PinnyPeptide

P21 (P021) vs PE22-28

Side-by-side comparison: effects, dosing ranges, side effects, regulatory status, and reconstitution.

Peptide A

P21 (P021)

Cognitive

Neurogenic, anti-tau peptide derived from ciliary neurotrophic factor — Alzheimer's research.

Peptide B

PE22-28

Cognitive

Fast-acting antidepressant peptide acting via TREK-1 channel inhibition.

Typical vial

5 mg

Typical dose

Per kg dosing mcg

Half-life

Variable; designed for sustained activity

FDA status

Not FDA approved.

Typical vial

5 mg

Typical dose

50-200 mcg

Half-life

Hours; precise value species-dependent

FDA status

Not FDA approved.

P21 (P021) effects

  • Promotes adult hippocampal neurogenesis
  • Increases dendritic spine density
  • Reduces tau hyperphosphorylation (anti-tauopathy)
  • Improves learning and memory in Alzheimer's mouse models
  • Crosses the blood-brain barrier after peripheral administration

PE22-28 effects

  • Selective TREK-1 potassium channel inhibition
  • Fast-onset antidepressant-like effects in rodent models
  • Increased serotonergic neuron firing in dorsal raphe
  • Enhanced BDNF / TrkB signaling downstream
  • Anti-anxiety effects in some assays

P21 (P021) side effects

  • Essentially uncharacterized in humans
  • Theoretical: off-target effects on CNTF / leptin receptor pathways
  • Possible effects on appetite and metabolism (CNTF-family signaling)
  • Injection-site reactions

PE22-28 side effects

  • Essentially uncharacterized in humans
  • Theoretical: TREK-1 inhibition off-target in heart, immune cells
  • Subjective reports of mood activation, occasional anxiety
  • Injection-site reactions
  • Sleep disturbance with late-day dosing

P21 (P021) dosing ranges

Neurogenesis research (preclinical)

40-200 mcg/kg · Daily or alternate-day SubQ · Per research protocol

PE22-28 dosing ranges

Antidepressant research (preclinical)

100-500 mcg/kg · Daily SubQ or IP · Per protocol

Self-experimentation (no clinical guidance)

50-200 mcg · Once or twice daily · 2-4 weeks per cycle

Full P21 (P021) guide → Full PE22-28 guide →

P21 (P021) vs PE22-28 — common questions

What is the difference between P21 (P021) and PE22-28?

P21 (P021): Neurogenic, anti-tau peptide derived from ciliary neurotrophic factor — Alzheimer's research. Typical dose Per kg dosing mcg. PE22-28: Fast-acting antidepressant peptide acting via TREK-1 channel inhibition. Typical dose 50-200 mcg. Both fall under the Cognitive category.

Can you stack P21 (P021) and PE22-28?

Stacking P21 (P021) with PE22-28 is a protocol-design question best raised with a clinician — it depends on your goal, current bloodwork, and whether both peptides target overlapping mechanisms. Both peptides should be tracked independently with separate injection sites and timing. PinnyPeptide supports multi-peptide stacks with automatic injection site rotation.

Which is dosed more frequently, P21 (P021) or PE22-28?

P21 (P021) is typically dosed: Daily or alternate-day SubQ for Neurogenesis research (preclinical). PE22-28 is typically dosed: Daily SubQ or IP for Antidepressant research (preclinical); Once or twice daily for Self-experimentation (no clinical guidance).

Are P21 (P021) and PE22-28 FDA approved?

P21 (P021): Not FDA approved. PE22-28: Not FDA approved.

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