Service Overview
Antibody-drug conjugates (ADCs) targeting TROP2 and HER2 have reshaped the treatment landscape for advanced breast cancer, but dynamic monitoring of target expression remains a critical gap in clinical development. Traditional tissue biopsies cannot capture the spatial and temporal heterogeneity that drives resistance. Our Liquid Biopsy Biomarker Development Service provides quantitative, real-time analysis of ADC target expression on circulating tumor cells (CTCs) harvested from a simple blood draw. By measuring target molecule density per CTC, we generate pharmacodynamic and resistance data that directly inform your go/no-go decisions, dose optimization, and patient stratification strategies.
This service is designed for biopharmaceutical R&D teams and CROs seeking to integrate a minimally invasive, longitudinal biomarker into their ADC programs. We apply validated CTC enrichment and immunofluorescence workflows to quantify TROP2 or HER2 expression across individual CTCs, delivering a rich dataset of expression dynamics that complements circulating tumor DNA (ctDNA) and exosomal analyses. The approach follows established liquid biopsy principles, leveraging the power of blood-based biomarkers to bridge preclinical models and clinical outcomes.
With applications spanning phase I dose-escalation trials through post-marketing surveillance, our service can be adapted to fit different stages of drug development. Serial blood sampling reduces patient burden and enables dense temporal data collection, which is particularly valuable for capturing early signs of target modulation or emergence of resistant subclones.
What We Deliver
Quantitative Target Density
We report the mean fluorescence intensity (MFI) of TROP2 or HER2 staining per CTC, providing a continuous quantitative readout of target expression levels. This metric enables you to track target modulation over the course of treatment, identify emergence of low-expressing clones, and correlate expression changes with clinical response.
Longitudinal Pharmacodynamic Profiles
Serial blood draws at baseline, on-treatment, and progression timepoints allow us to construct individual and cohort-level pharmacodynamic curves. We deliver time-stamped expression data that reveal when target downregulation occurs, how long it persists, and whether rebound expression precedes radiographic progression.
Resistance Mechanism Insights
By profiling CTC target expression at the single-cell level, we identify heterogeneous populations that may represent resistant subclones. Combined with optional ctDNA mutation analysis, our service helps pinpoint whether resistance arises from target loss, epitope masking, or activation of bypass signaling pathways.
How It Works
Peripheral blood (7.5–10 mL) is collected in CellSearch-compatible tubes. CTCs are enriched using EpCAM-based immunomagnetic capture followed by density gradient separation, ensuring high recovery of epithelial-derived tumor cells while minimizing leukocyte contamination. The enriched cell fraction is then transferred to coated slides for downstream staining.
Enriched cells are fixed, permeabilized, and stained with validated primary antibodies against TROP2 (clone MRQ-41) or HER2 (clone 4B5) alongside cytokeratin (CK) and CD45 markers for accurate CTC identification. A fluorescence-conjugated secondary antibody enables signal amplification. Each staining run includes matched isotype controls to assess background.
Slides are scanned using a high-content imaging system. CTCs are identified as CK+/CD45− events, and target expression per cell is quantified by mean fluorescence intensity (MFI) using image analysis software. Non-specific background is normalized using matched isotype controls. Multiple fields are analyzed per slide to ensure statistical robustness.
Each sample run includes positive (SK-BR-3 for HER2, MDA-MB-231 for TROP2) and negative (leukocytes) controls. We provide a comprehensive report with CTC counts, target MFI distributions, histograms, and pre-defined metrics such as percentage of CTCs above a clinically relevant expression threshold. Data integrity checks include replicate staining and inter-operator variability assessments when requested.
For longitudinal studies, we align expression data across timepoints using a common internal control, normalizing for batch effects. We deliver a summary plot showing trajectory of target expression per patient, with statistical measures of change (e.g., paired t-test or mixed-model analysis). Custom analyses, such as correlation with overall survival or progression-free survival, can be added on request.
Service Scope & Deliverables
| Item | Description |
|---|---|
| Sample type & volume | Peripheral blood, 7.5–10 mL per timepoint; CellSearch tube recommended |
| CTC enumeration | Number of CTCs per 7.5 mL blood (CK+/CD45−/DAPI+) |
| Target expression quantitation | Mean fluorescence intensity (MFI) per CTC for TROP2 or HER2, with histograms and descriptive statistics |
| Quality controls | Positive and negative cell line controls run per batch; replicate analysis available upon request |
| Report format | PDF summary plus raw data files (image stacks, per-cell MFI table) for downstream analysis |
| Turnaround time | 6–8 weeks from sample receipt to final report (typical for up to 20 timepoints) |
Key Advantages
Clinically validated antibodies
We use validated, clinically relevant antibodies for TROP2 (clone MRQ-41) and HER2 (clone 4B5) immunostaining, supporting translational relevance and reproducibility across programs.
Single-cell resolution
Unlike bulk ctDNA or exosome assays, our CTC-based readout provides cell-by-cell expression data, capturing intratumoral heterogeneity and enabling early detection of resistance subclones.
Minimally invasive serial monitoring
Blood draws are safer and more patient-friendly than repeated tissue biopsies, allowing dense serial sampling without added clinical risk.
Direct pharmacodynamic readout
Target expression on CTCs is a proximal biomarker of ADC mechanism of action, offering real-time evidence of target engagement and modulation during therapy.
Latest Evidence
Review
Liquid biopsy in cancer: current status, challenges and future prospects (Ma et al., 2024)
View on PubMedReady to Integrate Real-Time ADC Monitoring?
Contact our biomarker team to discuss your specific ADC program, target (TROP2, HER2, or others), and desired study design. We will tailor a feasibility plan, scope of work, and readout metrics to your development timeline.