P21 (P021)
Peptide 021; Ac-DGGLAG-NH2 (adamantylated CNTF mimetic); PB021 (Phanes Biotech designation). Synonyms: P-21, CNTF-derived neurotrophic peptide P021. Note: distinct from the p21/CDKN1A cell-cycle protein and from RAS-p21 peptides.
P21 (P021) is a synthetic tetrapeptide mimetic of ciliary neurotrophic factor (CNTF) designed to promote neurogenesis, enhance BDNF expression, and reduce tau/amyloid pathology. All evidence is preclinical (rodent models); no human clinical trials have been completed (.
Last updated: 2026-03-13
Safety Summary
All side effect data for P021 derives from preclinical rodent studies and anecdotal community reports -- no human clinical trial safety data exists. In chronic rodent studies up to 18 months, no systemic toxicity, weight loss, organ abnormalities, tumor formation, or mortality attributable to P021 was observed, and importantly, P021 did not produce the weight loss/anorexia seen with full-length CNTF. No immunogenicity (anti-drug antibody formation) detected in preclinical studies (. No evidence of tolerance, tachyphylaxis, or withdrawal effects in chronic preclinical dosing (. No drug-drug interaction studies have been conducted. Because P021 modulates pathways related to cell survival and apoptosis, there is a theoretical risk regarding tumor facilitation, though no cancer signals were seen in 18-month rodent studies. The absence of human safety data is the primary limitation; all frequency estimates are extrapolated from community reports with inherent reporting bias.
Known Side Effects
common
common
rare
rare
Who Should NOT Use This
Theoretical risk: p21 pathway modulation and anti-apoptotic effects could potentially facilitate tumor growth or reduce tumor-cell apoptosis. Expert summaries and safety monographs recommend against use in patients with active malignancy. No empirical evidence of tumor promotion in 18-month rodent studies, but the mechanism warrants caution.
No reproductive, embryo-fetal, teratogenicity, or lactation data available in any species for P021. Avoid use entirely.
Standard peptide hypersensitivity precaution. No specific immunogenicity documented but standard caution applies.
No dedicated PK/safety studies in renal impairment. Small peptides may have reduced renal clearance in severe dysfunction, leading to prolonged exposure. Dose adjustment considerations are unquantified.
No dedicated PK/safety studies in hepatic impairment. Standard peptide hepatic evaluation guidance applies but no P021-specific data available.
Talk to Your Doctor
Before considering P21 (P021), discuss it with your healthcare provider. Ask about potential interactions with your current medications, whether it is appropriate for your health conditions, and what monitoring may be needed.
Sources: [1-5]
Evidence Assessment
P21 (P021) has zero completed human clinical trials. All efficacy and safety data come exclusively from preclinical rodent models (mice and rats), including chronic studies in 3xTg-AD Alzheimer's mouse models and wild-type mice up to 18 months. No Phase I, II, or III human trials have been registered or completed on ClinicalTrials.gov as of March 2026. Phanes Biotech is developing PB021 but remains in preclinical stage. Evidence tier = 5 (preclinical only) citing ClinicalTrials.gov, Phanes Biotech, ADDF P021 report.
1Prevention of dendritic and synaptic deficits and cognitive impairment with a neurotrophic compoundPMID 28655344
Baazaoui N, Iqbal K - Alzheimer's Research & Therapy (PMC5488423) (2017) - Preclinical animal study - Mouse models (3xTg-AD and wild-type)
Chronic P021 administration prevented dendritic and synaptic deficits and cognitive impairment in Alzheimer's disease mouse models. No adverse effects observed in chronic dosing up to 18 months.
Limitations: Animal model only; no human data.
2P021 Cognitive Vitality Report
Alzheimer's Drug Discovery Foundation (ADDF) - ADDF Cognitive Vitality Reports (2021) - Expert review/monograph - N/A (review)
Comprehensive review of P021 preclinical evidence. Confirms no human trials. Reports favorable long-term preclinical safety profile (up to 18 months chronic dosing in rodents with no CNTF-like weight loss, immunogenicity, or organ toxicity). Notes efficacy in AD models for neurogenesis, tau reduction, and cognitive rescue.
Limitations: Expert review, not primary research. Preclinical data only, all citing this report.
3Neuroregeneration P021: Shifting the Balance
Phanes Biotech - Company website (2020) - Developer pipeline information - N/A
Phanes Biotech (PB021) is the primary developer of P021 for Alzheimer's disease. Preclinical stage; no registered clinical trials as of March 2026.
Limitations: Company-sourced information, not peer-reviewed.
4Neurotrophic peptides incorporating adamantane improve learning and memory, promote neurogenesis and synaptic plasticity in mice
Not specified in raw data - Pharmacology (inferred from URL) (2010) - Preclinical animal study - Mouse models
Adamantane-modified neurotrophic peptides (including P021 family) improved learning and memory, promoted neurogenesis and synaptic plasticity in mice.
Limitations: Preclinical only citations.
5Effects of a ciliary neurotrophic factor (CNTF) small-molecule peptide mimetic in an in vitro and in vivo model of CDKL5 deficiency disorder
Not specified in raw data - PMC (specific journal not extracted) (2024) - Preclinical in vitro and in vivo study - CDKL5 deficiency disorder models
A CNTF small-molecule peptide mimetic (related to P021 class) demonstrated effects in CDKL5 deficiency disorder models, expanding potential neurological applications beyond Alzheimer's disease.
Limitations: Preclinical only. Relationship to P021 specifically may be indirect.