Antisense oligonucleotides (ASOs) are short, modified pieces of DNA that are chemically modified. They can be used to induce exon skipping and treat Duchenne muscular dystrophy (DMD) patients by... Show moreAntisense oligonucleotides (ASOs) are short, modified pieces of DNA that are chemically modified. They can be used to induce exon skipping and treat Duchenne muscular dystrophy (DMD) patients by interfering with the splicing process so mutated dystrophin transcripts become readable allowing production of partially functional dystrophin proteins, rather than nonfunctional dystrophins. After over 2 decades of research, 4 ASOs are FDA approved for DMD, but clinical effects are suboptimal due to limited delivery to skeletal muscle. At the same time, ASOs for brain diseases result in much more functional impact, because local delivery allows higher exposure to the target tissue at a low dose and infrequent treatment regimen. This has opened the way to develop ASOs in an individualized setting, as was exemplified by the development of Milasen to treat a patient with CLN7 Batten disease. In this perspective paper I will share my personal journey as one of the pioneers of ASO-mediated exon skipping development for DMD, currently applying expertise gained and lessons learned along the way to develop exon skipping ASOs for eligible patients with genetic brain diseases in a national and international setting. Show less
Deutekom, J. van; Beekman, C.; Bijl, S.; Bosgra, S.; Eijnde, R. van den; Franken, D.; ... ; Datson, N.A. 2023
In the last two decades, antisense oligonucleotides (AONs) that induce corrective exon skipping have matured as promising therapies aimed at tackling the dystrophin deficiency that underlies the... Show moreIn the last two decades, antisense oligonucleotides (AONs) that induce corrective exon skipping have matured as promising therapies aimed at tackling the dystrophin deficiency that underlies the severe and progressive muscle fiber degeneration in Duchenne muscular dystrophy (DMD) patients. Pioneering first generation exon 51 skipping AONs like drisapersen and eteplirsen have more recently been followed up by AONs for exons 53 and 45, with, to date, a total of four exon skipping AON drugs having reached (conditional) regulatory US Food and Drug Administration (FDA) approval for DMD. Nonetheless, considering the limited efficacy of these drugs, there is room for improvement. The aim of this study was to develop more efficient [2 '-O-methyl-modified phosphorothioate (2 ' OMePS) RNA] AONs for DMD exon 51 skipping by implementing precision chemistry as well as identifying a more potent target binding site. More than a hundred AONs were screened in muscle cell cultures, followed by a selective comparison in the hDMD and hDMDdel52/mdx mouse models. Incorporation of 5-methylcytosine and position-specific locked nucleic acids in AONs targeting the drisapersen/eteplirsen binding site resulted in 15-fold higher exon 51 skipping levels compared to drisapersen in hDMDdel52/mdx mice. However, with similarly modified AONs targeting an alternative site in exon 51, 65-fold higher skipping levels were obtained, restoring dystrophin up to 30% of healthy control. Targeting both sites in exon 51 with a single AON further increased exon skipping (100-fold over drisapersen) and dystrophin (up to 40%) levels. These dystrophin levels allowed for normalization of creatine kinase (CK) and lactate dehydrogenase (LDH) levels, and improved motor function in hDMDdel52/mdx mice. As no major safety observation was obtained, the improved therapeutic index of these next generation AONs is encouraging for further (pre)clinical development. Show less
Aartsma-Rus, A.; Garanto, A.; Roon-Mom, W. van; McConnell, E.M.; Suslovitch, V.; Yan, W.X.; ... ; N 1 Collaborative 2022
Antisense oligonucleotides (ASOs) can modulate pre-mRNA splicing. This offers therapeutic opportunities for numerous genetic diseases, often in a mutation-specific and sometimes even individual... Show moreAntisense oligonucleotides (ASOs) can modulate pre-mRNA splicing. This offers therapeutic opportunities for numerous genetic diseases, often in a mutation-specific and sometimes even individual-specific manner. Developing therapeutic ASOs for as few as even a single patient has been shown feasible with the development of Milasen for an individual with Batten disease. Efforts to develop individualized ASOs for patients with different genetic diseases are ongoing globally. The N = 1 Collaborative (N1C) is an umbrella organization dedicated to supporting the nascent field of individualized medicine. N1C recently organized a workshop to discuss and advance standards for the rigorous design and testing of splice-switching ASOs. In this study, we present guidelines resulting from that meeting and the key recommendations: (1) dissemination of standardized experimental designs, (2) use of standardized reference ASOs, and (3) a commitment to data sharing and exchange. Show less
Aartsma-Rus, A.; Garanto, A.; Roon-Mom, W. van; McConnell, E.M.; Suslovitch, V.; Yan, W.X.; ... ; N 1 Collaborative 2022
Antisense oligonucleotides (ASOs) can modulate pre-mRNA splicing. This offers therapeutic opportunities for numerous genetic diseases, often in a mutation-specific and sometimes even individual... Show moreAntisense oligonucleotides (ASOs) can modulate pre-mRNA splicing. This offers therapeutic opportunities for numerous genetic diseases, often in a mutation-specific and sometimes even individual-specific manner. Developing therapeutic ASOs for as few as even a single patient has been shown feasible with the development of Milasen for an individual with Batten disease. Efforts to develop individualized ASOs for patients with different genetic diseases are ongoing globally. The N = 1 Collaborative (N1C) is an umbrella organization dedicated to supporting the nascent field of individualized medicine. N1C recently organized a workshop to discuss and advance standards for the rigorous design and testing of splice-switching ASOs. In this study, we present guidelines resulting from that meeting and the key recommendations: (1) dissemination of standardized experimental designs, (2) use of standardized reference ASOs, and (3) a commitment to data sharing and exchange. Show less
Introduction Exon skipping compounds restoring the dystrophin transcript reading frame have received regulatory approval for Duchenne muscular dystrophy (DMD). Recently, focus shifted to developing... Show moreIntroduction Exon skipping compounds restoring the dystrophin transcript reading frame have received regulatory approval for Duchenne muscular dystrophy (DMD). Recently, focus shifted to developing compounds to skip additional exons, improving delivery to skeletal muscle, and to genome editing, to restore the reading frame on DNA level. Areas covered We outline developments for reading frame restoring approaches, challenges of mutation specificity, and optimizing delivery. Also, we highlight ongoing efforts to better detect exon skipping therapeutic effects in clinical trials. Searches on relevant terms were performed, focusing on recent publications (<3 years). Expert opinion Currently, 3 AONS are approved. Whether dystrophin levels are sufficient to slowdown disease progression needs to be confirmed. Enhancing AON uptake by muscles is currently under investigation. Gene editing is an alternative, but one that involves practical and ethical concerns. Given the field's momentum, we believe the efficiency of frame-restoring approaches will improve. Show less
Putten, M. van; Tanganyika-de Winter, C.; Bosgra, S.; Aartsma-Rus, A. 2019
Duchenne muscular dystrophy is a severe, progressive muscle-wasting disease that is caused by mutations that abolish the production of functional dystrophin protein. The exon skipping approach aims... Show moreDuchenne muscular dystrophy is a severe, progressive muscle-wasting disease that is caused by mutations that abolish the production of functional dystrophin protein. The exon skipping approach aims to restore the disrupted dystrophin reading frame, to allow the production of partially functional dystrophins, such as found in the less severe Becker muscular dystrophy. Exon skipping is achieved by antisense oligonucleotides (AONs). Several chemical modifications have been tested in nonclinical and clinical trials. The morpholino phosphorodiamidate oligomer eteplirsen has been approved by the Food and Drug Administration, whereas clinical development with the 2 '-O-methyl phosphorothioate (2OMePS) AON drisapersen was recently stopped. In this study, we aimed to study various aspects of 2OMePS AONs in nonclinical animal studies. We show that while efficiency of exon skipping restoration is comparable in young and older C57BL/10ScSn-Dmd(mdx)/J (mdx/BL10) mice, functional improvement was only observed for younger treated mice. Muscle quality did not affect exon skipping efficiency as exon skip and dystrophin levels were similar between mdx/BL10 and more severely affected, age-matched D2-mdx mice. We further report that treadmill running increases AON uptake and dystrophin levels in mdx/BL10 mice. Finally, we show that even low levels of exon skipping and dystrophin restoration are sufficient to significantly increase the survival of mdx-utrn-/- mice from 70 to 97 days. Show less
Toonen, L.J.A.; Casaca-Carreira, J.; Pellise-Tintore, M.; Mei, H.L.; Temel, Y.; Jahanshahi, A.; Roon-Mom, W.M.C. van 2018
