Saturday, July 19, 2008

Single treatment with RNAi against prion protein rescues early neuronal dysfunction and prolongs survival in mice with prion

Single treatment with RNAi against prion protein rescues early neuronal dysfunction and prolongs survival in mice with prion

disease Melanie D. White*, Michael Farmer, Ilaria Mirabile, Sebastian Brandner, John Collinge, and Giovanna R. Mallucci† Medical Research Council (MRC) Prion Unit and Department of Neurodegenerative Disease, Institute of Neurology, University College London, London WC1N 3BG, United Kingdom Edited by Charles Weissmann, The Scripps Research Institute, Jupiter, FL, and approved June 3, 2008 (received for review March 19, 2008)

Prion diseases are fatal neurodegenerative conditions for which there is no effective treatment. Prion propagation involves the conversion of cellular prion protein, PrPC, to its conformational isomer, PrPSc, which accumulates in disease. Here, we show effective therapeutic knockdown of PrPC expression using RNAi in mice with established prion disease.Asingle administration of lentivirus expressing a shRNA targeting PrP into each hippocampus of mice with established prion disease significantly prolonged survival time. Treated animals lived 19% and 24% longer than mice given an ‘‘empty’’ lentivirus, or not treated, respectively. Lentivirally mediated RNAi of PrP also prevented the onset of behavioral deficits associated with early prion disease, reduced spongiform degeneration, and protected against neuronal loss. In contrast, mice receiving empty virus or no treatment developed early cognitive impairment and showed severe spongiosis and neuronal loss. The focal use of RNAi therapeutically in prion disease further supports strategies depleting PrPC, which we previously established to be a valid target for prion-based treatments. This approach can now be used to define the temporal, quantitative, and regional requirements for PrP knockdown for effective treatment of prion disease and to explore mechanisms involved in predegenerative neuronal dysfunction and its rescue.


Discussion The rescue of early neuronal dysfunction before neuronal loss is established is a clear goal for therapeutic intervention in neurodegenerative disease. Our previous findings that transgene-mediated PrP knockdown reversed predegenerative pathological changes and early behavioral deficits in prion disease led us to try to achieve the same effect therapeutically. PrPC knockout, both during development and postnatally, appears to be without detrimental effect (6, 21). We used RNAi to silence PrP expression in mice with established prion disease. Knockdown of PrP by RNAi (11) and resultant inhibition of PrPSc replication in cell culture have been described (12), and RNAi of PrP also works in vivo. Transgenic mice generated by lentiviral transduction of embryos stably express anti-PrP shRNAs and have increased resistance to prion infection because of RNAi-mediated reduced expression of endogenous PrP (13). However, until now, RNAi had not been used therapeutically in vivo in prion disease. Here, we have shown that treating mice with lentiviruses expressing shRNAs to knockdown PrP in established prion disease rescued early neuronal dysfunction and death in targeted areas and significantly prolonged survival. Injection of virus into the hippocampus 8 weeks after prion infection prevented the first behavioral deficits associated with early pathology of the CA1 region: loss of burrowing activity and object recognition memory (22) (Fig. 2). In our previous work, where PrP knockdown was due to recombination at the genomic level at 8 wpi, early deficits occurred but recovered rapidly in PrP-depleted animals. Here, injection of lentivirus expressing anti-PrP shRNAs at 8 wpi prevented their manifestation altogether, perhaps because posttranscriptional gene silencing is more rapid, or more tightly controlled temporally, than genetic excision of PrP encoding sequences after transgene expression. The benefits of RNAi treatment were also seen morphologically. There was significantly less spongiform degeneration and neuronal loss where anti-PrP lentivirus was delivered. These changes progress rapidly in RML-infected tg37 mice after 8 wpi, particularly in the hippocampus (4), and were marked in terminally ill LV-

Empty-treated animals at 12 wpi (Fig. 4). However, LV-MW1- treated mice culled up to 3 weeks later had minimal hippocampal spongiform change and neuronal loss (Fig. 4), suggesting sustained focal protection against neurotoxicity where PrP knockdown occurred. Interestingly, spongiosis was also reduced, although less significantly, in thalamus and cortex of animals treated with hippocampal injections (Fig. 5). PrPSc accumulation was also lower in animals with virally mediated RNAi of PrP in the hippocampus than in mock treated animals, and again this reduction was seen beyond the hippocampus, in thalamus and cortex. The more widespread changes are likely to reflect altered spread of prion infection after hippocampal PrP knockdown, as discussed below. Of note, PrPSc accumulation did not appear to affect neuronal function or survival, as reflected in preservation of hippocampal behaviors and structural neuronal integrity, and consistent with our observations in mice with Cre-mediated PrP depletion (5), which has implications for the level of knockdown required for therapeutic effect. Thus, simply slowing the rate of prion replication, here by reducing PrPC levels, may be effective for prevention of neurotoxic effects. The critical effect, however, was the effect of this treatment on survival of prion-infected mice. A single treatment with focal injection of virus resulted in significantly prolonged survival time of treated animals, compared with mock or untreated mice, with a mean increase in lifespan of 23.5% compared with untreated animals (Fig. 3). The spread of incubation times in the LV-MW1 group (87–129 days after inoculation, mean 105  4 days) is probably due to variation in neuronal transduction by virus seen in individual mice (data not shown) or variability between individual injections, with the highest levels of transduction affording the greatest protection and longest survival. The increased survival was strikingly large with respect to the very small volume of brain targeted. This may result from direct or indirect effects of localized neuroprotection or may simply be due to the reduction of PrP expression at a critical, or rate-limiting, site for prion replication. Prion incubation times are known to be inversely proportional to overall levels of PrP expression (3, 23, 24), and it is likely that regional variations also affect prion replication rates and incubation periods. The hippocampus is a focus of early prion replication and PrPSc deposition (see Fig. S3) both forRMLand other prion strains in various inbred lines and in some transgenic mice (25, 26), including tg37 mice, used here (4). We showed up to 80% reduction of hippocampal PrP mRNA expression (Fig. 1B) with single LV-MW1 administration; this localized knockdown may therefore eliminate a key area for early prion replication in this model. Further, we have found no evidence for the spread of lentivirus beyond the injection site, supporting the concept that it is the effect of localized hippocampal PrP depletion that alters the spread and replication of RML prions in this model. Clearly, all animals succumb eventually, presumably due to prion-mediated neurodegeneration in other critical brain regions, but the neuroprotective effects seen within the hippocampus and beyond are clearly a desirable effect of therapy. If transduction were to be more widespread, by pseudotyping lentiviruses with coat proteins that allow retrograde transport (27, 28) or using evolving mechanical techniques for enhanced delivery (29–31), more extensive neuroprotection and longer survival might ensue. Even focal targeting may have therapeutic application in some situations, however. In conclusion, we have used lentivirally mediated RNAi for treatment of established prion infection in mice. Even localized single administration of these viruses to the hippocampus prolonged the lifespan of infected mice, protected transduced neurons from degenerating, reduced PrPSc accumulation, and prevented the onset of the first behavioral deficits associated with the disease. Our findings urther support therapeutic strategies directed at PrP knockdown for the treatment of prion diseases and are also relevant for neurodegeneration more widely, highlighting the importance of intervention when neuronal dysfunction can still be reversed. The approach used here paves the way not only for possible future therapy but also for mechanistic dissection of toxicity and recovery in prion diseases. Further exploration of the extent and timing of RNAi-mediated PrP knockdown required for increased therapeutic effect in prion disease can now be undertaken. Methods...snip...end

White et al. PNAS  July 22, 2008  vol. 105  no. 29  10243 NEUROSCIENCE


Author contributions: G.R.M. designed research; M.D.W., M.F., I.M., and S.B. performed research; M.D.W., M.F., I.M., S.B., J.C., and G.R.M. analyzed data; and G.R.M. wrote the paper. Conflict of interest statement: J.C. is a director and shareholder of D-Gen Limited, an academic spin-out company working in the field of prion disease diagnosis, decontamination, and therapeutics. D-Gen markets the ICSM35 and ICS18 antibodies used in this study. This article is a PNAS Direct Submission. Freely available online through the PNAS open access option. *Present address: Centre for Neuroscience Research, University of Edinburgh, EH8 9XD, United Kingdom. †To whom correspondence should be addressed. E-mail: mhtml:%7B33B38F65-8D2E-434D-8F9B-8BDCD77D3066%7Dmid://00000004/! This article contains supporting information online at 0802759105/DCSupplemental. © 2008 by The National Academy of Sciences of the USA

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Wednesday, March 26, 2008

Intraventricular pentosan polysulphate in human prion diseases: an observational study in the UK

To cite this article: I. Bone, L. Belton, A. S. Walker, J. Darbyshire (2008)

Intraventricular pentosan polysulphate in human prion diseases: an observational study in the UK



Intraventricular pentosan polysulphate in human prion diseases: an observational study in the UK

I. BoneaaDepartment of Medical and Cardiovascular Studies, Western Infirmary, Glasgow, UK, L. BeltonbbMRC Clinical Trials Unit, London, UK, A. S. WalkerbbMRC Clinical Trials Unit, London, UK and J. DarbyshirebbMRC Clinical Trials Unit, London, UKaDepartment of Medical and Cardiovascular Studies, Western Infirmary, Glasgow, UK and bMRC Clinical Trials Unit, London, UK Prof. Ian Bone, Department of Medical and Cardiovascular Studies, Western Infirmary, Glasgow G11 6NT, UK (tel.: 44 1436 671472 e-mail:


Background and purpose: This observational study assessed the effect of continuous intraventricular infusion of pentosan polysulphate (PPS) in seven patients at different clinical centres in the UK.

Methods and results: Complications of intraventricular catheterization were frequent. PPS was well-tolerated over a wide dose range (11–110 µg/kg/day) during the 6-month study. Four patients were assessed for the entire study period: one remained stable, two showed minimal deterioration and one progressed significantly. Mean survival of all patients was longer than reported values for natural history of specific prion disorders.

Conclusion: Possible reasons for these findings are explored.


Disease duration and survival

Survival of the seven patients from estimated disease onset to death or last known alive (see clinical assessment  section) is documented in Table 1. Table 2 compares data for seven patients plus the extra case [14] with those of natural history patients. Individual survival of all patients in all disease groups (16–75 months) was at or beyond the reported means [20] and medians [M. Pocchiari, personal communication; 21]. All but one vCJD patient also survived beyond the ranges of survival determined by both Pocchiari (personal communication) and Stewart et al. [21].

Other investigations

Patients underwent various tests, including coagulation, electrolyte and cerebrospinal fluid protein 14-3-3 levels, differential cell counts, erythrocyte sedimentation rate, urinalysis, chest X-rays, analysis of gait, heart rate variability and detailed neuropsychometry. All had initial CT scans, and some had further CT/MRI monitoring (between 1 and 18 scans per patient). Sequential scans (Fig. 4) were carried out in only three patients.


PPS was administered by the intraventricular route and complications with the catheterization procedure occurred in four of seven patients, as previously observed [14,15]. Some catheters were positioned biventricular and some univentricular, though substances

injected into just one ventricle may distribute evenly throughout the CNS [22,23]. The extent of PPS distribution will be critical, given the diffuse pathology of the different prion disorders [24,25].

No safe or effective dosing regimen has been established for PPS in humans. Doses varied 10-fold in this study. The dose of 11 lg/kg/day, derived from animal studies [10] and calculated from total body area [14], may be an underestimate for infusion into a single compartment (M. Rawlins, personal communication). Doses up to 110 lg/kg/day were tolerated, with no toxicity, increase in seizures or haemorrhagic complications. The low patient numbers made conclusions of safety unreliable – only overt toxicity could be detected.

Standardized follow-up imaging, which might have allowed crude assessment of brain atrophy [26], was not performed regularly in these patients (not at all in one) [26]. Assessment was further confounded by movement artefacts. Sequential scans were rarely taken, but did reveal continuing atrophy throughout therapy (Fig. 4). Frisoni et al. [27] emphasize the need for prospective imaging to assess brain atrophy, preferably at a single site and with movement artefacts minimized. Of the four patients assessed prospectively for the entire 6-month study, one remained stable, two showed minimal deterioration and one deteriorated signifi- cantly. PPS efficacy was difficult to quantify because of the short time frame, low patient numbers, variable patient/disease characteristics and differences in management and assessment. It was not possible to recruit a control group with matching baseline features as planned in the initial protocol.

Survival, as measured by the interval between disease onset and death, can be a robust end-point for measuring efficacy. However, it is very difficult to establish retrospectively when the first symptoms emerged. Increased public awareness of these diseases and differences in the ability to identify/recall details of early nonspecific symptoms may mean that diagnosis is being made earlier in the disease course. Comparisons with previous data may, therefore, be subject to lead-time bias. Even if the precise point of onset can be determined, disease survival is probably to be influenced by age and gender, genotype, disease-modifying treatments, level of care, treatment complications, infections, immobility and nutritional status. A collaborative study [20] used data from 10 national registries of prion disorders, including untreated (natural history) cases, and revealed differences in survival in vCJD, iatrogenic (human growth hormone) and inherited (GSS) forms of the disease (Table 2). Additional survival data were provided by Stewart et al. [21] in a systematic review that included studies showing variability in disease progression, levels of care, lifeending decisions and life-prolonging interventions. Table 2 compares the survival of the seven patients with published figures [M. Pocchiari, personal communication; 21].

There are many possible reasons why survival of PPS-treated patients might appear longer compared with such untreated patients: including chance alone and biases such as lead-time bias from attentive carers diagnosing onset early; selection bias from included patients having prolonged survival whilst awaiting PPS or bias from increased use of active interventions for complications in more actively managed PPS patients amongst others. Self-selection related to longer survival is less probably in this study because there were variable delays from disease onset to treatment (4–19 months in vCJD cases; 7–11 months in iatrogenic cases and 29– 43 months in GSS cases).

Survival of all seven patients exceeded mean survival of natural history patients [20] but were within reported ranges for iatrogenic and inherited cases [21]. Three out of four vCJD patients (including the additional patient

from [14]) survived longer than the reported median and range for both natural history studies [M. Pocchiari, personal communication; 21]. By definition, for every new patient surviving longer than the median survival time, one will not – thus the probability of surviving longer than the median survival time is 0.5. If there were no effect of PPS on survival, the probability of two patients with iatrogenic or inherited prion disease both exceeding the median survival time of previous untreated patients just by chance is 0.25 (0.52). The probability of four vCJD patients exceeding the median survival time by chance alone is 0.0625 (0.54). Compared with natural history data [M. Pocchiari, personal communication; 21], the patients with inherited GSS had survival times of 52 and 64 months (last seen alive), which lie within reported range [21] for untreated patients and thus do not differ significantly. The two patients with iatrogenic disease died 29 and 32 months after diagnosis, both similar to the maximum reported by Stewart et al. [21]. Rank-sum testing suggests the probability of two treated patients surviving beyond the maximum of 111 untreated patients (if there were no difference between treated and untreated patients and also none of the other potential biases described above) is 0.02, which indicates there may be a very weak suggestion/ possibility of some effect given the fact that survival times were similar to the maximum, and the strong possibility of lead-time bias in this group of patients. Of the four vCJD patients, in whom untreated comparison patients are more contemporaneous, one survived for 16 months (beyond the median of 13 months in (M. Pocchiari, personal communication) and 14 months in [21]) and three are still alive in August 2007 (all exceeding the mean, median and range of untreated patients in both natural history studies). The probability of this occurring (if there were no difference between the treated and natural history patients and no other potential biases) is 0.01, indicating some suggestion/ possibility of an effect.

These findings must, of course, be interpreted cautiously because of the difficulty in determining disease onset from non-specific and subtle symptoms and the very small numbers. An accurate date of onset and a longer period of prospective assessment would yield more data for evaluating efficacy. However, if other explanations can be discounted, then prolonged survival in these patients may suggest a treatment effect of PPS.


This small case series found that widely varying doses of PPS delivered intraventricularly were safe, resulting in patient survival similar to or greater than in previously reported historical controls, in most cases. However, complications from the surgical procedures were common. Small observational studies with this much variability cannot quantify efficacy and offer only limited data on safety. They can, however, be valuable if procedural and follow-up protocols are strictly controlled. Recent draft guidelines on clinical trials in small populations by the Committee for Medicinal Products for Human Use recognize the importance of observational studies and case reports when data are collected in a controlled manner. They recommend use of a surrogate marker when recruitment of sufficient patients is difficult or will take a very long time. This commonly occurs in studies of the rare human prion diseases, yet there are no obvious surrogate markers. More experimental work in animal models is clearly needed, both on efficacy and on the distribution and binding of PPS following intraventricular administration. If results are encouraging, a controlled trial in human prion disease should be considered, having determined optimum doses. Until then, all patients with prion diseases considering PPS therapy should be informed of existing evidence and, if opting for treatment, managed and monitored in a standardized manner.


We thank the patients and families who participated in this study and the UK PPS-treating clinicians (UK PPS Treating Clinicians: J. Bamford, Leeds; A. Gale, London; P. Newman, Middlesbrough; C. Rickards, Swansea; S. Wimalaratna, Swindon) and Maria Hampshire for her help in manuscript preparation. This study was proposed by the Department of Health and funded by the UK Medical Research Council.


Subject: Findings of MRC monitoring study of Pentosan Polysulphate treatment in CJD patients does not stop the progression of vCJD and other prion diseases

Date: July 12, 2006 at 10:29 am PST

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Findings of MRC monitoring study of PPS (does not stop vCJD) Wed Jul 12, 2006 12:18

12 Jul: Pentosan Polysulphate & CJD

Findings of MRC monitoring study of Pentosan Polysulphate treatment in CJD patients

A Medical Research Council monitoring study of a small number of UK patients has found that a compound called Pentosan Polysulphate (PPS) does not stop the progression of vCJD and other prion diseases but the report recommends more research. The study provides qualified reassurance on some of the safety concerns that have been raised previously. The observational study of seven patients was carried out by Professor Ian Bone from Glasgow, Intraventricular Pentosan Polysulphate in Human Prion Diseases: A study of Experience in the United Kingdom, is a summary of the responses that people with prion diseases have shown to PPS.

The chemical nature of PPS means that it is unable to enter the brain if administered orally or intravenously. For the purposes of this treatment, therefore, it has been administered directly into the ventricles of each patient’s brain - a route known as intraventricular delivery. Fluid circulating around the brain from the ventricles potentially provides a route to spread PPS around the brain tissue.

Professor Bone carried out the study based on analysis of seven patients’ treatment and he stresses that the findings should not be taken as conclusive, because the report was based on a very small number of patients, treated in different ways, and because like-with-like comparisons with untreated patients were not possible. However any severe side-effects or clear benefit of PPS treatment in halting progression could have been revealed by this study. The findings are being made available now, to inform the debate over this treatment.

The MRC’s New Therapies Scrutiny Group endorsed the recommendations of Professor Bone’s report:

Further experimental work in animals will provide the most immediate source of evidence of whether or not PPS is likely to extend survival. We need better information on the extent to which PPS penetrates and spreads through the infected brain. The Medical Research Council will take this forward. Further clinical research could be undertaken. Ideally, a formal prospective longitudinal standardised follow-up study would be required but this must be dependent on the results of the experimental animal work being encouraging. In the meantime, newly diagnosed patients should be informed verbally and in writing about current knowledge of PPS, including the risks associated with intraventricular catheterisation, when treatment options are discussed. The Medical Research Council will take forward this recommendation with the Department of Health. Informed people opting for intraventricular PPS should undergo the procedure to fit the catheter and pump at a neurosurgical centre with appropriate experience of such surgery. However, dose initiation and escalation could be managed locally. People treated in this manner should be followed up through an approved protocol of clinical assessments and investigations. Current patients on PPS should continue to be monitored as part of a supportive, structured review, and should be given up to date information and advice. Professor Bone said: “Pentosan Polysulphate itself does not seem to carry a high probability of side effects from prolonged usage. However, the surgical complications of intraventricular catheter and pump placement were significant. The drug does not appear to halt the progression of the disease. Loss of brain function continues after treatment has started and, where measured by imaging, loss of brain tissue also continued. This is the first time that this mode of drug delivery has been carried out over such a prolonged period of time. The study shows that intraventricular delivery might provide a long-term alternative route for other future therapies that cannot enter the nervous system by oral or intravenous routes in situations where the surgical risks are justified.”

He went on: “The patients treated with PPS appear to have survived for unusually long periods. However, we cannot conclude with certainty that the treatment has a beneficial effect, because it was impossible to make direct comparison with similar but untreated patients. Moreover, with such small numbers the results might be a matter of chance. The report recommends specific laboratory experiments to address the uncertainties.”

Professor Ian Bone said “I am very grateful to the families and patients who participated in the study, and I hope that my report will help people who have to take difficult decisions about treatment in future. A report like this cannot always offer definite answers, and we urgently need further rigorous research to give scientists, doctors, patients and their families more information on which to base future treatment decisions.”

The co-chair of the committee, Professor Sir Michael Rawlins welcomed the study: “Professor Bone’s observations have helped cast light on a little known and difficult-to-research area. He has shown that Pentosan Polysulphate itself does not appear toxic at the modest doses given and leaves open the intriguing possibility that it may have some effect on the duration of survival. Sadly it seems that a loss of brain function continues in patients being treated with PPS. Professor Bone has also confirmed what we knew at the outset – that the surgical procedure needed to administer PPS carries a degree of risk, though is generally considered to be acceptable given the advanced stage of the disease in these patients. The recommendation that surgery be carried out in an experienced centre, and to an approved protocol, should help reduce complications associated with the surgery.”

Lester Firkins, the other co-chair, added: “This is a very important report which will inform current and future patients and their families – and also our collective knowledge of this tragic disease. I am very pleased that the MRC New Therapies Scrutiny Group agreed to advise MRC to carry out further research as a matter of urgency to fill in the gaps in the knowledge on PPS. Additionally, it should now be possible to help new patients and their families with better information on the risks of PPS by the publication of a balanced information leaflet. We are all indebted to the current patients and their families for participating in this study – and of course they must continue to benefit from appropriate monitoring and support.”

If you would like to arrange an interview please contact the MRC press office on 020 7637 6011

Notes for editors:

MRC New Therapies Scrutiny Group for Prion Disease

The MRC New Therapies Scrutiny Group for Prion Disease (NTSG) was established in 2005 at the request of the Chief Medical Officer (CMO), to provide an independent source of advice on research into the development of potential therapeutics or preventative agents for prion disease. NTSG will build upon the previous work of the Department of Health CJD Therapy Advisory Group (TAG).

NTSG reports to the Medical Research Council (and other bodies when appropriate). The Group will advise MRC on the development of new therapeutic agents that could possibly be brought to bear upon this disease and will also maintain an overview of other relevant research.

The Medical Research Council

The Medical Research Council (MRC) is funded by the UK tax-payer. It aims to improve human health. The research it supports and the scientists it trains meet the needs of the health services, the pharmaceutical and other health-related industries and universities. The MRC has funded work which has led to some of the most significant discoveries and achievements in medicine in the UK.

©2006 Medical Research Council


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CharlesWeissmann1 and Adriano Aguzzi2

1Department of Neurodegenerative Disease/MRC Prion Unit, Institute of Neurology,

Queen Square, London WC1N 3BG, United Kingdom;


2Institute of Neuropathology, University Hospital, CH-8091 Z¨urich, Switzerland;


Key Words transmissible spongiform encephalopathies, Creutzfeldt-Jakob

disease, bovine spongiform encephalopathy, proteinopathy, neuroblastoma cells

¦ Abstract

Devising approaches to the therapy of transmissible spongiform encephalopathies, or prion diseases, is beset by many difficulties. For one, the nature of the infectious agent, the prion, is understood only in outline, and its composition, structure, and mode of replication are still shrouded in mystery. In addition, the mechanism of pathogenesis is not well understood. Because clinical disease affects mainly the brain parenchyme, therapeutic agents must be able to traverse the brain-blood barrier (BBB) or have to be introduced directly into the cerebrospinal fluid or brain tissue. And finally, because the disease is usually recognized only after onset of severe clinical symptoms, the question arises as to whether the neurodegenerative processes can be reversed to any extent after a successful eradication of the agent.





The earliest attempts to treat human prion disease, performed when the agent was generally assumed to be a virus, were carried out with antiviral drugs, such as amantadine, and were unsuccessful (137).


Quinacrine, chlorpromazine, and some tricyclic derivatives with an aliphatic side chain were described as efficient inhibitors of PrPSc formation in murine neuroblastoma cells chronically infected with the Chandler scrapie isolate (138, 139). Because quinacrine and chlorpromazine have been used in human medicine as antimalarial and antipsychotic drugs, respectively, and because they cross the BBB, they were proposed as therapeutic agents for CJD patients (139). No therapeutic effectwas seen following quinacrine treatment of 20 patients (140) (A. Alperovich, quoted in Reference 141), although some transient improvement occasionally occurred (142). Subsequent animal experiments failed to demonstrate efficacy in the treatment of TSEs (141), even after intraventricular infusion (135).

Amphothericin B

Amphothericin B and some of its analogues delayed the appearance of spongiosis, astrogliosis, and PrPSc accumulation in the brain of scrapie-infected hamsters (125). However, an attempt to treat a CJD patient with amphothericin B was unsuccessful (143). In view of its high systemic toxicity, these results dampen any hopes that amphothericin B will prove useful in prion disease therapy.

Pentosan Polysulfate

Data presented at two prion meetings in 2002, and published recently (135), suggest that intraventricular administration of PPS to intracerebrally prion-infected mice prolonged incubation time. PPS is marketed in some countries as a treatment for interstitial cystitis and as an anticoagulant, although its side effects include hemorrhage and hypersensitivity reactions.


Recently a legal case was brought by two families whose children JS and PA, aged 18 and 16 respectively, suffered from vCJD [DS v JS and an NHS Trust and The Secretary of State for Health, intervenor; PA v JA and an NHS Trust and The Secretary of State for Health (2002) EWHC 2734 (Fam)]. They applied to the court to permit intraventricular administration of PPS, a treatment previously given only to rodents and dogs. The judge heard testimony from Doh-Ura, the Japanese researcher who had performed the animal studies; from a neurosurgeon


willing to administer the novel treatment; and from several respected neurologists who expressed reservations about it. The judge found that both young patients had “some enjoyment from life which is worth preserving” and that the treatment, as it was supported by medical opinion, would be in their “best interest” (the legal criterion for doctors to treat patients who lack capacity for personal decisions) (144). Treatment has been initiated, but no reports on the fate of the patients have been issued.

Physicians can thus come under pressure from the courts to allow new treatments to be used without having been tested in clinical trials, although the ruling described above implies that such decisions would have to withstand the “Bolam” test of being acceptable to a reasonable body of medical opinion. The ruling also upheld the application of the Human Rights Act in this area, citing Articles 2 and 8, the rights to life and to respect for family life. It is not inconceivable that such analysis could allow patients to circumvent clinical trials by asserting their rights to receive innovative therapy, and this development is of concern, particularly in the clinical field of human prion diseases.

We may at some stage be confronted with a therapy that can eradicate prion infection without reversing the neural damage, which in extreme cases could condemn patients to years or decades of severe disability and dementia. This would lead to an ethical dilemma as to whether treatment should be withheld if the disease has progressed to a severe stage. Such situations could be prevented if a diagnostic test could detect prion disease in its preclinical stage. Whether such a test, if it ever became available, would be applied to detect a disease with an incidence of 1 in a million per year is a matter of debate; clearly it would be practicable in the case of familial prion diseases.

The Annual Review of Medicine is online at

LITERATURE CITED...snip...end...tss


It is possible that this treatment will slow (or even halt) progression of disease but there is no guarantee and no present means of objectively quantifying the degree of possibility. Any such effect, IF it were to occur would probably be temporary. It is not possible to give any indication of any time limit on such an effect. The possibility that any such effect could continue throughout the duration of treatment cannot be absolutely excluded but it seems unlikely. Clearly, the later in the disease process that such a treatment were to be undertaken, the less likely any benefit would be seen. Also, in late stages of disease, slowing of progression might be difficult to objectively assess. There are, currently, no validated laboratory or imaging assessments that could be used to give unequivocal evidence of efficacy; one would have to rely on more subjective assessments including everyday functional ability and serial neurological impairment examinations, perhaps with the adjunct of neuropsychological assessments. However, research is being undertaken to see if certain tests could be useful in monitoring disease progression.

On the basis of current understanding, there is no realistic possibility of actual improvement in the sense of reversal of previously established neurological deficit. Again, this cannot be absolutely excluded but it seems highly improbable, especially in relatively late stages of disease.

To date, at least several human individuals with prion disease have been treated with intraventricular PPS. There are also families who have considered the treatment and decided that they do not wish for it. There are no hard data currently in the public domain. However, one individual (with vCJD) is said to have not shown any clear evidence of deterioration over a period of at least 23 months (as at February 2005). The person concerned was at a late stage of illness at the time of treatment, with very significant neurological impairment and it could be difficult to assess any signs of deterioration or minor improvement in this sort of situation. This period of apparent clinical stability could be taken as evidence that this treatment has indeed had a beneficial effect in this one individual. However, some individuals with prion diseases go through 'plateau' periods and, to some extent, survival in the later stages of illness depends on the level and quality of general nursing care provided . The present duration of apparent clinical stability must at least suggest the possibility of some treatment efficacy. In addition, there have been suggestions of minor clinical improvements. However, at present, it cannot be stated that this one treated individual provides definite evidence of efficacy of intraventricular PPS. No information is currently available on the other treated individuals.

The best possible outcome from intraventricular PPS

On the basis of the available evidence, the best possible outcome that could be expected after treatment with intraventricular PPS is that there may be some temporary slowing or halting of the disease progression. However, there is little likelihood of significant clinical improvement. Nor is there a likelihood of permanent halting of disease progression. Of course, to some extent, this might depend on the duration of intraventricular PPS administration. It is not clear on what basis one would decide on the duration of treatment.

Naturally, a treatment which stabilises an individual's condition could conceivably lead to an individual being in a state of potential suffering for a longer period of time. It might be proposed that any slowing of progression or halting of progression might allow an individual to survive longer and therefore receive future more beneficial treatment if it were to become available. However, this would be a speculative view and, while treatments for CJD are being researched, there is no realistic expectation of a complete cure in the immediate future.

Additional Comments

Any conclusion concerning these above considerations, in the context of an individual person, would necessarily involve a number of very difficult or personal judgements about quality of life and the degree of suffering experienced by an individual in a disease like CJD. Any such judgements are bound to be subjective and reflect both general belief systems and personal evaluations of the individual patient. There are clearly important issues of consent and also issues as to the full understanding of those involved as to the potential benefits and risks. Clearly, there are few hard data on which to make clear decisions. At this point, the human treatment data do not allow for any specific comments which can be made concerning problems or benefits, aside from the facts that there are no reported major serious complications and that there has been no obvious clinical deterioration over some months of treatment in at least one case.

Any decision about a given patient would have to be taken in an entirely individual way, based on a detailed assessment of both the patient and the concerned relatives. The overriding principle should be: What is in the best interests of the individual patient? bearing in mind that CJD is inevitably and invariably a progressive and fatal disease.

There is, of course, an argument that such treatment should be evaluated in the context of a properly organised clinical trial. There are no current plans to set up such a trial and, in relation to this specific issue, the comments of two relevant professional bodies (given in the section below) should be noted.

Advice from relevant professional bodies

The Department of Health have statements on intraventricular PPS on their website:

This includes statements of advice from the CJD Therapy Advisory Group and the CSM.

The advice from the CJD Therapy Advisory Group can be summarised as follows:

There are insufficient clinical data to support the claim that PPS is effective during clinical disease.

There are insufficient safety data on which to base a rational treatment regimen in humans.

Further animal model experimental work is warranted.

Nevertheless, at the dosage used in at least one individual, there have been no definite harmful effects attributable to the drug.

All patients with prion disease should undergo appropriate monitoring during disease progression, in a way that allows collection of data on the natural history of disease and on any treatments that might be given.

The advice from the CSM is similar and states further that:

"there is no evidence in support of its use as a treatment in late stage disease".

"In the light of the limited information on PPS treatment of clinically established vCJD it is impossible to assess the risk/benefit relationship of PPS in these indications".

There was insufficient information to reach any conclusions about the efficacy of treatment in [the single case known about at the time of the statement].

They also recommended that further study of PPS should be undertaken in a clinical trial setting.

Neither of these statements preclude the possibility of an individual clinician deciding to treat an individual patient; such decisions remain absolutely individual ones. However, clinicians would wish to consider any such decisions in the light of all the available information and advice.

The case of the first individual who received this treatment was referred to the High Court and there was a ruling in favour of this particular individual being allowed to receive such treatment, as being in that individual's overall best interests. However, this was an individual ruling relating to a particular individual. It is understood that other cases have been referred to court, but again on an individual basis.

There are important issues of consent regarding such 'experimental' treatment, both with regard to the age of some affected individuals and also with regard to competence (where disease affects the brain).

The Department of Health has sought to identify certain selected hospitals where IVPPS treatment might be instituted, if there is a strong desire for it by a family and agreement by their relevant clinician, so as to centralise any experience with this treatment. Such centres will develop protocols for the referral of patients and the process of arranging such treatment (including the various potential legal issues, such as consent) should thereby become simpler. However, there are no current plans to establish a formal scientific trial of intraventricular PPS and the treatment is one that is being given essentially on a speculative basis. The present provision of IVPPS remains an individual decision between patient, family and their immediately responsible clinician, after full understanding and discussion of the facts as detailed above.


A study published in 2004 (Otto et al.) reported some beneficial effects on cognitive function in patients with CJD but there is no evidence for increased survival with the treatment.


Otto M et al. Efficacy of flupirtine on cognitive function in patients with CJD: a double-blind study. Neurology 2004; 62: 714-718.


As indicated above, the MRC has funded a formal treatment trial of CJD. The trial commenced in 2004. It is, initially, aiming to study Quinacrine. However, it may study other possible treatments in the future. It will also be reviewing and assessing individuals without treatment to obtain comparative data of the natural course of illness.

Unsuccessful intraventricular PPS treatment of vCJD Sun Apr 9, 2006 09:59

1: Acta Neurochir (Wien). 2006 Apr 7; [Epub ahead of print]

Unsuccessful intraventricular pentosan polysulphate treatment of variant Creutzfeldt-Jakob disease.

Whittle IR, Knight RS, Will RG.

Department of Clinical Neurosciences and National CJD Surveillance Unit, Western General Hospital, Edinburgh, UK.

Pentosan polysulphate, delivered by chronic intraventricular infusion, has been proposed as a potential therapy for human prion disease. The first treated patient is still alive several years after treatment started. Here we describe in detail a case of variant Creutzfeldt-Jakob disease in which this treatment was started at a relatively early stage but had no definite clinical benefit. The patient died from disease progression 16 months after diagnosis and 5 months after pentosan polysulphate treatment was commenced.


In conclusion, cerebroventricular infusion of PPS at 11 mg/kg/d appears safe and well tolerated for continuous long-term application. Our patient has survived for 37 months after initial symptoms and 30 months after diagnosis of probable vCJD, while the median duration of illness with vCJD is 13 months (range 6–39)7. Further lessons have also been learned from this first case. Firstly, surgery in a brain affected by vCJD may result in a higher rate of surgical complications than might be expected in a normal patient. We suggest that in order to allow the catheter track to organise, drug infusion should be delayed for at least 7–10 days after implantation of the pump system. Regular neuroradiological followup throughout the treatment period is strongly recommended. Secondly, if clinically significant benefits are to be expected, PPS administration should start as early as possible in the course of the disease and before irreversible loss of neurological function has occurred. Further clinical, neuroradiological and laboratory investigations in the setting of a prospective clinical study with standardised follow-up protocol and data collection are essential in order to assess the efficacy of PPS administration in vCJD and in other prion diseases. ..........snip...end...TSS

Professor Will, well noted to me that "Unfortunately the treatment did not work in this individual but it is important not to conclude that the treatment could not work in other people."