Predicting Drug Hypersensitivity Reactions: Mechanistic and Clinical Implications

Adverse drug reactions (ADRs) are responsible for a high number of morbidities and mortalities worldwide and estimated to be the fourth most important cause of death in the US and Canada after heart diseases, cancer and stroke. ADRs are either type A (~80%) which are predictable, related to the drug pharmacology and dose-dependent or type B (~20%), which are unpredictable, unrelated to the drug pharmacology and have no clear dose-dependency. Drug hypersensitivity reactions (DHRs) represent the majority of type-B ADRs, which are rare but potentially fatal and unpredictable. The latter aspect makes DHRs very difficult to diagnose and necessitate the development of a reliable and safe in vitro diagnostic test to aid prediction and confirm diagnosis. The currently used tests are not well characterized and their predictive value is unknown. The aim of this work was to evaluate the clinical value of the currently used diagnostic tests for DHRs; to develop a simple, reliable and safe test; and to explore the pathophysiology of DHRs using different approaches for further understanding of the DHRs pathophysiology which will allow us to develop new means for prevention prediction and diagnosis. Methodology used involved performing systematic literature reviews, population survey on previously tested patients, patient recruitment and laboratory techniques that include preparation and testing of liver microsomes from human and animal origin, using hematopoietic cell lines and primary cultures of different blood cell types as a surrogate model to explore DHRs pathphysiology and test patient susceptibility for DHRs. Systematic review of available literature revealed that the currently used diagnostic tools for DHRs lack any characterization or standardization and much more work is needed to further characterize and improve these tools. We developed a novel laboratory approach for diagnosis of DHRs that proved to be less cumbersome and potentially more reliable than other currently used tests. Using different biochemical and genetic methods, we introduced novel concepts that explain some aspects of the pathophysiology of DHRs. The main achievement in this research was the development of a novel diagnostic test for DHRs, the in vitro platelet toxicity assay (iPTA), which has a great potential as a clinical tool due to its simple procedure and good reproducibility. We hope that these features will allow its wider clinical use as oppose to other currently used tests. In addition, expanding our understanding of the molecular pathophysiology of DHRs using recent technical advances in genetic analysis and laboratory techniques will have a great impact on the management of these cases

In vitro testing for diagnosis of idiosyncratic adverse drug reactions: Implications for pathophysiology

Idiosyncratic drug reactions (IDRs) represent a major health problem, as they are unpredictable, often severe and can be life threatening. The low incidence of IDRs makes their detection during drug development stages very difficult causing many post-marketing drug withdrawals and black box warnings. The fact that IDRs are always not predictable based on the drug\u27s known pharmacology and have no clear dose-effect relationship with the culprit drug renders diagnosis of IDRs very challenging, if not impossible, without the aid of a reliable diagnostic test. The drug provocation test (DPT) is considered the gold standard for diagnosis of IDRs but it is not always safe to perform on patients. In vitro tests have the advantage of bearing no potential harm to patients. However, available in vitro tests are not commonly used clinically because of lack of validation and their complex and expensive procedures. This review discusses the current role of in vitro diagnostic testing for diagnosis of IDRs and gives a brief account of their technical and mechanistic aspects. Advantages, disadvantages and major challenges that prevent these tests from becoming mainstream diagnostic tools are also discussed here

DRESS induced by amoxicillin-clavulanate in two pediatric patients confirmed by lymphocyte toxicity assay

Background: Drug reaction with eosinophilia and systemic symptoms (DRESS) is a rare but serious delayed hypersensitivity reaction that can be caused by antibiotic exposure. The reaction typically develops in 2 to 6 weeks. The pathophysiology is thought to involve toxic drug metabolites acting as a hapten, triggering a systemic response. The diagnosis is made clinically but can be confirmed using assays such as the lymphocyte toxicity assay (LTA), which correlates cell death upon exposure to drug metabolites with susceptibility to hypersensitivity reactions. Case presentations: Case 1 involves a previously healthy 11-month-old male with first exposure to amoxicillin-clavulanate, prescribed for seven days to treat a respiratory infection. The patient developed DRESS fourteen days after starting the drug and was successfully treated with corticosteroids. LTA testing confirmed patient susceptibility to hypersensitivity reactions with amoxicillin-clavulanate. Parental samples were also tested, showing both maternal and paternal susceptibility. Neither parent reported prior hypersensitivity reactions. Lifelong penicillin avoidance for the patient was advised along with the notation in medical records of penicillin allergy. The parents were advised to avoid penicillin class antibiotics and be monitored closely for DRESS if they are exposed. Case 2 involves an 11-year-old female with atopic dermatitis with first exposure to amoxicillin-clavulanate, prescribed for ten days to treat a secondary bacterial skin infection. She developed DRESS eleven days after starting antibiotics and was successfully treated with corticosteroids. LTA testing confirmed patient susceptibility to hypersensitivity reactions with amoxicillin-clavulanate. Maternal samples were also tested and showed sensitivity. The mother reported no prior hypersensitivity reactions. Lifelong penicillin avoidance for the patient was advised along with the notation in medical records of penicillin allergy. Conclusions: Amoxicillin-clavulanate is a commonly used antibiotic and the cases we have described suggest that it should be recognized as a potential cause of DRESS in pediatric patients. Furthermore, these cases contribute to current literature supporting that there may be a shorter latent period in DRESS induced by antibiotics. We have also shown that the LTA can be a helpful tool to confirm DRESS reactions, and that testing may have potential implications for family members

7th Drug hypersensitivity meeting: part two

No abstract availabl

Role of Oxidative Stress in Hypersensitivity Reactions to Sulfonamides

Antimicrobial sulfonamides are important medications. However, their use is associated with major immune-mediated drug hypersensitivity reactions with a rate that ranges from 3% to 4% in the general population. The pathophysiology of sulfa-induced drug hypersensitivity reactions is not well understood, but accumulation of reactive metabolites (sulfamethoxazole [SMX] hydroxylamine [SMX-HA] and SMX N-nitrosamine [SMX-NO]) is thought to be a major factor. These reactive metabolites contribute to the formation of reactive oxygen species (ROS) known to cause cellular damage and induce cell death through apoptosis and necroptosis. ROS can also serve as danger signals, priming immune cells to mount an immunological reaction. We recruited 26 sulfa-hypersensitive (HS) patients, 19 healthy control subjects, and 6 sulfa-tolerant patients to this study. Peripheral blood monocytes and platelets were isolated from blood samples and analyzed for in vitro cytotoxicity, ROS and carbonyl protein formation, lipid peroxidation, and GSH (glutathione) content after challenge with SMX-HA. When challenged with SMX-HA, cells isolated from sulfa-HS patients exhibited significantly (P ≤ .05) higher cell death, ROS and carbonyl protein formation, and lipid peroxidation. In addition, there was a high correlation between cell death in PBMCs and ROS levels. There was also depletion of GSH and lower GSH/GSSG ratios in peripheral blood mononuclear cells from sulfa-HS patients. The amount of ROS formed was negatively correlated with intracellular GSH content. The data demonstrate a major role for oxidative stress in in vitro cytotoxicity of SMX reactive metabolites and indicate increased vulnerability of cells from sulfa-HS patients to the in vitro challenge

DRESS induced by amoxicillin-clavulanate in two pediatric patients confirmed by lymphocyte toxicity assay

Background: Drug reaction with eosinophilia and systemic symptoms (DRESS) is a rare but serious delayed hypersensitivity reaction that can be caused by antibiotic exposure. The reaction typically develops in 2 to 6 weeks. The pathophysiology is thought to involve toxic drug metabolites acting as a hapten, triggering a systemic response. The diagnosis is made clinically but can be confirmed using assays such as the lymphocyte toxicity assay (LTA), which correlates cell death upon exposure to drug metabolites with susceptibility to hypersensitivity reactions. Case presentations: Case 1 involves a previously healthy 11-month-old male with first exposure to amoxicillin-clavulanate, prescribed for seven days to treat a respiratory infection. The patient developed DRESS fourteen days after starting the drug and was successfully treated with corticosteroids. LTA testing confirmed patient susceptibility to hypersensitivity reactions with amoxicillin-clavulanate. Parental samples were also tested, showing both maternal and paternal susceptibility. Neither parent reported prior hypersensitivity reactions. Lifelong penicillin avoidance for the patient was advised along with the notation in medical records of penicillin allergy. The parents were advised to avoid penicillin class antibiotics and be monitored closely for DRESS if they are exposed. Case 2 involves an 11-year-old female with atopic dermatitis with first exposure to amoxicillin-clavulanate, prescribed for ten days to treat a secondary bacterial skin infection. She developed DRESS eleven days after starting antibiotics and was successfully treated with corticosteroids. LTA testing confirmed patient susceptibility to hypersensitivity reactions with amoxicillin-clavulanate. Maternal samples were also tested and showed sensitivity. The mother reported no prior hypersensitivity reactions. Lifelong penicillin avoidance for the patient was advised along with the notation in medical records of penicillin allergy. Conclusions: Amoxicillin-clavulanate is a commonly used antibiotic and the cases we have described suggest that it should be recognized as a potential cause of DRESS in pediatric patients. Furthermore, these cases contribute to current literature supporting that there may be a shorter latent period in DRESS induced by antibiotics. We have also shown that the LTA can be a helpful tool to confirm DRESS reactions, and that testing may have potential implications for family members.Medicine, Faculty ofOther UBCNon UBCAllergy and Immunology, Division ofMedicine, Department ofPediatrics, Department ofReviewedFacult

Targeting Myristoylated Alanine-Rich C Kinase Substrate Phosphorylation Site Domain in Lung Cancer. Mechanisms and Therapeutic Implications

Rationale: Phosphorylation of myristoylated alanine-rich C kinase substrate (phospho-MARCKS) at the phosphorylation site domain (PSD) is crucial for mucus granule secretion and cell motility, but little is known concerning its function in lung cancer. Objectives: We aimed to determine if MARCKS PSD activity can serve as a therapeutic target and to elucidate the molecular basis of this potential. Methods: The clinical relevance of phospho-MARCKS was first confirmed. Next, we used genetic approaches to verify the functionality and molecular mechanism of phospho-MARCKS. Finally, cancer cells were pharmacologically inhibited for MARCKS activity and subjected to functional bioassays. Measurements and Main Results: We demonstrated that higher phospho-MARCKS levels were correlated with shorter overall survival of lung cancer patients. Using shRNA silencing and ectopic expression of wild-type and PSD-mutated (S159/163A) MARCKS, we showed that elevated phospho-MARCKS promoted cancer growth and erlotinib resistance. Further studies demonstrated an interaction of phosphoinositide 3-kinase with MARCKS, but not with phospho-MARCKS. Interestingly, phospho-MARCKS acted in parallel with increased phosphatidylinositol (3,4,5)-triphosphate pools and AKT activation in cells. Through treatment with a 25-mer peptide targeting the MARCKS PSD motif (MPS peptide), we were able to suppress tumor growth and metastasis in vivo, and reduced levels of phospho-MARCKS, phosphatidylinositol (3,4,5)-triphosphate, and AKT activity. This peptide also enhanced the sensitivity of lung cancer cells to erlotinib treatment, especially those with sustained activation of phosphoinositide 3-kinase/AKT signaling. Conclusions: These results suggest a key role for MARCKS PSD in cancer disease and provide a unique strategy for inhibiting the activity of MARCKS PSD as a treatment for lung cancer