Anti-prion drugs do not improve survival in novel knock-in models of inherited prion disease.

Prion diseases uniquely manifest in three distinct forms: inherited, sporadic, and infectious. Wild-type prions are responsible for the sporadic and infectious versions, while mutant prions cause inherited variants like fatal familial insomnia (FFI) and familial Creutzfeldt-Jakob disease (fCJD). Although some drugs can prolong prion incubation times up to four-fold in rodent models of infectious prion diseases, no effective treatments for FFI and fCJD have been found. In this study, we evaluated the efficacy of various anti-prion drugs on newly-developed knock-in mouse models for FFI and fCJD. These models express bank vole prion protein (PrP) with the pathogenic D178N and E200K mutations. We applied various drug regimens known to be highly effective against wild-type prions in vivo as well as a brain-penetrant compound that inhibits mutant PrPSc propagation in vitro. None of the regimens tested (Anle138b, IND24, Anle138b + IND24, cellulose ether, and PSCMA) significantly extended disease-free survival or prevented mutant PrPSc accumulation in either knock-in mouse model, despite their ability to induce strain adaptation of mutant prions. Our results show that anti-prion drugs originally developed to treat infectious prion diseases do not necessarily work for inherited prion diseases, and that the recombinant sPMCA is not a reliable platform for identifying compounds that target mutant prions. This work underscores the need to develop therapies and validate screening assays specifically for mutant prions, as well as anti-prion strategies that are not strain-dependent.

Altered properties of amyloidogenic prion protein in genetic Creutzfeldt-Jakob disease with PRNP V180I mutation in response to pentosan polysulfate.

Genetic Creutzfeldt-Jakob disease (gCJD) with V180I prion protein gene (PRNP) mutation shows weaker prion protein (PrP) deposition histologically compared with sporadic CJD, and it is more difficult to detect protease-resistant prion protein in immunoblotting. However, we previously reported the autopsy case of a patient with V180I gCJD who was treated with pentosan polysulfate sodium (PPS); this case had increased protease-resistant PrP deposition. It has been suggested that PPS might reduce protease-resistant PrP; however, the detailed pharmacological and histopathological effects of PPS in humans remain unknown. We examined autopsied human brain tissue from four cases with V180I gCJD that were added to our archives between 2011 and 2021: two cases treated with PPS and two cases without PPS. We conducted a neuropathological assessment, including immunohistochemistry for PrP. We also performed immunoblotting for PrP on homogenate samples from each brain to detect protease-resistant PrP using both a conventional procedure and size-exclusion gel chromatography for the purification of oligomeric PrP. Both PPS-treated cases showed long survival time over 5 years from onset and increased PrP deposition with a characteristic pattern of coarse granular depositions and congophilic PrP microspheres, whereas the cases without PPS showed around 1-year survival from onset and relatively mild neuronal loss and synaptic PrP deposition. Although cortical gliosis seemed similar among all cases, aquaporin 4-expression as a hallmark of astrocytic function was increased predominantly in PPS cases. Immunoblotting of non-PPS cases revealed protease-resistant PrP in the oligomeric fraction only, whereas the PPS-treated cases showed clear signals using conventional procedures and in the oligomeric fraction. These unique biochemical and histopathological changes may reflect the progression of V180I gCJD and its modification by PPS, suggesting the possible existence of toxic PrP-oligomer in the pathophysiology of V180I gCJD and beneficial effects of PPS toward the aggregation and detoxication of toxic PrP-oligomer.

Systematic review of pharmacological management in Creutzfeldt-Jakob disease: no options so far?

BACKGROUND: The Creutzfeldt-Jakob disease (CJD) is a spongiform encephalopathy that manifests as a rapidly progressive dementia syndrome. Currently, CJD has no cure, and many patients die within the first year, but some drugs are being studied as options for managing this condition. OBJECTIVE: To evaluate the effectiveness of pharmacological treatments offered to patients with CJD as a means to increase survival and reduce cognitive deterioration. METHODS: A systematic review of the literature was performed using 4 independent reviewers and 1 extra reviewer to resolve possible divergences in the search and analysis of papers indexed in MedLINE (PubMed), SciELO and Lilacs databases. The Medical Subject Heading (MeSH) terms used were: prion diseases, Creutzfeldt-Jakob disease, pharmacologic therapy, therapeutics, quinacrine, doxycycline, flupirtine, and pentosan polysulfate, with the Boolean operators AND and OR. This search included controlled clinical trials, uncontrolled clinical trials, and case series published from the year 2000 onwards, in the English language. RESULTS: A total of 85 papers were found using the descriptors used. At the end of the selection analyses, 9 articles remained, which were analyzed fully and individually. CONCLUSIONS: None of the drugs evaluated proved significantly effective in increasing survival in patients with CJD. Flupirtine appears to have a beneficial effect in reducing cognitive deterioration in patients with CJD. However, additional studies are needed to establish better evidence and therapeutic options for the management of patients with CJD.

ANTECEDENTES: A doença de Creutzfeldt-Jakob (DCJ) é uma encefalopatia espongiforme que se manifesta como síndrome demencial rapidamente progressiva. Atualmente, a DCJ não possui cura e muitos pacientes morrem no primeiro ano de doença, mas alguns medicamentos vêm sendo estudados como opções no manejo desta condição. OBJETIVO: Avaliar a eficácia dos tratamentos farmacológicos oferecidos aos pacientes com DCJ no aumento de sobrevida e na redução da deterioração cognitiva. MéTODOS: Foi realizada uma revisão sistemática da literatura utilizando 4 revisores independentes e 1 extra para resolver divergências eventuais na busca e na análise de trabalhos indexados nas bases de dados MedLINE (via PubMed), SciELO e Lilacs. Os termos Medical Subjects Heading (MeSH) utilizados foram: prion diseases, creutzfeldt jakob disease, pharmacologic therapy, therapeutics, quinacrine, doxycycline, flupirtine e pentosan polysulfate, com os operadores booleanos AND e OR. Essa pesquisa incluiu ensaios clínicos controlados, não controlados e séries de casos, publicados a partir do ano 2000 no idioma inglês. RESULTADOS: Ao todo, foram encontrados 85 trabalhos através dos descritores utilizados. Ao final das análises de seleção, restaram 9 artigos, que foram analisados na íntegra individualmente. CONCLUSõES: Nenhuma das drogas avaliadas se mostrou significativamente eficaz no aumento da sobrevida dos pacientes com DCJ. A flupirtina parece ter um efeito benéfico na redução da deterioração cognitiva dos pacientes com DCJ. Entretanto, estudos adicionais são necessários para o estabelecimento de melhores evidências e opções terapêuticas para o manejo dos pacientes com DCJ.

Curcumin: A small molecule with big functionality against amyloid aggregation in neurodegenerative diseases and type 2 diabetes.

Amyloidosis is a concept that implicates disorders and complications that are due to abnormal protein accumulation in different cells and tissues. Protein aggregation-associated diseases are classified according to the type of aggregates and deposition sites, such as neurodegenerative disorders and type 2 diabetes mellitus. Polyphenolic phytochemicals such as curcumin and its derivatives have anti-amyloid effects both in vitro and in animal models; however, the underlying mechanisms are not understood. In this review, we summarized possible mechanisms by which curcumin could interfere with self-assembly processes and reduce amyloid aggregation in amyloidosis. Furthermore, we discuss clinical trials in which curcumin is used as a therapeutic agent for the treatment of diseases linking to protein aggregates.

Human cerebral organoids as a therapeutic drug screening model for Creutzfeldt-Jakob disease.

Creutzfeldt-Jakob Disease (CJD) is a fatal, currently incurable, neurodegenerative disease. The search for candidate treatments would be greatly facilitated by the availability of human cell-based models of prion disease. Recently, an induced pluripotent stem cell derived human cerebral organoid model was shown to take up and propagate human CJD prions. This model offers new opportunities to screen drug candidates for the treatment of human prion diseases in an entirely human genetic background. Here we provide the first evidence that human cerebral organoids can be a viable model for CJD drug screening by using an established anti-prion compound, pentosan polysulfate (PPS). PPS delayed prion propagation in a prophylactic-like treatment paradigm and also alleviated propagation when applied following establishment of infection in a therapeutic-like treatment paradigm. This study demonstrates the utility of cerebral organoids as the first human 3D cell culture system for screening therapeutic drug candidates for human prion diseases.

Administration of FK506 from Late Stage of Disease Prolongs Survival of Human Prion-Inoculated Mice.

Human prion diseases are etiologically categorized into three forms: sporadic, genetic, and infectious. Sporadic Creutzfeldt-Jakob disease (sCJD) is the most common type of human prion disease that manifests as subacute progressive dementia. No effective therapy for sCJD is currently available. Potential therapeutic compounds are frequently tested in rodents infected with mouse-adapted prions that differ from human prions. However, therapeutic effect varies depending on the prion strain, which is one of the reasons why candidate compounds have shown little effect in sCJD patients. We previously reported that intraperitoneal administration of FK506 was able to prolong the survival of mice infected with a mouse-adapted prion by suppressing the accumulation of abnormal prion protein (PrP) and inhibiting the activation of microglia. In this study, we tested oral administration of FK506 in knock-in mice expressing chimeric human prion protein (KiChM) that were infected with sCJD to determine if this compound is also effective against a clinically relevant human prion, i.e., one that has not been adapted to mice. Treatment with FK506, started either just before or just after disease onset, suppressed typical sCJD pathology (gliosis) and slightly but significantly prolonged the survival of sCJD-inoculated mice. It would be worthwhile to conduct a clinical trial using FK506, which has been safety-approved and is widely used as a mild immunosuppressant.

Dynamically borrowing strength from another study through shrinkage estimation.

Meta-analytic methods may be used to combine evidence from different sources of information. Quite commonly, the normal-normal hierarchical model (NNHM) including a random-effect to account for between-study heterogeneity is utilized for such analyses. The same modeling framework may also be used to not only derive a combined estimate, but also to borrow strength for a particular study from another by deriving a shrinkage estimate. For instance, a small-scale randomized controlled trial could be supported by a non-randomized study, e.g. a clinical registry. This would be particularly attractive in the context of rare diseases. We demonstrate that a meta-analysis still makes sense in this extreme case, effectively based on a synthesis of only two studies, as illustrated using a recent trial and a clinical registry in Creutzfeld-Jakob disease. Derivation of a shrinkage estimate within a Bayesian random-effects meta-analysis may substantially improve a given estimate even based on only a single additional estimate while accounting for potential effect heterogeneity between the studies. Alternatively, inference may equivalently be motivated via a model specification that does not require a common overall mean parameter but considers the treatment effect in one study, and the difference in effects between the studies. The proposed approach is quite generally applicable to combine different types of evidence originating, e.g. from meta-analyses or individual studies. An application of this more general setup is provided in immunosuppression following liver transplantation in children.

Metal homeostasis disturbances in neurodegenerative disorders, with special emphasis on Creutzfeldt-Jakob disease - Potential pathogenetic mechanism and therapeutic implications.

Creutzfeldt-Jakob disease (CJD) is characterized by a rapidly progressive dementia often accompanied by myoclonus and other signs of brain dysfunction, relying on the conversion of the normal cellular form of the prion protein (PrPC) to a misfolded form (PrPSc). The neuropathological changes include spongiform degeneration, neuronal loss, astrogliosis, and deposition of PrPSc. It is still unclear how these pathological changes correlate with the development of CJD symptoms because few patients survive beyond 2 years after diagnosis. Inasmuch as the symptoms of CJD overlap some of those observed in Alzheimer's, Parkinson's, and Huntington's diseases, there may be some underlying pathologic mechanisms associated with CJD that may contribute to the symptoms of non-prion neurodegenerative diseases as well. Data suggest that imbalance of metals, including copper, zinc, iron, and manganese, induces abnormalities in processing and degradation of prion proteins that are accompanied by self-propagation of PrPSc. These events appear to be responsible for glutamatergic synaptic dysfunctions, neuronal death, and PrPSc aggregation. Given that the prodromal symptoms of CJD such as sleep disturbances and mood disorders are associated with brain stem and limbic system dysfunction, the pathological changes may initially occur in these brain regions, then spread throughout the entire brain. Alterations in cerebrospinal fluid homeostasis, which may be linked to imbalance of these metals, seem to be more important than neuroinflammation in causing the cell death. It is proposed that metal dyshomeostasis could be responsible for the initiation and progression of the pathological changes associated with symptoms of CJD and other neurodegenerative disorders.

Therapies for prion diseases.

Recent advances in understanding of the molecular biology of prion diseases and improved clinical diagnostic techniques might allow researchers to think about therapeutic trials in Creutzfeldt-Jakob disease (CJD) patients. Some attempts have been made in the past and various compounds have been tested in single case reports and patient series. Controlled trials are rare. However, in the past few years, it has been demonstrated that clinical trials are feasible. The clinicians might face several specific problems when evaluating the efficacy of the drug in CJD, such as rareness of the disease, lack of appropriate preclinical tests and heterogeneous clinical presentation in humans. These problems have to be carefully addressed in future.

Learning from history: Lord Brain and Hashimoto's encephalopathy.

We present two historic cases of severe encephalopathy associated with antithyroid antibodies. The first was published by Lord Brain of Eynsham, and the second was from our department's archives. Although both cases are from archival sources, they continue to inform current clinical care. We briefly review the poorly defined entity, Hashimoto's encephalopathy, and discuss diagnostic advances for autoimmune encephalopathy and for Creutzfeldt-Jakob disease. We advocate for giving a trial of corticosteroids to patients with 'encephalopathy, not otherwise specified' while awaiting antibody results or more definitive testing. Our case, initially diagnosed as having Creutzfeldt-Jakob disease, responded remarkably (with video evidence) to a trial of corticosteroids.

Rare histotype of sporadic Creutzfeldt-Jakob disease, clinically suspected as corticobasal degeneration.

Sporadic Creutzfeldt-Jakob disease (sCJD) is a rare neurodegenerative disease that can mimic other neurological disorders. We present a case of sCJD in a 64-year-old man that presented with corticobasal syndrome and survived for 3 years. He presented initially with dementia, hemiparkinsonism and alien limb phenomenon and was diagnosed with corticobasal degeneration, ultimately progressing to immobility and akinetic mutism. With a normal MRI 1 year before onset, his neuroimaging 1 year later revealed abnormal DaTscan, cortical and hippocampal atrophy with ventricular dilatation on MRI, and diffusion-weighted cortical ribboning and thalamic hyperintensity. Postmortem, the patient's brain was collected by the Parkinson's UK Tissue Bank. Prion protein immunohistochemistry revealed widespread diffuse microvacuolar staining without kuru-type plaques. Hyperphosphorylated tau was only found in the entorhinal cortex and hippocampus. This case highlights the clinical heterogeneity of sCJD presentation and the important inclusion of CJD in the differential diagnosis of atypical presentations of neurodegenerative disease.

Application of PMCA to screen for prion infection in a human cell line used to produce biological therapeutics.

Advances in biotechnology have led to the development of a number of biological therapies for the treatment of diverse human diseases. Since these products may contain or are made using human or animal (e.g. cattle) derived materials, it is crucial to test their safety by ensuring the absence of infectious agents; specifically prions, which are highly resilient to elimination and produce fatal diseases in humans. Many cases of iatrogenic Creutzfeldt-Jakob disease have been caused by the use of biological materials (e.g. human growth hormone) contaminated with prions. For this reason, it is important to screen cells and biological materials for the presence of prions. Here we show the utility of the Protein Misfolding Cyclic Amplification (PMCA) technology as a screening tool for the presence of human (vCJD) and bovine (BSE) prions in a human cell therapy product candidate. First, we demonstrated the sensitivity of PMCA to detect a single cell infected with prions. For these experiments, we used RKM7 cells chronically infected with murine RML prions. Serial dilutions of an infected cell culture showed that PMCA enabled prion amplification from a sample comprised of only one cell. Next, we determined that PMCA performance was robust and uncompromised by the spiking of large quantities of uninfected cells into the reaction. Finally, to demonstrate the practical application of this technology, we analyzed a human cell line being developed for therapeutic use and found it to be PMCA-negative for vCJD and BSE prions. Our findings demonstrate that the PMCA technology has unparalleled sensitivity and specificity for the detection of prions, making it an ideal quality control procedure in the production of biological therapeutics.

Inhibition of IL-1ß Signaling Normalizes NMDA-Dependent Neurotransmission and Reduces Seizure Susceptibility in a Mouse Model of Creutzfeldt-Jakob Disease.

Creutzfeldt-Jakob disease (CJD) is a neurodegenerative disorder caused by prion protein (PrP) misfolding, clinically recognized by cognitive and motor deficits, electroencephalographic abnormalities, and seizures. Its neurophysiological bases are not known. To assess the potential involvement of NMDA receptor (NMDAR) dysfunction, we analyzed NMDA-dependent synaptic plasticity in hippocampal slices from Tg(CJD) mice, which model a genetic form of CJD. Because PrP depletion may result in functional upregulation of NMDARs, we also analyzed PrP knock-out (KO) mice. Long-term potentiation (LTP) at the Schaffer collateral-commissural synapses in the CA1 area of ∼100-d-old Tg(CJD) mice was comparable to that of wild-type (WT) controls, but there was an inversion of metaplasticity, with increased GluN2B phosphorylation, which is indicative of enhanced NMDAR activation. Similar but less marked changes were seen in PrP KO mice. At ∼300 d of age, the magnitude of LTP increased in Tg(CJD) mice but decreased in PrP KO mice, indicating divergent changes in hippocampal synaptic responsiveness. Tg(CJD) but not PrP KO mice were intrinsically more susceptible than WT controls to focal hippocampal seizures induced by kainic acid. IL-1ß-positive astrocytes increased in the Tg(CJD) hippocampus, and blocking IL-1 receptor signaling restored normal synaptic responses and reduced seizure susceptibility. These results indicate that alterations in NMDA-dependent glutamatergic transmission in Tg(CJD) mice do not depend solely on PrP functional loss. Moreover, astrocytic IL-1ß plays a role in the enhanced synaptic responsiveness and seizure susceptibility, suggesting that targeting IL-1ß signaling may offer a novel symptomatic treatment for CJD.SIGNIFICANCE STATEMENT Dementia and myoclonic jerks develop in individuals with Creutzfeldt-Jakob disease (CJD), an incurable brain disorder caused by alterations in prion protein structure. These individuals are prone to seizures and have high brain levels of the inflammatory cytokine IL-1ß. Here we show that blocking IL-1ß receptors with anakinra, the human recombinant form of the endogenous IL-1 receptor antagonist used to treat rheumatoid arthritis, normalizes hippocampal neurotransmission and reduces seizure susceptibility in a CJD mouse model. These results link neuroinflammation to defective neurotransmission and the enhanced susceptibility to seizures in CJD and raise the possibility that targeting IL-1ß with clinically available drugs may be beneficial for symptomatic treatment of the disease.

NADPH oxidases as drug targets and biomarkers in neurodegenerative diseases: What is the evidence?

Neurodegenerative disease are frequently characterized by microglia activation and/or leukocyte infiltration in the parenchyma of the central nervous system and at the molecular level by increased oxidative modifications of proteins, lipids and nucleic acids. NADPH oxidases (NOX) emerged as a novel promising class of pharmacological targets for the treatment of neurodegeneration due to their role in oxidant generation and presumably in regulating microglia activation. The unique function of NOX is the generation of superoxide anion (O2•-) and hydrogen peroxide (H2O2). However in the context of neuroinflammation, they present paradoxical features since O2•-/H2O2 generated by NOX and/or secondary reactive oxygen species (ROS) derived from O2•-/H2O2 can either lead to neuronal oxidative damage or resolution of inflammation. The role of NOX enzymes has been investigated in many models of neurodegenerative diseases by using either genetic or pharmacological approaches. In the present review we provide a critical assessment of recent findings related to the role of NOX in the CNS as well as how the field has advanced over the last 5 years. In particular, we focus on the data derived from the work of a consortium (Neurinox) funded by the European Commission's Programme 7 (FP7). We discuss the evidence gathered from animal models and human samples linking NOX expression/activity with neuroinflammation in neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) and Creutzfeldt-Jakob disease as well as autoimmune demyelinating diseases like multiple sclerosis (MS) and chronic inflammatory demyelinating polyneuropathy (CIDP). We address the possibility to use measurement of the activity of the NOX2 isoform in blood samples as biomarker of disease severity and treatment efficacy in neurodegenerative disease. Finally we clarify key controversial aspects in the field of NOX, such as NOX cellular expression in the brain, measurement of NOX activity, impact of genetic deletion of NOX in animal models of neurodegeneration and specificity of NOX inhibitors.

Continues administration of Nano-PSO significantly increased survival of genetic CJD mice.

We have shown previously that Nano-PSO, a nanodroplet formulation of pomegranate seed oil, delayed progression of neurodegeneration signs when administered for a designated period of time to TgMHu2ME199K mice, modeling for genetic prion disease. In the present work, we treated these mice with a self-emulsion formulation of Nano-PSO or a parallel Soybean oil formulation from their day of birth until a terminal disease stage. We found that long term Nano-PSO administration resulted in increased survival of TgMHu2ME199K lines by several months. Interestingly, initiation of treatment at day 1 had no clinical advantage over initiation at day 70, however cessation of treatment at 9months of age resulted in the rapid loss of the beneficial clinical effect. Pathological studies revealed that treatment with Nano-PSO resulted in the reduction of GAG accumulation and lipid oxidation, indicating a strong neuroprotective effect. Contrarily, the clinical effect of Nano-PSO did not correlate with reduction in the levels of disease related PrP, the main prion marker. We conclude that long term administration of Nano-PSO is safe and may be effective in the prevention/delay of onset of neurodegenerative conditions such as genetic CJD.

Anti-Prion Screening for Acridine, Dextran, and Tannic Acid using Real Time-Quaking Induced Conversion: A Comparison with PrPSc-Infected Cell Screening.

Prion propagation is mediated by the structural alteration of normal prion protein (PrPC) to generate pathogenic prion protein (PrPSc). To date, compounds for the inhibition of prion propagation have mainly been screened using PrPSc-infected cells. Real time-quaking-induced conversion (RT-QuIC) is one alternative screening method. In this study, we assessed the propagation inhibition effects of known anti-prion compounds using RT-QuIC and compared the results with those from a PrPSc-infected cell assay. Compounds were applied to RT-QuIC reactions at 0 h or 22 h after prion propagation to determine whether they inhibited propagation or reduced amplified aggregates. RT-QuIC reactions in presence of acridine, dextran sulfate sodium (DSS), and tannic acid inhibited seeded aggregation with sporadic Creutzfeldt-Jakob disease at 0 h. After treatment at 22 h, amplified fluorescence was decreased in wells treated with either acridine or tannic acid. Compound activities were verified by western blot of RT-QuIC products and in a dye-independent conversion assay, the Multimer Detection System. Protease K-resistant PrPSc fragments (PrPres) were reduced by DSS and tannic acid in the PrPSc-infected cell assay. Importantly, these inhibitory effects were similar despite different treatment times (0 h versus 3 days). Consequentially, RT-QuIC enabled the more specific classification of compounds according to action (i.e., inhibition of prion propagation versus reduction of amplified aggregates). RT-QuIC addresses the limitations of cell-based screening methods and can be used to further aid our understanding of the mechanisms of action of anti-prion compounds.

Insights from Therapeutic Studies for PrP Prion Disease.

Although an effective therapy for prion disease has not yet been established, many advances have been made toward understanding its pathogenesis, which has facilitated research into therapeutics for the disease. Several compounds, including flupirtine, quinacrine, pentosan polysulfate, and doxycycline, have recently been used on a trial basis for patients with prion disease. Concomitantly, several lead antiprion compounds, including compound B (compB), IND series, and anle138b, have been discovered. However, clinical trials are still far from yielding significantly beneficial results, and the findings of lead compound studies in animals have highlighted new challenges. These efforts have highlighted areas that need improvement or further exploration to achieve more effective therapies. In this work, we review recent advances in prion-related therapeutic research and discuss basic scientific issues to be resolved for meaningful medical intervention of prion disease.

Doxycycline in early CJD: a double-blinded randomised phase II and observational study.

OBJECTIVES: The main objective of the present study is to study the therapeutic efficiency of doxycycline in a double-blinded randomised phase II study in a cohort of patients with sporadic Creutzfeldt-Jakob disease (sCJD). METHODS: From the National Reference Center of TSE Surveillance in Germany, patients with probable or definite sCJD were recruited for a double-blinded randomised study with oral doxycycline (EudraCT 2006-003934-14). In addition, we analysed the data from patients with CJD who received compassionate treatment with doxycycline in a separate group. Potential factors which influence survival such as age at onset, gender, codon 129 polymorphism and cognitive functions were evaluated. The primary outcome measure was survival. RESULTS: Group 1: in the double-blinded randomised phase II study, 7 patients in the treatment group were compared with 5 controls. Group 2: 55 patients with sCJD treated with oral doxycycline were analysed and compared with 33 controls by a stratified propensity score applied to a Cox proportional hazard analysis. The results of both studies were combined by means of a random-effects meta-analysis. A slight increase in survival time in the doxycycline treatment group was observed (p=0.049, HR=0.63 (95% CI 0.402 to 0.999)). CONCLUSIONS: On the basis of our studies, a larger trial of doxycycline should be performed in persons in the earliest stages of CJD. TRIAL REGISTRATION NUMBER: EudraCT 2006-003934-14; Results.