Identification of protein targets of nevirapine reactive metabolites using click chemistry and mass spectrometry-based differential proteomics

Abstract : Adverse drug reactions (ADRs) are undesirable effects caused after administration of a single dose or prolonged administration of drug or result from the combination of two or more drugs. Idiosyncratic drug reaction (IDR) is an adverse reaction that does not occur in most patients treated with a drug and does not involve the therapeutic effect of the drug. IDRs are unpredictable and often life-threatening. Idiosyncratic reaction is dependent on drug chemical characteristics or individual immunological response. IDRs are a major problem for drug development because they are usually not detected during clinical trials. In this study we focused on IDRs of Nevirapine (NVP), which is a non-nucleoside reverse transcriptase inhibitor used for the treatment of Human Immunodeficiency Virus (HIV) infections. The use of NVP is limited by a relatively high incidence of skin rash. NVP also causes a rash in female Brown Norway (BN) rats, which we use as animal model for this study. Our hypothesis is that idiosyncratic skin reactions associated with NVP treatment are due to post-translational modifications of proteins (e.g., glutathionylation) detectable by MS. The main objective of this study was to identify the proteins that are targeted by a reactive metabolite of Nevirapine in the skin. The specific objectives derived from the general objective were as follow: 1) To implement the click chemistry approach to detect proteins modified by a reactive NVP-Alkyne (NVP-ALK) metabolite. The purpose of using NVP-ALK was to couple it with Biotin using cycloaddition Click Chemistry reaction. 2) To detect protein modification using Western blotting and Mass Spectrometry techniques, which is important to understand the mechanism of NVP induced toxicity. 3) To identify the proteins using MASCOT search engine for protein identification, by comparing obtained spectrum from Mass Spectrometry with theoretical spectrum to find a matching peptide sequence. 4) To test if the drug or drug metabolites can cause harmful effects, as the induction of oxidative stress in cells (via protein glutathionylation). Oxidative stress causes cell damage that mediates signals, which likely induces the immune response. The results showed that Nevirapine is metabolized to a reactive metabolite, which causes protein modification. The extracted protein from the treated BN rats matched 10% of keratin, which implies that keratin was the protein targeted by the NVP-ALK.

Evaluating health policy and legal responses : how to reduce barriers and improve access to orphan drugs for rare diseases in Canada

Abstract : Rare diseases are debilitating conditions often leading to severe clinical manifestations for affected patients. Orphan drugs have been developed to treat these rare diseases affecting a small number of individuals. Incentives in the legal framework aimed to recoup the research and development cost of orphan drugs for pharmaceutical companies have been implemented in the United States and the European Union. At the present time, Canada is still lacking a legal and policy framework for orphan drugs. Several problems at the federal and provincial levels remain: lack of research funds for rare diseases, discrepancies on orphan drug policies between provinces, difficulties to access and reimburse these high price drugs. Recommendations and measures are proposed, such as a pan-Canadian (national) scientific committee to establish evidence-based guidelines for patients to access orphan drugs uniformly in all provinces with a disease specific registry, a formal agreement for a centralized Canadian public funding reimbursement procedure, and increasing the role of “guardian” for prices by the Patented Medicines Review Board in Canada. These recommendations and measures will be beneficial for the implementation of a policy framework for orphan drugs in Canada.