Question 1

What is P21?

Accepted Answer

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). Merit Verified tracks independent COA test results for P21 from multiple vendors.

Question 2

Which vendors sell P21 with independent COA testing?

Accepted Answer

2 vendors in the Merit Verified directory have independent COA evidence on file for P21 — 4 COAs total. COA coverage and test dates are listed on the P21 page at https://meritverified.org/peptides/p21.

Question 3

How do I verify the quality of P21 from a vendor?

Accepted Answer

To verify P21 quality, look for an independent certificate of analysis (COA) from a third-party lab — not a lab the vendor owns or pays directly. The COA should state the tested compound, lot number, purity percentage (identity and concentration), and the lab's name. Cross-reference the lot number against the vendor's current stock. Merit Verified indexes COAs for P21 at https://meritverified.org/peptides/p21 so you can compare evidence across vendors before buying.

Question 4

What is the regulatory status of P21?

Accepted Answer

P21 is tracked in the Merit Verified registry. Regulatory status for research peptides in the US has been evolving — the FDA has reclassified a number of peptides out of the 503A compounding ingredient list since 2025. Merit Verified does not provide legal or regulatory advice; check official FDA sources or consult a licensed professional for the current status of P21 in your jurisdiction.

P21

Pricing for P21

COAs for P21

20 citations indexed for P21

Exposure to high doses of tyre antioxidant 6PPD causes senescence to induce unexplained miscarriage by suppressing BAZ1B-mediated ubiquitination degradation of P21

CRISPR/Cas9 system-mediated p21 knockout impairs the MITF signaling pathway

Ubiquitin-dependent degradation of p27Kip1 and p21Waf1/Cip1 by AMBRA1 ensures G1 and S phase progression and limits replication stress

Transcription-independent induction of rapid-onset senescence is integral to healing

Dihydroxyacetone nanoparticles ameliorate osteoarthritis via P21-mediated regulation of chondrocyte repair

Subcellular compartmentalization dependent dichotomy of p21 in cancer