Side-by-side comparison of mechanisms, dosing, interactions, and stacking potential.
| LL-37 (Cathelicidin) | P21 (Cerebrolysin Analog) | |
|---|---|---|
| Category | Peptides | Peptides |
| Standard Dose | Research indicates 50-100 mcg daily via subcutaneous injection for immune support. | Research indicates 750 mcg-1 mg daily via intranasal administration or subcutaneous injection. |
| Timing | Morning administration preferred for immune support. Topical application directly to wound sites. | Morning dosing preferred for cognitive effects. |
| Cycle Duration | 4-8 week cycles. Short-term use preferred due to limited long-term safety data. | 4-8 week cycles with 4-week rest periods. |
| Evidence Level | animal_plus_anecdotal | animal_plus_anecdotal |
LL-37 is a 37-residue amphipathic helical antimicrobial peptide, the only human cathelicidin, that kills bacteria by forming tetrameric channels that perforate cytoplasmic membranes. Beyond direct antimicrobial activity, it modulates innate immunity through formyl-peptide receptor 2 (FPR2), induces chemotaxis of neutrophils and monocytes, upregulates CXCR4 and IL-8, and neutralizes bacterial endotoxins (LPS). It also promotes wound healing through keratinocyte migration and angiogenesis.
Research indicates 50-100 mcg daily via subcutaneous injection for immune support.
Morning administration preferred for immune support. Topical application directly to wound sites.
4-8 week cycles. Short-term use preferred due to limited long-term safety data.
P21 is a tetrapeptide (DGGL — Asp-Gly-Gly-Leu) derived from the most active region of ciliary neurotrophic factor (CNTF, residues 148-151), identified through reverse engineering of Cerebrolysin. An adamantylated glycine enhances BBB permeability and metabolic stability. P21 works through LIF/STAT3 pathway inhibition, BDNF/TrkB/CREB signaling enhancement, and restoration of synaptic proteins (synaptophysin, synapsin I) and glutamate receptors. It promotes neurogenesis and maturation of newborn neurons in the dentate gyrus.
Research indicates 750 mcg-1 mg daily via intranasal administration or subcutaneous injection.
Morning dosing preferred for cognitive effects.
4-8 week cycles with 4-week rest periods.
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