Muscular Atrophy, Spinal

In this study, researchers will learn more about the safety and effects of BIIB115, also known as salanersen. Specifically, researchers will learn more about how salanersen works in babies who have already been treated with onasemnogene abeparvovec (OA) after being diagnosed with SMA. Most people with SMA have changes in a gene called survival motor neuron 1, also known as SMN1. These changes lower the amount of SMN protein in their bodies. Without enough of this protein, motor neurons and muscles cannot work properly. A similar gene called SMN2 can help replace some of the lost SMN protein in the body. Salanersen works by helping the SMN2 gene to make more SMN protein. OA works by replacing the missing or abnormal SMN1 gene. Sometimes, OA treatment may not work as well as expected. As a result, researchers are exploring whether giving another drug after OA could lead to better outcomes for people with SMA. In this study, participants will have 2 SMN2 copies. The higher the copy number, the less severe the participant's SMA is. They will also have received treatment with OA by the time they were 42 days old and before showing any symptoms of SMA. The main goal of the study is to learn more about the safety of giving salanersen to babies after OA treatment. Researchers will also learn more about whether salanersen can help make SMA symptoms less serious. The main question researchers want to answer in this study is: • How many participants have adverse events and serious adverse events after treatment? Researchers will also learn more about: * The effects on participants' motor symptoms and how many new movement milestones participants achieve. * How many participants stay free of SMA symptoms. * How much neurofilament protein is found in the blood after treatment. * How much salanersen gets into the fluid surrounding the brain and spinal cord. * How much salanersen gets into the blood. Researchers will use different tests to learn if motor symptoms are changing, including the World Health Organization (WHO) motor milestones and Hammersmith Infant Neurological Examination (HINE) Section 2 motor milestones. The study will be done in 2 parts. Part A will last 1 year while Part B will last up to 4 years. The study will be done as follows: * First, participants will be screened to check if they can join the study. The screening period will be up to 6 months. Participants must have received OA treatment before the age of 42 days and started screening within 6 months of the OA dose. * Participants will be assigned to 1 of 2 treatment groups by chance. This is a "double blind" study which means neither the participants, study doctor, nor site staff will know which treatment group the participants are assigned to. * In this study, salanersen will be given as an intrathecal injection, which is an injection into the fluid surrounding the spine. This is done by a procedure called a lumbar puncture (LP) which involves inserting a needle into the lower back into the space around the spinal cord. * During Part A, one group will receive 80 milligrams (mg) of salanersen while another group receives a sham (fake) procedure. This means that a small needle prick will be done, but no injection will be given. * For each participant, the first visit of Part A will be 6 months after they receive OA treatment. * Part A will have up to 6 clinic visits and 2 phone calls and last up to 1 year. * During Part B, both groups of participants will receive 80 mg of salanersen once a year. * Part B will have up to 12 clinic visits and 14 phone calls and last up to 4 years. * In total, participants will be in the study for up to 5 and a half years.

In this study, researchers will learn more about the effects and safety of BIIB115, also known as salanersen. Specifically, researchers will learn more about how salanersen works in babies who have been diagnosed with SMA through genetic testing but have not yet started showing signs or symptoms. Most people with SMA have changes in a gene called survival motor neuron 1, also known as SMN1. These changes lower the amount of SMN protein in their bodies. Without enough of this protein, motor neurons and muscles cannot work properly. A similar gene called SMN2 can help replace some of the lost SMN protein in the body. Salanersen works by helping the SMN2 gene to make more SMN protein. In this study, participants will have either 2 SMN2 copies or 3 SMN2 copies. The higher the copy number, the less severe the participant's SMA is. The main goal of this study is to see if starting salanersen before signs or symptoms appear can prevent signs or symptoms of SMA or make them less severe. Researchers will use different tests to learn if motor symptoms are changing, including the World Health Organization (WHO) motor milestones. The main questions researchers want to answer in this study are: * How many participants with 2 copies of the SMN2 gene can sit without support at 12 months? * How many participants with 3 copies of the SMN2 gene can walk alone at 18 months? Researchers will also learn more about: * The effects on participants' motor symptoms and how many new movement milestones participants achieve. * How many participants stay free of SMA symptoms * How much salanersen gets into the fluid surrounding the brain and spinal cord. * How much salanersen gets into the blood. * How many participants have adverse events or serious adverse events. Adverse events are health problems that may or may not be caused by the study drug. This study will be done as follows: * First, participants will be screened to check if they can join the study. The screening period will be up to 28 days. * This is an "open label" study. This is a study in which the participants, study doctor, and site staff know which study drug participants are receiving. In this study, all participants will receive salanersen through an intrathecal injection, or one that is given into the fluid surrounding the brain and spinal cord. * There will be 2 parts in this study. During Part 1, participants will receive 2 doses of salanersen, about 12 months apart from each other. Part 1 will last up to 25 months. * During Part 2, participants will continue to receive salanersen. They will receive up to 3 doses, 12 months apart from each other. Part 2 will last up to 36 months. * During Part 1, participants will have up to 11 clinic visits and up to 3 phone calls. During Part 2, participants will have up to 7 clinic visits and up to 12 phone calls.

This is an open-label, single-arm, multicenter clinical study to evaluate the effectiveness and safety of risdiplam administered in pediatric participants with SMA and 2 SMN2 copies who previously received onasemnogene abeparvovec and experience a plateau or decline in function. Participants to be enrolled are children \<2 years of age genetically diagnosed with SMA.

This is an open-label, single-arm, multicenter clinical study to evaluate the effectiveness and safety of risdiplam administered as an early intervention in pediatric participants with spinal muscular atrophy (SMA) and 2 SMN2 copies who have previously received onasemnogene abeparvovec. Participants are children \< 2 years of age genetically diagnosed with SMA.

In this PIERRE-PK study, researchers will learn how the body processes nusinersen when it is given through the ThecaFlex DRx™ System, compared to when nusinersen is given by lumbar puncture (LP). The ThecaFlex DRx system is an investigational implantable medical device developed by Alcyone Therapeutics, Inc. It consists of a catheter, which is a flexible tube, connected to a port which is placed under the skin. Alcyone Therapeutics, Inc. has an ongoing study called PIERRE to test the ThecaFlex DRx system. Participants with spinal muscular atrophy (SMA) in the PIERRE study may be enrolled in the PIERRE-PK study. The main objective of the PIERRE-PK study is to learn how the body processes nusinersen when given by the ThecaFlex DRx system compared to a lumbar puncture. The main questions researchers want to answer are: * What is the highest amount of nusinersen found in the blood after dosing? * How much nusinersen is found in the blood over the first 24 hours after dosing? The PIERRE-PK study will be done as follows: * Participants will be screened to check if they can join the study. The screening period will be up to 30 days for this study and may overlap with the PIERRE study. * Participants will receive a dose of nusinersen by lumbar puncture. * The ThecaFlex DRx system will be implanted after the lumbar puncture, as part of the PIERRE study. * Participants will receive a dose of nusinersen by the ThecaFlex DRx system, as part of the PIERRE study. * Researchers will take blood samples before and after each dose. The last blood sample will be taken 24 hours after the dose. * The total study duration for each participant in the PIERRE-PK study will be approximately 5 months. This period will overlap with the participant's first 5 months in the PIERRE study.

In this study, researchers will know more about the effects of nusinersen, also known as Spinraza®, in pregnant participants with spinal muscular atrophy, also known as SMA. This is a drug available for doctors to prescribe for people with SMA. Due to the current treatment options that exist, people with SMA may now reach the age where they can become pregnant. But, there is not enough information known yet about what the effects of nusinersen may be on pregnant people with SMA or on their babies. This is known as an "observational" study, which collects health information about study participants without changing their medical care. The pregnant participants for this study will be found using 3 different groups of SMA study research centers: * ISMAR-US (International SMA Registry in the United States) * UK Adult SMA-REACH (Adult SMA Research and Clinical Hub in the United Kingdom) * SMArtCARE (Austria, Germany, and Switzerland) The main goal of this study is to collect birth and health information from 3 groups of participants and their babies. These groups are: * Those who received nusinersen 14 months before the first day of their last period before getting pregnant * Those who received nusinersen 14.5 months before the day they got pregnant * Those who received nusinersen during any time in their pregnancy The main questions researchers want to learn about in this study are: * Loss of pregnancy overall * Loss of pregnancy before the baby was 20 weeks old * Loss of pregnancy after the baby becomes 20 weeks old * Live births * Loss of the baby after birth * Babies who have problems in their body that develop during pregnancy * Babies who are small for their age while in the participant's uterus * Pregnancy that happens outside of the uterus * How many participants die during pregnancy, while the baby is being born, and up to 12 weeks after delivering the baby * Babies who develop problems in their body after birth Researchers will also compare this information to people without SMA who have not received nusinersen. This study will be done as follows: * Information will start being collected when the participant decides to join the study. * Participants will be contacted at each trimester (about every 3 months) to learn about their health and pregnancy. * Participants' doctors will be contacted at each trimester, when the participants are about 6 or 7 months pregnant, and about 4 weeks after the delivery of the baby. * The babies' doctors will be contacted when the baby is 1, 2, 6, 12, 18, and 24 months old. * Each participant will be in the study until the end of their pregnancy and for up to 12 weeks after delivery. Each baby will be in the study for up to 2 years after birth. * The study overall will last at least 10 years from when the first participant joins the study.

This is an investigator initiated observational study with the aim to record several aspects of function, care and adverse events in a large cohort of SMA patients followed longitudinally by using a structured academic disease registry.