New perspectives on study designs for evaluating neuroprotection in Parkinson's disease (original) (raw)

Seven Solutions for Neuroprotection in Parkinson's Disease

Movement Disorders, 2020

Parkinson's disease (PD) is a neurodegenerative disorder characterized by loss of dopaminergic neurons in the substantia nigra, and accumulation of iron and alpha-synuclein; it follows a characteristic pattern throughout the nervous system. Despite, decades of successful preclinical neuroprotective studies, no drug has then shown efficacy in clinical trials. Considering this dilemma, we have reviewed and organized solutions of varying importance that can be exclusive or additive and outline approaches to help generate successful development of neuroprotective drugs for PD: 1) select patients in which the targeted mechanism is involved in the pathological process associated with the monitoring of target engagement; 2) combine treatments that target multiple pathways; 3) establish earliest interventions and develop better prodromal biomarkers; 4) adopt rigorous methodology and specific disease-relevant designs for disease-modifying clinical trials; 5) customize drug with better brain biodistribution; 6) prioritize repurposed drugs as a first line approach; 7) adapt preclinical models to the targeted mechanisms with translational biomarkers to increase their predictive value.

Concerning neuroprotective therapy for Parkinson’s disease

Journal of Neural Transmission. Supplementa

Studying potential neuroprotective therapy for Parkinson's disease is conceptually problematic because of the heterogenous nature of the Parkinson's syndrome and complexities in operational definitions for neuroprotection. The current literature concerning neuroprotection provides no convincing evidence of any treatment as definitively neuroprotective in Parkinson's disease. Recent clinical trials and novel trial designs are reviewed that may identify meaningful therapy, resulting in maintenance of neurological function and quality of life for persons with Parkinson's disease.

Medical Management of Parkinsons Disease: Focus on Neuroprotection

Current Neuropharmacology, 2011

Neuroprotection refers to the protection of neurons from excitotoxicity, oxidative stress and apoptosis as principal mechanisms of cell loss in a variety of diseases of the central nervous system. Our interest in Parkinson's disease (PD) treatment is focused on drugs with neuroprotective properties in preclinical experiments and evidence-based efficacy in human subjects. To this date, neuroprotection has never been solidly proven in clinical trials but recent adequate markers and/or strategies to study and promote this important goal are described. A myriad of compounds with protective properties in cell cultures and animal models yield to few treatments in clinical practice. At present, markers of neuronal vitality, disease modifying effects and long term clinical stability are the elements searched for in clinical trials. This review highlights new strategies to monitor patients with PD. Currently, neuroprotection in subjects has not been solidly achieved for selegiline and pramipexole; however, a recent rasagiline trial design is showing new indications of disease course modifying effects. In neurological practice, it is of utmost importance to take into account the potential neuroprotection exerted by a treatment in conjunction with its symptomatic efficacy.

Neuroprotection in Parkinson’s disease: facts and hopes

Journal of Neural Transmission, 2019

Parkinson’s disease (PD) is the second most common neurodegenerative disease worldwide. Behind the symptoms there is a complex pathological mechanism which leads to a dopaminergic cell loss in the substantia nigra pars compacta. Despite the strong efforts, curative treatment has not been found yet. To prevent a further cell death, numerous molecules were tested in terms of neuroprotection in preclinical (in vitro, in vivo) and in clinical studies as well. The aim of this review article is to summarize our knowledge about the extensively tested neuroprotective agents (Search period: 1991–2019). We detail the underlying pathological mechanism and summarize the most important results of the completed animal and clinical trials. Although many positive results have been reported in the literature, there is still no evidence that any of them should be used in clinical practice (Cochrane analysis was performed). Therefore, further studies are needed to better understand the pathomechanism ...

Neuroprotection trials in Parkinson's disease: Systematic review

Movement Disorders, 2009

Treatments to slow the progression are a major unmet need in Parkinson's disease. Detailed assessment of randomized trials testing putative neuroprotective drugs was undertaken to inform the design, reporting, and interpretation of future studies. This study is a systematic review of trials testing neuroprotective drugs. Data were extracted independently by two coauthors. Fifteen completed, published trials involving 4,087 participants tested 13 different drugs in 18 double-blind comparisons with placebo. Seven comparisons involving 2,000 subjects assessed MAO-B inhibitors. The primary outcome was change in the Unified Parkinson's Disease Rating Scale score in eight trials and time to need for dopaminergic therapy in seven. Mean participant age was 62 years, 35% were women, the interval from diagnosis to entry averaged 11 months, and the number of participants averaged 272 (largest 5 806). Follow-up averaged <16 months in all but two trials. Detailed randomization methods and success of double-blinding were reported in 20% and 13%, respectively. Based on the investigators' conclusions, six trials were interpreted as consistent with a neuroprotective effect, three as negative, and five as either confounded or not meeting criteria for futility. Neuroprotection trials have involved relatively uniform groups of participants early in the clinical disease course, with outcomes weighted heavily toward motor deterioration. Future trials should include participants with wider ranges of disease stages and assess broader neurological outcomes.

Trial designs used to study neuroprotective therapy in Parkinson's disease

Movement Disorders, 2013

There have been numerous trials conducted to evaluate putative disease-modifying or neuroprotective treatments in Parkinson's disease. These trials have used several different study designs and outcome measures. Each of these has its own strengths and weaknesses. Confounding all studies is the potential symptomatic benefit that the treatment might have on the features of Parkinson's disease. In addition, patient-related factors such as age of onset and the nature of the dominant symptoms may have important impacts that are often not addressed. Here we provide an overview of the various trial designs that have been used and emphasize the challenges faced in attempting to study neuroprotection in Parkinson's disease and the advances needed before this goal can be successfully achieved. V

A responsive outcome for Parkinson's disease neuroprotection futility studies

Annals of Neurology, 2005

for the NET-PD Investigators Futility studies are designed to test new treatments over a short period in a small number of subjects to determine if those treatments are worthy of larger and longer term studies, or if they should be abandoned. An appropriate outcome measure for a neuroprotection futility study in Parkinson's disease (sensitive to tracking disease progression in the short-term) has not been determined. Data sets from three clinical trials were used to compare Parkinson's disease outcome measures. Total Unified Parkinson's Disease Rating Scale (UPDRS; Mentation + Activities of Daily Living + Motor) change and Motor plus Activities of Daily Living UPDRS change, measured in untreated patients, required the smallest sample sizes of all the outcome measures explored. Other outcomes (UPDRS Motor, UPDRS Activities of Daily Living, and time to need levodopa) required somewhat larger sample sizes. Futility designs in Parkinson's disease are feasible in terms of short duration and small sample size requirements, and this design is being applied in two ongoing Parkinson's disease studies to select agents for future larger and longer term neuroprotection studies.

Protection against Parkinson’s disease progression: Clinical experience

Neurotherapeutics, 2008

Treatments with potential neuroprotective capability for Parkinson's disease (PD) have been investigated in randomized, controlled, clinical trials and other studies since the mid-1980s. Although promising leads have arisen, no therapy has been proven to halt or slow disease progression. Several large-scale studies have highlighted progress in methodology, as well as the frustrations of translating laboratory science to practical applications. This review summarizes findings from clinical trials with several classes of compounds, including monoamine oxidase-B inhibitors (selegiline, lazabemide, rasa-giline), dopaminergic drugs (ropinirole, pramipexole, levodopa), antioxidant strategies (␣-tocopherol), mitochondrial energy enhancers (coenzyme Q 10 , creatine), antiapoptotic agents (TCH346, minocycline, CEP-1347), and antiglutamatergic compounds (riluzole). Beyond small-molecule pharmacology, gene therapy approaches, such as delivering neurotrophic substances (e.g., neurturin) by viral vector, are the next generation of treatment options.