PNC-28

A chimeric research peptide joining p53 residues 17-26, the HDM-2-binding part of the tumor suppressor's transactivation domain, to a penetratin leader sequence; studied preclinically for selective lysis of cancer cells carrying membrane-bound HDM-2.

Also referenced as: PNC28

What is PNC-28?

PNC-28 is a laboratory-designed chimeric peptide: residues 17-26 of human p53, part of the tumor suppressor’s amino-terminal transactivation domain that contacts HDM-2 (the human MDM2 protein), joined at its carboxyl end to penetratin, the membrane-crossing leader sequence derived from the Antennapedia homeodomain. It is the shorter member of a pair designed by one group working at SUNY Downstate Medical Center and the Brooklyn Veterans Affairs hospital: PNC-27 carries the longer p53 12-26 segment on the same leader and runs 32 residues in total, while PNC-28 is trimmed to 17-26, the span its designers describe as holding the p53 residues that make direct contact with HDM-2 (Kanovsky et al., PNAS, 2001; Pincus et al., Biomedicines, 2024). PNC-28 has never been an approved or clinically tested drug; it appears on the research-peptide market because of a preclinical cell-culture and mouse literature centered on pancreatic cancer, and it is sold as a laboratory reagent rather than a medicine.

How it works

• Binding to HDM-2 exposed on the cancer cell membrane — the proposed target is not intracellular HDM-2 but HDM-2 present in the outer membrane of transformed cells; normal cells are reported to carry little or none of it, which is the group’s stated basis for selectivity (Sarafraz-Yazdi et al., Biomedicines, 2022; Pincus et al., Biomedicines, 2024).
• Pore formation and necrosis, not apoptosis — in MiaPaCa-2 human pancreatic cancer cells, PNC-28 produced rapid lactate dehydrogenase release and membrane pore formation with dose-dependent killing, while the proapoptotic proteins characteristic of p53-driven apoptosis did not rise; the original cell-culture work likewise found no induction of Bax or p21(waf) (Kanovsky et al., PNAS, 2001; Bowne et al., Annals of Surgical Oncology, 2008).
• The penetratin leader drives the necrotic mode — the same experiments expressed the p53 17-26 segment inside MiaPaCa-2 cells from a plasmid, without the leader, and saw apoptosis instead, with high caspase-3 and caspase-7 and annexin V against background lactate dehydrogenase. The leader was attached at the carboxyl terminus by design, because its positively charged residues stabilize the active alpha-helical conformation when placed at that end (Kanovsky et al., PNAS, 2001; Bowne et al., Annals of Surgical Oncology, 2008).
• Activity independent of a cell’s p53 status — the peptides killed p53-null cancer lines as readily as lines with mutant or normal p53, which argues against restoration of p53 signaling as the mechanism (Kanovsky et al., PNAS, 2001).

Research status

The evidence for PNC-28 is entirely preclinical, and nearly all of it comes from one collaborating group and its successors. The few papers from outside that lineage are computational or nanoparticle-formulation studies of PNC-27 rather than independent replications.

• Design and first cytotoxicity data — Kanovsky et al. (2001), PNAS 98(22):12438-12443, synthesized three peptides from the mdm-2-binding domain of p53 — residues 12-26 (PNC-27), residues 12-20, and residues 17-26 (PNC-28) — each attached at its carboxyl terminus to the penetratin leader. All three were cytotoxic to human cancer lines in culture, an unrelated control peptide on the same leader was not, and none affected the growth of normal cells, including human cord blood-derived stem cells.
• Mouse work — Michl et al. (2006), International Journal of Cancer 119(7):1577-1585, tested PNC-28 in nude mice against BMRPA1.Tuc3, a ras-transformed rat pancreatic acinar carcinoma line. A two-week course into the peritoneal cavity destroyed tumors transplanted into that same cavity. Begun at a site remote from the tumor at the time of implantation, it blocked growth throughout treatment and for two weeks afterward, after which growth was weak and plateaued at low tumor sizes. Begun after tumors were already established at a remote site, it shrank them before slow regrowth that remained slower than with a control peptide. Untransformed rat pancreatic acinar (BMRPA1) cells and human breast epithelial cells were unaffected. The authors’ own conclusion was conditional, noting the approach may be effective “especially if delivered directly to the tumor.”
• Mechanism in pancreatic cancer cells — Bowne et al. (2008), Annals of Surgical Oncology 15(12):3588-3600, is the mechanistic paper most often cited for PNC-28; it established the necrosis-versus-apoptosis distinction described above in MiaPaCa-2 cells, using PNC-29 (an unrelated sequence carrying the same leader) and PNC-26 (the p53 12-26 segment without the leader) as controls.
• Later work has largely shifted to PNC-27 — the structural and pore-formation study (Sarafraz-Yazdi et al., Biomedicines, 2022), the ex vivo patient-derived ovarian cancer work (Sarafraz-Yazdi et al., Annals of Clinical and Laboratory Science, 2015, 45(6):650-658), the mitochondrial-disruption report (Krzesaj et al., Annals of Clinical and Laboratory Science, 2024, 54(2):137-148) and the cervical cancer report (Krzesaj et al., Annals of Clinical and Laboratory Science, 2025, 55(3):347-353) all use PNC-27. A 2024 review by Pincus et al. in Biomedicines proposes the term “poptosis” for the shared pore-forming mechanism and treats PNC-28 as the shorter analog with activity similar to PNC-27 rather than as the lead compound. Three authors of the 2022 paper disclose that they are inventors on intellectual property and patents covering PNC-27 and PNC-28, and one of them is affiliated with NomoCan Pharmaceuticals.
• No human trials — as of November 3, 2026, ClinicalTrials.gov holds no registered study of PNC-28 or of PNC-27, no results from any phase of human testing have been published, and there is no FDA-approved product containing the peptide. Claims that PNC-28 or PNC-27 has completed human safety testing correspond to no registry record or trial publication.

Common dosage forms

There is no approved or investigational pharmaceutical presentation of PNC-28, and no sterile, unit-dose or compounded product exists.

• Lyophilized powder in milligram-scale laboratory vials, the only presentation research suppliers list, usually as the acetate or trifluoroacetate salt and labeled for laboratory use, not for human or veterinary use.
• Analytical-grade reference peptide sold by reagent catalogs for assay and standards work, distinct from the research-market vials above.

Key considerations

• Regulatory status. The Research Market status reflects that no FDA-approved drug product contains PNC-28 and no human clinical development program for it is registered or publicly documented.
• The evidence base is narrow in a way that matters. A single research lineage, no independent replication of the in vivo results, all animal efficacy in immunodeficient nude mice against a transplanted rat-derived tumor, and the clearest tumor responses obtained when the peptide reached the tumor’s own compartment. No pharmacokinetic, systemic toxicology or human safety data of any kind has been published.
• Selectivity rests on an unquantified margin. The claim is that normal cells carry little or no membrane-bound HDM-2. Because the killing mechanism is membrane lysis driven by the penetratin leader, by the group’s own data, the margin between tumor-cell pore formation and nonspecific membranolysis in human tissue is unquantified, and the peptide’s behavior in an intact immune-competent animal is unreported.
• Naming is a frequent source of error. PNC-27 (p53 12-26 plus the leader) and PNC-28 (p53 17-26 plus the same leader) are distinct peptides; PNC-26 is the p53 12-26 segment without the leader and PNC-29 an unrelated control sequence carrying the leader, both controls rather than candidate compounds. HDM-2 is the human MDM2 protein, and the two names refer to the same thing.
• The “p53 apoptosis” description inverts the data. Descriptions circulating in the research-peptide market that credit PNC-28 with “activating p53-mediated apoptosis” invert the primary findings, which report necrosis rather than apoptosis and cytotoxicity that persists in p53-null cells.