Challenges and future perspective of antisense therapy for spinal muscular atrophy: A review

Fluoroscopic guidance for intrathecal delivery of nusinersen in pediatric patients with spinal muscular atrophy and complex spines

The introduction of nusinersen revolutionized the treatment of spinal muscular atrophy (SMA). However, nusinersen is administered by interlaminar intrathecal injection which is challenging in patients with severe scoliosis, a common comorbidity of advanced SMA. This study evaluated the technical benefits of fluoroscopic guidance of intrathecal nusinersen administration in complex SMA patients with or without a fixation device. The cohort included 12 patients aged 10-20 years (total 124 injections). The total success rate was 99 %, with failure to complete only one out of 124 procedures. Demographic characteristics were diverse. Mean age at first injection was 14.2 years. Mean duration of radiation exposure was 77 s; mean dose area product was 2.32 Gycm2; and mean cumulative air kerma was 20.91mGy. Adverse events included post-dural-puncture headache (4.8 % of procedures), mostly mild and self-limited, and one allergic reaction. Treatment was discontinued in 2 patients because of difficult intrathecal access, and in 2 for reasons unrelated to the injection technique. Fluoroscopy-guided nusinersen administration is a feasible option for patients with SMA and complex access. Success depends on proper patient positioning and expertise of the interventional radiologist. Radiation exposure is lower than with other techniques. Larger prospective studies are needed to confirm these findings.

Prenatal genetic counseling challenges with indeterminate SMA results

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular condition with complex genetic etiology. About 95% of individuals affected with this condition have a homozygous deletion of the SMN1 gene. One scenario that complicates risk is when a parent is identified as a possible silent carrier, meaning they have a [2 + 0] chromosome configuration. This configuration occurs when an individual has two copies of the SMN1 gene on one chromosome and no copies on the other chromosome. It is thought that 3.8-4.0% of the general population is a [2 + 0] carrier with a higher prevalence in African American and Hispanic populations. The [2 + 0] configuration makes it more difficult to calculate residual risk because testing cannot determine the difference between [2 + 0] carriers and [1 + 1] non-carriers, leading to indeterminate SMA carrier screening results. SMA was added to general population carrier screening in 2017, leading to an increase in the number of patients identified to have indeterminate results. Previous research has not examined how this addition has affected counseling practices involving indeterminate results. The purpose of this research was to gain a better understanding of the practices and challenges in this area, specifically within non-Ashkenazi Jewish (AJ) populations. This study utilized a quantitative survey with open-response questions. Responses from 49 prenatal genetic counselors from the United States and Canada were analyzed and it was found that genetic counselors face similar challenges when counseling indeterminate SMA results across all regions. These include negative patient emotions and both patient and referring provider misunderstanding, as highlighted in the qualitative data. Three major categories emerged including (1) challenges with patients, (2) challenges with referring providers, and (3) the effects of the 2017 addition to general population carrier screening. This study highlights the need for provider education surrounding indeterminate SMA results, the development of a visual aid, and future research from the patient and referring provider perspective.

Recent advances in RNA-based therapeutics for neurodevelopmental disorders

A significant proportion of neurodevelopmental disorders (NDDs) are caused by gain-of-function (GOF) or loss-of-function (LOF) of specific genes. Strategies to normalize disease gene expression offer therapeutic potential for these disorders. The success and approval of RNA-based therapeutics for various disorders have led to a surge in RNA-based therapeutic research for NDDs with antisense oligonucleotides leading the field. This review discusses recent advances in therapeutic strategies that target pre-mRNA or mRNA for GOF and LOF NDDs that have promising preclinical evidence. These developments highlight important considerations and exciting future avenues for the development of therapies for NDDs.

Strategies for programmable manipulation of alternative splicing

Alternative splicing (AS) plays a pivotal role in protein diversity and mRNA maturation. Programmable control of targeted AS events is of longstanding interest in RNA biology, promising correction of dysregulated splicing in disease and discovery of AS events. This review explores four main strategies for programmable splicing manipulation: (1) inhibiting splicing signals with antisense oligonucleotides (ASOs), exemplified by therapies approved by the U.S. Food and Drug Administration, (2) applying DNA-targeting clustered regularly interspaced short palindromic repeats systems to edit splicing signals, (3) using synthetic splicing factors, including synthetic proteins and ribonucleoproteins, inspired by natural RNA-binding proteins, and (4) guiding endogenous splicing machinery with bifunctional ASOs and engineered small nuclear RNAs. While ASOs remain clinically prominent, emerging technologies aim for broad, scalable, durable, and precise splicing modulation, holding promise for transformative advancements in RNA biology and therapeutic interventions.

Disproportionality Analysis of Nusinersen in the Food and Drug Administration Adverse Event Reporting System: A Real-World Postmarketing Pharmacovigilance Assessment

BACKGROUND

Nusinersen is the first drug for precise targeted therapy of spinal muscular atrophy, a rare disease that occurs in one of 10,000 to 20,000 live births. Therefore, thorough and comprehensive reports on the safety of nusinersen in large, real-world populations are necessary. This study aimed to mine the adverse event (AE) signals related to nusinersen through the Food and Drug Administration Adverse Event Reporting System (FAERS) database.

METHODS

We extracted reports of AEs with nusinersen as the primary suspect from FAERS between December 2016 and March 2023. Reporting odds ratio (ROR) and Bayesian confidence propagation neural network (BCPNN) were used for AE signal detection.

RESULTS

We extracted a total of 4807 suspected AE cases with nusinersen as the primary suspect from the FAERS database. Among them, 106 positive signals were obtained using the ROR and BCPNN. The highest frequency reported systemic organ class was general disorders and administration site conditions. Common clinical AEs of nusinersen were detected in the FAERS database, such as pneumonia, vomiting, back pain, headache, pyrexia, and post-lumbar puncture syndrome. In addition, we identified potential unexpected serious AEs through disproportionality analysis, including sepsis, seizure, epilepsy, brain injury, cardiorespiratory arrest, and cardiac arrest.

CONCLUSIONS

Analyzing large amounts of real-world data from the FAERS database, we identified potential new AEs of nusinersen by disproportionate analysis. It is advantageous for health care professionals and pharmacists to concentrate on effectively managing high-risk AEs of nusinersen, improve medication levels in clinical settings, and uphold patient medication safety.

Recent Progress in Gene-Targeting Therapies for Spinal Muscular Atrophy: Promises and Challenges

Spinal muscular atrophy (SMA) is a severe genetic disorder characterized by the loss of motor neurons, leading to progressive muscle weakness, loss of mobility, and respiratory complications. In its most severe forms, SMA can result in death within the first two years of life if untreated. The condition arises from mutations in the SMN1 (survival of motor neuron 1) gene, causing a deficiency in the survival motor neuron (SMN) protein. Humans possess a near-identical gene, SMN2, which modifies disease severity and is a primary target for therapies. Recent therapeutic advancements include antisense oligonucleotides (ASOs), small molecules targeting SMN2, and virus-mediated gene replacement therapy delivering a functional copy of SMN1. Additionally, recognizing SMA's broader phenotype involving multiple organs has led to the development of SMN-independent therapies. Evidence now indicates that SMA affects multiple organ systems, suggesting the need for SMN-independent treatments along with SMN-targeting therapies. No single therapy can cure SMA; thus, combination therapies may be essential for comprehensive treatment. This review addresses the SMA etiology, the role of SMN, and provides an overview of the rapidly evolving therapeutic landscape, highlighting current achievements and future directions.

Diving into progress: a review on current therapeutic advancements in spinal muscular atrophy

Spinal muscular atrophy (SMA) is an uncommon disorder associated with genes characterized by the gradual weakening and deterioration of muscles, often leading to substantial disability and premature mortality. Over the past decade, remarkable strides have been made in the field of SMA therapeutics, revolutionizing the landscape of patient care. One pivotal advancement is the development of gene-targeted therapies, such as nusinersen, onasemnogene abeparvovec and risdiplam which have demonstrated unprecedented efficacy in slowing disease progression. These therapies aim to address the root cause of SMA by targeting the survival motor neuron (SMN) gene, effectively restoring deficient SMN protein levels. The advent of these innovative approaches has transformed the prognosis for many SMA patients, offering a glimmer of hope where there was once limited therapeutic recourse. Furthermore, the emergence of small molecule compounds and RNA-targeting strategies has expanded the therapeutic arsenal against SMA. These novel interventions exhibit diverse mechanisms of action, including SMN protein stabilization and modulation of RNA splicing, showcasing the multifaceted nature of SMA treatment research. Collective efforts of pharmaceutical industries, research centers, and patient advocacy groups have played an important role in expediting the translation of scientific discoveries into visible clinical benefits. This review not only highlights the remarkable progress achieved in SMA therapeutics but also generates the ray of hope for the ongoing efforts required to enhance accessibility, optimize treatment strategies, rehabilitation (care and therapies) and ultimately pave the way for an improved quality of life for individuals affected by SMA.

Communicative development inventory in type 1 and presymptomatic infants with spinal muscular atrophy: a cohort study

OBJECTIVE

The aim of this study was to assess early language acquisitions in treated individuals with spinal muscular atrophy (SMA) type 1 and in infants identified by newborn screening (NBS).

METHODS

Parents of SMA individuals aged between 8 and 36 months were asked to fill in the MacArthur-Bates Communicative Development Inventory (MB-CDI) that assesses comprehension, gesture and expressive skills. A follow-up assessment was performed in 21 of the 36.

RESULTS

The MB-CDI was completed by parents of 24 type 1 and 12 infants identified by NBS. Comprehension skills were preserved in 81% of the type 1 SMA and in 87% infants identified by NBS. Gesture abilities were <5th centile in 55% of the type 1 SMA and in none of those identified by NBS. Lexical expressions were <5th centile in more than 80% type 1 SMA and in 50% of infants identified by NBS. At follow-up, despite an increase in lexical expression skills, the scores remained below the fifth centile in 43% type 1 SMA and in 86% of infants identified by NBS.

CONCLUSIONS

These results suggest that language and communication development may follow a similar pattern to that observed in motor function with the possibility to develop skills (eg, ability to say clear words) that are not usually present in untreated infants but with a level of performance that does not reach that of their typically developing peers.

Perspectives and perception of haemophilia gene therapy by French patients

INTRODUCTION AND AIM

A national survey was initiated by representatives of French patients with haemophilia (AFH) and the French reference centre for haemophilia, in order to appreciate the awareness and knowledge of these patients regarding haemophilia gene therapy (HGT) and understand better their position about this innovative treatment that will soon become available.

RESULTS

Of 143 answers received, 137 could be analysed, representing about 3.5% of patients with severe or moderate haemophilia over 16year-old. They were 80.3% with haemophilia A and 19.7 % with haemophilia B, with a severe form of the disease for 80.3 % of them. Curiosity for HGT was formulated by 64.2% of the participants, 33.6 % being interested by this approach as soon as it will be available and 38.7 % preferring to wait until more patients have been treated. Only 3.6 % of the participants would never consider receiving HGT. The level of awareness and knowledge was estimated to be limited by 39.5 % of the patients. More than 60 % of them declared having never or almost never discussed HGT with the team of their haemophilia centre. Before deciding to get HGT, 54.4 % of the participants considered that it will be very important to compare it with their current treatment and 53.7 % would like to be better informed by their care providers.

CONCLUSIONS

These results highlight the need for training and education for patients, but also for professionals at haemophilia centres, about HGT and the shared decision-making process. Objective, unbiased and transparent information must be available for patients about this very promising therapy which nonetheless carries more uncertainty and unknowns compared to other haemophilia treatments.

Enhancing Antisense Oligonucleotide-Based Therapeutic Delivery with DG9, a Versatile Cell-Penetrating Peptide

Antisense oligonucleotide-based (ASO) therapeutics have emerged as a promising strategy for the treatment of human disorders. Charge-neutral PMOs have promising biological and pharmacological properties for antisense applications. Despite their great potential, the efficient delivery of these therapeutic agents to target cells remains a major obstacle to their widespread use. Cellular uptake of naked PMO is poor. Cell-penetrating peptides (CPPs) appear as a possibility to increase the cellular uptake and intracellular delivery of oligonucleotide-based drugs. Among these, the DG9 peptide has been identified as a versatile CPP with remarkable potential for enhancing the delivery of ASO-based therapeutics due to its unique structural features. Notably, in the context of phosphorodiamidate morpholino oligomers (PMOs), DG9 has shown promise in enhancing delivery while maintaining a favorable toxicity profile. A few studies have highlighted the potential of DG9-conjugated PMOs in DMD (Duchenne Muscular Dystrophy) and SMA (Spinal Muscular Atrophy), displaying significant exon skipping/inclusion and functional improvements in animal models. The article provides an overview of a detailed understanding of the challenges that ASOs face prior to reaching their targets and continued advances in methods to improve their delivery to target sites and cellular uptake, focusing on DG9, which aims to harness ASOs' full potential in precision medicine.