P21
Also known as: P021
P21 (also P021) is a small peptidergic compound — the tetrapeptide core Asp-Gly-Gly-Leu with an N-terminal acetyl and a C-terminal adamantylated glycine amide (Ac-DGGL(A)G-NH2) — derived from an active region (residues ~148–151) of human ciliary neurotrophic factor (CNTF). It was designed and characterized in the Khalid Iqbal laboratory at the New York State Institute for Basic Research in Developmental Disabilities (NYS IBR). It is an experimental, preclinical compound — NOT FDA-approved and NOT tested in humans in published trials. Distinct from the cyclin-dependent kinase inhibitor protein p21/CDKN1A/WAF1 (a completely different gene product; the two share only the name).
Who's worth your money for P21
Every current seller, ranked by independent evidence — Merit Score, latest COA purity, and live $/mg (size-normalized). Prices refresh daily. Rankings are never paid.
Top Merit pick
Highest Merit Score (88) of 4 scored sellers
$38.00 · 5mg
Best value
Lowest $/mg among scored sellers
$119 · 10mg · 98.6% purity
Average price
$16.01/mg
Sellers
12
45-day trend
+10.9%
8 of 12 sellers have a current price· 4 unverified hidden
Top Merit pick
🇺🇸 Ruo Bio88✓ verified at source · 1h ago
$7.60/mg -52.5% vs avg$38.00
5mg
no purity- 🇺🇸 Verified Peptides86
via Disclosed Labs · 1h ago
$11.90/mg -25.7% vs avg$119
10mg
- 🇺🇸 Simple Peptide85
via Disclosed Labs · 1h ago
$19.80/mg +23.7% vs avg$198
10mg
no purity - 🇺🇸 Genetic Peptide71
✓ verified at source · 23h ago
$24.00/mg +49.9% vs avg$120
5mg
no purity
Prices observed from public storefronts (last 24h), normalized to $/mg. "Evidence" is Merit's 0–100 Merit Score, derived only from observable verification evidence (methodology on /about); "Purity" is the latest independent COA. Some buy links are affiliate links — Merit may earn a commission at no extra cost to you, and where a vendor offers one, the code shown gets you a discount at their checkout. Affiliate status never affects price data, ranking, or the Merit Score (full policy on /disclosure). Research use only.
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About P21
CAS
1246751-68-7
Molecular formula
C27H42N6O8
Sequence
DGGL
Typical dose range
500–750 mcg/day intranasal (research use); 250–1000 mcg/day range reported
Half-life
>6 hours (rodent; estimated, based on parent Peptide 6 and adamantane-modified stability)
COAs for P21
6 third-party tests across 2 vendors. Each card links to the full report.
For
P-21
by Verified Peptides· batch P2106260210B
For
P21 with Adamantane
by Verified Peptides· batch P210626010B
For
P-21
by Skye Peptides· batch P2125-10-001
Purity not on file
For
P21 with Adamantane
by Verified Peptides· batch P2106260210B
Purity not on file
For
P21
by Skye Peptides· batch P2125-10-001
Purity not on file
For
P21
by Skye Peptides· batch P2125-10-001
20 citations indexed for P21
Study
A programmable DNA circuit based on target recycling-assisted DNAzyme combined with elemental labeling ICP-MS for p21 mRNA detection
The strand displacement reaction (SDR) has shown considerable potential in bioanalysis due to its enzyme-free nature, predictable base-pairing behavior and excellent programmability.
Study · 2026
Histone lactylation-upregulated CEBPB transcriptionally activates CXCL12 and p21 to modulate vascular smooth muscle cell senescence and macrophage polarization
Background Abdominal aortic aneurysm (AAA) represents a widespread vascular disorder associated with high significant mortality rates, and the phenotypic transformation of vascular smooth muscle cells (VSMCs) acts as a crucial pathological characteristic during the advancement of this condition.
Study · 2026
The p53-Associated Regulation of ATF4 mRNA Expression Involves p21 and p130 in a Stress-Dependent Manner
p53-dependent signaling and the integrated stress response (ISR) are major stress response programs that coordinate cellular metabolism and cell fate decisions.
Study · 2026
Chronic Senolytic Treatment and/or Aerobic Exercise Reduce Senescence and Improve Myocardial Function During Aging in the Heart
Study · 2026
Targeting SUV39H2 exon skipping reverses resistance to CDK4/6 inhibitors via transcriptional activation of p21
Study · 2026
Polymorphism of carbonic acid (H<sub>2</sub>CO<sub>3</sub>) at low pressures
Carbonic acid (H 2 CO 3 ) has been detected on the surfaces of icy moons and has been suggested to occur in the interior of ice giants. Hence, understanding structure-property relations of phases in the H-C-O system is of significant interest to astrophysics and solid-state chemistry.