New and developing therapies in spinal muscular atrophy

Respiratory management of spinal muscular atrophy type 1 patients treated with Nusinersen

INTRODUCTION

The recent development of disease-modifying treatments in spinal muscular atrophy (SMA) type 1 shifted these patients' management from palliative to proactive. The aim of this study was to assess patients' nocturnal gas exchanges before noninvasive ventilation (NIV) initiation and their clinical evolution to determine if capnia is a good criterion to decide when to introduce respiratory support.

PATIENTS AND METHODS

This multicentric retrospective study reports the respiratory management and evolution of 17 SMA type 1 children (10 females) for whom treatment with Nusinersen was initiated between 2016 and 2018.

RESULTS

Median [interquartile range-IQR] age at diagnosis and at first Nusinersen injection was of 4 [3;8] and 4 [3;9] months, respectively. Patients were followed during 38 [24;44] months. Thirteen (76%) patients were started on NIV at a median [IQR] age of 12 [9;18] months. Repeated hospitalizations and intensive care unit admissions were needed for 11 of them. Blood gas and nocturnal gas exchange recordings performed before NIV initiation were always normal. 9/13 X-ray performed before NIV showed atelectasis and/or acute lower respiratory tract infections. There was a significant decrease in the total number of hospital admissions between the first and second year of treatment (p = 0.04).

CONCLUSION

This study shows that patients do not present with nocturnal hypoventilation before respiratory decompensations and NIV initiation, and suggests that a delay in NIV initiation might result in respiratory complications. There is a need for disease-centered guidelines for the respiratory management of these patients, including NIV indications.

Current and Future Prospects for Gene Therapy for Rare Genetic Diseases Affecting the Brain and Spinal Cord

In recent years, gene therapy has been raising hopes toward viable treatment strategies for rare genetic diseases for which there has been almost exclusively supportive treatment. We here review this progress at the pre-clinical and clinical trial levels as well as market approvals within diseases that specifically affect the brain and spinal cord, including degenerative, developmental, lysosomal storage, and metabolic disorders. The field reached an unprecedented milestone when Zolgensma® (onasemnogene abeparvovec) was approved by the FDA and EMA for in vivo adeno-associated virus-mediated gene replacement therapy for spinal muscular atrophy. Shortly after EMA approved Libmeldy®, an ex vivo gene therapy with lentivirus vector-transduced autologous CD34-positive stem cells, for treatment of metachromatic leukodystrophy. These successes could be the first of many more new gene therapies in development that mostly target loss-of-function mutation diseases with gene replacement (e.g., Batten disease, mucopolysaccharidoses, gangliosidoses) or, less frequently, gain-of-toxic-function mutation diseases by gene therapeutic silencing of pathologic genes (e.g., amyotrophic lateral sclerosis, Huntington's disease). In addition, the use of genome editing as a gene therapy is being explored for some diseases, but this has so far only reached clinical testing in the treatment of mucopolysaccharidoses. Based on the large number of planned, ongoing, and completed clinical trials for rare genetic central nervous system diseases, it can be expected that several novel gene therapies will be approved and become available within the near future. Essential for this to happen is the in depth characterization of short- and long-term effects, safety aspects, and pharmacodynamics of the applied gene therapy platforms.

The respiratory impact of novel therapies for spinal muscular atrophy

The phenotype of spinal muscular atrophy (SMA) has been changing with the recent availability of three FDA-approved treatments: intrathecal nusinersen, intravenous onasemnogene abeparvovec-xioi, and enteral risdiplam. The degree of improvement in muscle strength and respiratory health varies with SMA genotype, severity of baseline neuromuscular and pulmonary impairment, medication used, and timing of the first dose. A spectrum of pulmonary outcomes has been reported with these novel medications when used early and in conjunction with proactive multidisciplinary management of comorbidities. In this review, we summarize the reported impact of these novel therapies on pulmonary well-being and the improving trajectory of pulmonary morbidity, compared to the natural history of SMA. The importance of ongoing clinical monitoring albeit the improved phenotype is reiterated. We also discuss the limitations of the current SMA-therapy trials and offer suggestions for future clinical-outcome studies and long-term monitoring.

Treatment of Cystic Fibrosis: From Gene- to Cell-Based Therapies

Prognosis of patients with cystic fibrosis (CF) varies extensively despite recent advances in targeted therapies that improve CF transmembrane conductance regulator (CFTR) function. Despite being a multi-organ disease, extensive lung tissue destruction remains the major cause of morbidity and mortality. Progress towards a curative treatment strategy that implements a CFTR gene addition-technology to the patients’ lungs has been slow and not yet developed beyond clinical trials. Improved delivery vectors are needed to overcome the body’s defense system and ensure an efficient and consistent clinical response before gene therapy is suitable for clinical care. Cell-based therapy–which relies on functional modification of allogenic or autologous cells ex vivo, prior to transplantation into the patient–is now a therapeutic reality for various diseases. For CF, pioneering research has demonstrated proof-of-principle for allogenic transplantation of cultured human airway stem cells into mouse airways. However, applying a cell-based therapy to the human airways has distinct challenges. We review CF gene therapies using viral and non-viral delivery strategies and discuss current advances towards autologous cell-based therapies. Progress towards identification, correction, and expansion of a suitable regenerative cell, as well as refinement of pre-cell transplant lung conditioning protocols is discussed.

"We needed this": perspectives of parents and healthcare professionals involved in a pilot newborn screening program for spinal muscular atrophy

BACKGROUND

Newborn screening (NBS) for spinal muscular atrophy (SMA) is a recognised model through which health outcomes can be improved. However, perspectives of parents and healthcare professionals (HCPs) involved in such programs are largely unknown.

METHODS

A pilot program for SMA ran from August 2018-July 2020. Using a mixed-methods convergent methodology, we used a self-administered questionnaire to understand parents' perceptions and psychological impact of the program from diagnosis to treatment. We thematically analysed successes/challenges encountered by HCPs and recommendations for service improvement from both participant groups.

FINDINGS

202,388 infants were screened for SMA and the perceptions of 44 parents and HCPs affected by a positive result in eighteen newborns was ascertained. Parents (n=29, 100%) were satisfied with NBS for SMA. Although screen-positive result was distressing for all parents, quality of life improved over time [CarerQoL-7D baseline median score 4 (SD=1.4) vs six-month median score 8 (SD=1.3), p<0.001)]. Challenges for HCPs included managing the time-critical nature of the pathway whilst remaining cognisant of limitations associated with the predictive screening test.

INTERPRETATION

Interpretation: NBS for SMA fulfils criteria for population-wide screening. Net benefits are acknowledged by stakeholders to optimise lifelong outcomes. Harms including psychological distress associated with a screen-positive result may be managed by targeted psychosocial support, information provision and a personalised model of care together strengthening healthcare systems.

FUNDING

The NSW Pilot NBS study was funded by Luminesce Alliance. Dr Kariyawasam received funding from the RTP Scholarship, University of New South Wales and The Freedman Family Foundation Scholarship, Sydney Children's Hospital Foundation.

Drug Screening and Drug Repositioning as Promising Therapeutic Approaches for Spinal Muscular Atrophy Treatment

Spinal muscular atrophy (SMA) is the most common genetic disease affecting infants and young adults. Due to mutation/deletion of the survival motor neuron (SMN) gene, SMA is characterized by the SMN protein lack, resulting in motor neuron impairment, skeletal muscle atrophy and premature death. Even if the genetic causes of SMA are well known, many aspects of its pathogenesis remain unclear and only three drugs have been recently approved by the Food and Drug Administration (Nusinersen-Spinraza; Onasemnogene abeparvovec or AVXS-101-Zolgensma; Risdiplam-Evrysdi): although assuring remarkable results, the therapies show some important limits including high costs, still unknown long-term effects, side effects and disregarding of SMN-independent targets. Therefore, the research of new therapeutic strategies is still a hot topic in the SMA field and many efforts are spent in drug discovery. In this review, we describe two promising strategies to select effective molecules: drug screening (DS) and drug repositioning (DR). By using compounds libraries of chemical/natural compounds and/or Food and Drug Administration-approved substances, DS aims at identifying new potentially effective compounds, whereas DR at testing drugs originally designed for the treatment of other pathologies. The drastic reduction in risks, costs and time expenditure assured by these strategies make them particularly interesting, especially for those diseases for which the canonical drug discovery process would be long and expensive. Interestingly, among the identified molecules by DS/DR in the context of SMA, besides the modulators of SMN2 transcription, we highlighted a convergence of some targeted molecular cascades contributing to SMA pathology, including cell death related-pathways, mitochondria and cytoskeleton dynamics, neurotransmitter and hormone modulation.

The implementation of newborn screening for spinal muscular atrophy: the Australian experience

PURPOSE

To evaluate the implementation of the first statewide newborn screening (NBS) program for spinal muscular atrophy (SMA) in Australia. Processes that hinder and support clinical development, translation, and sustainability of the first primary genetic screening program in Australia are appraised.

METHODS

The study prospectively describes the course (timelines, health processes, and preliminary clinical outcomes) for SMA screen-positive newborns from 1 August 2018 to 31 July 2019 in New South Wales and Australian Capital Territory, Australia.

RESULTS

In the first year of the program, 103,903 newborns were screened. Ten newborns screened positive for SMA. Genetic confirmation of SMA occurred in 9/10 (90%) of infants. Clinical signs of SMA evolved in 4/9 (44%) within 4 weeks of life, heralded by hypotonia and weakness initially recognized in the neck. Median time to implementing a care plan (including commencement of disease-modifying therapies) was 26.5 days (16-37 days) from birth.

CONCLUSION

NBS is essential for early and equitable identification of patients with SMA. Expedient diagnosis and management are vital, as disease latency appears brief in some cases. NBS shows significant clinical utility to support early parental decision making, improve access to specialist neuromuscular expertise, and facilitate initiation of personalized therapeutic strategies.

Biomarkers and the Development of a Personalized Medicine Approach in Spinal Muscular Atrophy

Recent unprecedented advances in treatment for spinal muscular atrophy (SMA) enabled patients to access the first approved disease modifying therapy for the condition. There are however many uncertainties, regarding timing of treatment initiation, response to intervention, treatment effects and long-term outcomes, which are complicated by the evolving phenotypes seen in the post-treatment era for patients with SMA. Biomarkers of disease, with diagnostic, prognostic, predictive, and pharmacodynamic value are thus urgently required, to facilitate a wider understanding in this dynamic landscape. A spectrum of these candidate biomarkers, will be evaluated in this review, including genetic, epigenetic, proteomic, electrophysiological, and imaging measures. Of these, SMN2 appears to be the most significant modifier of phenotype to date, and its use in prognostication shows considerable clinical utility. Longitudinal studies in patients with SMA highlight an emerging role of circulatory markers such as neurofilament, in tracking disease progression and response to treatment. Furthermore, neurophysiological biomarkers such as CMAP and MUNE values show considerable promise in the real word setting, in following the dynamic response and output of the motor unit to therapeutic intervention. The specific value for these possible biomarkers across diagnosis, prognosis, prediction of treatment response, efficacy, and safety will be central to guide future patient-targeted treatments, the design of clinical trials, and understanding of the pathophysiological mechanisms of disease and intervention.

Characteristics and advantages of adeno-associated virus vector-mediated gene therapy for neurodegenerative diseases

Common neurodegenerative diseases of the central nervous system are characterized by progressive damage to the function of neurons, even leading to the permanent loss of function. Gene therapy via gene replacement or gene correction provides the potential for transformative therapies to delay or possibly stop further progression of the neurodegenerative disease in affected patients. Adeno-associated virus has been the vector of choice in recent clinical trials of therapies for neurodegenerative diseases due to its safety and efficiency in mediating gene transfer to the central nervous system. This review aims to discuss and summarize the progress and clinical applications of adeno-associated virus in neurodegenerative disease in central nervous system. Results from some clinical trials and successful cases of central neurodegenerative diseases deserve further study and exploration.