Peptides in Oncology Research: Targeted Delivery, Peptide-Drug Conjugates, and Radiopeptide Therapeutics 2026

Oncology Peptides | 2026-08-25 | 15 min read

2026 comprehensive guide to oncology peptides: peptide-drug conjugates (PDCs), radiopeptides, RGD targeting, somatostatin analogs, tumor homing peptides, and targeted cancer therapeutics.

Introduction: Peptides in Cancer Therapy

Peptides offer unique advantages for cancer therapy: specific targeting, efficient tumor penetration, and customizable payloads. This rapidly evolving field includes peptide-drug conjugates, radiopharmaceuticals, and targeted therapeutics.

This 2026 guide covers peptide-based oncology approaches from basic mechanisms to clinical applications.

Peptide-Drug Conjugates (PDCs)

Structure and Components

PDC Architecture | Component | Function | Design Considerations | |-----------|----------|----------------------| | Targeting peptide | Tumor selectivity | Receptor affinity, specificity | | Linker | Payload delivery | Cleavability, stability | | Cytotoxic payload | Tumor killing | Potency, mechanism | | Propeller (optional) | Enhanced internalization | Endosomal escape |

Payload Classes

Microtubule Disruptors | Drug | Mechanism | PDCs in Development | |------|----------|-------------------| | MMAE | Antimitotic | Brentuximab vedotin (ADC) | | MMAF | Antimitotic | Various | | Dolastatin 10 | Antimitotic | SGN-35 (ADC) |

DNA Damage Agents | Drug | Mechanism | Examples | |------|----------|----------| | Duocarmycin | Alkylation | - | | PBD | Crosslinking | ADCT-482 (ADC) | | Calicheamicin | Cleavage | Gemtuzumab (ADC) |

Linker Technologies

| Linker Type | Cleavage | Example | |-------------|----------|----------| | Lysosomal | Cathepsin B | Valine-citrulline | | Reductive | Glutathione | Disulfide | | Acidic | Low pH | Hydrazone | | Non-cleavable | Stable | Thioether |

Clinical PDCs

In Development/Pipeline | PDC | Target | Indication | Status | |-----|--------|------------|--------| | Melflufen-PEG-DM1 | Multiple myeloma | APDC | | Targeted doxorubicin | Various | Preclinical | | Gemtuzumab (ADC) | CD33 | Approved |

Radiopharmaceutical Peptides

Theranostic Concept

Precision Medicine Approach

• Diagnostic imaging to identify target expression
• Same peptide with therapeutic isotope
• Monitor treatment response
• Adjust therapy based on response

Somatostatin Receptor Imaging/Therapy

SSTR Subtypes | Receptor | Expression | Ligand Affinity | |----------|-----------|-----------------| | SSTR2 | NET, lymphoma | High | | SSTR5 | NET, pituitary | Moderate | | SSTR3 | Limited | Low |

Clinical Agents

| Agent | Isotope | Use | Status | |-------|---------|-----|--------| | DOTATATE | 68Ga | PET imaging | Approved | | DOTATOC | 68Ga | PET imaging | Approved | | DOTATATE | 177Lu | PRRT | Approved (Lutathera) | | DOTANOC | 177Lu | PRRT | Various |

Lutathera (177Lu-DOTATATE)

Clinical Data | Study | Population | Response | |-------|------------|----------| | NETTER-1 | Midgut NET | ORR 18% vs 3% | | Progression-free survival | Advanced | 28.4 vs 8.5 months |

Treatment Protocol

• 7.4 GBq every 8 weeks
• Up to 4 cycles
• Amino acid infusion for renal protection
• Somatostatin analog continuation

PSMA-Targeting Peptides

Prostate Cancer | Target | Peptide | Application | |--------|---------|-------------| | PSMA (glutamate carboxypeptidase) | PSMA-617 | Radioligand therapy | | PSMA | Mini-PSMA | Imaging |

Pluvicto (177Lu-PSMA-617)

• Approved for PSMA-positive mCRPC
• Second/third-line therapy
• Significant PSA responses

RGD Peptides in Oncology

Integrin Targets

αvβ3 and αvβ5 Integrins

• Overexpressed on:
• Tumor cells
• Angiogenic endothelium
• Osteoclasts
• Role in:
• Cell adhesion
• Migration
• Invasion
• Angiogenesis

Peptide Designs

Monomeric vs. Multimeric | Design | Affinity | Specificity | |--------|-----------|-------------| | Linear RGD | Moderate | Low | | Cyclic RGD | High | Improved | | Dimeric (E[RGDfK]2) | Very high | Excellent | | Tetrameric | Highest | Excellent |

Clinical Applications

| Application | Peptide | Status | |--------------|---------|--------| | Imaging | [18F]Galacto-RGD | Clinical trials | | PET | 68Ga-PRGD2 | Clinical trials | | Therapy | Cilengitide (αvβ3/5) | Discontinued |

Tumor-Homing Peptides

Tissue-Specific Targeting

Peptide Libraries

• Phage display screening
• In vivo selection
• Tissue/cell-specific sequences

Examples | Peptide | Target | Application | |---------|--------|--------------| | NGR peptide | CD13 on angiogenesis | Tumor vasculature | | RGD | Integrins | Angiogenesis | | iRGD | Tumor penetration | Enhanced delivery | | LyP-1 | p32 on tumor cells | Lymphatic targeting |

iRGD Peptide

Mechanism

• iRGD (CRGDKGPDC) binds αv integrin
• Proteolytic cleavage exposes CendR motif
• Neuropilin-1 binding triggers penetration
• Enhanced tumor accumulation

Advantages

• Deep tumor penetration
• Co-delivery of other agents
• Enhanced efficacy

Delivery Strategies

Enhanced Permeability and Retention (EPR)

Tumor Microenvironment

• Disorganized vasculature
• Impaired lymphatic drainage
• Enhanced permeability to macromolecules

Peptide Advantages

• Size > 40 kDa (depends on conjugate)
• Longer circulation (modifications)
• Tumor accumulation

Active Targeting

Multi-Step Approaches

• Tumor recognition (peptide)
• Internalization
• Endosomal escape
• Payload release
• Subcellular targeting

Preclinical Considerations

In Vitro Studies

| Assay | Endpoint | |-------|----------| | Receptor binding | IC50, Kd | | Internalization | Flow cytometry, microscopy | | Cytotoxicity | IC50 determination | | Payload release | Lysosomal assays |

In Vivo Models

| Model | Applications | |-------|-------------| | Xenograft | Efficacy, PK | | Orthotopic | Metastatic spread | | Patient-derived | Translational | | Transgenic | Carcinogenesis |

Clinical Development Pathway

Regulatory Considerations

| Requirement | Guidance | |-------------|----------| | Companion diagnostics | CDx development | | Dosimetry | Patient-specific dosing | | Safety monitoring | Hematologic, renal | | Manufacturing | cGMP radiopharmacy |

Challenges

| Challenge | Mitigation | |-----------|-----------| | Heterogeneous expression | Patient selection | | Resistance | Combination approaches | | Radiation safety | Specialized facilities | | Cost | Reimbursement strategies |

Future Directions

Emerging Technologies

• **Protein degradation**: PROTACs with peptide targeting
• **Bispecific peptides**: Dual targeting
• **Stimuli-responsive**: Tumor-activated delivery
• **Combination regimens**: Synergistic mechanisms

Next-Generation PDCs

| Innovation | Potential Impact | |------------|------------------| | Novel payloads | New mechanisms | | Self-immolative linkers | Controlled release | | Linker-payload combinations | Optimized profiles | | Multivalent targeting | Enhanced selectivity |

Conclusion

Peptide-based oncology represents a major frontier in targeted cancer therapy:

Key developments:

• Radiopharmaceuticals (Lutathera, Pluvicto) demonstrated clinical success
• PDCs offer tumor-targeted payload delivery
• RGD and somatostatin analogs enable tumor imaging and therapy
• Emerging tumor-homing peptides improve delivery

Future directions:

• Combination therapies
• Companion diagnostics
• Novel targets and payloads
• Personalized treatment approaches

The field continues to evolve rapidly with multiple promising candidates in development.

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