Efficacy and safety of onasemnogene abeparvovec in children with spinal muscular atrophy type 1: real-world evidence from 6 infusion centres in the United Kingdom

Safety of Onasemnogene Abeparvovec Administration to Type 1 SMA Patients Who Have Received Risdiplam

ABSTRACT

Three therapies are now available for the treatment of type 1 spinal muscular atrophy: onasemnogene abeparvovec (OA), nusinersen, and risdiplam. We present a retrospective, single-center case series detailing our center's experience with six patients diagnosed with type 1 spinal muscular atrophy who switched from risdiplam to OA. Risdiplam was discontinued the day before the OA infusion, and we evaluate the safety aspects of this switch. All patients continued risdiplam until the day before administration of OA, with a wash out period of between 24 and 33 hours prior. All patients have had follow-up for at least 12 weeks, while 3 patients who lived locally received ongoing follow-up ranging from 14 to 27 months after OA infusion. All patients remained stable or improved in their motor scores and need for ventilatory support and feeding support requirement. Adverse events reported after OA switch included tachycardia, fever, nausea, vomiting, raised transaminases, and mild neutropenia. All adverse events in these children were either known adverse events of OA or were not considered secondary to OA or risdiplam treatment. No unexpected adverse event was demonstrated post-OA in patients stopping risdiplam a day before OA infusion. Data presented here suggest that stopping risdiplam a day before OA treatment did not seem to be associated with increased risk.

Safety and Efficacy of IV Onasemnogene Abeparvovec for Pediatric Patients With Spinal Muscular Atrophy: The Phase 3b SMART Study

BACKGROUND AND OBJECTIVES

Safety and efficacy of IV onasemnogene abeparvovec has been demonstrated for patients with spinal muscular atrophy (SMA) weighing <8.5 kg. SMART was the first clinical trial to evaluate onasemnogene abeparvovec for participants weighing 8.5-21 kg.

METHODS

SMART was an open-label, multicenter, phase 3b study conducted across 13 sites in 9 countries (NCT04851873). Symptomatic pediatric participants with SMA (any type; treatment-naïve or had discontinued prior treatment) were stratified into 3 weight cohorts (≥8.5-13, >13-17, and >17-21 kg), administered onasemnogene abeparvovec, and followed for 52 weeks. Corticosteroids were initiated 24 hours before infusion with dose increases in response to adverse events (AEs) and subsequent tapering at investigator discretion. The primary objective was safety. Secondary objective was efficacy (motor function/motor milestones).

RESULTS

Twenty-four participants were enrolled; the majority had SMA type 2 (n = 11), 3 SMN2 copies (n = 18), and prior treatment (n = 21). All participants completed the study; no deaths occurred. All participants had ≥1 treatment-related AE(s), 7 of 24 (29%) had serious treatment-related AEs, and 23 of 24 (96%) had ≥1 AE of special interest. Twenty of 24 participants (83%) had asymptomatic hepatotoxicity events, which were primarily transaminase elevations. No participant had bilirubin elevations >2× upper limit of normal, developed symptomatic hepatotoxicity, or met Hy law criteria. Transient asymptomatic thrombocytopenia events were reported in 17 of 24 participants (71%); all resolved spontaneously with no related bleeding events reported. Three of 24 participants (13%) had cardiac AEs (all unrelated to treatment). No thrombotic microangiopathy or dorsal root ganglionopathy-related AEs were reported. AE frequency and severity were similar across weight groups, although corticosteroid exposure was greater for the 2 heavier cohorts (median 135.0, 201.0, and 194.0 days, respectively) with 37% and 33% still on corticosteroids at the study end. By week 52, most participants maintained or improved motor function (Hammersmith Functional Motor Scale-Expanded 16/18; Revised Upper Limb Module 15/17); 4 participants (all 3 SMN2 copies) achieved new motor milestones.

DISCUSSION

Onasemnogene abeparvovec safety profile was similar across weight groups in this heterogenous participant population. Frequency and duration of asymptomatic aminotransferase elevations and thrombocytopenia are notable findings. Most participants demonstrated maintenance or improvement of motor function, suggesting clinical benefit for patients with SMA weighing up to 21 kg.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov identifier (NCT04851873, clinicaltrials.gov/study/NCT04851873) submitted April 19, 2021. First participant enrolled on September 8, 2021.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that intravenous onasemnogene abeparvovec is safe in pediatric patients with SMA who weigh 8.5-21 kg.

Comprehensive analysis of adverse events associated with onasemnogene abeparvovec (Zolgensma) in spinal muscular atrophy patients: insights from FAERS database

Onasemnogene Abeparvovec (Zolgensma) is a gene therapy for the treatment of Spinal Muscular Atrophy (SMA) with improved motor neuron function and the potential for a singular treatment. Information on its adverse drug reactions is mainly from clinical trials and real-world studies with extensive sample sizes are lacking. In this study, we analyzed the U.S. Food and Drug Administration's Adverse Event Reporting System (FAERS) database to assess the drug safety profile of Zolgensma. A total of 1951 adverse event reports associated with onasemnogene abeparvovec (Zolgensma), containing 778 import important medical event (IME) signals, were identified from the FAERS database, and multiple disproportionate analysis algorithms were used to determine the significance of these adverse events. This study identified 281 onasemnogene abeparvovec-related adverse events (AEs), including some significant adverse events not mentioned in the product labelling. Elevated liver enzymes, fever, vomiting, and thrombocytopenia were the most common adverse reactions. Most adverse events manifested within the initial month of onasemnogene abeparvovec use, especially the first 8 days, but some may still occur after 1 year of treatment. Sex-specific scrutiny revealed differing risk levels for adverse events among women and men. Thrombocytopenia and thrombotic microangiopathy are more common in patients weighing ≥8.5 kg, and changes in renal function need to be closely monitored if thrombotic microangiopathy occurs. The above findings provide valuable insights into optimizing the utilization of onasemnogene abeparvovec, improving its effectiveness, and minimizing potential side effects, thereby greatly facilitating its practical application in clinical settings.

Treatment of spinal muscular atrophy

PURPOSE OF REVIEW

The aim of the review was to provide an overview of safety and efficacy of the available treatments including information from both clinical trials and real-world data. Additional information form ongoing studies using other approaches than increasing SMN protein are also reported.

RECENT FINDINGS

In the last 3 years, there have been over 24 studies reporting safety and the impact of the available drugs on different aspects of function, including respiratory and bulbar function. These findings, obtained in a real-world setting, are extremely important to define the spectrum of responses in individuals with different age, weight, SMN2 copies, and other variables and will be of help to the families and the clinicians to set up the right expectations at the time of starting a new treatment.

SUMMARY

The large number of studies that became available in the last few years support and expand the information on safety and efficacy provided by the clinical trials.

A systematic review of immunosuppressive protocols used in AAV gene therapy for monogenic disorders

The emergence of adeno-associated virus (AAV)-based gene therapy has brought hope to patients with severe monogenic disorders. However, immune responses to AAV vectors and transgene products present challenges that require effective immunosuppressive strategies. This systematic review focuses on the immunosuppressive protocols used in 38 clinical trials and 35 real-world studies, considering a range of monogenic diseases, AAV serotypes, and administration routes. The review underscores the need for a deeper understanding of immunosuppressive regimens to enhance the safety and effectiveness of AAV-based gene therapy. Characterizing the immunological responses associated with various gene therapy treatments is crucial for optimizing treatment protocols and ensuring the safety and efficacy of forthcoming gene therapy interventions. Further research and understanding of the impact of immunosuppression on disease, therapy, and route of administration will contribute to the development of more effective and safer gene therapy approaches in the future.

Treatment Options in Spinal Muscular Atrophy: A Pragmatic Approach for Clinicians

Spinal muscular atrophy (SMA) is a rare neurodegenerative neuromuscular disorder with a wide phenotypic spectrum of severity. SMA was previously life limiting for patients with the most severe phenotype and resulted in progressive disability for those with less severe phenotypes. This has changed dramatically in the past few years with the approvals of three disease-modifying treatments. We review the evidence supporting the use of currently approved SMA treatments (nusinersen, onasemnogene abeparvovec, and risdiplam), focusing on mechanisms of action, side effect profiles, published clinical trial data, health economics, and pending questions. Whilst there is robust data from clinical trials of efficacy and side effect profile for individual drugs in select SMA populations, there are no comparative head-to-head clinical trials. This presents a challenge for clinicians who need to make recommendations on the best treatment option for an individual patient and we hope to provide a pragmatic approach for clinicians across each SMA profile based on current evidence.

Motor and neurocognitive profiles of children with symptomatic spinal muscular atrophy type 1 with two copies of SMN2 before and after treatment: a longitudinal observational study

Introduction

Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by mutations in the survival motor neuron 1 (SMN1) gene. In clinical studies, gene replacement therapy with onasemnogene abeparvovec (formerly AVXS-101, Zolgensma®, Novartis) was efficacious in improving motor functioning in children with SMA. However, its effects on cognitive and language skills are largely unknown.

Methods

This longitudinal observational study evaluated changes in motor and neurocognitive functioning over a 1-year period after administration of onasemnogene abeparvovec in 12 symptomatic SMA type 1 patients with two copies of SMN2 aged 1.7-52.6 months at administration. Motor functioning was measured using the Children's Hospital of Philadelphia Infant Test for Neuromuscular Disorders (CHOP-INTEND) while neurocognitive assessment was measured using Griffiths III. Motor milestones and language ability were also assessed at each timepoint.

Results and discussion

Statistically significant increases in median CHOP-INTEND scores from baseline were observed at 1, 3, 6, and 12 months after onasemnogene abeparvovec administration (all p ≤ 0.005). Most (91.7%) patients were able to roll over or sit independently for >1 min at 12 months. Significant increases in the Griffiths III Foundations of Learning, Language and Communication, Eye and Hand Coordination, and Personal-Social-Emotional subscale scores were observed at 12-months, but not in the Gross Motor subscale. Speech and language abilities progressed in most patients. Overall, most patients showed some improvement in cognitive and communication performance after treatment with onasemnogene abeparvovec in addition to significant improvement in motor functioning and motor milestones. Evaluation of neurocognitive function should be considered when assessing the global functioning of patients with SMA.