclic Glycine-Proline (cGP) is a naturally occurring cyclic dipeptide derived from the enzymatic cleavage of insulin-like growth factor-1 (IGF-1). When IGF-1 is metabolized, it first produces glycine-proline-glutamate (GPE) from its N-terminal tripeptide. GPE is highly unstable in plasma (half-life under 4 minutes) and is rapidly converted into cGP, a stable 2,5-diketopiperazine with a molecular weight of just 154.2 Da. This small, lipophilic molecule is endogenous to the human body and has been detected in plasma, cerebrospinal fluid, and breast milk. cGP's primary function is regulating IGF-1 bioavailability. It competes with IGF-1 for binding to insulin-like growth factor binding protein-3 (IGFBP-3), the main carrier protein that sequesters IGF-1 in an inactive state. By displacing IGF-1 from IGFBP-3, cGP increases the pool of free, bioactive IGF-1 available to tissues. What makes this mechanism particularly interesting is its bidirectional nature — cGP promotes IGF-1 activity when it's insufficient but can inhibit it when it's excessive, functioning as a true homeostatic regulator. The cGP/IGF-1 molar ratio has emerged as a biomarker of functional IGF-1 status. Research shows that a healthy increase in this ratio with age correlates with normal cognition, while a declining ratio is associated with dementia in Parkinson's disease patients. Stroke patients with higher baseline cGP/IGF-1 ratios demonstrate better neurological recovery at 90 days. In preclinical studies, cGP administration has reduced amyloid plaque burden and improved spatial memory in Alzheimer's mouse models, normalized systolic blood pressure in diet-induced obese rats, and protected neural tissue from hypoxic-ischemic injury. It also acts as a positive allosteric modulator of AMPA receptors and upregulates brain-derived neurotrophic factor (BDNF) signaling.