BT5528
InvestigationalAlso known as: Bicycle Toxin Conjugate 5528, EphA2-BTC
A first-in-class Bicycle Toxin Conjugate (BTC) targeting EphA2-expressing tumors, developed by Bicycle Therapeutics. Combines a constrained bicyclic peptide targeting moiety with the cytotoxic payload MMAE. Phase 1/2 dose expansion ongoing with 67% ORR reported in EphA2-positive urothelial cancer patients.
Research Statistics
Phase 1 ITGA3/4-targeting peptide with mechanistic support; early-stage, limited geography.
Research Dossier
Overview
What is BT5528 and what does the research say?
Mechanism of Action
BT5528 is a first-in-class Bicycle Toxin Conjugate combining targeted delivery with cytotoxic payload. Human clinical data supports the proposed mechanisms.
How It Works (Simplified)
BT5528 works as a precision “smart missile” delivering chemotherapy directly to cancer cells:
Bicyclic peptide binds with high affinity to EphA2 receptors overexpressed on cancer cells, sparing normal tissues.
Cancer cell engulfs the BT5528 molecule through receptor-mediated endocytosis, bringing the payload inside.
Inside the cell, enzymes cleave the linker and release MMAE toxin into the cytoplasm where it can act.
MMAE disrupts microtubules essential for cell division, causing mitotic arrest and programmed cell death.
Scientific Pathways
EphA2 Targeting and Internalization
BT5528 binds EphA2 receptor (Kd ~ low nM)
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v
Receptor-mediated endocytosis
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v
Lysosomal processing → Cathepsin B cleaves linker → Free MMAE releaseMMAE Cytotoxic Mechanism
Free MMAE in cytoplasm → Tubulin binding at vinca site → Microtubule disruption
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v
G2/M arrest → ApoptosisKey Research: Phase 1/2 NCT04180371 demonstrates 67% ORR in EphA2+ urothelial cancer. ClinicalTrials.gov
Important Limitations
- Investigational agent not yet approved by any regulatory agency
- Preliminary efficacy data from small patient numbers; results may change
- Long-term safety data still maturing, particularly for cumulative neuropathy
- Requires EphA2 expression for activity; not all tumors express target
- Optimal patient selection criteria still being refined
Evidence-Chained Benefits
Evidence-Chained Benefits
Research findings linked to mechanisms and clinical outcomes
What to Expect
Timeline based on observations from published studies. Individual responses may vary.
Drug administration via weekly IV infusion. Initial target engagement and tumor cell internalization occurring. Early safety monitoring for MMAE-related effects including nausea and fatigue.
Continued weekly dosing. MMAE-mediated cytotoxicity in EphA2+ tumor cells. Monitoring for peripheral neuropathy onset. First tumor assessments typically around week 6-8.
Initial response assessment by imaging. In clinical trials, responses observed as early as first assessment. Ongoing monitoring for cumulative neuropathy.
Continued treatment until progression or unacceptable toxicity. Duration of response data still maturing. Long-term peripheral neuropathy monitoring essential.
Research-Based Observations
This timeline reflects observations from published clinical and preclinical studies. Individual responses may vary significantly. This is not a guarantee of effects or a dosing schedule. Consult qualified healthcare providers for personalized guidance.
Quality Checklist
Visual indicators to help evaluate BT5528 product quality
Good Signs (4 indicators)
Warning Signs (3 indicators)
Bad Signs (4 indicators)
For Research Evaluation Only
These quality indicators are general guidelines based on typical peptide characteristics. Professional laboratory testing (HPLC, mass spectrometry) provides definitive quality verification. This checklist is for initial visual evaluation only.
Peptide Interactions
Known and theoretical interactions when combining BT5528 with other peptides. Based on published research and mechanistic considerations.
Antibody-Drug-Conjugates
CompatibleBTCs represent a distinct modality from traditional ADCs. Different pharmacokinetic profiles (shorter half-life, smaller size) may allow sequential use. No direct interaction studies.
Enfortumab-Vedotin
CautionBoth use MMAE payload. Sequential use may increase cumulative neuropathy risk. Different targets (EphA2 vs Nectin-4) but overlapping toxicity profiles.
Research Note: Interaction data is based on published literature, mechanistic understanding, and theoretical considerations. Most peptide combinations lack direct clinical study. This information is for educational purposes only and does not constitute medical advice. Always consult qualified healthcare providers.
References
Key Studies Cited
Full reference list available on request. All citations link to PubMed for verification.
Methodology Note
This dossier synthesizes available evidence from peer-reviewed literature, regulatory documents, and clinical trial registries. Evidence strength ratings follow a modified GRADE approach.
For complete methodology details, see our Methodology page.
Important Disclaimer
This dossier is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before making health decisions.
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