Clearing the hurdle: a smarter approach to host cell protein detection in biopharmaceutical manufacturing.

As biotherapeutics grow more complex, from monoclonal antibodies to bispecifics and antibody-drug conjugates, the pressure to detect and monitor HCPs with greater sensitivity and confidence has never been higher.

Marissa Camarillo, lead developer behind BioLegend's HCP ELISA kits, discusses the technical challenges of HCP detection, the design principles behind the approach, and what the future holds for analytical technologies in an era of next-generation biologics.

Setting the scene: the HCP challenge

Q: For scientists who may be newer to HCP monitoring, can you explain why HCP pose such a significant challenge in protein therapeutic development and manufacturing?

Marissa: Host cell proteins are naturally produced by the expression system and can remain as residual impurities throughout the manufacturing process. Even at very low levels, certain HCPs can impact product stability, efficacy, or patient safety, by inducing unwanted immune responses or degrading the therapeutic protein.

Because HCP composition changes throughout purification and varies between manufacturing processes, sensitive and reliable monitoring is essential to ensure product quality and regulatory compliance.

Q: What are the most common pain points you've observed when bioprocess teams try to implement HCP testing in their workflows? Where do existing solutions fall short?

Marissa: One of the biggest challenges is balancing sensitivity, broad HCP coverage, and workflow efficiency. Scientists need assays that are easy to implement while maintaining confidence that a diverse range of HCPs is being detected.

Long assay times, limited sensitivity, and inconsistent performance can slow development and complicate process decisions.

Q: How have regulatory expectations around HCP detection evolved in recent years, and what pressure does that put on analytical method development?

Marissa: Regulators increasingly expect manufacturers to demonstrate a thorough understanding of residual HCP risk, rather than relying solely on a single numerical result.

This has increased the importance of well-characterized assays, robust validation, and complementary analytical approaches that provide confidence throughout process development and commercial manufacturing.

The solution: HCP ELISA

Q: Walk us through the key design principles behind BioLegend's HCP ELISA kit. What specific technical innovations allow them to address the challenges you just outlined?

Marissa: Our goal was to develop assays that combine high sensitivity with a streamlined workflow while maintaining strong analytical performance.

We focused on optimizing antibody performance, assay robustness, and ease of use, so scientists can generate reliable results without unnecessary complexity. The result is an assay designed to support both routine testing and process development with confidence.

Q: One critical concern for bioprocess scientists is HCP coverage, ensuring the assay can detect the broad, diverse population of HCPs. How did you approach this challenge, and what validation data supports your coverage claims?

Marissa: We evaluated HCP coverage using 2D differential in-blot electrophoresis (2D-DIBE) combined with Western blotting, enabling separation and visualization of complex host cell protein mixtures.

Validation demonstrated high antibody coverage across supernatants from three commonly used CHO cell lines - CHO-S, CHO-K1, and CHO-DG44 - supporting broad detection of HCPs relevant to biotherapeutic manufacturing.

Q: Sensitivity and dynamic range are crucial for detecting low-level HCPs in purified drug substances. Can you share performance metrics that demonstrate how these kits perform across different stages of the purification process?

Marissa: Conditioned media from three CHO-K1-derived cell lines demonstrated excellent linearity and spike recovery across the assay's dynamic range, with all samples meeting the predefined 80–120% average acceptance criteria. The assay also achieved a minimum detectable concentration of 1.07 ng/mL, enabling sensitive detection of low-level CHO host cell proteins.

Q: Time-to-result and ease of use matter in fast-paced development environments. How do these kits streamline the workflow compared to traditional methods, and what feedback have you received from early users?

Marissa: There are several reasons why this method stands out. There is little to no assay prep required, and run time is typically under 4 hours. The assay supports high throughput - up to 25 samples at once in triplicate - and results are straightforward to interpret, with controls, standard curves, and quantification providing accurate and reliable outputs.

Compared to traditional methods such as mass spectrometry, which can involve days of run time, low sample throughput, and complex data interpretation, the ELISA method is far better suited to routine testing. Internally, we use these kits to test BioLegend's GMP recombinant proteins for residual HCP analysis, which makes our GMP products competitive with many industry-leading companies while keeping QC release testing costs to a minimum.

Looking ahead: the future of HCP detection

Q: As the industry moves toward more complex modalities- bispecifics, ADCs, cell and gene therapies - how do you see HCP detection technologies needing to evolve?

Marissa: As biologics become increasingly complex, analytical tools must become more sensitive, more flexible, and more informative. Future HCP assays will need to support a broader range of expression systems while integrating with orthogonal analytical techniques to provide a more comprehensive understanding of product quality. Our team continues to explore technologies that improve sensitivity, workflow efficiency, and characterization capabilities to meet these evolving needs.

Q: There's growing interest in orthogonal methods like mass spectrometry for HCP characterization. How do you see ELISA-based platforms fitting into a multi-method analytical strategy?

Marissa: ELISA and mass spectrometry serve complementary roles. ELISA remains the preferred method for routine, high-throughput quantitation. It is sensitive, reproducible, and practical for process monitoring.

Mass spectrometry provides additional insight into the identity of individual HCP species when further characterization is required. Together, these methods provide a comprehensive strategy for HCP risk assessment.

Q: If you could give one piece of advice to bioprocess scientists who are building or optimizing their HCP testing strategy today, what would it be?

Marissa: Successful HCP assay development is a team effort. Collaborating closely with immunogen design, antibody development, and upstream process development teams early in the project can greatly improve assay performance and ensure the final product is representative of the manufacturing process.

Strong cross-functional communication not only accelerates development, it also leads to more robust, reliable assays that better support bioprocess scientists throughout the product lifecycle.