Reproductive findings in male animals exposed to selective survival of motor neuron-2 (SMN2) gene splicing modifying agents

Fertility Outcomes in Risdiplam-Treated Male Patients with Spinal Muscular Atrophy: A Multicenter Case Series

INTRODUCTION

Spinal muscular atrophy (SMA) is a genetic, progressive neuromuscular disease caused by pathogenic variants in the survival of motor neuron survival of motor neuron (SMN) 1 gene leading to a deficiency in SMN protein. Three disease-modifying therapies are available for the treatment of SMA, affording many with the opportunity for family planning. Fertility outcomes in patients with SMA treated with risdiplam have not been previously reported.

METHODS

This study was a multicenter, non-interventional retrospective case review that included three adult male patients with SMA from three sites in Austria and the USA. The primary objective was to characterize the reproductive history and fertility journey of men with SMA who were exposed to risdiplam and whose partner had conceived.

RESULTS

Three male patients aged 21-34 years with late-onset SMA were taking risdiplam during the window of conception. Of the three resultant pregnancies, two were full term and resulted in healthy babies and one was voluntarily terminated. The babies were healthy and developing normally.

CONCLUSIONS

This series presents three cases of successful conception while a male patient was receiving risdiplam, a US Food and Drug Administration-approved treatment for SMA. Although there were reproductive concerns due to impairment in spermatogenesis that arose during nonclinical studies, this case series demonstrates that there was sufficient sperm production while on risdiplam to result in pregnancy. More research is needed to provide a complete understanding of the effects of risdiplam on male fertility in humans. Graphical abstract available for this article.

Clinical Application of Risdiplam in 5q Spinal Muscular Atrophy: A Narrative Review

5q spinal muscular atrophy (SMA) is caused by mutations in the survival motor neuron (SMN) gene located on chromosome 5, leading to insufficient SMN protein levels. Risdiplam is an RNA splicing modifier that modifies pre-mRNA splicing of the SMN2 gene, thereby promoting the production of functional survival motor neuron protein (SMN-fl). This article reviews the drug trials of Risdiplam, summarizes the actual clinical data, and systematically evaluates the effectiveness and safety of this drug. By discussing the mechanism of action and economic cost of this drug and comparing it to other SMA drugs, this paper provides a reference for the clinical use of the drug and an idea for future clinical research.

Spinal muscular atrophy is also a disorder of spermatogenesis

BACKGROUND

Spinal muscular atrophy (SMA) patients benefit from pre-mRNA splicing modifiers targeting the SMN2 gene, which aims to increase functional SMN production. The animal toxicity affecting spermatogenesis associated with one such treatment raised questions about male SMA patients' spermatogenesis.

METHODS

This descriptive, cross-sectional study was conducted from June 2022 to July 2023. The study involved adult male patients with genetically confirmed SMA type 2 (SMA2) or SMA3 from 13 French neuromuscular centers. The patients' general data, motor severity, urological history, exposure to certain factors, parenthood, and spermogram results were obtained. All patients were enrolled prior to exposure to risdiplam.

FINDINGS

Sixty-eight patients were enrolled ( 36 SMA2 and 32 SMA3 patients). Forty-one patients had fertility data (parenthood history and spermogram analyses) and underwent 33 spermograms. Fertility disorders were identified in 27 of the 41 patients (65·9%, 95%CI 51·3-80·4%) in particular SMA2 patients: 19 cases (90.5%, CI 77·9-100%) (SMA3: 8 cases (40%, CI 18·5-61·5%). Among the patients with available spermograms, 81% (27/33) had abnormal sperm concentration; 30% presented azoospermia. These abnormalities were significantly associated with SMA type (more prevalent in SMA2 patients, p < 0·001), disease motor severity, which included age at the loss of walking ability and wheelchair use duration (p < 0·001). The Motor Function Measure (MFM) determined that the sperm counts were also correlated with disease severity (p < 0·01).

INTERPRETATION

The fertility disorders were correlated with SMA severity and were particularly evident in SMA2 patients. In the latter, sperm concentration positively correlated with MFM. This study is the first one to link fertility disorders with spermogram abnormalities in SMA males. Understanding spermatogenesis in SMA is crucial, especially with new therapies such as risdiplam. Consequently, conducting systematic spermogram studies prior to SMA treatment is recommended.

Developmental variations of the reproductive organs of ganders from different goose breeds and the underlying mechanisms

A deep understanding of the dynamics and mechanisms of male reproductive tract development is necessary for adoption of either genetic techniques or environmental management practices for improving fertility and hatchability in poultry. However, compared with other poultry such as chickens and ducks, less is known about the age- and breed-related changes in the reproductive tract development of domestic goose ganders exhibiting relatively poor reproductive performance as well as the regulatory mechanisms. In the present study, by taking 2 Chinese domestic goose breeds (Sichuan White goose, SW and Gang goose, GE; Anser cygnoides) and one European goose breed (Landes goose, LD; Anser anser) as the experimental objects, we comprehensive analyzed the morphological, histological, and genome-wide transcriptomic variations in their testicular and external genital development during the period from hatching to sexual maturity. Results from histomorphological analysis demonstrated that the reproductive tract of all goose breeds developed in both age- and breed-dependent manners, and the left and right testis developed asymmetrically throughout posthatch development. The tenth week posthatch was a critical developmental stage for all goose ganders, because both the testicular and external genital histomorphological parameters significantly changed before and after this period. During the first 10 wk posthatch, the weight, organ index, or size of male reproductive organs developed more rapidly in SW than in LD, and so were the testicular parenchymal-to-interstitial ratio and the external genital lymphatic lumen diameter. However, the testicular seminiferous epithelium thickness, seminiferous tubule diameter, and Leydig cell number, as well as the external genital keratinized epithelium thickness were significantly higher in LD than in SW at 10 wk of age. Through comparative transcriptomics analysis and RT-qPCR validation, several pathways related to germ and somatic cell function, organ remodeling, and energy metabolism were thought to be responsible for the developmental variations in the early testicular development between Chinese and European domestic ganders, where 10 hub genes involved in the cell cycle, RNA polymerase II-dependent transcription, and mitotic cell division pathways might play essential roles. These data shed new light on the interbreed differences in the male goose reproductive tract development and the molecular mechanisms regulating male goose testicular functions and fertility.

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.

Male Reproduction in Spinal Muscular Atrophy (SMA) and the Potential Impact of Oral Survival of Motor Neuron 2 (SMN2) Pre-mRNA Splicing Modifiers

Spinal muscular atrophy (SMA) is a neuromuscular disease caused by deletions or mutations in the survival of motor neuron 1 (SMN1) gene resulting in reduced levels of SMN protein. SMN protein is produced by cells throughout the body, and evidence suggests that low SMN protein can have systemic implications, including in male reproductive organs. However, a paucity of research exists on this important topic. This article will discuss findings from non-clinical studies on the role of SMN in the male reproductive system; additionally, real-world observational reports of individuals with SMA will be examined. Furthermore, we will review the non-clinical reproductive findings of risdiplam, a small-molecule SMN2 splicing modifier approved for the treatment of SMA, which has widespread distribution in both the central nervous system and peripheral organs. Specifically, the available non-clinical evidence of the effect of risdiplam on male reproductive organs and spermatogenesis is examined. Lastly, the article will highlight available capabilities to assess male fertility as well as the advanced reproductive technologies utilized to treat male infertility. This article demonstrates the need for further research to better understand the impacts of SMA on male fertility and reproduction.

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.

Exploration of adverse events associated with risdiplam use: Retrospective cases from the US Food and Drug Administration Adverse Event Reporting System (FAERS) database

Risdiplam is a new drug for treating spinal muscular atrophy (SMA). However, pharmacovigilance analyses are necessary to objectively evaluate its safety-a crucial step in preventing severe adverse events (AEs). Accordingly, the primary objective of the current study was to examine the AEs associated with risdiplam use based on real-world data obtained from the US Food and Drug Administration Adverse Event Reporting System (FAERS) database. More specifically, we examined incidents reported between the third quarter of 2020 and the second quarter of 2023. The imbalance of risdiplam-related AEs was evaluated by computing the reporting odds ratio. A total of 5,406,334 reports were thoroughly reviewed. By removing duplicate reports, we identified 1588 reports in which risdiplam was the main suspected drug whose use was accompanied by 3470 associated AEs. Among the included AEs, 703 were categorized as serious and 885 as non-serious. Risdiplam use induced AEs across 18 organ systems, resulting in 130 positive signals. Notably, we detected new AE signals, including cardiac arrest, nephrolithiasis, tachycardia, loss of libido, and elevated hepatic enzyme activities; however, no ophthalmologic toxicity was reported. Although these new adverse reaction signals associated with risdiplam have been defined, long-term clinical studies are needed to confirm these findings. Nevertheless, our findings provide a valuable reference for improving the clinical management of SMA.