Spinal muscular atrophy (SMA) type I (Werdnig-Hoffmann disease)

Emerging Gene Therapy Approaches in the Management of Spinal Muscular Atrophy (SMA): An Overview of Clinical Trials and Patent Landscape

Spinal muscular atrophy (SMA) is a rare autosomal recessive neuromuscular disease that is characterized by progressive muscle atrophy (degeneration), including skeletal muscles in charge of the ability to move. SMA is caused by defects in the SMN1 gene (Survival of Motor Neuron 1) which encodes a protein crucial for the survival and functionality of neuron cells called motor neurons. Decreased level of functioning SMN protein leads to progressive degeneration of alpha-motor neurons performing muscular motility. Over the past decade, many strategies directed for SMN-level-restoration emerged, such as gene replacement therapy (GRT), CRISPR/Cas9-based gene editing, usage of antisense oligonucleotides and small-molecule modulators, and all have been showing their perspectives in SMA therapy. In this review, modern SMA therapy strategies are described, making it a valuable resource for researchers, clinicians and everyone interested in the progress of therapy of this serious disorder.

Cognitive performance of adult patients with SMA before and after treatment initiation with nusinersen

BACKGROUND

Spinal muscular atrophy (SMA) is a genetic neuromuscular disease caused by mutations of the SMN1 gene. Deficient SMN protein causes irreversible degeneration of alpha motor neurons characterized by progressive muscle weakness and atrophy. Considering that SMA is a multi-systemic disorder and SMN protein was found to be expressed in cortical structures, the cognitive profile of adult patients with SMA has recently been of particular interest. With nusinersen, a novel, disease-modifying drug has been established, but its effects on neuropsychological functions have not been validated yet. Aim of this study was to investigate the cognitive profile of adult patients with SMA during treatment initiation with nusinersen and to reveal improvement or deterioration in cognitive performance.

METHODS

This monocentric longitudinal study included 23 patients with SMA type 2 and 3. All patients were assessed with the Edinburgh Cognitive and Behavioral ALS Screen (ECAS) before and after 14 months of treatment initiation with nusinersen. Additionally, motor function was evaluated by Hammersmith Functional Motor Scale Expanded (HFMSE), Revised Upper Limb Module (RULM) and Amyotrophic Lateral Sclerosis Functional Rating Scale Revised (ALSFRS-R).

RESULTS

Of the treatment-naive patients, only three were below the age- and education-matched cut-off for cognitive impairment in the ECAS total score. Significant differences between SMA type 2 and 3 were only detected in the domain of Language. After 14 months of treatment, patients showed significant improvement of absolute scores in all three ALS-specific domains, in the non-ALS-specific domain of Memory, in both subscores and in the ECAS total score. No associations were detected between cognitive and functional outcome measures.

CONCLUSIONS

In some adult patients with SMA abnormal cognitive performance in ALS-specific functions of the ECAS was evident. However, the presented results suggest no clinically significant cognitive changes during the observed treatment period with nusinersen.

Exploratory evaluation of an eye-tracking system in patients with advanced spinal muscular atrophy type I receiving nusinersen

Objective

This study evaluated the feasibility of a matching-pair test using eye-tracking technology to assess nusinersen effectiveness in patients with advanced spinal muscular atrophy (SMA) type I.

Methods

This prospective, observational study enrolled patients with 5q-SMA type I who had lost gross motor function. Three different levels of matching-pair tests were conducted using the eye-gaze system (My Tobii; TobiiDynavox Inc.) at baseline, and after 9 and 24 weeks of nusinersen treatment. The primary endpoint was the change from baseline in matching-pair test scores and response times (i.e., the time to answer matching-pair test) at 24 weeks from baseline. Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND), Pediatric Quality of Life inventory for patients with Neuromuscular Disease (PedsQL-NM) and Numerical Rating Scale (NRS) scores were also assessed as secondary endpoints. Analysis of ocular fixation was performed as an additional analysis. This study was registered at https://www.umin.ac.jp/ctr/ (UMIN000033935).

Results

Seven patients (one male, six female) aged 5–21 years (median 11 years) were enrolled; all patients were bedridden and six patients were ventilated. All seven patients were able to conduct level 1 matching-pair tests at each assessment; five patients were also able to conduct levels 2 and 3. Two patients (those with the highest CHOP-INTEND scores) were able to complete all tests correctly within 60 s. There was a non-significant trend toward improvement in CHOP-INTEND, PedsQL-NM, and NRS scores over the 6-month period. There were no significant differences in the number of actions, errors, correct answers, or response times between baseline and Week 9 or 24 at any level. However, the result of an additional analysis suggests that detection of eye movement would be useful to evaluate for advanced SMA.

Conclusions

Eye-tracking systems are possibly feasible for the assessment of treatment efficacy in patients with advanced SMA type I.

Onasemnogene abeparvovec for presymptomatic infants with two copies of SMN2 at risk for spinal muscular atrophy type 1: the Phase III SPR1NT trial

SPR1NT ( NCT03505099 ) was a Phase III, multicenter, single-arm study to investigate the efficacy and safety of onasemnogene abeparvovec for presymptomatic children with biallelic SMN1 mutations treated at ≤6 weeks of life. Here, we report final results for 14 children with two copies of SMN2, expected to develop spinal muscular atrophy (SMA) type 1. Efficacy was compared with a matched Pediatric Neuromuscular Clinical Research natural-history cohort (n = 23). All 14 enrolled infants sat independently for ≥30 seconds at any visit ≤18 months (Bayley-III item #26; P < 0.001; 11 within the normal developmental window). All survived without permanent ventilation at 14 months as per protocol; 13 maintained body weight (≥3rd WHO percentile) through 18 months. No child used nutritional or respiratory support. No serious adverse events were considered related to treatment by the investigator. Onasemnogene abeparvovec was effective and well-tolerated for children expected to develop SMA type 1, highlighting the urgency for universal newborn screening.