A personalised approach to manage adverse reactions to CFTR modulator therapy in patients with cystic fibrosis

Adverse drug reactions are a major health concern and an impediment to the development of new medicines. Approximately 1 in 16 hospital admissions in the UK are due to some form of adverse drug reaction. One of the best known, but least understood drug side-effects is T-lymphocyte-mediated hypersensitivity. Such reactions are unpredictable with respect to the chemistry of the drug and the biology of the patient. CFTR modulator therapies are now widely available as dual or triple therapy and these have transformed cystic fibrosis (CF) into a much milder disease. However, adverse reactions to CFTR modulator therapy such as cutaneous drug hypersensitivity and liver injury can result in drug discontinuation and deleterious clinical outcome. The objective of this proposal is to relate drug exposure, HLA allele expression and drug-specific immune responses to clinical outcome in patients exposed to CFTR modulator therapies. Our approach will provide a framework to more effectively assess patients hypersensitive to this important class of drug. By collecting blood samples during reintroduction of CFTR modulator therapies, we will then define how the drug-specific T-cell response develops during treatment and the pathways that regulate effector T-cell responses.

T-cells are involved in the decision process that determines whether drug exposure will lead to a hypersensitivity reaction. Thus, using PBMC and drug-responsive cloned T-cells from patients with skin and liver reactions, we will define a hypersensitivity phenotype and identify pathways of drug-specific T-cell activation. These data will identify the drug(s) associated with adverse events and provide valuable information on the disease pathogenesis. Resulted will be compared with de-novo priming experiments and used to stratify patients with adverse events.

Analysis of patient cells, although important, provides no information about the primary T-cell response. Thus, we will utilize our healthy donor HLA genotyped PBMC bank to study the origin of drug-specific T-cells. Our assessment will involve characterization of CFTR modulator drug-specific stimulation of naïve/memory T-cells with assessment of the pre-curser T-cell frequency and the phenotype and function of drug-specific T-cells.

Access to a repository of PBMC from patients with CF (with and without CFTR modulator therapy hypersensitivity) will allow us to conduct HLA sequence-based genotyping. Any associations will allow us to define of the role of specific HLA molecules in CFTR modulator drug presentation to T-cells and may pave the way to genetic testing prior to drug use.

We have recently utilized mass spectrometry to characterize drugs, drug metabolites and drug protein adducts and relate exposure to the activation of a drug-specific T-cell response. We will now use these methods to quantify CFTR modulator drug and metabolite levels in human plasma and relate exposure to patient outcome (health benefit or adverse event). Similar methods will be used to assess CFTR modulator drug metabolism by CYP3A4 expressing HepG2 cells in an immune cell co-culture system to relate metabolite formation to the activation of human T-cells.

Several patients with immunologically confirmed adverse events will be offered alternative therapies or the same therapy at reduced dose or through drug provocation or drug desensitisation. Blood sampling will be undertaken prior to, during and after treatment to explore: (i) how the drug-specific effector T-cell response develops; (ii) expression of effector and regulatory cytokines, and (iii) suppression through the function of Tregs and co-inhibitory molecules. Once we have developed a robust assessment that will risk stratify individual patients with CFTR modulator therapy adverse events it could be applied to other patient groups, including those receiving novel medicines.

Background: Drug hypersensitivity is one of the best known, but least understood drug side-effects. Recently, we have shown that CFTR modulator drugs can activate T-cells in hypersensitive patients. We have also confirmed that desensitisation is an important tool in the treatment of hypersensitive patients with cystic fibrosis. Despite this, knowledge of the pathways through which sensitisation is acquired, and how drug re-exposure serves to modify those mechanisms, have not been defined.
Objectives: We propose to relate drug exposure, HLA expression and drug-specific immune responses to clinical outcome in patients exposed to CFTR modulator therapy. Our experiments will provide a framework to more effectively assess hypersensitive patients and design personalized treatment strategies. By collecting blood during re-exposure, we will define how the drug-specific and regulatory immune response develops.
Methods: Patient drug-specific T-cell responses, HLA genotyping and the priming of naïve T-cells will be measured using established methods. HLA-restriction, cellular phenotype/function, and cross reactivity will be assessed with T-cell clones. Access to a CYP3A4 expressing liver cell line will allow us to explore drug metabolite T-cell responses. Mass spectrometry will be used to quantify drug exposure in vitro and in plasma. When drug re-exposure is offered to hypersensitive patients blood will be collected to measure attenuation of the effector T-cell response and regulatory parameters.
Impact: A better understanding of drug hypersensitivity will support personalised management strategies that determine whether a patient should be re-exposed to the drug and the need for desensitisation. By relating immune responses to clinical outcome, we will define a clear hypersensitivity phenotype, paving the way for the development of diagnostic tests. New insights into drug exposure levels may indicate that lower doses will reduce the chances of hypersensitivity.