pe
pep-05220 v1 CC-BY-SA-4.0

Waprin-Phi3 anticancer peptide

An experimental peptide studied for its ability to attack cancer cells; not an approved drug.

statusbioassayed targetANTICANCER length58 aa refs3
anticancer
EARLY ENTRY This candidate is newly indexed — supporting evidence is still being added. Have a paper or data point? Contribute below.
status 2 / 5 · 0 verified on platform
prediction metrics boltz-2 2.2.1
ipTM0.000
pTM0.405
avg pLDDT56.7
ranking score0.535
STRUCTURE · PEP-05220 × ANTICANCER
ranking0.535
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RECEPTOR UNKNOWN
peptide conformation only · no target structure
target interface 4.5Å peptide drag rotate · ctrl+scroll zoom · right-click pan
sequence58 aa
151015202530354045505558
KTTKQLRLPKVKPGECPKVK IPPDYPCNQYCVWDFDCEGN KKCCPVGCAKECFPPGPL
in the news 27 articles
Hypotheses6 directions▾ collapse

Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.

openupdated 2026-06-05

Could this protein stop cancer by targeting a specific enzyme, rather than just attacking cells blindly?

Many cancer enzymes called proteases act like scissors that let tumors cut through tissue and spread. If Waprin-Phi3 works by jamming one of these scissors, it would be a more precise tool than a general cell-killer, which could mean fewer side effects and a clearer path to combining it with other drugs. This is unproven, but the structure of the molecule fits the job in a way that makes it worth testing.

The hypothesis
Waprin-Phi3 selectively inhibits cancer-upregulated serine proteases, specifically urokinase-type plasminogen activator (uPA) or matriptase, via its WFDC domain scaffold, rather than acting through direct membrane disruption.
Why it’s plausible
Waprin-Phi3 belongs to the waprin family, which share the WAP four-disulfide core (WFDC) domain. Mammalian WFDC proteins such as SLPI and elafin are canonical serine protease inhibitors. The sequence contains 8 cysteines consistent with the 4-disulfide WFDC architecture. uPA and matriptase are serine proteases dramatically overexpressed on cancer cell surfaces and are directly implicated in tumor invasion and metastasis. No molecular target is annotated for this peptide, making a protease-inhibitor mechanism an untested but structurally plausible hypothesis.
Why it matters
If Waprin-Phi3 kills cancer cells by inhibiting a surface serine protease rather than by membrane lysis, it would have a defined druggable target, a cleaner selectivity profile, and a rationale for combination with protease-activatable prodrugs. This reframes the peptide from a membrane-disruptor to a targeted inhibitor with a defined mechanism.
Plausibility.56
Novelty.72
Impact.83
Basis · grounding1 paper · 2 computed/notes
[1]
sequence8 cysteines (positions 16, 28, 31, 38, 44, 45, 51, 54) consistent with the 4-disulfide WFDC motif that underlies serine protease inhibitory function in mammalian WAP domain proteins
[2]
notePeptide name Waprin-Phi3 places it in the waprin/WFDC family derived from snake venom, a class with known structural homology to SLPI and elafin
[3]
paper
Review documents anticancer and immunomodulatory activity of egg proteins, which include WFDC-domain ovomucoid; mechanistic parallels with venom waprins are implicit
doi: 10.3382/ps/pez381
openupdated 2026-06-05

Could a single molecule tackle both antibiotic-resistant infections and cancer at the same time?

Cancer patients undergoing treatment often have weakened immune systems and are especially vulnerable to dangerous drug-resistant bacteria like MRSA. If Waprin-Phi3 turns out to be active against both, it could potentially address two serious threats at once for the same patient. That is still a hypothesis, but it would open a much wider development path than cancer alone.

The hypothesis
Waprin-Phi3, as a WFDC-family venom peptide with serine-protease-inhibitory structural potential, is active against drug-resistant bacteria (specifically Gram-positive pathogens such as MRSA) in addition to cancer cells, and its anticancer and antimicrobial activities share the same structural epitope.
Why it’s plausible
Multiple characterized venom waprins (waprin-Om1a from Oxyuranus microlepidotus, waprins from Naja naja) have documented antimicrobial activity against Gram-positive bacteria. The WFDC fold with its cationic surface is a canonical antimicrobial scaffold. The cationic N-terminal region (KTTKQLRLPKVK) and the amphipathic KVKIPP segment of Waprin-Phi3 are consistent with bacterial membrane disruption. The anticancer literature context for this peptide (review refs on egg protein hydrolysates) may have overlooked its antimicrobial activity entirely. If both activities map to the same structural surface, engineering selectivity for one without destroying the other becomes a defined problem.
Why it matters
A peptide with dual antimicrobial and anticancer activity would be valuable in oncology settings where immunocompromised patients face opportunistic MRSA infections, offering a single agent addressing two clinical problems. It would also reposition Waprin-Phi3 in a much larger antimicrobial peptide development pipeline.
Plausibility.70
Novelty.57
Impact.65
Basis · grounding1 paper · 2 computed/notes
[1]
noteWaprin family name directly links this peptide to a class where antimicrobial activity is documented in multiple members from elapid venom; Waprin-Phi3 is named but its antimicrobial activity has not been reported
[2]
sequenceKTTKQLRLPKVK N-terminal cationic stretch and KVKIPP internal segment are consistent with amphipathic helical structures implicated in bacterial membrane disruption by antimicrobial peptides
[3]
paper
Distinguishes peptides selective for cancer cells from those (like LL-37, melittin) that are toxic to both bacteria and cancer cells via related membrane disruption mechanisms, suggesting dual activity is achievable in cationic structured peptides
doi: 10.2147/idr.s514825
openupdated 2026-06-05

Could this molecule last long enough in the body to actually reach and affect a tumor?

Most small protein drugs fall apart in blood within minutes before they reach a tumor. The tight knot-like structure of Waprin-Phi3 might shield it from the enzymes that would normally chew it up. If that holds, it could work when injected into the bloodstream, which is a much more practical route than local injection and a bar most similar molecules fail to clear.

The hypothesis
Waprin-Phi3 retains anticancer activity under the proteolytically hostile conditions of the tumor microenvironment because its disulfide-stabilized WFDC fold resists serum proteases, giving it a longer effective half-life than linear anticancer peptides of comparable length and charge.
Why it’s plausible
The tumor microenvironment is rich in matrix metalloproteases, serine proteases, and cathepsins. Linear cationic anticancer peptides are typically degraded within minutes in serum. Waprin-Phi3 has 4 disulfide bonds that constrain the backbone and block protease access to cleavage sites by steric shielding, a mechanism documented for other disulfide-rich venom peptides like defensins and cyclotides. The cationic N-terminus KTTKQLRLPKVK is the most accessible linear region and likely the first protease target; if loss of this region does not ablate activity, the disulfide core itself may be the active moiety with intrinsic stability.
Why it matters
Confirming proteolytic resistance would distinguish Waprin-Phi3 from the majority of anticancer peptides that fail in vivo due to rapid degradation, and would make it a candidate for systemic (rather than only local) administration without chemical modifications such as D-amino acid substitution or PEGylation.
Plausibility.77
Novelty.37
Impact.70
Basis · grounding2 papers · 1 computed/note
[1]
paper
Quantifies that serum proteases rapidly degrade peptides in circulation, and that proteolytic stability is the primary barrier for anticancer peptide clinical translation
doi: 10.1371/journal.pone.0012684
[2]
sequence8 cysteines forming 4 disulfides create a compact, proteolysis-resistant fold; backbone amides involved in secondary structure are shielded from protease access in WFDC-family peptides
[3]
paper
Notes that disulfide-rich AMP scaffolds confer proteolytic resistance as a class property distinguishing them from linear ACPs
doi: 10.1038/s41467-023-37003-z
openupdated 2026-06-05

Is it the overall folded shape of the molecule, rather than its positive charge, that does the actual work?

Knowing what part of a molecule drives its effect matters enormously for making better versions. If the folded structure is what kills cancer cells, then a simpler version of the molecule without those internal bonds might be inactive, and the design rules change completely. It also raises a practical question: the tumor environment is chemically reducing, which could unfold the molecule and either switch it off or, potentially, trigger a release effect.

The hypothesis
The anticancer activity of Waprin-Phi3 depends primarily on its disulfide-stabilized tertiary structure rather than on primary sequence cationicity, such that reduction of its four disulfide bonds abolishes cytotoxicity.
Why it’s plausible
The sequence contains a cationic N-terminal region (KTTKQLRLPKVK) that could support membrane interaction, but many cationic anticancer peptides are disordered and act by carpet-model membrane disruption. Waprin-Phi3 carries 8 cysteines forming up to 4 disulfides, creating a compact, proteolysis-resistant fold. For WFDC-family peptides the active conformation is entirely determined by the disulfide topology, not by primary sequence charge. If the fold, not the charge, drives target engagement, reductive conditions (as found in the tumor microenvironment where glutathione is elevated) could abolish or modulate activity, and this is testable.
Why it matters
Understanding whether the disulfide core is essential for activity would determine whether redox-triggered release in the tumor microenvironment is an asset or liability, and whether linear analogs can be developed for cheaper solid-phase synthesis.
Plausibility.76
Novelty.38
Impact.65
Basis · grounding2 papers · 1 computed/note
[1]
sequenceKTTKQLRLPKVKPGECPKVKIPPDYPCNQYCVWDFDCEGNKKCCPVGCAKECFPPGPL contains 8 cysteines and a strongly cationic N-terminal region; both structural and electrostatic mechanisms are plausible from primary sequence alone
[2]
paper
Review of anticancer peptide mechanisms distinguishes membrane-lytic from receptor/target-mediated modes and notes that structural rigidity from disulfide bonds is a distinguishing mechanistic feature
doi: 10.1016/j.cbi.2022.110194
[3]
paper
Manufacturing review notes that disulfide-rich peptides beyond 50 aa pose synthesis challenges, implying that disulfide topology is load-bearing for these scaffolds
doi: 10.1038/s41467-023-37003-z
openupdated 2026-06-05

Could scientists attach a targeting signal to this molecule so it only attacks a chosen type of cancer?

Antibody-drug conjugates, the current gold standard for targeted cancer delivery, are expensive and complex to manufacture. A small, rugged protein scaffold that is already toxic to cancer cells, and could be fitted with a homing tag in one of its flexible loops, would be a much simpler alternative. This is an engineering hypothesis, not a proven capability, but the structural precedent from related proteins exists.

The hypothesis
The 58-residue length and 4-disulfide architecture of Waprin-Phi3 make it a suitable scaffold for grafting short linear tumor-homing sequences into its surface loops without disrupting the WFDC core fold, enabling targeted delivery to specific cancer types.
Why it’s plausible
WFDC-scaffold proteins have been engineered in analogous mammalian proteins (e.g., SLPI loop-grafting) to redirect protease inhibitory specificity without disturbing the core disulfide topology. The waprin fold has several inter-cysteine loops of varying length visible in the sequence (e.g., C16...C28 = 12-residue loop; C31...C38 = 7-residue loop) that are structurally exposed and tolerant of substitution. Grafting peptide ligands that bind tumor-specific markers (e.g., integrins, EGFR, or PS-binding motifs) into these loops could convert Waprin-Phi3 from a broadly cytotoxic peptide into a tumor-homing agent while retaining its intrinsic anticancer activity.
Why it matters
A WFDC scaffold with dual intrinsic cytotoxicity and grafted tumor-targeting would be a compact (58 aa), proteolysis-resistant bispecific agent, avoiding the manufacturing burden and immunogenicity of antibody-drug conjugates.
Plausibility.52
Novelty.62
Impact.63
Basis · grounding2 papers · 1 computed/note
[1]
sequenceInter-cysteine loop lengths: C16-C28 (12 aa), C28-C31 (3 aa), C31-C38 (7 aa), C38-C44 (6 aa), C44-C45 (1 aa), C45-C51 (6 aa), C51-C54 (3 aa), multiple surface-accessible loops available for grafting
[2]
paper
Reviews peptide-protein conjugation as a strategy to improve tumor targeting and delivery, noting albumin and scaffold-based approaches
doi: 10.1039/d5ra03731j
[3]
paper
Highlights manufacturing cost and length constraints for solid-phase synthesis, motivating compact disulfide-rich scaffolds over longer peptides
doi: 10.1038/nbt1267
openupdated 2026-06-05

Does this molecule naturally gravitate toward cancer cells because of a marker that healthy cells keep hidden?

A known weakness of cancer-killing molecules is that they can attack healthy cells too. Most cancer cells expose a fat molecule called phosphatidylserine on their outer surface, which normal cells keep tucked inside. If Waprin-Phi3 is preferentially drawn to that exposed signal, it could explain why it might be selective, and would mean its activity would not depend on any single cancer mutation, potentially making it relevant across many tumor types.

The hypothesis
Waprin-Phi3 achieves cancer-cell selectivity through preferential interaction with phosphatidylserine (PS) externalized on the outer leaflet of cancer cell membranes, driven by the cationic cluster KVKIPP and the downstream tryptophan-containing segment WDFD.
Why it’s plausible
Cancer cells constitutively externalize PS on their outer membrane leaflet, unlike normal cells where PS is sequestered in the inner leaflet. Cationic segments such as KVKIPP provide electrostatic docking to anionic PS, while the aromatic tryptophan in WDFD inserts into the lipid bilayer interface. This two-step electrostatic-then-hydrophobic model is well established for selective anticancer peptides. The waprin family has not been analyzed in this framework. The sequence contains both elements: a defined cationic patch and an aromatic residue embedded in a hydrophobic context near a loop freed by a disulfide.
Why it matters
A PS-targeting mechanism would make Waprin-Phi3 broadly active against PS-externalizing tumor types regardless of oncogenic driver, and would suggest synergy with PS-exposing chemotherapeutics. It would also constrain the membrane-composition requirements for activity, informing selectivity windows for normal cell toxicity.
Plausibility.60
Novelty.37
Impact.58
Basis · grounding2 papers · 1 computed/note
[1]
sequenceKVKIPP (positions 18-23) is a cationic insertion-prone segment; W37 in context CVWDFD provides an aromatic residue capable of membrane insertion at a bilayer interface
[2]
paper
Review explicitly links cancer-cell selectivity of anticancer peptides to PS externalization and the anionic outer-leaflet charge of cancer cells as the primary selectivity determinant
doi: 10.2147/idr.s514825
[3]
paper
Notes that cancer cell membranes co-express multiple receptors and anionic components that can be exploited for selective peptide targeting
doi: 10.7150/thno.4024
details expand to inspect
full evidence table1 metrics
metricvaluetool
ranking score 0.5345109105110168 boltz-2
3-letter notation
Lys-Thr-Thr-Lys-Gln-Leu-Arg-Leu-Pro-Lys-Val-Lys-Pro-Gly-Glu-Cys-Pro-Lys-Val-Lys-Ile-Pro-Pro-Asp-Tyr-Pro-Cys-Asn-Gln-Tyr-Cys-Val-Trp-Asp-Phe-Asp-Cys-Glu-Gly-Asn-Lys-Lys-Cys-Cys-Pro-Val-Gly-Cys-Ala-Lys-Glu-Cys-Phe-Pro-Pro-Gly-Pro-Leu
recipeboltz-2 2.2.1
parametervalue
modelboltz-2 2.2.1
weights
hardwarevast_v100_32gb
mlx version
python
random seed1
msa strategynone_monomer
runtime
predicted by
predicted at2026-05-23
citationbibtex
peptidemodel (2026). Waprin-Phi3 anticancer peptide (pep-05220, v1). PeptideModel. https://peptidemodel.com/card/pep-05220
@peptide{pep05220,
  sequence = {KTTKQLRLPKVKPGECPKVKIPPDYPCNQYCVWDFDCEGNKKCCPVGCAKECFPPGPL},
  target   = {anticancer},
  author   = {peptidemodel},
  year     = {2026},
  status   = {bioassayed}
}
related peptides 5 by signal overlap
references 3 papers
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