A multidisciplinary approach to dosing nusinersen for spinal muscular atrophy

Clinical perspectives: Treating spinal muscular atrophy

Spinal muscular atrophy is a rare and progressive neuromuscular disease that, without treatment, leads to progressive weakness and often death. A plethora of studies have led to the approval of three high-cost and effective treatments since 2016. These treatments, nusinersen, onasemnogene abeparvovec, and risdiplam, have not been directly compared and have varying challenges in administration. In this review, we discuss the evidence supporting the use of these medications, the process of treatment selection, monitoring after treatment, the limited data comparing treatments, as well as future directions for investigation and therapy.

Nusinersen Initiation After Onset of Weakness Does Not Prevent Progression of Hip Instability

BACKGROUND

We report changes in the natural history of hip instability with nusinersen treatment among patients with spinal muscular atrophy (SMA) type II after onset of weakness, historically wheelchair-bound but now potentially ambulatory in the era of disease-modifying therapy.

METHODS

Patients with genetically confirmed diagnoses of SMA type II who received intrathecal nusinersen from January 1, 2018, to June 30, 2022, were screened for inclusion. Patients with less than 6 months of follow-up, or prior hip surgeries were excluded. Primary clinical outcome measures included scores from Hammersmith motor functional scale expanded (HMFSE), revised upper limb module (RULM), 6-minute walk test (6MWT), and ambulatory status. Radiographic outcomes, including Reimer migration index, the presence of scoliosis, and pelvic obliquity, were also assessed. Secondary outcomes involved comparisons with a historical cohort of SMA type II patients treated at our institution who never received nusinersen.

RESULTS

Twenty hips from 5 boys and 5 girls were included in the analysis, with a mean follow-up of 3 years and 8 months. The median age at time of nusinersen initiation was 6.8 years old, ranging between 2.5 and 10.3 years. All patients developed lower limb motor weakness before nusinersen initiation. After treatment with nusinersen, 1 previously stable hip (5%) developed subluxation, 15 hips (75%) remain subluxated, 3 hips (15%) remain dislocated, and 1 hip (5%) remained stable, with a statistically significant difference between the pretreatment and posttreatment groups ( P <0.01). Six patients (60%) were ambulatory at latest follow-up. Six patients (60%) had improved ambulatory ability; 2 had static ambulatory ability (20%); and 2 had deterioration in their walking ability. The median HFMSE score improved from 18.5 (range 0 to 46) to 22 (range 0 to 49) ( P =0.813), whereas the median RULM score improved from 17 (range 2 to 28) to 21.5 (range 5 to 37), which was statistically significant ( P =0.007).

CONCLUSIONS

Hip instability persists despite treatment with nusinersen among patients with SMA type II who received nusinersen after onset of lower limb weakness.

LEVEL OF EVIDENCE

Therapeutic Level IV.

Adherence and Persistence Among Risdiplam-Treated Individuals with Spinal Muscular Atrophy: A Retrospective Claims Analysis

INTRODUCTION

Spinal muscular atrophy (SMA) is a neuromuscular disease caused by deletions and/or mutations in the survival of motor neuron 1 (SMN1) gene. Risdiplam, the first and only oral SMN2 pre-mRNA splicing modifier, is US Food and Drug Administration-approved for the treatment of pediatric and adult patients with SMA. For patients with SMA, long-term adherence to and persistence with an SMA treatment may be important for achieving maximum clinical benefits. However, real-world evidence on patient adherence to and persistence with risdiplam is limited.

METHODS

This retrospective study examined real-world adherence and persistence with risdiplam from a specialty pharmacy in patients with SMA over a 12-month period. Adherence was estimated by using proportion of days covered (PDC) and was calculated over variable (time between first and last fill) and fixed (time from first fill to study period end) intervals. Persistence was defined as no gap in supply ≥ 90 days. Patients were included if the time between the index date and study observation period was ≥ 12 months, if they initiated risdiplam between August 2020 and September 2022, received ≥ 2 risdiplam fills, and had an SMA diagnosis associated with a risdiplam fill. Subgroup analyses of risdiplam adherence and persistence were performed by age and primary payer type.

RESULTS

The proportion of patients (N = 1636) adherent at 12 months based on variable and fixed interval PDC was 93% and 79%, respectively. Adherence was high among patients on commercial insurance, Medicaid, or Medicare (range 86-96%). Mean persistence was 330.4 days. The highest proportion of patients who were persistent were on Medicaid (81%).

CONCLUSION

These findings demonstrate that patient adherence to and persistence with risdiplam treatment were high, including across all subgroups tested.

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.

Treatment of Symptomatic Spinal Muscular Atrophy with Nusinersen: A Prospective Longitudinal Study on Scoliosis Progression

Background

Nusinersen treatment has demonstrated efficacy in improving clinical outcomes for spinal muscular atrophy (SMA), yet its impact on scoliosis progression remains unclear.

Objective

This study aimed to assess the progression of scoliosis in pediatric patients with SMA undergoing nusinersen treatment.

Methods

In this prospective study, data were systematically collected from Hong Kong pediatric SMA patients receiving nusinersen between 2018 and 2023. All patients had longitudinal radiographic studies pre-nusinersen, and at half-yearly or yearly intervals during treatment based on the scoliosis severity. Motor function evaluations were conducted pre-nusinersen, and after starting treatment at 6- and 12-month intervals.

Results

Twenty-three patients ((SMA type 1 (SMA1) = 8, SMA type 2 (SMA2) = 7, SMA type 3 (SMA3) = 8)) with a median age of 5.8 years (range: 0.4-17.5 years) at nusinersen initiation, and median follow-up duration of 3.4 years (range: 1.1-5.2 years) were included. During the study period, motor scores remained stable or improved in 83% of patients. However, scoliosis progressed across all subtypes, with mean annual progression rates of 5.2, 11.9, and 3.6 degrees in SMA1, SMA2, and SMA3 respectively. Patients initiating nusinersen between ages 5 and 11 years exhibited the most rapid progression, with rates of 11.8, 16.5, and 7.3 degrees per year in SMA1, SMA2, and SMA3 respectively. Positive correlations were observed between the difference in CHOP-INTEND score post-nusinersen and scoliosis progression in SMA1 (rs = 0.741, p = 0.041). Conversely, negative correlations were found between the difference in HFMSE score post-nusinersen and scoliosis progression in SMA2 (rs =-0.890, p = 0.012) and SMA3 (rs =-0.777, p = 0.028).

Conclusions

This study reveals that nusinersen treatment in symptomatic pediatric SMA patients with motor improvement is linked to increased scoliosis progression in SMA1, whereas it is associated with decreased progression in SMA2 and SMA3. Age, baseline Cobb angle, and motor milestone improvement are influential factors in scoliosis progression.

Nucleic acid-based therapeutics for the treatment of central nervous system disorders

Nucleic acid-based therapeutics (NBTs) are an emerging class of drugs with potential for the treatment of a wide range of central nervous system conditions. To date, pertaining to CNS indications, there are two commercially available NBTs and a large number of ongoing clinical trials. However, these NBTs are applied directly to the brain due to very low blood brain barrier permeability. In this review, we outline recent advances in chemical modifications of NBTs and NBT delivery techniques intended to promote brain exposure, efficacy, and possible future systemic application.

Adherence and Persistence to Nusinersen for Spinal Muscular Atrophy: A US Claims-Based Analysis

INTRODUCTION

Spinal muscular atrophy (SMA) is a genetic, neuromuscular disease caused by deletions and/or mutations in the survival of motor neuron 1 (SMN1) gene leading to reduced SMN protein levels. Nusinersen, an intrathecally administered antisense oligonucleotide therapy that increases SMN protein levels, is approved for use in adult and pediatric patients with SMA. Data to inform real-world patient adherence and persistence to nusinersen are limited, with disparities in the population with SMA, study design, and results. The objective of this study is to characterize real-world nusinersen adherence and persistence in patients with SMA.

METHODS

This retrospective study examined nusinersen adherence and persistence over a 2-year period in patients with SMA in the USA from the IQVIA PharMetrics Plus claims database. Patients were followed from the date of first evidence of nusinersen treatment (occurring after 1 July 2017) until the end of the study period (31 December 2019) or end of continuous pharmacy and medical benefit enrollment, whichever came first. Subgroup analyses for nusinersen adherence and persistence were performed on the basis of age and presence or absence of spinal complications.

RESULTS

The final cohort consisted of 179 patients with SMA treated with nusinersen. Adherence to nusinersen treatment was 41% at 56 weeks and 39% at 104 weeks. In the base-case persistence analysis, there was a decrease in persistence before 6 months (67%) and further decline at 1 (57%) and 2 years (55%). Patients with spinal complication versus without had numerically higher persistence with nusinersen.

CONCLUSIONS

The findings suggest that adherence and persistence to nusinersen treatment appear low. Demographic (age ≥ 18 years) and clinical factors (no spinal complications) may contribute to nusinersen treatment discontinuation. Future research should explore possible reasons for low adherence and persistence to nusinersen treatment, such as clinical or logistical factors, patient preferences, and payer restrictions.

Volumetric MRI Findings in Mild Traumatic Brain Injury (mTBI) and Neuropsychological Outcome

Region of interest (ROI) volumetric assessment has become a standard technique in quantitative neuroimaging. ROI volume is thought to represent a coarse proxy for making inferences about the structural integrity of a brain region when compared to normative values representative of a healthy sample, adjusted for age and various demographic factors. This review focuses on structural volumetric analyses that have been performed in the study of neuropathological effects from mild traumatic brain injury (mTBI) in relation to neuropsychological outcome. From a ROI perspective, the probable candidate structures that are most likely affected in mTBI represent the target regions covered in this review. These include the corpus callosum, cingulate, thalamus, pituitary-hypothalamic area, basal ganglia, amygdala, and hippocampus and associated structures including the fornix and mammillary bodies, as well as whole brain and cerebral cortex along with the cerebellum. Ventricular volumetrics are also reviewed as an indirect assessment of parenchymal change in response to injury. This review demonstrates the potential role and limitations of examining structural changes in the ROIs mentioned above in relation to neuropsychological outcome. There is also discussion and review of the role that post-traumatic stress disorder (PTSD) may play in structural outcome in mTBI. As emphasized in the conclusions, structural volumetric findings in mTBI are likely just a single facet of what should be a multimodality approach to image analysis in mTBI, with an emphasis on how the injury damages or disrupts neural network integrity. The review provides an historical context to quantitative neuroimaging in neuropsychology along with commentary about future directions for volumetric neuroimaging research in mTBI.

Understanding European patient expectations towards current therapeutic development in spinal muscular atrophy

Following the 2017 approval of a first spinal muscular atrophy (SMA) treatment by the European Medicines Agency, SMA Europe launched a Europe-wide survey with the goal of understanding patients' treatment expectations, realities of daily living and access to clinical trials and therapy, and how this varied according to parameters such as age and disease severity. A response rate of 31% yielded 1474 completed surveys from 26 European countries. In line with findings from a 2015 SMA Europe-led survey, participants considered stabilization of their condition to be progress. Notably, responses indicated that the current classification of SMA at diagnosis by 'type' often does not reflect current mobility level. Large gaps in treatment access were identified that varied in particular between age and disease severity groups, yet there was high interest in clinical trial participation. In addition, alternative treatment options, including combination therapies, are now expectations. These perspectives should be central considerations through the research and development processes of new SMA therapies, through data generation and discussions on access to therapies. Results from this survey indicate that collaboration between stakeholders is essential to the foundation upon which innovative approaches for SMA treatments and access can be explored.

Clinical Experience of Nusinersen in a Broad Spectrum of Spinal Muscular Atrophy: A Retrospective Study

Background:

Nusinersen has recently been approved and more widely used as first-line treatment of spinal muscular atrophy (SMA). This study aimed to evaluate the real-world experience of nusinersen use for patients with a broad spectrum of SMA.

Methods:

We reviewed consecutive patients with SMA treated with nusinersen from April 2018 to April 2020. Data collected included clinical and diagnostic characteristics, molecular genetics, functional motor outcomes, and adverse events.

Results:

Seven patients including four with SMA type 1 and three with SMA type 2 were treated with nusinersen. The median disease duration at the time of the first dose and the median follow-up duration were 37 months (range: 0.5–254 months) and 6.1 months (range: 2.1–22.1 months), respectively. Of the 41 lumbar punctures (LPs), seven fluoroscopy-guided LPs were successfully performed for two patients without sedation. All patients showed improvement in motor function even though the current tools for motor assessment seemed unable to detect subtle subjective improvement. All patients maintained a stable respiratory status. No patient has experienced a severe adverse event or discontinued treatment so far.

Conclusion:

Although the number of patients in this study was small, our results suggest that nusinersen is effective even in patients with a later stage of the disease. Additional long-term prospective studies with more number of patients having a broad spectrum of diseases are needed to identify meaningful improvement in the motor function and quality of life after nusinersen treatment.

Pediatric SMA patients with complex spinal anatomy: Implementation and evaluation of a decision-tree algorithm for administration of nusinersen

The approval of nusinersen for the treatment of spinal muscular atrophy (SMA) has significantly changed the natural history of the disease. Nevertheless, scoliosis secondary to axial muscle weakness occurs at some point in most of patients with SMA and a conventional posterior interlaminar approach for intrathecal administration of nusinersen can be particularly challenging to perform in patients with severe scoliosis and/or previous spine fusion surgeries. We developed a protocol for the administration of nusinersen in pediatric patients, which includes a decision-tree algorithm that categorizes patients according to the estimated technical difficulty for the intrathecal administration. Complex spine patients were defined as those with a Cobb angle greater than 50° and/or a history of spinal surgery, while the rest of patients were considered non-complex. Nusinersen was successfully administered through a conventional non-CT-guided lumbar puncture in all 14 non-complex spine patients (110 out of 110 procedures; 100%). The feasibility of the intrathecal injection in the 15 complex spine patients was assessed by 3D CT. Administration was considered unfeasible in 7 out of these 15 patients according to imaging. In the 8 complex spine patients in whom the administration was considered feasible, conventional non-CT-guided lumbar punctures were successful only in 19 out of 53 procedures (36%). The remaining 34 procedures (64%) were guided by CT scan, all successful. Our work demonstrates that a cut-off point of 50° in Cobb angle and history of spinal surgery can reliably be used to anticipate the need for CT guidance in nusinersen administration.

Multicenter Experience with Nusinersen Application via an Intrathecal Port and Catheter System in Spinal Muscular Atrophy

Nusinersen, an antisense oligonucleotide enhancing the production of the survival motor neuron protein, is approved for the treatment of spinal muscular atrophy (SMA) but requires repetitive lumbar punctures. Application via a subcutaneous port connected to a permanent intrathecal catheter has been proposed as an alternative for patients with severe scoliosis, spinal fusion, or comorbidities, rendering serial interlaminar punctures complicated and risky. Since experience with this technique is sparse and follow-up data are lacking, we assessed feasibility, safety, and tolerability of this approach in eight patients with SMA II/SMA III receiving Nusinersen in a multicenter study. Median age at port implantation was 21 years (range: 10-30 years), and median follow-up time thereafter was 19 months (range: 7-24 months). Leakage of the port catheter occurred in two patients, promptly resolving after resuturing. No further complications such as infection, dislocation, kinking, or obstruction of the port were noted in any of the patients. These findings suggest that application via an intrathecal port and catheter system represents a safe and feasible option for Nusinersen treatment in subjects with SMA. However, to detect rare adverse events longer term follow-up in a larger study cohort is warranted.