Complement Activation Assays

Why assess complement activation in drug development?

The complement system is a complex network of over 50 plasma and cell surface proteins organized into three interconnected activation pathways: the classical, alternative, and lectin. Each pathway plays a crucial role in immune surveillance, recognizing and eliminating pathogens. The complement system cannot only cross-talk with plasma activation cascades but also serves as a bridge between innate and adaptive immunity. These proteins can trigger a massive immune response, starting a cascading reaction that stimulates phagocyte activation, inflammation, and membrane attack complex (MAC). The unintended activation of the complement system presents a significant challenge in drug development. Understanding the mechanisms behind this activation and recognizing the potential for adverse effects is crucial for developing safer therapies.

As per the FDA Guideline “Nonclinical Evaluation of the Immunotoxic Potential of Pharmaceuticals” from June 2023, it is recommended to include the assessment of C3a, C5a, and Bb split products to evaluate the potential immunotoxicity of pharmaceuticals. The ID.Flow system is capable of providing detailed information on complement activation, cytokine release, as well as platelet and immune cell activation using fresh human whole blood. This makes it an excellent tool for gaining a comprehensive understanding of the human immune response to a drug.

The Figure above shows a study of complement activation in ID.Flow.  The figure shows the activation of complement subunits C3a and C5a as assessed by ELISA in fresh human blood from five healthy donors. The donor responses are compared to PBS (vehicle) and different monoclonal antibody controls in ID.Flow as compared to blood collected before addition to ID.Flow (zero sample).

The service:

• Assessment of FDA’s recommended readouts on complement activation:  C3a, C5a and Bb split product.
• Design and guidance by our Scientific Advisors, Immunology.
• You send the test substances to our test site in Sweden.
• We recruit blood donors and initiate the analysis immediately upon blood draw.
• Ex-vivo assessment.
• Statistical analysis and interpretation.
• Raw data files and scientific report, including review rounds.
• Meeting, presentation and discussion.