Rationale for delayed-start study of pramipexole in Parkinson's disease: the PROUD study

Early dopaminergic replacement treatment initiation benefits motor symptoms in patients with Parkinson's disease

Background

Parkinson's disease (PD) generally progresses slowly, but it is controversial whether delaying treatment accelerates the progression.

Objective

Determine the correlation between the time of dopaminergic replacement treatment initiation and the severity of clinical symptoms in PD, including motor and non-motor symptoms.

Methods

PD patients were divided between 155 people who were diagnosed de novo and 165 PD patients receiving dopamine replacement therapy. Basic patient characteristics included gender, age, age at onset, disease duration, and the time of dopaminergic replacement treatment initiation. We used MDS-UPDRS scores to evaluate the severity of motor symptoms and we also used the scale to assess the severity of non-motor symptoms such as cognition, mood, sleep, and quality of life.

Results

The mean time between symptom onset and the initiation of drug treatment was 31.0 (22.5) months. After adjusting for age, sex, age at onset, and disease duration, we found that the MDS-Unified Parkinson's Disease Rating Scale (UPDRS)-III score increased faster in the de novo group with a similar disease duration (F = 8.7, p = 0.0034) than the treatment group. The cumulative incidence of progression to H-Y score 3 in de novo PD group over disease duration was 39.7% in 50months and 92.2% in 100 months, while in treated group such cumulative incidence was 15.5% in 50 months, 51.4% in 100 months and 81.5% in 150 months. The cumulative incidence of patients in the de novo PD group was higher than that in the treated group (p = 0.001), suggesting that untreated patients were more likely to progress to the advanced stages. Symptoms onset, the time between symptom onset and treatment initiation, age, sex, and disease duration explained 28.95% of the total variation in the MDS-UPDRS-III score for motor symptoms. In drug-naïve patients, the time between symptom onset and treatment initiation explained 20.1% of the total variation in the MDS-UPDRS-III score for motor symptoms (t = 6.15, p < 0.001).

Conclusions

These data in our study showed that early dopaminergic replacement treatment have played a positive role in PD patients, while dopaminergic replacement delayed treatment might be detrimental to motor symptoms and non-motor state of PD patient. Recognizing early stage symptoms of PD and early diagnosis are of great significance to treatment.

Neuroactive gonadal drugs for neuroprotection in male and female models of Parkinson's disease

The existence of sex differences in Parkinson's disease (PD) incidence is well documented with greater prevalence and earlier age at onset in men than in women. These reported sex differences could be related to estrogen exposure. In PD animal models, estrogen is well documented to be neuroprotective against dopaminergic neuron loss induced by neurotoxins. Using the 1-methyl 4-phenyl-1,2,3,6 tetrahydropyridine (MPTP) mouse model, we showed that several compounds are neuroprotective on dopaminergic neurons including estrogen, the selective estrogen receptor modulator raloxifene, progesterone, dehydroepiandrosterone, the estrogen receptor alpha (ERα) agonist PPT as well as the G protein-coupled membrane estrogen receptor (GPER1) specific agonist G1. Accumulating evidence suggests that GPER1 could be implicated in the neuroprotective effects of estrogen, raloxifene and G1 in collaboration with ERα. We recently reported that the 5α-reductase inhibitor Dutasteride is also neuroprotective and could bring an alternative to estrogens for therapy in male. Additional studies are needed to optimize therapies with these gonadal drugs into safe personalized treatments according to sex for treatment of PD.

Early versus delayed initiation of pharmacotherapy in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease and pathologically is characterised by a progressive loss of dopaminergic cells of the nigrostriatal pathway. Clinically, PD is mainly defined by the presence of the motor symptoms of bradykinesia, rigidity, rest tremor and postural instability, but non-motor symptoms such as depression, dementia and autonomic disturbances are recognised as integral parts of the disease. Although pharmacotherapy for PD was introduced almost 50 years ago, and has improved significantly over the intervening period, the timing of initiation of treatment in newly diagnosed PD remains controversial. While some physicians favour an early start of pharmacotherapy at or soon after diagnosis, others prefer to delay pharmacological treatment until a certain degree of disability has developed. This article aims to discuss the advantages and disadvantages of both strategies by exploring their effects on symptoms, disease progression and quality of life. Although the data on putative disease-modifying effects of early pharmacological intervention in PD are still inconclusive, we believe that the most important indication for an early initiation of anti-parkinsonian treatment should be to maintain the quality of life of PD patients and to secure their socioeconomic status as long as possible.

Parkinson disease: from pathology to molecular disease mechanisms

Parkinson disease (PD) is a complex neurodegenerative disorder with both motor and nonmotor symptoms owing to a spreading process of neuronal loss in the brain. At present, only symptomatic treatment exists and nothing can be done to halt the degenerative process, as its cause remains unclear. Risk factors such as aging, genetic susceptibility, and environmental factors all play a role in the onset of the pathogenic process but how these interlink to cause neuronal loss is not known. There have been major advances in the understanding of mechanisms that contribute to nigral dopaminergic cell death, including mitochondrial dysfunction, oxidative stress, altered protein handling, and inflammation. However, it is not known if the same processes are responsible for neuronal loss in nondopaminergic brain regions. Many of the known mechanisms of cell death are mirrored in toxin-based models of PD, but neuronal loss is rapid and not progressive and limited to dopaminergic cells, and drugs that protect against toxin-induced cell death have not translated into neuroprotective therapies in humans. Gene mutations identified in rare familial forms of PD encode proteins whose functions overlap widely with the known molecular pathways in sporadic disease and these have again expanded our knowledge of the neurodegenerative process but again have so far failed to yield effective models of sporadic disease when translated into animals. We seem to be missing some key parts of the jigsaw, the trigger event starting many years earlier in the disease process, and what we are looking at now is merely part of a downstream process that is the end stage of neuronal death.

Pramipexole in patients with early Parkinson's disease (PROUD): a randomised delayed-start trial

BACKGROUND

In models of dopaminergic neuronal loss, the dopamine agonist pramipexole has exhibited neuroprotective properties. The Pramipexole On Underlying Disease (PROUD) study was designed to identify whether early versus delayed pramipexole initiation has clinical and neuroimaging benefits in patients with Parkinson's disease (PD).

METHODS

Between May 24, 2006, and April 22, 2009, at 98 centres, we recruited patients with PD diagnosed within 2 years and aged 30-79 years. We randomly assigned eligible patients (ratio 1:1), by a centralised, computerised randomisation schedule, to receive double-blind either placebo or pramipexole (1·5 mg a day) and followed them up for 15 months. At 9 months, or as early as 6 months if considered necessary, placebo recipients were assigned to pramipexole. In a neuroimaging substudy, striatal dopamine-transporter binding was assessed by SPECT. All patients, investigators, and independent raters were masked to study treatment. The primary endpoint was the 15-month change from baseline in total score on the unified Parkinson's disease rating scale (UPDRS). This trial is registered with ClinicalTrials.gov, number NCT00321854.

FINDINGS

Of 535 patients, 261 were randomly assigned to receive pramipexole and 274 to receive placebo. At 15 months (n=411), adjusted mean change in UPDRS total score showed no significant difference between early and delayed pramipexole (-0·4 points, 95% CI -2·2 to 1·4, p=0·65). 62 patients in the early pramipexole group and 61 patients in the delayed pramipexole group were included in the neuroimaging substudy, for which the adjusted mean 15-month change in striatal (123)I-FP-CIT binding was -15·1% (SE 2·1) for early and -14·6% (2·0) for delayed pramipexole (difference -0·5 percentage points, 95% CI -5·4 to 4·4, p=0·84). Overall, 180 (81%) of patients given early pramipexole and 179 (84%) patients given delayed pramipexole reported adverse events (most frequently nausea), and 22 (10%) patients in the early pramipexole group and 17 (8%) in the delayed pramipexole group had serious events, two of which (hallucinations and orthostatic hypotension) were deemed related to study drug.

INTERPRETATION

By clinical and neuroimaging measures, pramipexole showed little evidence differentiating 15-month usage from usage delayed for 6-9 months. The results do not support the hypothesis that pramipexole has disease-modifying effects.

FUNDING

Boehringer Ingelheim GmbH.

Pramipexole reduces phosphorylation of α-synuclein at serine-129

α-Synuclein is a central component of the pathogenesis of Parkinson’s disease (PD). Phosphorylation at serine-129 represents an important post-translational modification and constitutes the major form of the protein in Lewy bodies. Several kinases have been implicated in the phosphorylation of α-synuclein. The targeting of kinase pathways as a potential to influence the pathogenesis of PD is an important focus of attention, given that mutations of specific kinases (LRRK2 and PINK1) are causes of familial PD. Pramipexole (PPX) is a dopamine agonist developed for the symptomatic relief of PD. Several in vitro and in vivo laboratory studies have demonstrated that PPX exerts neuroprotective properties in model systems of relevance to PD. The present study demonstrates that PPX inhibits the phosphorylation of α-synuclein and that this is independent of dopamine receptor activation. PPX blocks the increase in phosphorylated α-synuclein induced by inhibition of the ubiquitin proteasomal system. The phosphorylation of α-synuclein occurs in part at least through casein kinase 2, and PPX in turn reduces the phosphorylation of this enzyme, thereby inhibiting its activity. Thus, PPX decreases the phosphorylation of α-synuclein, and this mechanism may contribute to its protective properties in PD models.

Review: management of Parkinson's disease

Parkinson's disease (PD) is one of the most frequent neurological diseases. Despite the modern imaging and nuclear techniques which help to diagnose it in a very early stage and lead to a better discrimination of similar diseases, PD has remained a clinical diagnosis. The increasing number of available treatment options makes the disease management often complicated even when the presence of PD seems undoubted. In addition, nonmotor symptoms and side effects of some therapies constitute some pitfalls already in the preclinical state or at the beginnings of the disease, especially with the progressive effect on patients. Therefore, this review aimed to summarize study results and depict recommended medical treatments for the most common motor and nonmotor symptoms in PD. Additionally, emerging new therapeutic options such as continuous pump therapies, eg, with apomorphine or parenteral levodopa, or the implantation of electrodes for deep brain stimulation were also considered.

The evidence for disease modification in Parkinson's disease

Disease modification or slowing the progression of any neurodegenerative disorder represents a dire unmet need. There have been trials for several decades specifically designed to help evaluate whether a specific therapy might be able to slow the progression of Parkinson's disease (PD) or be disease modifying. Trials evaluating the use of coenzyme Q10, pramipexole, and levodopa suggest that these medications offer symptomatic benefit uniquely, while other studies reveal that rasagiline and selegiline may be disease modifying. This review will discuss in detail the design and results of clinical trials for varied medical therapies that were specifically undertaken to discern whether a particular treatment might be disease modifying in the treatment of PD.

Disease modification in Parkinson’s disease: are we there yet with currently available therapies?

SUMMARY Management of Parkinson’s disease (PD) is currently based primarily on dopamine-replacement therapy for the alleviation of motor symptoms. Current medical and surgical therapies can provide long-lasting symptomatic benefit, but they do not modify progression of the disease. Research is ongoing to find a therapy that can provide neuroprotection, defined herein as preventing vulnerable neurons from dying. Studies of neuroprotection are limited by a lack of adequate biomarkers of PD progression and by the confounding symptomatic effects of many putative neuroprotective therapies. Studies have shown that levodopa prolongs life, but they have not clearly shown that it modifies disease progression. Trials of dopamine agonists have demonstrated symptomatic effect but no unequivocal neuroprotective benefits. While some studies of monamine oxidase B inhibitors have been promising, they have not conclusively proven disease modification. Exercise provides many benefits to patients with PD, may modify the progression of the disease and should be part of each patient’s treatment plan.

Enhancing dopamine treatments: worth the effort?

SUMMARY Dopamine-based treatments underlie our current management of the motor symptoms of Parkinson’s disease. In this article, we look at the development of levodopa therapy, combination therapies with levodopa/dopa decarboxylase inhibitors, use of dopamine agonists, monoamine oxidase inhibitors, catechol-O-methyl transferase inhibitors and the development of nonoral delivery methods, in particular in the treatment of motor complications in later PD. There are some shortcomings of dopamine-based therapies including a limited benefit on the non-motor manifestations of Parkinson’s disease. We conclude by looking at the themes for future developments to further enhance dopamine delivery methods.

Mitochondrial pathology in Parkinson's disease

The last 25 years have witnessed remarkable advances in our understanding of the etiology and pathogenesis of Parkinson's disease. The ability to undertake detailed biochemical analyses of the Parkinson's disease postmortem brain enabled the identification of defects of mitochondrial and free-radical metabolism. The discovery of the first gene mutation for Parkinson's disease, in alpha-synuclein, ushered in the genetic era for the disease and the subsequent finding of several gene mutations causing parkinsonism, 15 at the time of writing. Technological advances both in sequencing technology and software analysis have allowed association studies of sufficiently large size accurately to describe genes conferring an increased risk for Parkinson's disease. What has been so surprising is the convergence of these 2 separate disciplines (biochemistry and genetics) in terms of reinforcing the importance of the same pathways (ie, mitochondrial dysfunction and free-radical metabolism). Other pathways are also important in pathogenesis, including protein turnover, inflammation, and post-translational modification, particularly protein phosphorylation and ubiquitination. However, even these additional pathways overlap with each other and with those of mitochondrial dysfunction and oxidative stress. This review explores these concepts with particular relevance to mitochondrial involvement.

Assessment of Parkinson disease: what do we need to show neuroprotection?

To date, no pharmacological agent has convincingly demonstrated the ability to slow the progression of Parkinson disease (PD). The development of treatments that slow down the progressive degeneration of the nigrostriatal dopaminergic system (true neuroprotection), which is ultimately responsible for the patients' functional decline, has become one of the basic goals of PD research. In this review, we have attempted to analyze the role of different methods that measure PD severity (basically, clinical scales, timed tests, and neuroimaging techniques) in the evaluation of the "neuroprotection" provided by different types of treatment for the disease, on the basis of clinical evidence.

Pramipexole for the treatment of early Parkinson's disease

Pramipexole is a nonergolinic dopamine agonist, with high affinity for the D2 subfamily of dopamine receptors. Pramipexole is efficacious for the symptomatic treatment of early Parkinson's Disease (PD) and its early use, before that of levodopa can delay the emergence of levodopa-related motor complication. Dosage should be increased gradually from a starting dose of 0.375 mg/day up to a maximum of 4.5 mg/day in equally divided doses taken three times per day with pramipexole immediate-release or equivalent daily dosages once-daily with pramipexole extended-release. Pramipexole can also improve depressive symptoms and possibly health-related quality of life in PD. Nonetheless, its use is not devoid of tolerability problems. While peripheral adverse drug reactions, such as nausea, vomiting or orthostatic hypotension, can be effectively treated and usually pose few problems to most patients, neuropsychiatric events can seriously limit the use of pramipexole in some cases. Indeed, excessive daytime somnolence, impulse-control disorders, hallucinations or delusions can severely affect patients, causing important personal or social handicap. Patients should be informed about the risk of such neuropsychiatric complications and their presence should be actively detected at each consultation. More effort will have to be put into further studying the risk-benefit ratio of pramipexole and other dopamine agonists in the treatment of early PD.

The Parkinson Progression Marker Initiative (PPMI)

The Parkinson Progression Marker Initiative (PPMI) is a comprehensive observational, international, multi-center study designed to identify PD progression biomarkers both to improve understanding of disease etiology and course and to provide crucial tools to enhance the likelihood of success of PD modifying therapeutic trials. The PPMI cohort will comprise 400 recently diagnosed PD and 200 healthy subjects followed longitudinally for clinical, imaging and biospecimen biomarker assessment using standardized data acquisition protocols at twenty-one clinical sites. All study data will be integrated in the PPMI study database and will be rapidly and publically available through the PPMI web site- www.ppmi-info.org. Biological samples including longitudinal collection of blood, cerebrospinal fluid (CSF) and urine will be available to scientists by application to an independent PPMI biospecimen review committee also through the PPMI web site. PPMI will rely on a partnership of government, PD foundations, industry and academics working cooperatively. This approach is crucial to enhance the potential for success of this ambitious strategy to develop PD progression biomarkers that will accelerate research in disease modifying therapeutics.

Pramipexole and its extended release formulation for Parkinson's disease

Pramipexole has been a widely used dopamine agonist for the last decade. Recently an extended release formulation of pramipexole has been introduced as both monotherapy for patients with early Parkinson’s disease as well as for patients with more advanced disease, as an adjunct to L-DOPA. Along with the enhanced patient compliance seen with once a day dosing, there are other potential advantages of extended release preparations of dopamine agonists. Patients initiated on pramipexole have a lower incidence of developing motor fluctuations including dyskinesia than those initiated on L-DOPA. Pramipexole requires a prolonged dose titration compared to L-DOPA, and generally does not have the efficacy of L-DOPA. The extended release form of pramipexole shows comparable mean and peak serum levels with once a day dosing as seen with three times a day dosing of the immediate release preparation. The extended release preparation has been studied in randomized multicenter clinical trial against both placebo and the immediate release preparation in the setting of early Parkinson’s disease as monotherapy and in more advanced patients with motor fluctuations on L-DOPA. In both settings the extended release preparation was superior to placebo and comparable to the immediate release form in efficacy with a similar side effect profile including nausea, sleepiness, leg edema, dyskinesias, hallucinations and impulse control disorders.

Available and emerging treatments for Parkinson's disease: a review

Parkinson's disease is a commonly encountered neurodegenerative disorder primarily found in aged populations. A number of medications are available to control symptoms, although these are less effective in advanced disease. Deep brain stimulation provides a practicable alternative at this stage, although a minority of patients meet the strict criteria for surgery. Novel medications that provide enhanced symptomatic control remain in developmental demand. Both gene and cell-based therapies have shown promise in early clinical studies. A major unmet need is a treatment that slows or stops disease progression.