Immunotoxicology

Drugs designed for their therapeutic benefits can unfortunately also be associated with unwanted serious adverse drug reactions (ADRs), which can sometimes be fatal in a small proportion of susceptible individuals. ADRs are clinically diverse and can be broadly classified as type A and B. Type A reactions are an extension of the known pharmacological effect of the drug(s) and are thus predictable. In contrast, type B reactions are off-target and unrelated to the known pharmacology of the ‘culprit’ drug(s). Type B reactions are also referred to as drug hypersensitivity reactions.

Drug hypersensitivity is a serious idiosyncratic immune-mediated ADR to an otherwise safe and efficacious therapeutic agent. These delayed-type reactions are rare and the deleterious events associated with their onset are known to be mediated by drug-specific T-cells. Indeed, such entities have been identified in cutaneous blister fluid and liver biopsies obtained from hypersensitive individuals. Downstream targets are numerous and include the skin, liver, kidneys, lungs and blood.

Drug hypersensitivity often occur after drugs have been licenced for clinical use and administered to a significant number of patients. Substantial information is known about the disease, drug target and the chemistry of new drugs in development. However, it is currently impossible to define in advance the specific individual susceptibility factors responsible for drug hypersensitivity in the clinic during the initial phases of drug development. In addition to inter-individual differences in detoxification pathways, the immunoregulatory system that preserves tolerance to neoantigens differs between individuals and can be influenced by genetic and environmental risk factors as well as disease. These susceptibility factors are idiosyncratic and difficult to recapitulate in existing in vitro assays.

Cyprotex is currently developing a battery of in vitro assays to enable early prediction of drugs with potential immunotoxicity during early drug development. These assays will utilise primary human immune cells isolated from whole blood obtained from consenting donors to investigate the effect of drug exposure on the innate and adaptive immune system. We will offer assays using peripheral blood mononuclear cells (PBMC), CD14 positive monocytes, dendritic cells (DC), naïve T-cells, memory T-cells and neutrophils. The assays to investigate potential immunotoxicity of drugs in development include:

PBMC cytotoxicity assay

• PBMC cytotoxicity assays utilises cells isolated from multiple individuals which are cryopreserved in our biobank.
• The assay provides a high throughput assessment of the cytotoxicity of candidate compounds in vitro and measures drug-induced cellular ATP depletion and LDH release.
• It can also provide an initial insight into how immune cells from different donors respond to candidate drugs in development.

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PBMC proliferation assay

• This assay investigates the immunogenicity of test articles based upon their potential to stimulate PBMC proliferation.
• Inter-individual variability in immunogenicity can also be examined by assessing PBMC isolated from multiple donors (>6 donors available for multi-donor studies).
• Supernatants from test article-treated cells are also profiled to determine the nature of the drug-induced cytokine profile.

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Dendritic cell perturbation assay

• Dendritic cells (DC) are innate immune cells that provide a critical link to the adaptive immune system.
• DC are antigen presenting cells responsible for the recognition, capture, processing and presentation of antigens to T-cells.
• DC biology and function are vital for the polarisation and differentiation of effector T cells.
• This assay also explores drug-induced changes in DC surface marker expression (CD14, CD80, CD86 and MHC class II) and cytokine secretion profiles using flow cytometry.
• High content screening (HCS) is also used to investigate compound-induced changes in stress signalling pathways including oxidative stress, glutathione content, mitochondrial membrane potential and Nrf2 activation.

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