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`
`process of drug development, as well as for metabolic
`research in drug metabolism and disposition in general.
`On 16 October 20l3, the FDA issued a further directive
`recommending that "drug companies and researchers
`avoid using oral ketoconazole in drug
`interaction
`studies.,,3
`Given the importance of ketoconazole both in clinical
`therapeutics and in biomedical research, and the extensive
`body of information that has been generated to date with
`this probe CYP3A inhibitor, an evaluation ofthe evidence
`is needed to determine whether the new regulatory
`guidelines are in the interest of the public health. The
`purpose of this article is to examine the reasons for the
`FDA's warning, and to formulate an evidence-based
`opinion on the validity and public health benefit of the
`regulatory action based on the available published
`literature.
`
`Overview of Ketoconazole
`From the late 1950s until 1981, amphotericin B was the
`principal pharmacologic treatment available for systemic
`fungal disease.4
`,5 However amphotericin B had signifi(cid:173)
`cant drawbacks in that it is not orally absorbable, and the
`side effect profile was an important concern. Ketocona(cid:173)
`zole was introduced in 1981 as the first in a series of azole
`antifungal agents, characterized structurally by at least
`one five-membered, nitrogen-containing ring.6,7 The
`azoles act by
`inhibiting
`the enzyme C-14 alpha
`demethylase, which is necessary for the synthesis of
`ergosterol, a key component of fungal cell membranes.
`The deficiency in ergosterol leads to increased membrane
`permeability and interference with growth and replica(cid:173)
`tion. The azoles have been successfully used in the
`treatment of most systemic or deep-seated fungal
`infections, such as candidasis, cryptococcosis, endemic
`mycoses, and aspergillosis?
`The most commonly reported side effects of ketoco(cid:173)
`nazole are reversible gastrointestinal disturbances such as
`nausea, vomiting, or abdominal discomfort, which occur
`in an estimated 3 to 10% of patients. More serious adverse
`reactions (common with amphotericin B) occur in less
`than 1% of patients.6 Fungal resistance to ketoconazole
`and other azoles was considered to be uncommon except
`in HIV -positive populations-another advantage for the
`azoles over amphotericin B.
`In addition to having antifungal properties, ketocona(cid:173)
`zole was also became recognized as a potent inhibitor of
`human drug metabolism (specifically via CYP3A iso(cid:173)
`forms), beginning with reports around 1982 describing
`inhibition of cyc1osporine clearance. 8 Ketoconazole also
`inhibits a number of CYP enzymes
`involved
`in
`steroidogenesis, leading to reports of adrenal insufficien(cid:173)
`cy in some clinical situations? Inhibition of testosterone
`synthesis via CYP3A inhibition probably explains the
`
`anti-androgen effects ofketoconazole, underlying reports
`of gynecomastia as an infrequent side effect,6-9 as well as
`the potential applicability of high-dose ketoconazole for
`treatment of hormone-refractory prostate cancer. 10,11
`Ketoconazole has also been reported as a pharmacologic
`treatment for Cushing disease because of its ability to
`inhibit adrenal steroidogenesis. 12
`,13 The role of ketoco(cid:173)
`nazole as a CYP3A inhibitor is discussed further below.
`
`Early Reports of Ketoconazole
`Hepatotoxicity
`By 1984, cases of possible ketoconazole-associated
`hepatotoxicity, rarely fatal, had been reported world(cid:173)
`wide. 14-16 An early estimate by Van Tyle6 reported DILl
`as occurring in 0.1 to 1.0% of patients, with no apparent
`association with dosage. Evidence at the time suggested
`that hepatitis, if seen with ketoconazole, appeared to be
`mild and reversible upon discontinuation of the drug.
`Lake-Bakaar et al 14 described 64 cases of hepatic injury in
`the United Kingdom, as defined by significantly elevated
`levels of alanine transaminase (AL T) and alkaline
`phosphatase. Each case had a "possible" or "probable"
`association with ketoconazole treatment, although cau(cid:173)
`sality could not be proven. Five of the cases were fatal.
`Lake-Bakaar estimated the prevalence of serious hepato(cid:173)
`toxicity at one in 15,000 patients, concluding that "most
`patients recovered when they stopped taking the drug, the
`results of their liver function tests returning to normal
`within an average of 3.1 months." Como and Dismukes 7
`also noted that ketoconazole may cause clinically
`important, even fatal hepatitis, although they did not
`speculate upon what fraction of cases presented with
`"clinically important" as opposed to asymptomatic
`hepatotoxicity.
`Within five years of the introduction of ketoconazole
`into clinical practice, the possibility of hepatotoxicity was
`widely recognized, as was the need for monitoring ofliver
`function. Nonetheless. much of the evidence indicated
`that hepatic injury was usually asymptomatic, reaching
`clinical importance in less than one percent of patients.
`Hepatotoxicity also appeared to be reversible in the great
`majority of cases, but there was little epidemiological data
`to indicate how often liver damage might be irreversible,
`and what the predisposing factors might be. There was
`also no well-established link between DILl and either
`dose or duration of exposure, although Lake-Bakaar
`et al14 suggested that the risks of hepatitis seem to be
`greater with prolonged treatment.
`
`Possible Mechanisms of Hepatotoxicity
`Most of the evidence dealing with the possible mecha(cid:173)
`nisms ofketoconazole-associated hepatotoxicity is based
`on experimental animal models. Early studies of cultured
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`
`rat hepatocytes indicated that ketoconazole produced
`direct hepatocellular toxicity that was concentration(cid:173)
`dependent. 17,18 Subsequently it became evident that
`ketoconazole is biotransformed in vitro and in vivo to
`N-desacetyl-ketoconazole (DAK) via a number of
`enzymes including flavin-containing monooxygenases
`(FMOs). DAK had greater intrinsic toxicity than the
`parent compound, possibly explained by further biotrans(cid:173)
`formation by FMOs to reactive metabolites. 19.20 Toxicity
`produced by both ketoconazole and DAK-evident as
`cellular leakage of alanine transaminase (ALT) or lactic
`dehydrogenase (LDH)-was dose- and concentration(cid:173)
`dependent, and associated with covalent binding to
`hepatic protein, as well as glutathione depletion.21 In
`vivo toxicokinetic studies in rabbits demonstrated that
`ketoconazole hepatotoxicity was associated with net
`systemic exposure to the drug, as measured by total area
`under the plasma concentration curve (AUC).22
`Although there is
`little direct evidence on the
`mechanism of ketoconazole hepatotoxicity in humans,
`the experimental data suggests that ketoconazole and
`DAK produce direct hepatocellular toxicity as opposed to
`immunologically-mediated toxicity. The extent of hepatic
`damage appears related to concentration, and to net
`systemic exposure.
`
`Prevalence of Hepatotoxicity in
`Clinical Use
`A number of reviews, case surveys, and registry reports
`from sources around the world have been published since
`2002, dealing with the general topic of drug-induced
`hepatitis, liver injury, or liver failure. 23
`35 In essentially
`-
`all ofthese publications, ketoconazole is mentioned not at
`all, or only minimally, as a potential cause of liver injury.
`The possible reasons for low mention of ketoconazole
`include one or more of the following: 1) ketoconazole(cid:173)
`associated hepatic injury is unusual; 2) overall worldwide
`clinical exposure to ketoconazole is low. The FDA
`estimated only 609,000 prescriptions for orally-adminis(cid:173)
`tered ketoconazole in the United States in calendar year
`2012; 1 3) ketoconazole-associated hepatotoxicity, when it
`occurs, is of minimal clinical concern, and may be
`undetected and! or unreported.
`Nonetheless, data derived from registries or collections
`of case reports do not provide information on the
`incidence, prevalence, or risk of liver injury associated
`with the clinical use ofketoconazole. Generation of valid
`absolute or comparative incidence/prevalence data is not
`straightforward, and would require random allocation of
`candidate patients
`to ketoconazole and comparator
`treatment groups, with a standardized scheme of
`follow-up assessment of liver function. Chien et a136
`reported such a study, in which a series of 211 patients
`with onchomycoses were randomized to treatment with
`
`ketoconazole or griseofulvin. Subclinical hepatic dys(cid:173)
`function was detected in 18% of ketoconazole-treated
`patients, and "overt" hepatitis in 3%. The median time
`between initiation of therapy and detection of hepatic
`abnormalities was 6 weeks. Liver function tests returned
`to normal in all patients. No patients in the griseofulvin(cid:173)
`treated group had evidence of hepatic dysfunction.
`Other data sources derive from population bases for
`which estimates are available for the overall exposure to
`ketoconazole and to comparator treatments. Incidences
`and prevalences of hepatotoxicity can be quantitated in
`this context, but the estimates are subject to the same
`sources of bias and uncertainty as are the case report(cid:173)
`based compilations. Specifically: 1) patients are as(cid:173)
`signed to treatment groups by physicians' choice rather
`than random allocation; 2) factors predisposing to liver
`disease are unknown and/or uncontrolled; 3)
`the
`occurrence of liver injury is based on spontaneous
`clinical report rather
`than systematic prospective
`evaluation.
`Despite the limitations, the population-based studies
`provide some useful information on risk. One of these
`studies37 was cited by the FDA as a part of the basis for
`their regulatory decision.
`The study by Garcia Rodriguez and associates37
`assessed a cohort of users of oral antifungal agents in
`the general population of the United Kingdom. A total of
`69,830 patients with no pre-existing liver disease were
`followed, of whom 1052 had been prescribed ketocona(cid:173)
`zole. Of these patients, two presented with liver injury.
`This amounted to a rate of 19 cases per 10,000 patients, or
`134.1 per 100,000 person-months. Corresponding rates
`per 100,000 person-months for other anti-fungals were:
`lOA for itraconazole, 2.5 for terbinafine, and zero for
`fluconazole and griseofulvin. All patients recovered(cid:173)
`there were no fatal outcomes, and no mention of liver
`transplantation. Based on these data and similar data for
`other azoles, the conclusions were: 1) the absolute risk for
`all antifungals is low; 2) the relative risk for ketoconazole
`compared to other treatments is high.
`The FDA Communication 1 discusses
`the Garcia
`Rodriguez study as follows: "One published study in
`the U.K. General Practice Research Database suggested a
`risk of acute liver injury (defined as patients presenting
`with symptoms of liver disorder: nausea, vomiting,
`abdominal pain, and/or jaundice requiring referral to a
`specialist or hospitalization and free of history of liver
`disease and other chronic illnesses in the past 5 years) of
`approximately 1 in 500 patients, and analysis of liver
`transplantation data indicates that hepatotoxicity from
`ketoconazole accounted for proportionately more liver
`transplants than hepatotoxicity from other antifungal
`drugs. However, in view of various methodological
`limitations, there was uncertainty in quantifying precise
`estimates of the risk of acute liver injury for Nizoral
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`
`to other marketed oral azole
`
`tablets compared
`antifungals. "
`Two other published epidemiologic studies were not
`discussed by the FDA. One of these is a large population(cid:173)
`based study, in which Kao and associates38 evaluated a
`total of 57,321 Taiwanese patients receiving ketocona(cid:173)
`zole, as well as 33,526 patients receiving other antifungal
`agents. The overall incidence rate of DILl for ketocona(cid:173)
`zole was 4.9 cases per 10,000 patients, compared to 31.6
`for fluconazole, 3.6 for
`itraconazole, and 1.6 for
`terbinafine. Of six fatalities, one occurred in a patient
`receiving ketoconazole (who had also been exposed to
`fluconazole). Additionally, Kao et al examined the
`relationship between DILl incidence rate and duration
`of exposure. The greatest incidence rate occurred in
`patients with more
`than 60 days of exposure
`to
`ketoconazole. The sample size for this group was 234
`out of the total of 57,321; the next greatest incidence rate
`occurred in the group with 30 days of exposure (n 622).
`The study concluded that longer treatment duration may
`increase the risk of liver injury. The data also suggested
`that old age predisposed patients to adverse outcomes, as
`all six fatalities occurred in patients over 60; all, however,
`had been exposed to fluconazole. Overall, Kao38 and
`Garcia Rodriguez3? both reached the conclusion that DILl
`rates were elevated in antifungal users compared to non(cid:173)
`users. Together, however, their data did not conclusively
`establish which antifungal agent posed the greatest risk of
`hepatotoxicity.
`In a third study, Ying and associates39 conducted a
`meta-analysis of the literature on ketoconazole-associated
`hepatotoxicity. The majority of the studies included in the
`analysis involved ketoconazole doses in the range of 200
`to 400 mg per day, which is within the range recom(cid:173)
`mended in the American product label. Across a total of
`204 papers in Chinese and English, the overall incidence
`of hepatotoxicity associated with ketoconazole was found
`to be between 3.6 and 4.2%. The study did not identify the
`severity or consequences of hepatotoxicity, as the marker
`was usually evidence of increased AL T levels. Also, there
`were no comparator treatment groups. There was no
`conclusive evidence linking dose or duration of exposure
`to rates of hepatotoxicity, and the elderly did not appear to
`be at higher risk. Finally, they noted that the rate of DILl
`in off-label ketoconazole users was 5.7%. However the
`reason for the apparently higher risk in that group was not
`established.
`Taken together, these three studies suggest that DILl is
`more common in ketoconazole users than in untreated
`controls. For the most part, the studies do not deal with the
`severity of the cases, or whether the patients were
`symptomatic. The reports also do not conclusively
`support a relationship between dose, duration of exposure,
`or age of patients on the rate of hepatotoxicity. Also not
`considered is the relationship of liver injury to other
`
`factors often discussed as potential correlates of DILl,
`such as gender, ethnic origin, obesity, diet, and pre(cid:173)
`existing or concurrent liver disease.40,41 Finally, the
`studies do not provide information on the potential benefit
`of ketoconazole treatment in relation to the risk of
`hepatotoxicity.
`
`Metabolic Effects of Ketoconazole:
`Drug-drug Interactions
`The FDA Safety Communication 1 points out two
`additional safety issues associated with ketoconazole:
`Adrenal gland problems (adrenal insufficiency), and drug
`interactions. Both of these issues, insofar as they are of
`clinical importance, are attributable to the property of
`ketoconazole as an inhibitor of human CYP3A isoforms,
`responsible for the biotransformation of a number of
`endogenous steroids, and for many prescription medi(cid:173)
`cations commonly used in clinical practice. Shortly after
`the introduction of ketoconazole in the early 1980s,
`observations were reported indicating that co-administra(cid:173)
`tion of ketoconazole with cyclosporine lead to impaired
`metabolic clearance and increased plasma concentrations
`of cyclosporine.42 Biochemical and clinical research in
`the years that followed identified CYP3A4 as a specific
`metabolic enzyme localized in human liver and in
`gastrointestinal tract mucosal cells.43--45 Ketoconazole
`was further characterized as a highly potent and relatively
`specific inhibitor of CYP3A isoforms, based on models
`using biotransformation of various substrate drugs and
`chemicals by human liver micro somes in vitro, as well as
`in clinical studies showing inhibition ofbiotransformation
`and increased systemic exposure of CYP3A substrate
`drugs (including cyclosporine) due to co-administration
`of usual therapeutic doses of ketoconazole.45--49 CYP3A
`inhibition by ketoconazole is reversible, occurring by a
`mixture of competitive and noncompetitive mecha(cid:173)
`nisms.50 The newer azole antifungal itraconazole has
`CYP3A inhibiting properties similar to ketoconazole,
`while fluconazole is somewhat is less potent as an
`inhibitor.46,51-54
`An in vitro inhibition constant (Kj ) for ketoconazole
`versus biotransformation of a CYP3A substrate typically
`falls in the range of 0.1 micromolar,54.55 whereas plasma
`concentrations ofketoconazole during clinical use usually
`exceed 1.0 micromolar.42 The tenfold or more excess of in
`vivo exposure compared to in vitro Kj indicates the
`likelihood of quantitatively large and clinically important
`drug interactions, which in fact have been verified through
`numerous clinical observations and controlled human
`pharmacokinetic studies.46,4?,53,54 Generally these inter(cid:173)
`actions are considered to be potentially hazardous if
`exposure to the substrate drug is increased to a range that
`might produce excessive drug effects. On the other hand,
`a drug interaction deliberately produced via the CYP3A
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`Greenblatt and Greenblatt
`
`1325
`
`inhibiting property of ketoconazole can be exploited for
`favorable
`therapeutic purposes,
`in which case
`the
`interaction is termed phannacokinetic "augmentation,"
`"boosting," or "dose-sparing." The most familiar example
`is ketoconazole augmentation of cyclosporine in the
`prevention of organ rejection in transplant patients.
`Cyclosporine is a costly medication. Co-administration
`of cyclosporine with ketoconazole allows target plasma
`concentrations of cyclosporine to be attained with a
`substantially reduced dosage requirement, and reduced
`dollar cost of treatment. 56-63 It is of interest that the
`majority of studies of cyclosporine dose-sparing by
`ketoconazole report a negligible incidence of ketocona(cid:173)
`zole-associated liver toxicity.
`CYP3A inhibition by ketoconazole has assumed major
`importance in drug metabolism research and the drug
`development process. 8 If a candidate drug is identified as
`a possible or probable substrate for biotransformation via
`CYP3A
`isoforms, a controlled ketoconazole drug
`interaction study can address critical clinical and safety
`issues. In a typical study of this type, the candidate
`(substrate) drug is administered to healthy volunteers
`once in the control state with no inhibitor, and on another
`occasion during co-treatment with ketoconazole during
`which the subjects assume what has been termed "human
`CYP3A phenotypic knockout status." The increase in
`the substrate (AUC) due to
`systemic exposure
`to
`ketoconazole co-treatment provides quantitative data on
`the contribution of CYP3A to net clearance, and well as
`the "worst case" drug interaction scenario in which
`concentrations of the substrate drug then reflect those
`achievable under maximal CYP3A inhibition.45-47.64,65 If
`the candidate drug itself is a suspected CYP3A inhibitor,
`its inhibitory potency can be compared to ketoconazole in
`a similarly designed study in which the CYP3A substrate
`drug is a known index compound such as midazolam,
`triazolam, or buspirone. The extensive scientific literature
`base that exists for ketoconazole as a prototype inhibitor
`provides important context for new interactions involving
`inhibition of CYP3A.
`Hundreds of ketoconazole drug interaction studies
`have been done in the last decade. The duration of
`exposure to ketoconazole is typically brief (several days),
`and study participants are young healthy volunteers who
`are screened to exclude pre-existing liver disease or other
`predisposing factors. The outcome of many of the studies
`is reported in biomedical literature publications. We know
`of no published report in which a volunteer participant in a
`ketoconazole drug
`interaction study has developed
`evidence of serious liver injury.
`
`Alternatives to Ketoconazole
`Itraconazole, fluconazole, voriconazole, and terbinafine
`are available alternatives
`to ketoconazole for oral
`
`antifungal therapy. 66-71 Whether a specific alternative
`agent is therapeutically equivalent to ketoconazole would
`be a judgment of the treating physician. In this context it
`cannot be assumed that the alternative agents have an
`advantage over ketoconazole in terms of the risk of liver
`dysfunction. The available published literature does not
`allow a clear judgment of whether itraconazole or
`fluconazole carries a
`lower, equivalent, or higher
`associated risk of hepatic injury compared to ketocona(cid:173)
`zole. Likewise, drug-drug interactions due to inhibition of
`CYP3A-mediated drug metabolism are clearly associated
`with itraconazole and fluconazole.46,47,53,54
`In the context of drug metabolism research and the
`drug development process,
`the discouragement or
`prohibition of the use of ketoconazole as the prototype
`inhibitor is a significant obstacle. 8
`strong CYP3A
`Itraconazole and clarithromycin have been presented as
`alternatives, 1,72 but neither is equivalent to ketoconazole.
`Itraconazole is less potent than ketoconazole as a CYP3A
`inhibitor in vitro,51,52 though this is partially offset by the
`high lipid-solubility and concentrative hepatic uptake of
`itraconazole,75 and by the presence of itraconazole
`inhibi(cid:173)
`themselves are CYP3A
`metabolites
`that
`tors.51 ,52,76,77 Clarithromycin is only a "moderate"
`CYP3A inhibitor, and does not create the "worst-case
`scenario" in clinical studies.72 Further, CYP3A inhibition
`by clarithromycin is "time-dependent" or "mechanism(cid:173)
`based," such that several days of pre-exposure to
`clarithromycin may be required for inhibition to be fully
`74 As such, clarithromycin is not a suitable
`evident. 72
`-
`index inhibitor, since a key objective of inhibition studies
`is to produce concentrations of the victim (substrate) drug
`achievable with maximum CYP3A inhibition, so that
`safety concerns can be evaluated and addressed.
`We evaluated seven published clinical pharmacoki(cid:173)
`netic drug interaction studies in which oral triazolam was
`used as the index CYP3A substrate. Studies were
`designed as described above: Triazolam was given once
`in the control state with no inhibitor, and on another
`occasion with coadministration of ketoconazole, itraco(cid:173)
`nazole, clarithrornycin, or ritonavir. Figure 1 shows mean
`(± standard error) triazolam AUC ratios (AUC with
`inhibitor divided by AUC without inhibitor) for each of
`the studies. AUC ratios with ketoconazole as inhibitor
`80 For itraconazole, the ratios
`ranged from 9.2 to 22.4. 78
`-
`in two studies were 4.5 and 27.1.80,81 The AUC ratio for
`the one study ofclarithromycin was 5.3.82 For two studies
`of ritonavir as inhibitor, the ratios were 20.4 and 39.2. 83,84
`Based on this data and other literature publications,
`we conclude that itraconazole might be a reasonable
`alternative to ketoconazole as a CYP3A inhibitor in
`the research context. Clarithromycin is clearly not a
`suitable alternative. Ritonavir may be
`the most
`appropriate alternative to ketoconazole. Ritonavir, as a
`highly potent CYP3A inhibitor, can be given in low
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`References
`I. FDA Drug Safety Communication: FDA limits usage of Nizoral
`(ketoconazole) oral tablets due to potentially fatal liver injury and
`risk of drug interactions and adrenal gland problems. UCM 362444:
`26 July 2013.
`2. European Medicines Agency recommends suspension of marketing
`authorisations for oral ketoconazole. Benefit of oral ketoconazole
`does not outweigh risk of liver injury in fungal infections. EMAI
`458028/2013. 26 July 2013.
`3. FDA advises against using oral ketoconazole in drug interaction
`studies due to serious potential side effects. UCM 371017: 16
`October 2013 ..
`4. MedoffG, Brajtburg J, Kobayashi GS, Bolard J. Antifungal agents
`infections. Annu Rev
`useful in therapy of systemic fungal
`Pharmacol Toxicol. 1983;23:303-330.
`5. Graybill JR, Craven Pc. Antifungal agents used in systemic
`mycoses. Activity and therapeutic use. Drugs. 1983;25:41-62.
`6. Van Tyle JH. Ketoconazole. Mechanism of action, spectrum of
`activity, pharmacokinetics, drug interactions, adverse reactions and
`therapeutic use. Pharmacotherapy. 1984;4:343-373.
`7. Como JA, Dismukes WE. Oral azole drugs as systemic antifungal
`therapy. N Engl J Med. 1994;330:263-272.
`8. Greenblatt DJ. The ketoconazole legacy. Clin Pharmacol Drug
`Dev.2014;3:1-3.
`9. Deepinder F, Braunstein GD. Drug-induced gynecomastia:
`an evidence-based review. Expert Opin Drug Sa! 2012;11:779-
`795.
`10. Harris KA, Weinberg V, Bok RA, Kakefuda M, Small EJ. Low dose
`ketoconazole with replacement doses of hydrocortisone in patients
`with progressive androgen independent prostate cancer. J Urol.
`2002;168:542-545.
`11. Kim W, Ryan CJ. Androgen receptor directed therapies in
`castration-resistant metastatic prostate cancer. Curr Treat Options
`Oncol.2012;13:189-200.
`12. Newell-Price J. Ketoconazole as an adrenal steroidogenesis
`inhibitor: Effectiveness and risks in the treatment of Cushing's
`disease. J Clin Endocrinol Metab. 2014;99:1586-1588.
`13. Castinetti F, Guignat L, Giraud P, et al. Ketoconazole in Cushing's
`disease: Is it worth a try. J Clin Endocrinol Metab. 2014;99:1623-
`1630.
`14. Lake-Bakaar G, Scheuer PJ, Sherlock S. Hepatic reactions
`associated with ketoconazole in the United Kingdom. Br Med J
`(Clin Res Ed). 1987;294:419-422.
`15. Lewis JH, Zimmerman HJ, Benson GD, Ishak KG. Hepatic injury
`associated with ketoconazole therapy. Analysis of 33 cases.
`Gastroenterology. 1984;86:503-513.
`16. Stricker BH, Blok AP, Bronkhorst FB, van Parys GE, Desmet Vl
`Ketoconazole-associated hepatic injury. A clinicopathological
`study of 55 cases. J Hepatol. 1986;3:399-406.
`17. Buchi KN, Gray PD, Tolman KG. Ketoconazole hepatotoxicity: an
`in vitro model. Biochem Pharmacol. 1986;35:2845-2847.
`18. Rodriguez RJ, Acosta D. Comparison of ketoconazole- and
`fluconazole-induced hepatotoxicity in a primary culture system of
`rat hepatocytes. Toxicology. 1995;96:83-92.
`19. Rodriguez RJ, Proteau PJ, Marquez BL, Hetherington CL,
`Buckholz CJ, O'Connell KL. Flavin-containing monooxygenase(cid:173)
`mediated metabolism of N-deacetyl ketoconazole by rat hepatic
`microsomes. Drug Metab Dispos. 1999;27:880-886.
`20. Rodriguez RJ, Acosta D. N-deacetyl ketoconazole-induced
`hepatotoxicity in a primary culture system of rat hepatocytes.
`Toxicology. 1997;117:123-131.
`21. Rodriguez RJ, Buckholz CJ. Hepatotoxicity of ketoconazole in
`Sprague-Dawley rats: glutathione depletion, flavin-containing
`monooxygenases-mediated bioactivation and hepatic covalent
`binding. Xenobiotica. 2003;33:429-441.
`
`22. Ma YM, Ma ZQ, Gui CQ, Yao JS, Sun RY. Hepatotoxicity and
`toxicokinetics of ketoconazole in rabbits. Acta Pharmacol Sin.
`2003;24:778-782.
`23. Sgro C, Clinard F, Ouazir K, et al. Incidence of drug-induced
`hepatic injuries: a French population-based study. Hepatology.
`2002;36:451-455.
`24. Lee WM. Drug-induced hepatotoxicity. N Engl J Med. 2003;349:
`474-485.
`25. de Abajo FJ, Montero D, Madurga M, Garcia Rodriguez. Acute and
`clinically relevant drug-induced liver injury: a population based
`case-control study. Br J Clin Pharmacol. 2004;58:71-80.
`26. Russo MW, Galanko JA, Shrestha R, Fried MW, Watkins P. Liver
`transplantation for acute liver failure from drug induced liver injury
`in the United States. Liver Transpl. 2004;10(8):1018-1023.
`27. Andrade RJ, Lucena MI, Fernandez MC, et al. Drug-induced liver
`injury: an analysis of 461 incidences submitted to the Spanish registry
`over a 10-year period. Gastroenterology. 2005;129:512-521.
`28. Watkins PB, Seeff LB. Drug-induced liver injury: summary of a
`single topic clinical research conference. Hepatology. 2006;43:
`618-631.
`29. Andrade RJ, Robles M, Fernandez-Castaner A, Lopez-Ortega S,
`Lopez-Vega MC, Lucena Ml. Assessment of drug-induced
`hepatotoxicity in clinical practice: a challenge for gastroenterolo(cid:173)
`gists. World J Gastroenterol. 2007;13:329-340.
`30. Chalasani N, Fontana RJ, Bonkovsky HL, et al. Causes, clinical
`features, and outcomes from a prospective study of drug-induced
`liver injury in the United States. Gastroenterology. 2008;135:1924-
`1934.
`31. Suzuki A, Andrade RJ, Bjornsson E, et al. Drugs associated with
`hepatotoxicity and their reporting frequency ofliver adverse events
`in VigiBase: unified list based on international collaborative work.
`Drug Sa! 2010;33:503-522.
`32. Reuben A, Koch DG, Lee WM. Drug-induced acute liver failure:
`results of a U.S. multicenter, prospective study. Hepatology.
`20 I 0;52:2065-2076.
`33. Suk KT, Kim DJ, Kim CH, et al. A prospective nationwide study of
`drug-induced liver injury in Korea. Am J Gastroenterol. 2012;107:
`1380-1387.
`34. Bjornsson ES, Bergmann OM, Bjornsson HK, Kvaran RB, Olafsson
`S. Incidence, presentation, and outcomes in patients with drug(cid:173)
`in the general population of Iceland.
`induced liver injury
`Gastroenterology. 2013;144: 1419-1425.
`35. Leise MD, Poterucha JJ, Talwalkar JA. Drug-induced liver injury.
`Mayo Clin Proc. 2014;89:95-106.
`36. Chien RN, Yang LJ, Lin PY, Liaw YF. Hepatic injury during
`ketoconazole therapy in patients with onychomycosis: a controlled
`cohort study. Hepatology. 1997;25:103-107.
`37. Garcia Rodriguez, Duque LA, Castellsague A, Perez-Gutthann J,
`Stricker S. A cohort study on the risk of acute liver injury among
`users of ketoconazole and other antifungal drugs. Br J Clin
`Pharmacol. 1999;48:847-852.
`38. Kao WY, Su CW, Huang YS, et al. Risk of oral antifungal agent(cid:173)
`induced liver injury
`in Taiwanese. Br J Clin Pharmacol.
`2014;77: 180-189.
`39. Yan JY, Nie XL, Tao QM, Zhan SY, Zhang YD. Ketoconazole
`associated hepatotoxicity: a systematic review and meta-analysis.
`Biomed Environ Sci. 2013;26:605-610.
`40. Tarantino G, Di Minno MN, Capone D. Drug-induced liver injury: is
`it somehow foreseeable. World J Gastroenterol. 2009;15:2817-
`2833.
`41. Tarantino G, Conca P, Basile V, et al. A prospective study of acute
`drug-induced liver injury in patients suffering from non-alcoholic
`fatty liver disease. Hepatol Res. 2007;37:410-415.
`42. Daneshmend TK, Warnock DW. Clinical pharmacokinetics of
`ketoconazole. Clin Pharmacokinetics. 1988;14:13-34.
`
`Teva Pharmaceuticals USA, Inc. v. Corcept Therapeutics, Inc.
`PGR2019-00048
`Corcept Ex. 2052, Page 7
`
`

`

`1328
`
`The Journal of Clinical Pharmacology / Vol 54 No 12 (2014)
`
`43. Guengerich FP. Cytochrome P450: What have we learned and what
`are the future issues? What have we learned and what are the future
`issu197. Drug Metab Rev. 2004;36:159-197.
`44. Watkins PB. Drug metabolism by cytochromes P450 in the liver and
`small bowel. Gastroenterol c/in North Am. 1992;21:511-526.
`45. Greenblatt DJ, He P, von Moltke LL, Court MH. The CYP3 family.
`Ioannides C, ed. Cytochrome P 450: Role in the Metabolism and
`Toxicology o/Drugs and Other Xenobiotics. Cambridge UK: Royal
`Society of Chemistry. 2008:354-383.
`46. Venkatakrishnan K, von Moltke LL, Greenblatt DJ. Effects of the
`antifungal agents on oxidative drug metabolism in humans: clinical
`relevance. Clin Pharmacokinet. 2000;38:111-180.
`47. Venkatakrishnan K, von Moltke LL, Obach RS, Greenblatt DJ.
`Drug metabolism and drug interactions: application and clinical
`value of in vitro models. Curr Drug Metab. 2003;4:423--459.
`48. Volak LP, Greenblatt DJ, von Moltke LL. In vitro approaches to
`anticipating clinical drug interactions. Albert P Li, ed. Drug-drug
`interactions in pharmaceutical development. Hoboken, NJ: John
`Wiley & Sons. 2008:75-93.
`49. Farkas D, Shader RI, von Moltke LL, Greenblatt DJ. Mechanisms
`and consequences of drug-drug interactions. Gad SC, ed. Preclini(cid:173)
`cal development handbook: ADME and