F tier · safety concern
There are zero registered clinical trials of PNC-27 anywhere and no published human trial; the only regulatory action on record is an FDA safety communication warning cancer patients not to use it, after FDA testing found the bacteria Variovorax paradoxus and Ralstonia insidiosa in PNC-27 product samples. Anticancer claims with no human evidence and a contamination finding in the marketed product is the clearest possible F.
pnc-27
PNC-27 is a 32-residue synthetic chimera in which a fragment of the p53 transactivation domain is fused to a membrane-penetrating leader sequence, reported by a small group of investigators to kill cancer cells by binding HDM-2 in their plasma membranes and forming pores. The work is almost entirely in cultured cells and comes from a narrow set of collaborating laboratories. No clinical trial has ever been registered or published, and in 2017 the FDA warned cancer patients not to use PNC-27 products after finding bacterial contamination in samples sold as a cancer cure.
the explanation
PNC-27 is a lab-made peptide that in dishes of cells appears to punch holes in cancer cells while leaving normal cells alone. It has never been tested in a proper human trial anywhere in the world. In 2017 the US regulator warned cancer patients not to use it and said samples of the product being sold contained bacteria.
regulatory status
Unapproved; subject of an FDA safety communication warning patients not to use it
PNC-27 has no marketing authorisation from the FDA, EMA or MHRA, is not a licensed medicinal product in the UK, and is not a lawful dietary-supplement ingredient; lawful supply is as a laboratory research reagent only, not for human use. On 10 January 2017 (updated 27 March 2017) the FDA issued a safety communication stating that it 'has not evaluated or approved PNC-27 as safe and effective to treat any disease, including any form of cancer', that the product was being promoted and sold as a treatment or cure for cancer, and that FDA testing had identified the bacteria Variovorax paradoxus in a PNC-27 solution sample for inhalation and Ralstonia insidiosa in a subsequent sample. In the UK, promoting an unlicensed substance for the treatment of cancer engages both medicines law and the Cancer Act 1939. PNC-27 is not named on the WADA Prohibited List but falls within class S0 (Non-Approved Substances) as a substance with no current approval by any governmental regulatory health authority for human therapeutic use.
how it works · proposed mechanism
PNC-27 was designed from conformational analysis of the p53 transactivation domain: the idea was that a peptide reproducing the HDM-2 binding conformation of p53 residues 12–26 could interfere with the p53–HDM-2 interaction, and that a membrane-residency leader would get it into cells. The reported mechanism then shifted away from intracellular p53 rescue toward something quite different — direct binding to HDM-2 present in the plasma membrane of cancer cells, followed by pore formation and lysis.
Two modules, one of them intrinsically membrane-active
The construct is a p53-derived 15-residue segment plus a 17-residue penetratin-type leader. Cell-penetrating leaders of this class are cationic and amphipathic and can perturb membranes on their own. Attributing the killing specifically to HDM-2 recognition therefore requires ruling out generic membranolysis, which is the hardest control to satisfy and the one an independent laboratory would need to reproduce.
Necrosis, not apoptosis
The reported cell death is lytic and necrotic rather than apoptotic, consistent with pore formation rather than with restoring p53 transcriptional function. That distinction matters because it means the mechanism has drifted away from the p53 rationale that gives the peptide its name and its marketing appeal.
Selectivity rests on membrane HDM-2
The claimed sparing of normal cells is attributed to cancer cells displaying HDM-2 in the plasma membrane, which normal cells are said not to do. That is an unusual localisation for a nuclear E3 ubiquitin ligase, and the entire therapeutic proposition depends on it being both real and quantitatively sufficient across tumour types.
The evidence base is cells, from a small network of laboratories
Published work is dominated by cultured cell lines and ex vivo patient-derived material, reported largely by the same collaborating investigators over roughly two decades. There is no independent, large-scale replication and no clinical trial. A mechanism can be internally consistent across twenty papers from one group and still not be established.
what’s reported
evidence shape
6 sourcesThe composition of the cited literature by study type. This describes the shape of the evidence, not its quality — and it does not by itself set the grade.
⚠ the catch
PNC-27 is sold with the most serious claim a substance can carry — that it treats cancer — on the strength of zero human trials. ClinicalTrials.gov returns no registered study of it at all. The only regulator that has looked at the marketed product did so to warn patients away from it: in January 2017 the FDA stated it had not evaluated or approved PNC-27 as safe and effective for any disease, and reported finding Variovorax paradoxus in a PNC-27 solution sample intended for inhalation and Ralstonia insidiosa in a further sample. A contaminated, unapproved injectable or inhaled peptide marketed to people with cancer also carries the risk that they defer effective treatment, which is a harm that no laboratory result can offset.
key published findings
- ClinicalTrials.gov contains zero registered studies of PNC-27 — no phase 1, no observational study, nothing.
- The FDA's 10 January 2017 safety communication (updated 27 March 2017) states that FDA 'has not evaluated or approved PNC-27 as safe and effective to treat any disease, including any form of cancer' and that it was being promoted and sold as a treatment or cure for cancer.
- FDA testing identified the bacterium Variovorax paradoxus in a PNC-27 solution sample for inhalation, and a subsequent sample tested positive for Ralstonia insidiosa.
- PNC-27 is a 32-residue chimera, PPLSQETFSDLWKLLKKWKMRRNQFWVKVQRG, combining an HDM-2 binding domain with a cell-penetrating leader; the sequence's computed formula and mass match the PubChem record exactly (C188H293N53O44S, 4032).
- The mechanistic claim — that PNC-27 adopts an HDM-2-binding conformation and kills cancer cells by binding HDM-2 in their membranes — was published in PNAS in 2010 (107:1918–1923) and elaborated in Biomedicines in 2022, both from the same collaborating group.
- Reported cell death is lytic necrosis from membrane pore formation rather than apoptosis, meaning the effect does not depend on restoring p53 transcriptional activity despite the p53-derived branding.
limitations of the evidence
- No human trial has ever been registered or published, so there is no evidence of efficacy, tolerability or pharmacokinetics in people at any dose or by any route.
- The published literature originates from a small network of collaborating laboratories, with no independent replication of the membrane-HDM-2 selectivity claim.
- The membrane-active leader sequence is itself capable of perturbing membranes, so generic cytotoxicity is difficult to exclude as an explanation for the observed lysis.
- In vitro and ex vivo cell killing has repeatedly failed to predict clinical anticancer activity for far better-supported agents, and there is no animal survival or randomised evidence here to bridge that gap.
- Products sold under this name have been shown by FDA testing to be non-sterile, so even the identity and quality of the material consumers receive is not established.
- Because the compound is marketed for cancer, the most serious limitation is not pharmacological but behavioural: use in place of evidence-based treatment.
documented safety signals
- FDA found bacterial contamination in PNC-27 product samples — Variovorax paradoxus in a solution for inhalation and Ralstonia insidiosa in a further sample — an infection risk for immunocompromised cancer patients.
- The FDA issued a safety communication advising patients who have used PNC-27 to contact their health care provider and advising cancer patients to discuss approved treatment options with a licensed professional.
- The construct is a cationic amphipathic membrane pore former, a chemical class associated with haemolysis and nonspecific cytotoxicity; no human tolerability data exist to bound that risk.
- Marketing an unapproved peptide as a cancer cure creates a documented risk of patients delaying or forgoing effective therapy, which the FDA communication explicitly addresses.
- No human adverse-event dataset exists at all, so the absence of reported toxicity reflects the absence of any controlled study rather than demonstrated safety.
identity
| full name | PNC-27, a chimeric peptide joining p53 residues 12–26 to a penetratin-type membrane-residency leader sequence |
| category | Other |
| modality | peptide |
| formula | C188H293N53O44S |
| molar mass | 4032 g/mol |
| cas | 1159861-00-3 |
| sequence | PPLSQETFSDLWKLLKKWKMRRNQFWVKVQRG (32 aa; p53 residues 12–26 fused to a 17-residue penetratin-type membrane-residency leader) |
laboratory handling
| storage | Supplied as a lyophilised solid. Store the dry peptide at -20 °C or below, desiccated, protected from light, in a tightly sealed container; the tryptophan residues are photosensitive and the methionine is oxidation-prone, so avoid ambient light and oxidising conditions. Reconstituted stock should be aliquoted immediately and stored at -80 °C, with freeze-thaw cycles minimised because this hydrophobic, amphipathic chimera aggregates and adsorbs readily. Equilibrate sealed vials to room temperature before opening. |
| solubility | Poorly soluble in plain water because of the hydrophobic p53-derived segment; laboratory practice is to dissolve first in a small volume of DMSO or dilute aqueous acid and then dilute into aqueous buffer, keeping organic solvent content low enough not to perturb the cell system. Solutions are prone to aggregation and to loss on glass and standard plasticware, so low-binding tubes and freshly prepared dilutions are preferred. Confirm clarity before use, since visible opalescence indicates aggregation that will invalidate membrane assays. |
Handling information describes laboratory practice for a research reagent. It is not a preparation guide for use in humans.
the receipts
6 citedU.S. Food and Drug Administration · 2017 · official
ClinicalTrials.gov, U.S. National Library of Medicine · 2026 · official
Proceedings of the National Academy of Sciences · 2010 · preclinical
Biomedicines · 2022 · preclinical
Transporter Classification Database (TCDB) · 2026 · reference
PubChem, National Library of Medicine · 2026 · reference
others in Other