1. Introduction
2. Past therapeutic attempts and
rationales
3. Past clinical trials: strategies
and difficulties
4. Ongoing or future possible
trials
5. Conclusions
6. Expert opinion
Review
The future for treatingCreutzfeldt--Jakob diseaseVito Vetrugno, Maria Puopolo, Franco Cardone, Fiorentino Capozzoli,Anna Ladogana & Maurizio Pocchiari†
Istituto Superiore di Sanit�a, Department of Cell Biology and Neurosciences, Roma, Italy
Introduction: Creutzfeldt--Jakob disease (CJD) is a rare, transmissible and fatal
neurodegenerative illness that affects people worldwide with a prevalence of
about 1 -- 2 cases per million people. Early diagnosis of CJD is still difficult
despite recent development of novel assays for detecting the pathological
prion protein, the only reliable marker of disease found in the cerebrospinal
fluid, urine and mucosa olfactoria.
Areas covered: This analysis covers attempts of therapy in CJD and related dis-
eases. It looks at problems encountered in designing and interpreting the few
available trials with the aim that learning from past experiences would
improve future clinical experimentations.
Expert opinion: The future of therapeutic intervention in CJD should begin
with the identification of novel compounds with strong antiprion effects.
These need validating in animal models of disease before their use in humans.
Improvement of preclinical studies according to internationally recognized
guidelines should cover critical aspects that have been poorly followed in
the past. The use of more than one model of prion infection should also be
encouraged. Novel international diagnostic criteria for including CJD patients
in clinical trials in an early stage are needed and consensus should be reached
for determining the most meaningful criteria to evaluate the progression
of disease.
Keywords: Creutzfeldt--Jakob disease, dementia, neurodegenerative disorders, therapy
Expert Opinion on Orphan Drugs (2015) 3(1):57-74
1. Introduction
Clinical and pathological features of Creutzfeldt--Jakob disease (CJD) weredescribed about one century ago, but understanding the mechanisms of pathologicalprocesses only begun in the late 60s when the disease was successfully transmitted tonon-human primates and thought to be caused by a slow and unconventionalvirus [1]. This finding neared CJD to kuru, an exotic disease of the Fore-speakingpeople in Papua New Guinea and now disappearing [2], and scrapie, an endemic dis-ease affecting herds of sheep and goats in most of the world [3]. However, until thelate 70s to early 80s, there was limited knowledge on clinical and epidemiologicaldata, and factors influencing disease duration were unknown or poorly under-stood [4,5]. A better understanding of the natural history of the disease came inthe 90s from the establishment of national surveillance systems in European andnon-European countries [6,7], and from understanding the pathogenic mechanismof disease, which basically consists in the poorly known process that misfolds thecellular prion protein (PrPc) into different pathological conformers (type 1, 2Aand 2B PrPTSE) with high beta-chain contents [8].
The majority of CJD cases apparently occur spontaneously (sporadic CJD),about 10 -- 20% within families (genetic CJD; Gerstmann--Straussler--Scheinkerdisease [GSS] and fatal familial insomnia [FFI]) in people carrying a pathogenicpoint or insert mutation in one allele of the prion protein gene (PRNP), and a
10.1517/21678707.2015.994605 © 2015 Informa UK, Ltd. e-ISSN 2167-8707 57All rights reserved: reproduction in whole or in part not permitted
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few cases are related to medical procedures (iatrogenicCJD) [7,9] or to the consumption of bovine spongiformencephalopathy-contaminated food (variant CJD) [10].Sporadic CJD occurs with different clinical phenotypes and
it is usually difficult to make a correct early diagnosis [11].Dementia usually occurs in the early phase of disease, butthere are cases where patients present other neurologicalsymptoms (i.e., ataxia or visual disturbances) at onset. Thedisease usually progresses rapidly with death occurringbetween 3 and 6 months in about 60% of cases [12]. Supportfrom clinical diagnosis comes from the electroencephalogram(EEG), cerebrospinal fluid (CSF) exams and brain MRI, butso far no disease-specific markers are included in the interna-tional diagnostic criteria for human prion diseases (Table 1) [13].EEG shows a characteristic generalized bi- or triphasic peri-odic sharp wave complexes with a frequency of around1 -- 2 per second in about 60% of sporadic CJD but it mightappear late in the course of disease and, occasionally, in otherconditions [14,15]. Typical EEG is present in some forms ofgenetic prion diseases (genetic CJD), but not in others(GSS, FFI) nor in variant CJD [16]. Routine CSF analysesare usually normal, but in the majority of sporadic CJD casesthe 14-3-3 proteins test results positive and tau is highly ele-vated [17]. The presence of 14-3-3 proteins in the CSF, how-ever, is not specific for prion diseases and it acquires adiagnostic value only in combination with CJD-specific
neurological signs [18]. Moreover, in about 50% of variantCJD this test is negative, therefore of no diagnostic value [19].Finally, brain MRI shows signal abnormalities in the anteriorbasal ganglia (caudate/putamen) and often in the cortex insporadic CJD, while signal abnormalities are observed inabout 90% of variant CJD in the posterior thalamic region(pulvinar) [13,20]. Brain MRI is also useful for excluding otherneurological conditions, some of which might be susceptibleto pharmacological or surgical treatment [21]. The geneticforms of prion diseases are easily recognized by the combina-tion of neurological signs in patients presenting specific insertor point mutations in the open reading frame of the PRNPgene [22]. The analysis of the PRNP gene in people belongingto affected families is also a powerful tool for the identifica-tion of potentially high-risk subjects, although it is usually dif-ficult to predict when people carrying a PRNP mutation willdevelop disease [22,23] and in several occasions carriers do notdevelop disease at all [23,24].
In the last 10 years, there have been substantial improve-ments in the detection of the only disease-specific marker ofdisease (i.e., PrPTSE) that finally translated into the develop-ment of novel diagnostic tools that have achieved enough sen-sitivity for assessing PrPTSE in easily accessible tissues or bodyfluids [25]. Among them, the in vitro amplification of the mis-folded prion protein has, in preliminary studies, successfullydetected PrPTSE in CSF [26,27], in nasal swab samples of spo-radic CJD [28] and urine of variant CJD [29] with no false-positive signals, while an adapted solid-state binding matrixassay is apparently able to detect PrPTSE in blood samples ofvariant CJD patients with over 70% sensitivity and 100%specificity [30]. As soon as these methods are fully validated,it would be possible to improve the correctness of an earlydiagnosis, thus allowing a faster enrolment of CJD patientsin clinical trials.
Attempts of therapy in patients with CJD and related dis-eases have been extensively reviewed in recent years [31-37],with the conclusion that none of the tested drugs has convinc-ingly shown a significant impact on the natural history of thedisease with the exception of the intraventricular infusion ofthe pentosan polysulfate (PPS) in variant CJD patients [38].To date, this conclusion still holds. This updated reviewfocuses on the appropriateness of these treatments with thehope that learning from past weaknesses will improve thefuture of therapy in prion diseases.
2. Past therapeutic attempts and rationales
Except for several and inconclusive reports on isolated casestreated with a variety of drugs (see [31] for a comprehensivereview), there are only five compounds that have been testedin comparative studies in patients with prion diseases.
2.1 AmantadineIn the early 70s, soon after the successful transmission of CJDto non-human primates suggested a viral origin of the disease,
Article highlights.
. Four randomized double-blind placebo-controlled clinicaltrial studies were attempted in Creutzfeldt--Jakobdisease (CJD) patients showing no efficacy, but provingthat clinical trials are feasible in CJD, though withsome difficulties.
. Analyses of past clinical trials revealed the importance ofrecruiting patients at national or international levelbecause of the rarity of disease, the difficulty inrecruiting patients at an early stage of disease and someannoyance by patients or caregivers in acceptingrandomization because of the rapidlyprogressive disease.
. Preclinical studies were often overinterpreted. Mostcompounds showed preventive rather than therapeuticeffects in preclinical studies but this finding was oftennot fully considered.
. There is only one preventive treatment in people at riskof developing prion disease. This ongoing trial withdoxycycline is in healthy carriers of the pathogenicmutation of the PRNP gene responsible for the fatalfamilial insomnia.
. Internationally recognized guidelines for performing validand relevant preclinical studies should be required forplanning future therapy in humans.
. It is necessary to develop international diagnostic criteriafor including CJD patients in clinical trials in a very earlystage by using new PrPTSE amplification techniques inbody fluids or easily accessible relevant tissues.
This box summarizes key points contained in the article.
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Table
1.History
andfuture
developments
ofdiagnostic
criteriaforsp
oradic
Creutzfeldt--Jakobdisease.
*Clinicalsignsaddedin
Europeancriteria.
CJD:Creutzfeldt--Jakobdisease;CSF:
Cerebrospinalfluid;EEG:Electroencephalogram;OM:Olfactory
mucosa;RT-Q
uIC:Realtimequackinginducedconversion.
The future for treating Creutzfeldt--Jakob disease
Expert Opinion on Orphan Drugs (2015) 3(1) 59
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therapy with the antiviral drug amantadine was comprehensi-bly attempted in a bunch of single CJD cases with somereported beneficial effects [39-41]. The rationale of two observa-tional studies [42,43] was to clarify the previously questionableeffect of the drug in CJD patients, despite the failure of pro-longing survival in experimental models of prion diseasewere already available (Table 2) [44,45]. Both studies concludedthat treatment did not substantially modify the course of dis-ease, although Terzano et al. [42] reported some clinicalimprovements. Formal clinical trials were likely not per-formed because of the great difficulties to recruit a reasonablenumber of patients in those years when only a small percent-age of CJD cases were recognized and no neurological centrehad the chance to observe more than a handful number ofpatients in years of activity. Because no clinical trials haveever been performed and preclinical studies with amantadinein animal models are limited, it is difficult to draw any defin-itive conclusion on the efficacy of this and other antiviraldrugs, such as acyclovir [46,47], vidarabine [48] and IFN [49] inCJD patients. However, with the current knowledge of thepathogenic mechanisms of prions and considering the avail-able, although scanty clinical studies, it is reasonable to con-clude that available antiviral therapies are ineffective in thetreatment of CJD patients.
2.2 FlupirtineIn 2004, Otto et al. [50] tested the effect of the non-opioid anal-gesic flupirtine versus placebo in 28 patients with CJD with theaim of determining the influence of the drug in the rate of cog-nitive decline. The study showed a transient beneficial effect offlupirtine in delaying the cognitive decline of CJD patients butno changes in survival times (Table 2). In in vitro studies, flupir-tine prevented apoptosis in neural cell culture exposed to a vari-ety of toxic agents, including A-beta and a short (21 aminoacids) fragment of PrP (PrP106-126) [51-53], but it had neverbeen tested in animal models of prion or other neurodegenera-tive disorders, making disputable its use in CJD patients. Theauthors did not comment on the rationale for the possible ben-eficial effect of flupirtine in delaying cognitive decline in CJDapart from reporting the in vitro cytoprotective activity.Otto et al., however, had the great merit to show that double-blind randomized controlled studies were feasible in CJD,despite the rarity of disease, the difficulties in getting a correctclinical diagnosis and the relative short clinical duration.
2.3 QuinacrineCompassionate therapy with quinacrine began > 10 years agosoon after the group of the Nobel Laureate Stanley Prusinerconfirmed a previous study [54], showing that this tricyclicderivative of acridine potently inhibits PrPTSE formation inscrapie-infected neuroblastoma cell cultures [55]. Becausequinacrine was used for decades in humans against malariaand crosses the blood--brain-barrier, Korth et al. [55] suggestedits immediate use in patients with CJD and related diseaseswithout waiting for confirmatory preclinical studies. In several
countries, the compassionate use of quinacrine in CJDpatients was initially done under the great pressure of familieswith the authorization of competent government authorities;in the USA, it was advertised in neurology journals, officialwebsites and by letters to the US neurologists. Overall, therationale for these observational studies were based on theantiprion effect of quinacrine in cell culture, its long andsafety use in humans and because it reaches the CNS. Treat-ment of isolated CJD or FFI patients with quinacrine showedeither no benefit [56-59] or a transient improvement of clinicalconditions [60-63], and observational studies gave ambiguousresults (Tables 2 and 3). Haik et al. [64] reported neither clinicalimprovement nor prolonged survival, Collinge et al. [65]
reported a transient response on neurological rating scales in afew patients but no effect in survival, while Geschwind et al.[66] reported a prolonged survival. All observational studieswith quinacrine started to recruit patients between 2000 and2001, just before the reported failure of quinacrine to prolongthe incubation periods in mice intracerebrally injected with aCJD-adapted strain [67]. Quinacrine inefficacy in animalmodelsof prion diseases was further confirmed in the followingyears [68-70]. Finally, in 2013 Geschwind et al. reported theonly randomized double-blind placebo-controlled clinical trial(RCT-DB) to quinacrine or placebo [66]. Patients were recruitedbetween 2005 and 2009, with the rationale that the sameauthors previously observed a positive effect of quinacrine inprolonging survival in CJD patients in an observationalstudy [66]. This study finally showed the inefficacy of quinacrineto improve survival in sporadic CJD patients (Tables 2 and 3)and likely represents the end of the therapeutic use of quinacrinein prion diseases.
2.4 DoxycyclineTetracycline antibiotics revert in vitro the protease resistanceof PrPTSE extracted from brain tissue of patients withCJD [71]. Doxycycline, a tetracycline derivative, shares thesame antiprion effect with the advantage of poor toxicityand of efficiently crossing the blood--brain barrier [72]. Basedon these observations, the group of Fabrizio Tagliavini atCarlo Besta Neurological Institute in Milan, Italy, pioneeredin 2002 the compassionate therapy with doxycycline forCJD patients (Tagliavini, pers. commun.). A few years later,De Luigi et al. [73] reported that doxycycline efficiently pro-longs the incubation period of hamsters peripherally inocu-lated with the 263K strain of scrapie and that theintracerebroventricular infusion of liposome-entrapped doxy-cycline in hamsters with early clinical signs delays diseaseduration confirming its potential use for human therapy.Data from observational studies in Italy [74] andGermany [33,75] also showed that treatment with doxycyclineextends between 4 and 7 months the survival of CJD patientscompared with historical controls (Tables 2 and 4). Thesefindings prompted an Italian-French RCT-DB Phase II studythat, however, did not confirm the positive findings of theobservational studies [76].
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Table
2.Attempts
oftherapyin
patients
withpriondiseases.
Drug
Studydesign
Ref.
Year
Country
Disease
Treated:
controls
Authorco
nclusion
Authors’rationale
Comments
Amantadine
Observational
[42]
1983
Italy
CJD
(likely
sporadic)
4:5
Noeffect
onsurvival
Partialclinicalbenefit
Antiviraleffect
Possible
beneficialeffects
oncase
reports
Absence
ofefficacy
on
incubationperiodsin
anim
almodelswas
alreadyavailable
atthe
timeofthestudies
[43]
1984
Italy
CJD
(likely
sporadic)
4:4
Noeffect
onsurvival
Noclinicalbenefit
Uncertainness
ofTerzano
etal.data
andpossible
beneficialeffectsoncase
reports
Flupirtine
RCT-DB
[50]
2004
Germ
any
Sporadic
and
geneticCJD
13:15
Noeffect
onsurvival
Benefitofcognitive
functions
Cytoprotectiveactivityin
vitroandin
vivo
on
neuronsinducedto
undergoapoptosis
Reductionofin
vitro
PrP106-126neurotoxicity
Nopreclinicalstudiesin
anim
almodels
Quinacrine
Observational
[64]
2004
France
Sporadic
and
variantCJD
32:125
(historical)
Noeffect
onsurvival
Invitroantiprionactivity
Possible
effect
inpatients
withvariantCJD
Thisstudybegunwhen
preclinicalstudiesin
anim
alstudieswere
not
yetreported
Open-label,
patient
preference
trial
(Observational)
[65]
2009
UK
Sporadic,iatrogenic,
variant,and
geneticCJD
32:69
Noeffect
onsurvival
Transientresponse
on
neurologicalrating
scalesin
4patients
Invitroantiprionactivity
RequestedbytheBritish
ChiefMedicalOfficer
Absence
ofefficacy
on
incubationperiodsin
anim
almodelswas
alreadyavailable
atthe
timeofthestudy
Observational
[66]
2013
USA
Sporadic
CJD
29:58
Increase
insurvival
Invitroantiprionactivity
Thisstudybegunwhen
preclinicalstudiesin
anim
alstudieswere
not
yetreported
RCT-DB(Phase
IIB)
[66]
2013
USA
Sporadic
CJD
23:28
Noim
provementin
2-m
onthssurvival
Noclinicalim
provement
Increase
survivalin
the
observationalstudy
previouslyconductedby
theAuthors
Absence
ofefficacy
on
incubationperiodsin
anim
almodelswas
alreadyavailable
atthe
timeofthestudy
Doxycycline
Observational
[74]
2008
Italy
CJD
(likely
sporadic)
21:78
Increase
survival
Extendedsurvivalin
experimentalmodels
-
[33]
2009
Germ
any
Sporadic
and
geneticCJD
51:not
reported
Increase
survival
Extendedsurvivalin
experimentalmodels
Controlswere
takenfrom
historicalcollections
RCT-DB(Phase
II)[76]
2014
Italyand
France
Sporadic,
iatrogenic,
variantand
geneticCJD
62:59
Noeffect
onsurvival
Extendedsurvivalin
observationalstudies
-
CJD:Creutzfeldt--Jakobdisease;GSS:Gerstm
ann--Straussler--Scheinkerdisease;PPS:Pentosanpolysulfate;RCT-DB:Randomizeddouble-blindplacebo-controlledclinicaltrial.
The future for treating Creutzfeldt--Jakob disease
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2.5 Intraventricular infusion of PPSAttempts of therapy with intraventricular infusion of PPS(iPPS) began in January 2003 [77] soon after Doh-Ura et al.reported in an international meeting in Paris (2002 [78],then published in 2004 [69]) the successful effect of this treat-ment in rodents experimentally infected with different strainsof prions. The antiprion efficacy of intraperitoneal adminis-tration of PPS and other polyanionic compounds was estab-lished since 1984 [79] and then confirmed in other studies inperipherally or intracerebrally scrapie-infected mice or ham-sters [80], but its efficacy was limited to treatment given justbefore or after prion inoculation, a situation non-applicablefor human therapy. Despite these experimental data, therapywith oral administration of low molecular weight PPS wasreported in eight Japanese CJD patients [81] with no success.
The finding that iPPS was modestly effective even whengiven at the beginning of clinical signs in prion-infectedmice reawaken interest in this drug for human therapy [69].In 2003, Dealler and Rainov [82] reported on the potentialtherapeutic use of iPPS for CJD patients based on the exper-imental findings and on the poor side effects of PPS infusion.Treatment was then given to several other patients with vari-ous forms of CJD. In 2007, Rainov et al. [83] in reviewing26 attempts of therapy with iPPS (4 variant, 8 sporadic,7 iatrogenic and 1 genetic CJD; 5 GSS and 1 unspecifiedcase) reported that it appears reasonably safe but survivalwas convincingly prolonged only in variant CJD. Bone et al.[84] and Tsuboi et al. [85] reached similar conclusions in British(3 variant, 2 iatrogenic CJD; 2 GSS) and Japanese (6 sporadic,2 iatrogenic and 2 genetic CJD; 1 GSS) patients. A recentoverall picture of the effect of iPPS in prolonging diseaseduration in variant British CJD patients showed that four offive treated patients survived well beyond untreated patients(Tables 2 and 5) [38].
3. Past clinical trials: strategies anddifficulties
Only 4 RCT-DB studies were attempted in CJD patientsdespite 14 drugs were occasionally tested in the last 40 years [31].All RCT-DB studies showed no efficacy of the investigateddrugs, but they prove that clinical trials are also feasible inCJD, though with some difficulties. The analysis of the prob-lems encountered in designing and interpreting the trialsmight contribute to improve future clinical experimentations.
In the following pages, we present the major difficultiesthat challenged the design of RCT-DB studies for prion dis-eases, such as the definition of the end points, the approachfor recruiting a significant number of patients, the diagnosticcriteria for including or excluding patients to the study, thedesigning of the randomized trial and the ethical considera-tions for obtaining the consent to the experimentation or forusing a placebo in an otherwise deadly disease.T
able
2.Attempts
oftherapyin
patients
withpriondiseases(continued).
Drug
Studydesign
Ref.
Year
Country
Disease
Treated:
controls
Authorco
nclusion
Authors’rationale
Comments
Intraventricular
infusionofPPS
Review
[83]
2007
-Sporadic,iatrogenic,
variantandgenetic
CJD;GSS
26:0
Increase
survivalin
variantCJD
Extendedsurvivalin
experimentalmodelswith
direct
PPSbrain
infusions
Nocontrolpopulation
Observational
[84]
2008
UK
Iatrogenicand
variantCJD;GSS
7:0
Possible
positive
effect
onsurvival
invariantCJD
Extendedsurvivalin
experimentalmodelswith
direct
PPSbrain
infusions
Increase
survivalin
other
observationalstudies
Controlswere
takenfrom
historicalcollections
Observational
[85]
2009
Japan
Sporadic,iatrogenic
andgeneticCJD;GSS
11:0
Noeffect
on
neurological
deficits;possible
extendedsurvival
Extendedsurvivalin
experimentalmodelswith
direct
PPSbrain
infusions
Nocontrolpopulation
Case
report
andreview
[38]
2014
UK
VariantCJD
5:171
Extendedsurvival
on4/5
Extendedsurvivalin
experimentalmodelswith
direct
PPSbrain
infusions
4of5treatedpatients
hadasurvivallongerthat
allotherhistoricalcases
CJD:Creutzfeldt--Jakobdisease;GSS:Gerstm
ann--Straussler--Scheinkerdisease;PPS:Pentosanpolysulfate;RCT-DB:Randomizeddouble-blindplacebo-controlledclinicaltrial.
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3.1 End point(s) and minimum clinically relevant
differencesPrimary end points represent the bases for determining thesample size of a clinical trial. Except for the flupirtine trial [50],which was designed to detect cognitive (ADAS-Cog test) dif-ferences between baseline and best score under treatment, theprimary end points of the other three trials were time ofsurvival, though with some differences among studies in termsof minimum clinically relevant differences (Table 6).Collinge et al. (quinacrine) [65] were looking at a reductionin 2-year mortality from 50 to 22%; Geschwind et al. (quin-acrine) [66] at doubling of mean survival from 0.9 to1.8 months after 2 months from randomization; Haik et al.(doxycycline) [76] at doubling survivors after 1 year of ran-domization from 30 to 60% (Italian patients) or increasingmean survival from 6.2 to 11 months (French patients). Thecalculated sample sizes varied accordingly, but overall itranged between 30 and ‡ 160 patients and took between2 and 4 years for recruiting this significant number of patients(Table 6). Patients were followed-up in a single neurologicalcenter for the flupirtine [50] and both the US [66] andUK [65] quinacrine studies, while for the doxycycline study [76]
patients were recruited and followed-up in either three centers(Italian patients) or by multiple and not predetermined neu-rological units for French patients. Secondary end pointsaim to assess possible clinical improvements related to therapywere considered in all studies but were finally difficult to eval-uate mostly because of the serious and advanced clinical phaseof enrolled patients.
Considering the rarity of CJD, the number of patients thatneeds to be recruited requires national, or better international-based studies for speeding the completion of clinical trials. Onthe other hand, the recruitment of patients on national orinternational base might prevent simultaneous investigationsof different drugs with delay in testing novel and promisingtherapeutic approaches.
Sample size is strongly influenced by the choice of the min-imum clinically relevant differences; conspicuous clinicaleffects require small sample size but might be unrealistic, beresponsible for closing the trial for futility (improbable todetect prefixed effects) and therefore undermining future eval-uations of that specific treatment. On the other hand, minorbut realistic clinical improvements would require a large andunfeasible number of patients. On top of that, the compute
Table 3. Quinacrine.
BSE: Bovine spongiform encephalopathy; CJD: Creutzfeldt--Jakob disease; ic: Intracerebral; ip: Intraperitoneal; RCT-DB: Randomized double-blind placebo-controlled
clinical trial; RML: Rocky mountain laboratory; Ukn: Unknown.
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Table
4.Tetracyclic
compounds.
BSE:Bovinespongiform
encephalopathy;
CJD:Creutzfeldt--Jakobdisease;GSH:GoldenSyrianhamster;ic:Intracerebral;im
:Intramuscular;IDX:4’-iodo-4’-deoxy-doxorubicin;RCT-DB:Randomizeddouble-blind
placebo-controlledclinicaltrial;sc:Subcutaneous;
Ukn:Unknown.
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of the sample size needs to account for multiple testing ininterim analyses for an ethical assessment on whether to ter-minate the study earlier than planned because of consistentevidences of futility, efficacy or safety.
3.2 Diagnostic criteriaThe presence of sporadic, genetic, iatrogenic and variantprion diseases as well as criteria for diagnostic accuracy (possi-ble, probable and definite) based upon clinical, laboratory andinstrumental analyses (Table 1) require the a priori selection ofpatients based on disease variability and diagnostic accuracy.
Two studies (UK quinacrine [65] and doxycycline [76])included all forms of probable or definite prion diseases, thoughwith minor differences, while the other two (flupirtine [50] andUS quinacrine [66]) selected only probable or definite sporadicCJD patients. However, in these two last studies, > 5% ofenrolled sporadic CJD patients finally were classified as geneticprion diseases. This is because the result of the genetic screeningrequires time and is therefore available only after randomizationand family history is often unremarkable and does not reveal thesuspicion of a genetic trait in these patients.
The authors of the flupirtine study [50] finally decided toinclude genetic patients in the analyses of the study whilethose of the US quinacrine [66] did not. Because clinical fea-tures of genetic prion diseases are heterogeneous, mostlydepending on the type of PRNP mutation, it is reasonableto include only genetic forms of CJD (i.e., the E200K and
V210I mutations) strongly resembling sporadic CJD for clin-ical presentation, age at onset and disease duration, andexclude others (i.e., GSS or FFI) that significantly differfrom the sporadic forms. This last approach was adopted inthe doxycycline study [76] for the Italian patients.
All studies included only patients with high (> 90%) diag-nostic accuracy (i.e., probable or definite cases according tointernational classifications). This obligatory strategy, how-ever, has the great limitation of including most of the patientsin an advanced stage of disease and, therefore, with short nat-ural survival [86]. In our data set from over 1000 definite spo-radic CJD cases collected since 1993 during the nationalprogram of surveillance, the median interval between onsetand in vitam diagnosis of ‘probable’ CJD was 3 months(interquartile range, 3 months) and from the diagnosis ofprobable to death only 1 month (interquartile range,3 months). The two major determinants of survival, that is,codon 129 polymorphism and PrPTSE isotype [12], influencethe interval between onset and diagnosis of ‘probable’ butnot from here to death. These data indicate the urgency ofrevising diagnostic criteria for the inclusion of CJD patientsin future clinical trials (Table 1).
3.3 RandomizationThe golden standard for clinical trials is the allocation ofpatients to experimental arms by a randomized procedurefor minimizing biases caused by unknown confounding
Table 5. Intraventricular infusion of pentosan polysulfate.
CJD: Creutzfeldt--Jakob disease; GSS: Gerstmann--Straussler--Scheinker disease; RML: Rocky mountain laboratory.
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Table 6. Clinical trials in prion diseases.
Drug (vs placebo) Flupirtine Quinacrine Quinacrine Doxycycline
Ref. and year ofpublication
[50], 2004 [65], 2009 [66], 2013 [76], 2014
Aim Efficacy Efficacy and safety Efficacy Efficacy and tolerabilityPrimary end points Difference in cognitive
performance (ADAS-Cog)between baseline andtreatment
Survival and clinicalimprovement or lack ofdeterioration
Survival at 2 monthsfrom randomization
Survival time fromrandomization
Type of study RCTNational (Germany)
Patient-preference trial-partially randomized butfinally an observationalstudyNational (UK)
RCTNational (USA)
RCTInternational (Italy andFrance)
Inclusion criteria Probable sporadic CJDwho scored ‡ 50% in atleast 2 of 12 subtests ofADAS-Cog andGoettingen CJD dementiatests
All definite or probablehuman prion diseases
Definite or probablesporadic CJD
Italy: Definite or probablesporadic and genetic CJDwith disease duration£ 6m;France: All definite orprobable human priondiseases
Randomization/blinding Yes/double-blinding Choice betweenrandomization or norandomization/double-blinding
Yes/double-blindingfor the first 2 months,then open
Yes/double-blinding
Procedure ofrandomization
Simple Stratified by type ofdisease
Stratified by theBarthel Index Score
Italy: Minimizationmethod by sex, age atonset, months since CJDclinical onset, codon 129PRNP genotype.France: Simple
Randomization ratio 1:1 1:1 1:1 1:1Informed consent(provided by)
Yes (unspecified) Yes (patients or familymembers or independentneurologists)
Yes (patients or legallyauthorizedrepresentative)
Yes (patients orcaregivers)
Minimum clinicalsignificant difference
Difference (‡ 4) betweenbaseline and treatment(ADAS-Cog)
Reduction in 2 yearmortality from 50 to 22%
Increase in meansurvival time sincerandomization from0.9 to 1.8 months
Italy: Doubling thepercentage of survivors at1 year (from 30 to 60%);France Increase in meansurvival time since onsetfrom 6.2 to 11 months
a; statistical power 0.05; 0.70 0.05; 0.80 0.05; 0.80 0.05; 0.80;Calculated sample size 30 160 60 Italy: 63
France: sequential design,interim analysis after first80 patients enrolled andevery 20 patientsthereafter
Number of patientsassessed for eligibility orreferred to the centres
682 (assessed foreligibility)
221 (referred to thenational Prion Clinic)
425 (referred to theUCSF)
103 in Italy and 560 inFrance (screened foreligibility)
Number of patientsenrolled
28 84 54 121 (Italy: 55; France: 66)
% of enrolled patients 5% 38% 47% Italy: 53%; France:12%Number of patients perarm
Flupirtine: 13Placebo: 15
Chose immediatequinacrine: 24Chose no quinacrine: 59Chose random allocation:1
Quinacrine: 23Placebo: 28
Doxycycline: 62Placebo: 59
Status Completed Closed Completed Stopped for futility at firstinterim analysis
CJD: Creutzfeldt--Jakob disease; RCT: Randomized controlled trial.
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factors, immeasurable variables or both. Informed consent isasked to patients, often caregivers, when patients have seriouscognitive deficits, who need to accept the gamble of beingassigned to the arm of the putative active drug. This difficultchoice is clearly exemplified in the UK quinacrine study [65],where patients (or the caregivers) had the choice to take thedrug, not take it or accept randomization to immediate quin-acrine versus 6-months deferred quinacrine. Only 2 of84 enrolled patients chose randomization, 23 immediatequinacrine and 59 no quinacrine resulting in an observationalrather than a RCT study. Interestingly, the most and leastseverely affected patients did not choose treatment with quin-acrine. In the US quinacrine [66], flupirtine [50] and doxycy-cline [76] studies, however, randomization was successfulsuggesting that RCT-DB studies are feasible, though withsome difficulties. In the US quinacrine study [66], 87% of sur-viving patients in the placebo arm and 100% in the quina-crine arm returning for the 2-month visit and preferredtreatment with quinacrine in contrast with the trend of theBritish study [65], where only 27% of recruited patients askedfor the putative active drug.
A variety of randomization procedures were adopted inCJD trials; simple random procedures in the flupirtine [50]
and doxycycline (French patients) [76] studies, stratified bytype of disease in the UK quinacrine [65], stratified by perfor-mance in daily living activities (Barthel Index) in the US quin-acrine [66], and minimization by sex, age at onset, monthssince CJD clinical onset and codon 129 PRNP genotype inthe doxycycline (Italian patients) study [76]. This last random-ization procedure was adopted for improving the control ofknown predictors of survival [12]. Despite differences in therandomization procedures, all studies adopted the question-able choice, in a fatale and untreatable disease, of a 1:1 ratiobetween the active drug arm and the placebo arm.
Overall, these data indicate caution in oversimplifying theexperience of a single study in terms of feasibility in conduct-ing an RCT-DB study or in accepting treatment with anexperimental drug, though with uncertain efficacy, by patientswith CJD or their caregivers.
4. Ongoing or future possible trials
Despite the appearance of increasing number of scientificarticles reporting novel therapeutic approaches in in vitro orin vivomodels of prion diseases [35,87,88], the only ongoing clin-ical trials in human prion diseases is limited to the doxycyclinepreventive treatment in healthy members of a large Italian fam-ily affected by FFI [36,89]. The only other treatments in advancedstage for a first-in-human safety study are, to the best of ourknowledge, the MRC Prion Unit’s PRN100 antibody [90,91]
and the oligomer modulator Anle138b [92].
4.1 Doxycycline preventive treatment in FFIFFI is a rare genetic prion disease linked to the presence of theD178N mutation coupled with methionine at the
polymorphic codon 129 (D178N/M129) of the PRNP geneand characterized by severe insomnia, autonomic disturbances,cognitive changes, ataxia and endocrine manifestations [93,94].Most of mutated subjects develop disease during their lifetime,usually in the 50s, and inevitably die in about 12months [93,94].Because therapy is unavailable, Forloni et al. proposed tomembers of one large affected kindred in northern Italy alife-long preventive therapy with doxycycline [36,89], which inexperimental models of prion diseases efficiently delay onsetof disease if given before onset of clinical signs [73]. Currently,11 healthy carriers and 19 non-carriers belonging to the abovekindred and born between 1958 and 1969 are blinded treatedwith a daily dose of 100 mg doxycycline (mutated carriers) orplacebo (non-mutated subjects) for 11 years. Young familymembers will be included in the study as soon as they reach41 years of age. Participants of the study are requested toundertake a complete neurological examination every 2 yearsincluding neuropsychological assessment, autonomic nervoussystem assessment, polysomnographic EEG recording, actigra-phy, brain MRI and FDG-PET [95]. The aim of this study is toassess the delay (or prevention) of disease onset in people whoare predestined to develop FFI in their middle age. The ratio-nale of this trial is based on the observation in animal modelsthat therapy with doxycycline and all other antiprion drugs ismuch more effective when given before clinical onset [73].The ambitious result of the study is to observe a 50% reduc-tion of mortality in treated carriers over 10 years of treatmentwith respect to historical familial data. The success of thisstudy will open the possibility of preventive treatment ingenetic prion diseases [22] and eventually in people at highrisk of developing iatrogenic CJD [9].
4.2 MRC Prion Unit’s PRN100 antibodyIn 2003, White et al. [96] showed that ICSM35 andICSM18 mAbs directed against the a-helix-1 of PrP [97]
strongly delay onset of scrapie disease in intraperitoneallyinfected mice. Although treatment was only effective if startedbefore clinical onset, the finding that these antibodies did notcause any brain damages fostered the possibility of their use forhuman therapy [98]. The MRC Pion Unit followed this line ofthought and developed a human analogue of ICSM18 (namedPRN100), which showed no CNS toxicity in cynomolgusmacaques at intravenous doses (up to 200 mg/kg) suggestinga safe use for human studies [90]. With these bases, the MRCPrion Unit (UK) has designed a clinical trial, waiting for finalapprovals, to simultaneously evaluate safety and efficacy on asmall number of CJD patients [91]. There are, however, issuesthat need clarification. One is on the real efficacy of passiveimmunization therapy in prion diseases. Petsch et al. [99]
showed that treatments with the mAb W226, which binds tothe same epitopes of ICSM18, is unable to protect micefrom an intraperitoneal prion infection, arguing that the ther-apeutic efficacy likely depends also on the genetic backgroundof the host (Petsch et al. [99] and White et al. [96] used differentstrains of mice) or differences in the antibody sequences
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(ICSM18 and W226 show significant differences in thesequence of the hypervariable complementarity determiningregions), which might influence the half-life of the compoundor its efficacy to reach the CNS. The other issue is safety,which remains unsettled because of contrasting experimentaldata between mAbs binding overlapping epitopes on a-helix-1of PrP. ICSM18 [100], D18 [101] and PRN100 [90] look safewhile POM1 shows severe neuronal loss [102]. Understandingthe mechanisms that differentiate mAbs with the same bindingepitopes on PrP in terms of efficacy and safety is mandatorybefore starting any clinical trial in patients with CJD.
4.3 3-(1,3-Benzodioxol-5-yl)-5-(3-bromophenyl)-1H-
pyrazole (anle138b)Anle138b is a synthetic compound with a di-phenyl-pyrazolestructure that selectively inhibits pathological oligomer accu-mulation of PrPTSE and a-synuclein without interferingwith the physiological functions of the non-pathologicalmonomeric isoforms [103]. The finding that anle138b is effec-tive in preventing PrPTSE formation from different prionstrains and a-synuclein suggests that it targets commonstructure-dependent epitopes responsible for the oligomericformation of pathological proteins. Experimental data alsoshowed that anle138b prolongs the incubation period ofscrapie-infected mice and inhibits disease progression in aParkinson mouse model, even when treatment is started afterdisease onset [103,104]. The spin-off company (MODAGGmbH) from the Ludwig-Maximilians-Universitat Munchenand the Max Planck Society plans to develop anle138b up tomarket maturity for a Phase I/II clinical trial in CJD andother neurodegenerative diseases [105]. Although the com-pound has an excellent oral bioavailability, efficiently bypassesthe blood--brain barrier and shows no toxicity at therapeuticdoses, it would be wise to improve preclinical data (i.e., prov-ing efficacy in mice with different genetic backgrounds andinoculated with a variety of prion strains, including sporadicCJD) before its use in human therapy.
5. Conclusions
In the last few years, treatment of patients with CJD has beensuccessfully approached with RCTs [50,66,76]. Although theoutcome of these initial trials was substantially negative,they establish the feasibility of RCTs in rare and rapidly pro-gressive diseases such as CJD. The failure of these trialsdepends on several factors, which include the difficulty of anearly clinical diagnosis and the consequent short intervalbetween treatment and death [86], the variability of clinicalduration of illness [12], the absence of reliable disease-modifiermarkers [25] and validated clinical scales [106,107] and often theoverinterpretation of preclinical data.Patients are usually recruited when clinical signs and instru-
mental features fulfill the diagnosis of probable CJD (Table 1),which occurs relatively late in the course of illness and it isinevitably accompanied by an irreversible brain damage.
Novel diagnostic procedures, based on the signal amplifica-tion of the misfolded prion protein in body fluids, that is,CSF [26,27] and urine [29], or easily accessible tissues, such asnasal olfactory mucosa [28] would likely anticipate the timefor an accurate diagnosis of CJD. Whether PrPTSE in bodyfluids and nasal olfactory mucosa would be a useful markerfor monitoring the effect of future therapy is still unknown.
Variability in disease duration depends on known factors(codon 129 polymorphism, type of PrPTSE deposition in theCNS, gender and age at onset) [12] that were partially consid-ered during randomization [76], but survival significantly varieseven within these categories [12] for yet unknown reasons,likely including the poorly controllable supportive care of fam-ily members [108]. A boost in searching for such factors is com-ing from genome-wide association studies, which might soonidentify novel genes able to modulate disease duration [109,110].
Finally, the rationales leading to the use of compoundsentering into human therapy were either poorly supportedby preclinical data or these studies were overinterpreted. Quin-acrine, for example, was initially given to CJD patients basedonly on in vitro studies [54,55] without waiting for confirmatoryefficacy in animal models, which finally did not confirm theantiprion effect [67,68] and doxycycline was given to patientslate in the course of disease despite preclinical studies showedonly modest, if any, therapeutic effect in early diseasedprion-infected rodents [73].
6. Expert opinion
The future of therapeutic intervention in CJD starts from theidentification of novel compounds with strong antiprioneffects. Based on the only undisputed pathogenic mechanismof disease, novel drugs are usually selected for their action onhalting PrPTSE formation or increasing its clearance byin silico technology [111] or through the screening of largechemical libraries containing hundreds of thousands ofcompounds [111-115]. These ongoing activities have alreadyidentified a number of potential antiprion compounds thatwould now being further tested for determining their efficacyin animal models of prion disease, CNS bioavailability andtoxicity before their possible use in humans. Other potentialantiprion candidates are biological products, either in termsof passive or active immunization with mAbs targeting spe-cific PrPC epitopes [116-118], by using small interfering RNAsthat downregulate PrPC expression [119,120], or targeting novelpathway of neurodegeneration [121,122]. Immunological thera-pies in Alzheimer’s disease, another protein misfolding CNSpathology, yield some positive results, which were, however,so far overcome by serious safety issues [123,124]. The futureof immunological treatments in neurodegenerative diseasesis promising but some adjustments of the molecules are likelyneeded to minimize adverse effects.
Prion diseases have the great advantage over other neurode-generative diseases of excellent animal models that mimic clin-ical, pathological and biochemical features of human diseases,
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but their use for the design and interpretation of preclinicalstudies were often poorly performed or misinterpreted.A boost in getting valid and relevant preclinical studies for plan-ning future therapy in humans would come from the develop-ment of an ad hoc internationally recognized guideline forpreclinical studies in prion diseases based on available check-lists [125]. This guideline should cover critical aspects that havebeen poorly followed in past preclinical prion studies, such asthe adoption of a randomized procedure for the allocation ofanimals, the use of appropriate controls, the blindness of theinvestigators during the experiment and a power calculationperformed a priori to determine sample size. Other importantaspects should include the use of more than one model of prioninfection considering that available data showed that drugsmight be effective in one model and not in others [126-129], thechoice of relevant models, for example, mice [130] or bankvoles [131] infected with and reproducing human PrPTSE
type 1 or type 2 [8] rather than animal strains, the route of infec-tion and the need of confirming efficacy by independentresearch groups. Finally, it is important to define the relevanttiming and route of treatment administration in relation tothe aim of the study. Researchers often inferred that drugswith strong preventive effects in preclinical studies, that is,given during the preclinical phase of disease, would have thera-peutic effects despite countless evidences that treatments areineffective or poorly effective when given at early clinical phasesor even close to onset of disease [69,73,80]. Overall, these preclin-ical studies show that brain damage is already too severe at onsetof clinical signs for attempting any possible therapy and there-fore suggest that any potential treatment in CJD patientsshould begin as soon as possible. This is in contrast with pastclinical trials where patients were enrolled only when they ful-filled the diagnostic criteria of probable CJD, which inevitablyoccurs at a late stage of disease [86]. Thus, it would be necessaryto develop novel international diagnostic criteria for includingCJD patients in clinical trials in a very early stage by using thenew approaches of PrPTSE amplification and identification inthe CSF [26,27], urine [29] or olfactory mucosa (Table 1) [28].Although these assays need further validations before their usein diagnostic criteria for surveillance, they might be adequatefor the selection and inclusion of patients in clinical trials atan early stage of disease. Autopsy should be performed in allenrolled patients to confirm clinical diagnosis and for deter-mining PrPTSE type accumulation, which is an importantdeterminant of survival in sporadic CJD [12].
Future clinical studies in CJD need some rethinking interms of the choice of end points, the design of randomized
trials and the ethical considerations for obtaining the consentto the experimentation or for using a placebo in an otherwisedeadly disease [132,133].
Survival is a robust end point in prion diseases but drugs,such as antibiotics (e.g., doxycycline), able to improve thegeneral conditions of terminally ill patients, might give false-positive outcomes. The identification of disease-modified bio-markers, the use of internationally validated prion ratingscales or both might represent valid alternatives [106,107]. How-ever, consensus is needed on the minimal clinically importantchanges because a high expectancy [134] might be unrealisticand will make future trials ending for futility, or be ethicallycontroversial [132,133].
Improvement in the design of trials for rare, fatal and rap-idly progressive diseases such as CJD is strongly needed, espe-cially if treatments with striking efficacy become available. Insuch circumstances, study designs should rapidly prove or dis-prove efficacy. Randomized trials have the advantage of pre-venting biases but there are still uncertainties whetherrandomization is always necessary [135] or ethicallyacceptable [133,136-138]. It is of note that 33% of the pivotal tri-als of orphan drugs for neurological diseases approved by theUS FDA did not use placebo controls, 27% were not doubleblind and 12% were not randomized [139]. Properly collectedhistorical controls might be a valid alternative [133], but biasesin terms of selection of patients based on those who consent totake the active drugs and assessment of primary end pointsshould be considered.
Acknowledgments
We acknowledge funding from the Ministry of Health,National Centre for Disease Prevention and Control, CentralActions ‘Sorveglianza della Malattia di Creutzfeldt--Jakob’.We thank D Meloni for critical reading of the manuscriptand A Garozzo for technical support.
Declaration of interest
The Italian Ministry of Health has supported this work. Theauthors have no other relevant affiliations or financial involve-ment with any organization or entity with a financial interestin or financial conflict with the subject matter or materials dis-cussed in themanuscript. This includes employment, consultan-cies, honoraria, stock ownership or options, expert testimony,grants or patents received or pending or royalties.
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BibliographyPapers of special note have been highlighted as
either of interest (�) or of considerable interest(��) to readers.
1. Gibbs CJ, Gajdusek DC, Asher DM,
et al. Creutzfeldt-Jakob disease
(spongiform encephalopathy):
transmission to the chimpanzee. Science
1968;161:388-9
2. Alpers MP. The epidemiology of kuru:
monitoring the epidemic from its peak to
its end. Philos Trans R Soc Lond B
Biol Sci 2008;363:3707-13
3. Detwiler LA, Baylis M. The
epidemiology of scrapie. Rev Sci Tech
2003;22:121-43
4. Brown P, Cathala F, Gajdusek DC.
Creutzfeldt-Jakob disease in France: III.
Epidemiological study of 170 patients
dying during the decade 1968-1977.
Ann Neurol 1979;6:438-46
5. Masters CL, Harris JO, Gajdusek DC,
et al. Creutzfeldt-Jakob disease: patterns
of worldwide occurrence and the
significance of familial and sporadic
clustering. Ann Neurol 1979;5:177-88
6. Will RG, Alperovitch A, Poser S, et al.
Descriptive epidemiology of Creutzfeldt-
Jakob disease in six European countries,
1993-1995. EU collaborative study group
for CJD. Ann Neurol 1998;43:763-7
7. Ladogana A, Puopolo M, Croes EA,
et al. Mortality from Creutzfeldt-Jakob
disease and related disorders in Europe,
Australia, and Canada. Neurology
2005;64:1586-91
8. Poggiolini I, Saverioni D, Parchi P.
Prion protein misfolding, strains, and
neurotoxicity: an update from studies on
Mammalian prions. Int J Cell Biol
2013;2013:910314
9. Brown P, Brandel JP, Sato T, et al.
Creutzfeldt-Jakob disease, final
assessment. Emerg Infect Dis
2012;18:901-7
10. Ward HJ, Everington D, Cousens SN,
et al. Risk factors for variant Creutzfeldt-
Jakob disease: a case-control study.
Ann Neurol 2006;59:111-20
11. Graziano S, Pocchiari M. Management
and prevention of human prion diseases.
Curr Neurol Neurosci Rep 2009;9:423-9
12. Pocchiari M, Puopolo M, Croes EA,
et al. Predictors of survival in sporadic
Creutzfeldt-Jakob disease and other
human transmissible spongiform
encephalopathies. Brain
2004;127:2348-59
.. Reports the determinants of survival in
Creutzfeldt--Jakob disease
(CJD) patients.
13. Zerr I, Kallenberg K, Summers DM,
et al. Updated clinical diagnostic criteria
for sporadic Creutzfeldt-Jakob disease.
Brain 2009;132:2659-68
14. Geschwind MD, Shu H, Haman A,
et al. Rapidly progressive dementia.
Ann Neurol 2008;64:97-108
15. Collins SJ, Sanchez-Juan P, Masters CL,
et al. Determinants of diagnostic
investigation sensitivities across the
clinical spectrum of sporadic Creutzfeldt-
Jakob disease. Brain 2006;129:2278-87
16. Heath CA, Cooper SA, Murray K, et al.
Diagnosing variant Creutzfeldt-Jakob
disease: a retrospective analysis of the
first 150 cases in the UK. J Neurol
Neurosurg Psychiatry 2011;82:646-51
17. Sanchez-Juan P, Green A, Ladogana A,
et al. CSF tests in the differential
diagnosis of Creutzfeldt-Jakob disease.
Neurology 2006;67:637-43
18. Zerr I, Pocchiari M, Collins S, et al.
Analysis of EEG and CSF
14-3-3 proteins as aids to the diagnosis
of Creutzfeldt-Jakob disease. Neurology
2000;55:811-15
19. Green AJ, Thompson EJ, Stewart GE,
et al. Use of 14-3-3 and other brain-
specific proteins in CSF in the diagnosis
of variant Creutzfeldt-Jakob disease.
J Neurol Neurosurg Psychiatry
2001;70:744-8
20. Summers DM, Collie DA, Zeidler M,
Will RG. The pulvinar sign in variant
Creutzfeldt-Jakob disease. Arch Neurol
2004;61:446-7
21. Chitravas N, Jung RS, Kofskey DM,
et al. Treatable neurological disorders
misdiagnosed as Creutzfeldt-Jakob
disease. Ann Neurol 2011;70:437-44
22. Kovacs GG, Puopolo M, Ladogana A,
et al. Genetic prion disease: the
EUROCJD experience. Hum Genet
2005;118:166-74
23. Pocchiari M, Poleggi A, Puopolo M,
et al. Age at death of Creutzfeldt-Jakob
disease in subsequent family generation
carrying the E200K mutation of the
prion protein gene. PLoS One
2013;8:e60376
24. Ladogana A, Puopolo M, Poleggi A,
et al. High incidence of genetic human
transmissible spongiform
encephalopathies in Italy. Neurology
2005;64:1592-7
25. Properzi F, Pocchiari M. Identification of
misfolded proteins in body fluids for the
diagnosis of prion diseases. Int J
Cell Biol 2013;2013:839329
26. Atarashi R, Satoh K, Sano K, et al.
Ultrasensitive human prion detection in
cerebrospinal fluid by real-time quaking-
induced conversion. Nat Med
2011;17:175-8
. Development of a novel and powerful
diagnostic test based on the detection
of PrPTSE in cerebrospinal fluid (CSF).
27. McGuire LI, Peden AH, Orr�u CD, et al.
Real time quaking-induced conversion
analysis of cerebrospinal fluid in sporadic
Creutzfeldt-Jakob disease. Ann Neurol
2012;72:278-85
. Development of a novel and powerful
diagnostic test based on the detection
of PrPTSE in CSF of sporadic
CJD patients.
28. Orr�u CD, Bongianni M, Tonoli G, et al.
A test for Creutzfeldt-Jakob disease using
nasal brushings. N Engl J Med
2014;371:519-29
. Development of a novel and powerful
diagnostic test based on the detection
of PrPTSE in the olfactory mucosa of
sporadic and genetic CJD patients.
29. Moda F, Gambetti P, Notari S, et al.
Prions in the urine of patients with
variant Creutzfeldt-Jakob disease. N Engl
J Med 2014;371:530-9
. Development of a novel and powerful
diagnostic test based on the detection
of PrPTSE in urine of variant
CJD patients.
30. Jackson GS, Burk-Rafel J, Edgeworth JA,
et al. Population screening for variant
Creutzfeldt-Jakob disease using a novel
blood test: diagnostic accuracy and
feasibility study. JAMA Neurol
2014;71:421-8
31. Stewart LA, Rydzewska LHM,
Keogh GF, et al. Systematic review of
therapeutic interventions in human prion
disease. Neurology 2008;70:1272-81
.. A detailed overview of treatment
attempts in CJD.
V. Vetrugno et al.
70 Expert Opinion on Orphan Drugs (2015) 3(1)
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ert O
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on o
n O
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rugs
Dow
nloa
ded
from
info
rmah
ealth
care
.com
by
Inst
ituto
Sup
erio
re d
i San
ita o
n 12
/23/
14Fo
r pe
rson
al u
se o
nly.
32. Sim VL, Caughey B. Recent advances in
prion chemotherapeutics. Infect Disord
Drug Targets 2009;9:81-91
33. Zerr I. Therapeutic trials in human
transmissible spongiform
encephalopathies: recent advances and
problems to address. Infect Disord
Drug Targets 2009;9:92-9
34. Appleby BS, Lyketsos CG. Rapidly
progressive dementias and the treatment
of human prion diseases.
Expert Opin Pharmacother 2011;12:1-12
35. Sim VL. Prion disease: chemotherapeutic
strategies. Infect Disord Drug Targets
2012;12:144-60
36. Forloni G, Artuso V, Roiter I, et al.
Therapy in prion diseases. Curr Top
Med Chem 2013;13:2465-76
37. Roettger Y, Du Y, Bacher M, et al.
Immunotherapy in prion disease.
Nat Rev Neurol 2013;9:98-105
38. Newman PK, Todd NV, Scoones D,
et al. Postmortem findings in a case of
variant Creutzfeldt-Jakob disease treated
with intraventricular pentosan
polysulfate. J Neurol
Neurosurg Psychiatry 2014;85:921-4
39. Braham J. Jakob-Creutzfeldt disease:
treatment by amantadine. Br Med J
1971;4:212-13
40. Sanders WL, Dunn TL.
Creutzfeldt-Jakob disease treated with
amantadine. A report of two cases.
J Neurol Neurosurg Psychiatry
1973;36:581-4
41. Braham J. Amantadine in the treatment
of Creutzfeldt-Jakob disease. Arch Neurol
1984;41:585-6
42. Terzano MG, Montanari E, Calzetti S,
et al. The effect of amantadine on
arousal and EEG patterns in Creutzfeldt-
Jakob disease. Arch Neurol
1983;40:555-9
43. Neri G, Figa-Talamanca L,
Di Battista GC, et al. Amantadine in
Creutzfeldt-Jakob disease. Review of the
literature and case contribution.
Riv Neurobiol 1984;30:47-56
44. Kimberlin RH, Walker CA. Antiviral
compound effective against experimental
scrapie. Lancet 1979;2:591-2
45. Tateishi J. Antibiotics and antivirals do
not modify experimentally-induced
Creutzfeldt-Jakob disease in mice.
J Neurol Neurosurg Psychiatry
1981;44:723-4
46. David AS, Grant R, Ballantyne JP.
Unsuccessful treatment of Creutzfeldt-
Jakob disease with acyclovir. Lancet
1984;1:512-13
47. Newman PK. Acyclovir in Creutzfeldt-
Jakob disease. Lancet 1984;1:793
48. Furlow TWJ, Whitley RJ, Wilmes FJ.
Repeated suppression of Creutzfeldt-
Jakob disease with vidarabine. Lancet
1982;2:564-5
49. Kovanen J, Haltia M, Cantell K. Failure
of interferon to modify Creutzfeldt-Jakob
disease. Br Med J 1980;280:902
50. Otto M, Cepek L, Ratzka P, et al.
Efficacy of flupirtine on cognitive
function in patients with CJD: a double-
blind study. Neurology 2004;62:714-18
. The first randomized double-blind
placebo-controlled clinical trial (RCT-
DB) study in CJD patients.
51. Perovic S, Pergande G, Ushijima H,
et al. Flupirtine partially prevents
neuronal injury induced by prion protein
fragment and lead acetate.
Neurodegeneration 1995;4:369-74
52. Perovic S, Schroder HC, Pergande G,
et al. Effect of flupirtine on Bcl-2 and
glutathione level in neuronal cells treated
in vitro with the prion protein fragment
(PrP106-126). Exp Neurol
1997;147:518-24
53. Perovic S, Bohm M, Meesters E, et al.
Pharmacological intervention in age-
associated brain disorders by Flupirtine:
Alzheimer’s and prion diseases.
Mech Ageing Dev 1998;101:1-19
54. Doh-ura K, Iwaki T, Caughey B.
Lysosomotropic agents and cysteine
protease inhibitors inhibit scrapie-
associated prion protein accumulation.
J Virol 2000;74:4894-7
55. Korth C, May BCH, Cohen FE, et al.
Acridine and phenothiazine derivatives as
pharmacotherapeutics for prion disease.
Proc Natl Acad Sci USA
2001;98:9836-41
56. Bertrand A, Martinez-Almoyna L,
De Broucker T. Hereditary Creutzfeldt-
Jakob disease caused by a mutation at
codon 200. Rev Neurol 2005;161:351-4
57. Martinez-Lage JF, Rabano A, Bermejo J,
et al. Creutzfeldt-Jakob disease acquired
via a dural graft: failure of therapy with
quinacrine and chlorpromazine.
Surg Neurol 2005;64:542-5
58. Scoazec JY, Krolak-Salmon P, et al.
Quinacrine-induced cytolytic hepatitis in
sporadic Creutzfeldt-Jakob disease.
Ann Neurol 2003;53:546-7
59. Benito-Leon J. Combined quinacrine and
chlorpromazine therapy in fatal familial
insomnia. Clin Neuropharmacol
2004;27:201-3
60. Josefson D. Drugs for malaria and
psychosis may offer hope to people with
CJD. BMJ 2001;323:416
61. Kobayashi Y, Hirata K, Tanaka H,
Yamada T. Quinacrine administration to
a patient with Creutzfeldt-Jakob disease
who received a cadaveric dura mater graft
- an EEG evaluation.
Rinsho Shinkeigaku 2003;43:403-8
62. Nakajima M, Yamada T, Kusuhara T,
et al. Results of quinacrine
administration to patients with
Creutzfeldt-Jakob disease.
Dement Geriatr Cogn Disord
2004;17:158-63
63. Satoh K, Shirabe S, Eguchi K, et al.
Toxicity of quinacrine can be reduced by
co-administration of p-glycoprotein
inhibitor in sporadic Creutzfeldt-Jakob
disease. Cell Mol Neurobiol
2004;24:873-5
64. Haik S, Brandel JP, Salomon D, et al.
Compassionate use of quinacrine in
Creutzfeldt-Jakob disease fails to show
significant effects. Neurology
2004;63:2413-15
65. Collinge J, Gorham M, Hudson F, et al.
Safety and efficacy of quinacrine in
human prion disease (PRION-1 study):
a patient-preference trial. Lancet Neurol
2009;8:334-44
66. Geschwind MD, Kuo AL, Wong KS,
et al. Quinacrine treatment trial for
sporadic Creutzfeldt-Jakob disease.
Neurology 2013;81:2015-23
. This study provides conclusive
evidence that quinacrine does not
improve survival in sporadic
CJD patients.
67. Collins SJ, Lewis V, Brazier M, et al.
Quinacrine does not prolong survival in
a murine Creutzfeldt-Jakob disease
model. Ann Neurol 2002;52:503-6
68. Barret A, Tagliavini F, Forloni G, et al.
Evaluation of quinacrine treatment for
prion diseases. J Virol 2003;77:8462-9
69. Doh-ura K, Ishikawa K,
Murakami-Kubo I, et al. Treatment of
transmissible spongiform encephalopathy
by intraventricular drug infusion in
The future for treating Creutzfeldt--Jakob disease
Expert Opinion on Orphan Drugs (2015) 3(1) 71
Exp
ert O
pini
on o
n O
rpha
n D
rugs
Dow
nloa
ded
from
info
rmah
ealth
care
.com
by
Inst
ituto
Sup
erio
re d
i San
ita o
n 12
/23/
14Fo
r pe
rson
al u
se o
nly.
animal models. J Virol
2004;78:4999-5006
70. Ghaemmaghami S, Ahn M, Lessard P,
et al. Continuous quinacrine treatment
results in the formation of drug-resistant
prions. PLoS Pathog 2009;5:e1000673
71. Tagliavini F, Forloni G, Colombo L,
et al. Tetracycline affects abnormal
properties of synthetic PrP peptides and
PrP(Sc) in vitro. J Mol Biol
2000;300:1309-22
72. Forloni G, Iussich S, Awan T, et al.
Tetracyclines affect prion infectivity.
Proc Natl Acad Sci USA
2002;99:10849-54
73. De Luigi A, Colombo L, Diomede L,
et al. The efficacy of tetracyclines in
peripheral and intracerebral prion
infection. PLoS One 2008;3:e1888
74. Tagliavini F. Prion therapy: tetracyclic
compounds in animal models and
patients with Creutzfeldt-Jakob disease.
Alzheimers Dement
2008;4(Suppl):T149-50
75. Ponto C, Zerr I.
Prionerkrankungen-welche Rolle spielen
sie heute? InFo Neurologie Psychiatrie
2013;15:2-8
76. Haik S, Marcon G, Mallet A, et al.
Doxycycline in Creutzfeldt-Jakob disease:
a phase 2, randomised, double-blind,
placebo-controlled trial. Lancet Neurol
2014;13:150-8
.. The first multinational RCT-DB
studies in CJD patients.
77. Todd NV, Morrow J, Doh-ura K, et al.
Cerebroventricular infusion of pentosan
polysulphate in human variant
Creutzfeldt-Jakob disease. J Infect
2005;50:394-6
78. Doh-ura K, Ishikawa K,
Murakami-Kubo I, et al. Intraventricular
infusion of pentosan polysulfate as an
immediately applicable treatment for
prion diseases [abstract No. 0-07].
International Congress on New
Perspectives for Prion Therapeutics
Meeting; 1 -- 3 December 2002; Paris
79. Ehlers B, Diringer H. Dextran sulphate
500 delays and prevents mouse scrapie
by impairment of agent replication in
spleen. J Gen Virol 1984;65:1325-30
80. Ladogana A, Casaccia P, Ingrosso L,
et al. Sulphate polyanions prolong the
incubation period of scrapie-infected
hamsters. J Gen Virol 1992;73:661-5
81. Shirabe S, Satoh K, Eguchi K, et al.
Effect of oral administration of pentosan
polysulfate for patients with Creutzfeldt-
Jakob disease (CJD) and new design for
low molecular-weight of pentosan
polysulfate. In: Kitamoto T, editor.
Prions, food and drug safety.
Springer-Verlag; Tokyo: 2005. p. 269-70
82. Dealler S, Rainov NG. Pentosan
polysulfate as a prophylactic and
therapeutic agent against prion disease.
IDrugs 2003;6:470-8
83. Rainov NG, Tsuboi Y, Krolak-Salmon P,
et al. Experimental treatments for human
transmissible spongiform
encephalopathies: is there a role for
pentosan polysulfate? Expert Opin
Biol Ther 2007;7:713-26
84. Bone I, Belton L, Walker AS,
Darbyshire J. Intraventricular pentosan
polysulphate in human prion diseases:
an observational study in the UK.
Eur J Neurol 2008;15:458-64
85. Tsuboi Y, Doh-Ura K, Yamada T.
Continuous intraventricular infusion of
pentosan polysulfate: clinical trial against
prion diseases. Neuropathology
2009;29:632-6
86. Paterson RW, Torres-Chae CC, Kuo AL,
et al. Differential diagnosis of Jakob-
Creutzfeldt disease. Arch Neurol
2012;24:1-5
87. Trevitt CR, Collinge J. A systematic
review of prion therapeutics in
experimental models. Brain
2006;129:2241-65
.. A comprehensive systematic review on
treatment attempts in experimental
models of prion diseases.
88. Brazier MW, Wall VA, Brazier BW,
et al. Therapeutic interventions
ameliorating prion disease. Expert Rev
Anti Infect Ther 2009;7:83-105
89. Fatal familial insomnia: preventive
treatment with doxycycline of at risk
individuals. EU Clinical Trials Register,
EudraCT Number: 2010-022233-28.
Available from: https://www.
clinicaltrialsregister.eu/ctr-search/trial/
2010-022233-28/IT [Last accessed
2 October 2014]
90. Klyubin I, Nicoll AJ, Khalili-Shirazi A,
et al. Peripheral administration of a
humanized anti-PrP antibody blocks
Alzheimer’s disease Ab synaptotoxicity.
J Neurosci 2014;34:6140-5
91. CureFFI.org. MRC Prion Unit discusses
possible clinical trial of
PRN100 antibody.
2013. Available from: http://www.cureffi.
org/2013/07/31/mrc-prion-unit-discusses-
possible-clinical-trial-of-prn100-antibody/
[Last accessed 2 October 2014]
92. Giese A, Bertsch U, Kretzschmar H,
et al. New drug for inhibiting
aggregation of proteins involved in
diseases linked to protein aggregation
and/or neurodegenerative diseases.
US0293520A1; 2011
93. Montagna P, Gambetti P, Cortelli P,
Lugaresi E. Familial and sporadic fatal
insomnia. Lancet Neurol 2003;2:167-76
94. Capellari S, Strammiello R, Saverioni D,
et al. Genetic Creutzfeldt-Jakob disease
and fatal familial insomnia: insights into
phenotypic variability and disease
pathogenesis. Acta Neuropathol
2011;121:21-37
95. CureFFI.org. Clinical trial for
doxycycline in FFI carriers will run from
2011-2022.
2012. Available from: http://www.cureffi.
org/2012/01/18/clinical-trial-for-
doxycycline-in-ffi-carriers-will-run-from-
2011-2022/ Last accessed 2 October
2014]
96. White AR, Enever P, Tayebi M, et al.
Monoclonal antibodies inhibit prion
replication and delay the development of
prion disease. Nature 2003;422:80-3
97. Freir DB, Nicoll AJ, Klyubin I, et al.
Interaction between prion protein and
toxic amyloid b assemblies can be
therapeutically targeted at multiple sites.
Nat Commun 2011;2:336
98. Collinge J, Hawke S. Treatment of
prion-induced diseases by administration
for anti-prion antibodies. WO050120A2;
2004
99. Petsch B, Muller-Schiffmann A, Lehle A,
et al. Biological effects and use of PrPSc-
and PrP-specific antibodies generated by
immunization with purified full-length
native mouse prions. J Virol
2011;85:4538-46
100. Kl€ohn PC, Farmer M, Linehan JM, et al.
PrP antibodies do not trigger mouse
hippocampal neuron apoptosis. Science
2012;335:52
101. Solforosi L, Criado JR, McGavern DB,
et al. Cross-linking cellular prion protein
triggers neuronal apoptosis in vivo.
Science 2004;303:1514-16
V. Vetrugno et al.
72 Expert Opinion on Orphan Drugs (2015) 3(1)
Exp
ert O
pini
on o
n O
rpha
n D
rugs
Dow
nloa
ded
from
info
rmah
ealth
care
.com
by
Inst
ituto
Sup
erio
re d
i San
ita o
n 12
/23/
14Fo
r pe
rson
al u
se o
nly.
102. Sonati T, Reimann RR, Falsig J, et al.
The toxicity of antiprion antibodies is
mediated by the flexible tail of the prion
protein. Nature 2013;501:102-6
103. Wagner JRyazanov SLeonov A, et al.
Anle138b: a novel oligomer modulator
for disease-modifying therapy of
neurodegenerative diseases such as prion
and Parkinson’s disease.
Acta Neuropathol 2013;125:795-813
104. Levin J, Schmidt F, Boehm C, et al. The
oligomer modulator anle138b inhibits
disease progression in a Parkinson mouse
model even with treatment started after
disease onset. Acta Neuropathol
2014;127:779-80
105. Max-Planck. Gesellschaft. New drug
against Alzheimer’s and Parkinson’s on
the way.
2014. Available from: http://www.mpg.
de/7955496/
anle138b_alzheimer_parkinson [Last
accessed 2 October 2014]
106. Thompson AG, Lowe J, Fox Z, et al.
The Medical Research Council prion
disease rating scale: a new outcome
measure for prion disease therapeutic
trials developed and validated using
systematic observational studies. Brain
2013;136:1116-27
107. Tiraboschi P, Tagliavini F. Prion disease:
a promising rating scale for prion disease
clinical research. Nat Rev Neurol
2013;9:366-7
108. Pocchiari M, Ladogana A, Graziano S,
Puopolo M. Creutzfeldt-Jakob disease:
hopes for therapy. Eur J Neurol
2008;15:435-6
109. Mead S, Uphill J, Beck J, et al.
Genome-wide association study in
multiple human prion diseases suggests
genetic risk factors additional to PRNP.
Hum Mol Genet 2012;21:1897-906
110. Sanchez-Juan P, Bishop MT,
Aulchenko YS, et al. Genome-wide study
links MTMR7 gene to variant
Creutzfeldt-Jakob risk. Neurobiol Aging
2012;33:1487.e21-8
111. Ferreira NC, Marques IA,
Conceicao WA, et al. Anti-prion activity
of a panel of aromatic chemical
compounds: in vitro and in silico
approaches. PLoS One 2014;9:e84531
. An effective combined in vitro and
in silico approach for screening
potential antiprion drugs.
112. Thompson MJ, Borsenberger V,
Louth JC, et al. Design, synthesis, and
structure-activity relationship of
indole-3-glyoxylamide libraries possessing
highly potent activity in a cell line model
of prion disease. J Med Chem
2009;52:7503-11
113. Ghaemmaghami S, May BC, Renslo AR,
Prusiner SB. Discovery of 2-
aminothiazoles as potent antiprion
compounds. J Virol 2010;84:3408-12
114. Berry DB, Lu D, Geva M, et al. Drug
resistance confounding prion
therapeutics. Proc Natl Acad Sci USA
2013;110:4160-9
115. Karapetyan YE, Sferrazza GF, Zhou M,
et al. Unique drug screening approach
for prion diseases identifies tacrolimus
and astemizole as antiprion agents.
Proc Natl Acad Sci USA
2013;110:7044-9
. An effective approach describing the
screening of thousands of compounds
in search for novel antiprion drugs.
116. Aguzzi A, Nuvolone M, Zhu C. The
immunobiology of prion diseases.
Nat Rev Immunol 2013;13:888-902
.. An overview on potential
immunotherapeutical approaches in
prion diseases.
117. Brazier MW, Mot AI, White AR,
Collins SJ. Immunotherapeutic
approaches in prion disease: progress,
challenges and potential directions.
Ther Deliv 2013;4:615-28
118. Rovis TL, Legname G. Prion protein-
specific antibodies-development, modes
of action and therapeutics application.
Viruses 2014;6:3719-37
119. White MD, Farmer M, Mirabile I, et al.
Single treatment with RNAi against
prion protein rescues early neuronal
dysfunction and prolongs survival in
mice with prion disease. Proc Natl Acad
Sci USA 2008;105:10238-43
120. Boese AS, Majer A, Saba R, Booth SA.
Small RNA drugs for prion disease:
a new frontier. Expert Opin
Drug Discov 2013;8:1265-84
121. Moreno JA, Halliday M, Molloy C,
et al. Oral treatment targeting the
unfolded protein response prevents
neurodegeneration and clinical disease in
prion-infected mice. Sci Transl Med
2013;5:206ra138
122. Halliday M, Mallucci GR. Targeting the
unfolded protein response in
neurodegeneration: a new approach to
therapy. Neuropharmacology
2014;76(Pt A):169-74
123. Farlow MR, Brosch JR. Immunotherapy
for Alzheimer’s disease. Neurol Clin
2013;31:869-78
124. Wisniewski T, Goni F. Immunotherapy
for Alzheimer’s disease.
Biochem Pharmacol 2014;88:499-507
125. Henderson VC, Kimmelman J,
Fergusson D, et al. Threats to validity in
the design and conduct of preclinical
efficacy studies: a systematic review of
guidelines for in vivo animal
experiments. PLoS Med
2013;10:e1001489
126. Berry DB, Lu D, Geva M, et al. Drug
resistance confounding prion
therapeutics. Proc Natl Acad Sci USA
2013;110:4160-9
127. Bian J, Kang HE, Telling GC.
Quinacrine promotes replication and
conformational mutation of chronic
wasting disease prions. Proc Natl Acad
Sci USA 2014;111:6028-33
128. Ghaemmaghami S, Russo M, Renslo AR.
Successes and challenges in phenotype-
based lead discovery for prion diseases.
J Med Chem 2014;57:6919-29
129. Hannaoui S, Gougerot A, Privat N, et al.
Cycline efficacy on the propagation of
human prions in primary cultured
neurons is strain-specific. J Infect Dis
2014;209:1144-8
130. Bishop MT, Will RG, Manson JC.
Defining sporadic Creutzfeldt-Jakob
disease strains and their transmission
properties. Proc Natl Acad Sci USA
2010;107:12005-10
131. Nonno R, Di Bari MA, Cardone F,
et al. Efficient transmission and
characterization of Creutzfeldt-Jakob
disease strains in bank voles.
PLoS Pathog 2006;2(2):e12
132. Bechtel K, Geschwind MD. Ethics in
prion disease. Prog Neurobiol
2013;110:29-44
133. Puopolo M, Pocchiari M, Petrini C.
Clinical trials and methodological
problems in prion diseases.
Lancet Neurol 2009;8:782
134. Mead S, Ranopa M, Gopalakrishnan GS,
et al. PRION-1 scales analysis supports
use of functional outcome measures in
prion disease. Neurology
2011;77:1674-83
The future for treating Creutzfeldt--Jakob disease
Expert Opinion on Orphan Drugs (2015) 3(1) 73
Exp
ert O
pini
on o
n O
rpha
n D
rugs
Dow
nloa
ded
from
info
rmah
ealth
care
.com
by
Inst
ituto
Sup
erio
re d
i San
ita o
n 12
/23/
14Fo
r pe
rson
al u
se o
nly.
135. Kurzrock R, Stewart DJ. Equipoise
abandoned? Randomization and clinical
trials. Ann Oncol 2013;24:2471-4
136. Gifford F. The conflict between
randomized clinical trials and the
therapeutic obligation. J Med Philos
1986;11:347-66
137. Freedman B. Equipoise and the ethics of
clinical research. N Engl J Med
1987;317:141-5
138. Miller FG, Joffe S. Equipoise and the
dilemma of randomized clinical trials.
N Engl J Med 2011;364:476-80
139. Mitsumoto J, Dorsey ER, Beck CA,
et al. Pivotal studies of orphan drugs
approved for neurological diseases.
Ann Neurol 2009;66:184-90
140. Budka H, Aguzzi A, Brown P, et al.
Tissue handling in suspected Creutzfeldt-
Jakob disease (CJD) and other human
spongiform encephalopathies (prion
diseases). Brain Pathol 1995;5:319-22
141. World Health Organization, WHO/
EMC/ZDI/98.9. Global surveillance,
diagnosis and therapy of human
transmissible spongiform
encephalopathies: report of a WHO
consultation.
1998. Available from: www.who.int/csr/
resources/publications/bse/
whoemczdi989.pdf [Last accessed
5 October 2014]
142. Tagliavini F, McArthur RA, Canciani B,
et al. Effectiveness of anthracycline
against experimental prion disease in
Syrian hamsters. Science
1997;276:1119-22
AffiliationVito Vetrugno PhD, Maria Puopolo DStat,
Franco Cardone PhD, Fiorentino Capozzoli MD,
Anna Ladogana MD & Maurizio Pocchiari† MD†Author for correspondence
Istituto Superiore di Sanit�a, Department of Cell
Biology and Neurosciences, Viale Regina Elena
299, Roma 00161, Italy
E-mail: [email protected]
V. Vetrugno et al.
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ert O
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care
.com
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erio
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/23/
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