Side-by-side comparison of mechanisms, dosing, interactions, and stacking potential.
| P21 (Cerebrolysin Analog) | SS-31 (Elamipretide) | |
|---|---|---|
| Category | Peptides | Peptides |
| Standard Dose | Research indicates 750 mcg-1 mg daily via intranasal administration or subcutaneous injection. | Research indicates 0.05-0.25 mg/kg daily via subcutaneous injection. Clinical trials used 4-40 mg/day IV or SC. |
| Timing | Morning dosing preferred for cognitive effects. | Morning dosing preferred. No food timing restrictions. |
| Cycle Duration | 4-8 week cycles with 4-week rest periods. | Clinical trials ranged from single dose to 48 weeks. Optimal cycle length not established. |
| Evidence Level | animal_plus_anecdotal | Emerging (Phase 2/3 trials) |
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.
SS-31 (D-Arg-Dmt-Lys-Phe-NH2, also known as elamipretide/Bendavia) is a cell-permeable tetrapeptide that localizes to the inner mitochondrial membrane and binds cardiolipin via electrostatic interactions. This stabilizes cardiolipin against oxidative damage, preserving cristae integrity, reducing ROS production, and maintaining mitochondrial ATP production. SS-31 interacts with proteins in two functional groups: oxidative phosphorylation complexes and 2-oxoglutarate metabolic enzymes — all known cardiolipin binders. It restores mitochondrial function without acting as a direct antioxidant.
Research indicates 0.05-0.25 mg/kg daily via subcutaneous injection. Clinical trials used 4-40 mg/day IV or SC.
Morning dosing preferred. No food timing restrictions.
Clinical trials ranged from single dose to 48 weeks. Optimal cycle length not established.
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