P21 Peptide

The P21 Peptide evidence base cited here is 7 sources — 5 preclinical, 2 review. Critically, that evidence is almost entirely preclinical (animal and in-vitro) — no human clinical trials are cited, so efficacy and safety in people remain unproven. Regulatory status: Not FDA-approved.

• p21/CDKN1A is the primary effector of p53-driven cell cycle arrest and a central mediator of cellular senescence; it can function as both a classical tumor suppressor (arresting damaged cells) and, paradoxically, as a proto-oncogenic survival factor in established tumors, with its role determined by cellular context, subcellular localization, and interaction partners.
• A 2021 Science study found that p21-activated cells produce a bioactive secretome (PASP, including CXCL14) that recruits macrophages for immunosurveillance of stressed and precancerous cells — a tumor-suppressive mechanism; persistent p21 expression triggers M1 macrophage polarization and cytotoxic T-cell recruitment, placing stressed cells under immune clearance.
• Peptides derived from the p21 PIP-box domain can be delivered into cells using cell-penetrating sequences (e.g., Tat48-60); these constructs induce selective apoptosis in glioma and ovarian cancer cells by disrupting nuclear PCNA function, establishing proof-of-concept for p21-derived therapeutic peptides in oncology.

All citations link to the original source (PubMed, journal site, or regulatory filing). Independent research database — no vendor influence on what's cited.