Poster 19: Validation of the Modified Motor Score (mMS): A Subscale of the Unified Huntington's Disease Rating Scale (UHDRS) Motor Score

The Efficacy and Safety of Pridopidine on Treatment of Patients with Huntington's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Pridopidine is a novel drug that helps stabilize psychomotor function in patients with Huntington's disease (HD) by activating the cortical glutamate pathway. It promises to achieve the unmet needs of current therapies of HD without worsening other symptoms.

OBJECTIVE

To review the literature discussing the efficacy of pridopidine in alleviating motor symptoms and its safety in patients with HD.

METHODS

We searched Scopus, Web of Science, the Cochrane Library, Wiley, and PubMed for randomized controlled trials (RCTs) of pridopidine on HD. Data from eligible studies were extracted and pooled as mean differences for efficacy and risk ratios (RRs) for safety using RevMan software version 5.3.

RESULTS

A total of 4 relevant RCTs with 1130 patients were selected (816 in the pridopidine group and 314 in the placebo group). The pooled effect size favored pridopidine over placebo insignificantly in the Unified Huntington's Disease Rating Scale Total Motor Score (mean difference [MD], -0.93; 95% confidence interval [CI], -2.01 to 0.14; P = 0.09), whereas the effect size of 3 studies significantly favored pridopidine over placebo in the Unified Huntington's Disease Rating Scale Modified Motor Score (MD, -0.81; 95% CI, -1.48 to -0.13; P = 0.02). Pridopidine generally was well tolerated. None of the adverse effects were considerably higher in the case of pridopidine compared with placebo in overall adverse events (RR, 1.03; 95% CI, 0.94-1.13; P = 0.49) and serious adverse events (RR, 1.62; 95% CI, 0.88-2.99; P = 0.12).

CONCLUSION

The effects of pridopidine on motor functions (especially voluntary movements) in patients with HD are encouraging and provide a good safety profile that motivates further clinical trials on patients to confirm its effectiveness and safety.

Rating Scales for Motor Symptoms and Signs in Huntington's Disease: Critique and Recommendations

Motor symptoms are a major feature of Huntington's disease (HD). The International Parkinson and Movement Disorder Society (MDS) commissioned the assessment of the clinimetric properties of motor rating scales in HD to make recommendations regarding their use, following previously established standardized criteria. After a systematic literature search, a total of 6 rating scales assessing motor symptoms and signs in HD were included for review. Performance testing (reviewed elsewhere) and quantitative motor rating methods were excluded. Only the Unified Huntington's Disease Rating Scale-Total Motor Score (UHDRS-TMS) was classified as "recommended" for assessing the severity of motor signs in HD. The following scales were classified as "suggested": Abnormal Involuntary Movement Scale, the UHDRS-TMS4, the Quantified Neurological Examination, and the Marsden and Quinn Chorea Severity Scale. The committee also concluded that further assessment of existing rating scales, including the UHDRS-TMS, is necessary to determine sensitivity to change and to screening for the presence of motor signs specific to HD. There is also a need to develop a motor rating scale to be used in positive gene carriers with subtle but not definite motor signs.

A randomized, controlled trial of a multi-modal exercise intervention in Huntington's disease

INTRODUCTION

This study aimed to evaluate the feasibility and benefit of a structured exercise intervention in people with Huntington's Disease (HD).

METHODS

This study was conducted at 6 sites, and participants were randomized into either exercise or control (usual care) groups, and were assessed at baseline, 13 and 26 weeks. The intervention was a 12 week, three times per week progressive exercise program, including aerobic (stationary cycling) and upper and lower body strengthening exercise with tapered 1:1 support for 20 of 36 sessions.

RESULTS

314 adults were assessed for eligibility: 248 did not meet inclusion criteria, 34 declined, and 32 were recruited and randomized. Three individuals in the intervention group were withdrawn within the first month due to concomitant medical conditions, resulting in 14 participants in intervention and 15 in control groups. There were two AEs in the intervention group, both related to previous medical conditions, and there were two SAEs, both in the control group. The intervention group had better fitness (predicted VO₂ max difference: 492.3 ml min^-1, 95% CI: [97.1, 887.6]), lower UHDRS mMS (difference 2.9 points, 95% [-5.42, -0.32]) and lower weight at Week 13 (difference 2.25 kg, 95% CI: [-4.47, -0.03]).

CONCLUSION

This study demonstrates that a short-term exercise intervention is safe and feasible. Individuals with HD may benefit from structured exercise, and intensity, monitoring and support may be key factors in optimizing response. Larger scale trials are now required to fully elucidate the extended clinical potential of exercise in HD.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN11392629.

Pridopidine, a dopamine stabilizer, improves motor performance and shows neuroprotective effects in Huntington disease R6/2 mouse model

Huntington disease (HD) is a neurodegenerative disorder for which new treatments are urgently needed. Pridopidine is a new dopaminergic stabilizer, recently developed for the treatment of motor symptoms associated with HD. The therapeutic effect of pridopidine in patients with HD has been determined in two double-blind randomized clinical trials, however, whether pridopidine exerts neuroprotection remains to be addressed. The main goal of this study was to define the potential neuroprotective effect of pridopidine, in HD in vivo and in vitro models, thus providing evidence that might support a potential disease-modifying action of the drug and possibly clarifying other aspects of pridopidine mode-of-action. Our data corroborated the hypothesis of neuroprotective action of pridopidine in HD experimental models. Administration of pridopidine protected cells from apoptosis, and resulted in highly improved motor performance in R6/2 mice. The anti-apoptotic effect observed in the in vitro system highlighted neuroprotective properties of the drug, and advanced the idea of sigma-1-receptor as an additional molecular target implicated in the mechanism of action of pridopidine. Coherent with protective effects, pridopidine-mediated beneficial effects in R6/2 mice were associated with an increased expression of pro-survival and neurostimulatory molecules, such as brain derived neurotrophic factor and DARPP32, and with a reduction in the size of mHtt aggregates in striatal tissues. Taken together, these findings support the theory of pridopidine as molecule with disease-modifying properties in HD and advance the idea of a valuable therapeutic strategy for effectively treating the disease.

An evidence-based approach in the treatment of Huntington's disease

Huntington's disease (HD) is a neurodegenerative disease with diverse symptoms for which there is no curative or disease-modifying treatment available. Currently, tetrabenazine is the only drug approved for HD by a regulatory agency, and only for the treatment of chorea. In the current review, we present updated results from recent clinical trials and ongoing clinical research efforts to find effective and safe treatments for HD motor, and neuropsychiatric and cognitive symptoms. We used a systematic review approach that included data from well-designed randomised controlled trials. The authors conclude that there is weak evidence to support most of the treatment decisions in HD and thus clinicians may be guided only by expert opinion-based therapeutic recommendations. Ongoing research is considerable and is expected to have an impact in the management of HD in upcoming years.