Out of 18,820 patients; 6.5% were admitted to hospital through an ADROut of 3695 patients, 15% experience an ADR that lengthened their hospital stay.Out of the 3695 patient episodes assessed for ADRs, 545 (14.7%) experienced one or more ADRs.Half of ADRs were definitely or possibly avoidable.The patients experiencing ADRs were more likely to be older, female, taking a larger number of medicines, and had a longer length of stay than those without ADRs.The only significant predictor of ADRs, was the number of medicines taken by the patient with each additional medication multiplying the hazard of an ADR episode by 1.14 (95% CI 1.09, 1.20).
Different chemical classesAnd different therapeutic areas
Move K18 to later
Histo and Caspase 3
Both APAP and one metabolite of NVP are amenable to 1,4 addition of GSHTwo reactive metabolites of NVP and 2 forms of toxicity.The questions we want to ask is whether one metabolite could be responsible for liver and one for skin toxicity.
Jack also sees covalent binding in the liver, yet no toxicity.So this is another case where covalent binding is seen yet no toxicity observed.
Mechanistic Investigations in Drug Safety <br />Introduction<br />ADRs<br />On and off target toxicity<br />Acetaminophen model of murine toxicity<br />Mechanistic markers of injury progression<br />Apoptosis (K18), necrosis (HMGB-1), inflammation (Ac-HMGB-1)<br />Fed and fasted animal models<br />Nevirapine hypersensitivity<br />Man vs animal model<br />Chemical similarities<br />
Adverse Drug Reactions (ADRs)<br /><ul><li>patient morbidity
attrition</li></li></ul><li>Lessons for the future<br />Inform mechanism and pathogenesis<br />Inform the Medicinal Chemist<br />Inform the Clinician<br />Inform the Regulator<br />Inform the Public – what is feasible<br />Develop biomarkers for integrated patient, in vitro & animal studies<br />
Classification of Adverse Drug Reactions<br />ON TARGET <br />Reactions that are predictable from the known primary or secondary pharmacology of the drug. <br />Often representing an exaggeration of the pharmacological effect of the drug.<br />– clear dose-dependent relationship within the individual patient.<br />OFF TARGET <br />These are not predictable from a knowledge of the basic pharmacology of the drug and can exhibit marked inter-individual susceptibility (idiosyncratic).<br />– complex dose dependence. <br />
ADRs: Drug-Induced Liver Injury<br />Leading cause of acute liver failure1<br /><ul><li>APAP 46% of all cases
12% other drugs</li></ul>High morbidity & mortality2<br /><ul><li>20% survival without transplant</li></ul>Main reason for late stage termination or withdrawal2<br /><ul><li>1975-1999 - 548 new drugs
4 were withdrawn</li></ul>1 Lee AASLD, 2009; 2 Verma & Kaplowitz 2009<br />
Drug-Induced Liver Injury: issues<br />In vivo biomarkers used for non-invasive DILI assessment <br /><ul><li>Clinic & pre-clinical toxicity screening</li></ul>Why is DILI in man still:<br /><ul><li> Main reason for late drug attrition
Leading cause of ALF</li></ul>Animal–human concordance is 50%1,2,3<br /><ul><li> Attrition in biomarker translation </li></ul>Caveats with current biomarkers3,4<br /><ul><li> ALT in muscle & kidney
LDH not specific</li></ul>Better biomarkers are required<br />Mechanistic understanding of perturbed physiological processes<br />1Olson et al.2000; 2Greaves et al. 2004; Amacher. 2010; 4Dufour et al., 2000<br />
Mechanisms of Drug Induced Liver Injury<br />Hepatic Injury<br />Biological stratification<br />Drug<br /><ul><li> accumulation
Full length K18 released by necrosis</li></ul>Apoptotic Cell<br />Release of<br />Keratin-18<br />fragment<br />Antoine et al., 2009<br />N=6 ±SEM. *p<0.05, **p<0.01, ***p<0.005 compared to control<br />
Keratin-18 : biomarker of APAP apoptosis and necrosis<br />Release of full-length Keratin-18 due to necrosis<br />Correlation* of K18 fragment (apoptosis) vs<br />full-length K18 (necrosis) <br />Necrotic hepatocyte<br />DALD/SS motif<br />Release of fragmented Keratin-18 due to apoptosis<br />Apoptotic Hepatocyte<br />*individual mice (10 h); APAP (530 mg/kg)<br />
Hepatic Markers of Apoptosis<br />Hepatic DNA laddering<br />Hepatic pro-caspase-3 processing<br />Hepatic active caspase-3 IHC (3hr)<br />Antoine et al., 2009<br />
Nevirapine: Skin rash in an animal model <br />Nevirapine<br />12-OH NVP<br />Skin rash in Brown Norway rats is due to 12-OH Nevirapine pathway:<br />12-OH-NVP caused a rash at a lower dose than NVP<br />Less severe rash when CH3 hydrogens substituted by deuterium <br />Incidence of rash is increased by co-treatment with ABT<br />(ABT increases 12-OH NVP by blocking oxidation to 4-carboxy metabolite)<br />Quinone methide is potential reactive metabolite <br />NVP 12-O-sulfonate<br />NVP-12-mercapturate<br />Chen J, Mannargudi BM, Xu L, Uetrecht J (2008). Chem Res Toxicol 21:1862-1870<br />Uetrecht J (2006). Drug Metab Rev 38:745-753<br />Popovic M, Caswell JL,.Mannargudi B et al (2006). Chem Res Toxicol 19:1205-1214<br />Shenton J (2007).In: Pichler WJ (ed) Drug Hypersensitivity Karger AG, Basel, pp 115-128<br />
Complete Metabolic Profile of NVP in Man<br />Labels in red represent % metabolite in urine<br />Proportions represent the induced metabolic profile. <br />Riska et al. (1999a), Erickson et al. (1999), Wen et al. (2009), Srivastava et al. (2010)<br />
Complete Metabolic Profile of NVP in Rat<br />CYP3A1?<br />Riska et al. (1999b), Chen et al. (2008), Srivastava et al. (2010)<br />
Chemical Rationale:<br />12-OH Nevirapine is responsible for the Brown Norway Rat skin rash <br />12-OH NVP<br />Nevirapine<br />Quinone methide<br />12-OH NVP<br />NVP-12-mercapturate<br />Higher incidence of skin toxicity<br />Quinone methide<br />Epoxide<br />Next Question:<br />Could the epoxide which forms NVP-3-mercapturate be responsible for liver toxicity ?<br />NVP-12-mercapturate<br />NVP-3-mercapturate<br />Lower incidence of skin toxicity<br />
Mechanistic Drug Safety: Integrated Approach <br />Model hepatotoxins,<br />withdrawn drugs:<br />Drugs in clinical use:<br />
Mechanistic Drug Safety: Integrated Approach <br /><ul><li>Integrated safety / toxicity screens are required to study the multiplebiological consequences of cell defence and cell destruction.
If the pharmacophore and toxicophore cannot be separated, rational risk assessment cannot be performed.
Integrated chemical,biological and genomic systems are required for a complete mechanistic understanding of the chemical, molecular, cellular and immunological basis of idiosyncratic drug toxicity.
Idiosyncratic drug toxicity cannot be predicted from the chemistry of the drug and/or its metabolite because such reactions are by definition (largely) a function of the biology of the individual.</li></ul>Biology of individual<br />Occurrence, Frequency<br />& Severity of<br />Drug Hepatotoxicity<br />f1<br />f2<br />+<br />=<br />Chemistry<br />of drug<br />