The CHOP-INTEND test was designed to evaluate the motor skills of infants with significant motor weakness. It included 16 items (capturing neck, trunk, and proximal and distal limb strength), nine of which were scored 0, 1, 2, 3, or 4, five were scored as 0, 2, or 4, one was scored as 0, 1, 2, or 4, and one as 0, 2, 3, or 4 with higher scores indicating greater muscle strength and function. Total score was calculated as the sum of scores for each item. Total score ranged from 0 (worst possible score) and 64 (best possible score). The change from baseline to Day 183 in the CHOP-INTEND total score was compared to CS3B study (NCT02193074) sham control group using the joint-rank methodology to account for mortality.

As planned, analysis was performed in the Matched sham set. Matched sham set comprised of sham control participants of the CS3B study (NCT02193074) identified by a matching algorithm and all of current study 50/28 mg participants that were included in the ITT set.

An adverse event (AE) was any unfavorable & unintended sign (including an abnormal assessment such as an abnormal laboratory value), symptom, or disease temporally associated with use of an investigational product, whether or not related to investigational product. An SAE was any untoward medical occurrence that at any dose resulted in death, in the view of Investigator, placed participant at immediate risk of death, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, resulted in a birth defect. AE and SAEs were regarded as treatment-emergent if it was present prior to receiving first dose of nusinersen in this current study and subsequently worsened in severity or was not present prior to receiving first dose of nusinersen and subsequently appeared.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study.

Blood chemistry parameters included protein, albumin, creatinine, blood urea nitrogen, bilirubin (total and direct), alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transferase, glucose, calcium, phosphorus, bicarbonate, chloride, sodium, potassium, cystatin C, and creatine kinase. These parameters were flagged as low, normal, or high relative to parameter's normal range or as unknown if no result was available, by the Investigator. Here, shift to low indicates values that were normal, high or unknown at baseline and shifted to low values postbaseline. Shift to high indicates values that were normal, low or unknown at baseline and shifted to high values postbaseline. The categories with at least one participant with shift from baseline in these parameters are reported.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study. Number analyzed 'n' indicates the number of participants evaluable for analysis of the specified parameter.

Hematology parameters included complete blood cell count, with differential and platelet count, and absolute neutrophil count. These parameters were flagged as low, normal, or high relative to parameter's normal range or as unknown if no result was available, by the Investigator. Here, shift to low indicates values that were normal, high or unknown at baseline and shifted to low values postbaseline. Shift to high indicates values that were normal, low or unknown at baseline and shifted to high postbaseline values. The categories with at least one participant with shift from baseline in these parameters are reported.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study. 'Number analysed (n)' indicates the number of participants evaluable for the specified hematology parameter.

Urinalysis included assessments of urine total protein, specific gravity, pH, protein, glucose, ketones, bilirubin, blood, red blood cells (RBC), white blood cells (WBC), epithelial cells, bacteria, casts and crystals. These parameters were flagged as low, normal, or high relative to parameter's normal range or as unknown if no result was available, by the Investigator. Here, shift to low indicates values that were normal, high or unknown at baseline and shifted to low values postbaseline. Shift to high indicates values that were normal, low or unknown at baseline and shifted to high postbaseline. The categories with at least one participant with shift from baseline in these parameters are reported.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study. 'Number analysed (n)' indicates the number of participants evaluable for the specified urinalysis parameter.

CSF parameters included cell count, total protein, and glucose. These parameters were flagged as low, normal, or high relative to parameter's normal range or as unknown if no result was available, by the Investigator. Here, shift to low indicates values that were normal, high or unknown at baseline and shifted to low values postbaseline. Shift to high indicates values that were normal, low or unknown at baseline and shifted to high values postbaseline. The categories with at least one participant with shift from baseline in these parameters are reported.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study. 'Number analysed (n)' indicates the number of participants evaluable for the specified urinalysis parameter.

The ECGs were assessed by the investigator to be normal, abnormal and abnormal AE. The number of participants with ECG shifts from normal to each of the categorical values denoting an abnormal scan (abnormal not AE, abnormal AE) was assessed. Shift from baseline to worst post-baseline values were reported. The categories with at least one participant with shift from baseline in ECG are reported.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study.

Vital sign assessment included temperature, pulse rate, systolic blood pressure, diastolic blood pressure, and respiratory rate. As pre-specified in protocol, the criteria for determining potentially clinically relevant abnormalities in vital signs included: temperature < 36.0 and > 38.0 degrees Celsius (C), pulse rate < 60 and > 100 beats per minute (bpm), systolic blood pressure [< 90, > 140 and > 160 millimeters of mercury (mmHg)], diastolic blood pressure < 50, > 90 and > 100 mmHg and respiratory rate < 12 and > 20 breaths per minute. The categories with at least one participant with clinically relevant vital sign abnormalities are reported.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

As pre-specified in the protocol, head circumference was measured for participants with infantile-onset SMA only.

ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

As pre-specified in protocol, chest circumference was measured for participants with infantile-onset SMA only.

ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

As pre-specified in the protocol, arm circumference was measured for participants with infantile-onset SMA. Here, negative change from baseline indicated reduction in arm circumference.

ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

As pre-specified in the protocol, ulnar length was measured for participants with later-onset SMA.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

World Health Organization (WHO) child growth standards (2006) was used to calculate the weight for age percentile in the infantile-onset participants while the 2000 Centers for Disease Control and Prevention (CDC) Growth Charts was used to calculate the weight for age percentile for later-onset participants. Negative change from baseline indicates low weight for age percentile.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

As pre-specified in the protocol, weight for length ratio was assessed only for the participants with infantile-onset SMA.

ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

As pre-specified in the protocol, head to chest circumference ratio was assessed only for the participants with infantile-onset SMA.

ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

Activated partial thromboplastin time was evaluated to assess safety. "Shift to low" measured change in normal, high and unknown values of aPTT at baseline to low values postbaseline. "Shift to high" measured change in normal, low and unknown values of aPTT at baseline to high values postbaseline.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C:ITT set included all participants who received at least one dose of nusinersen in the current study. 'Number analysed (n)' signifies number of participants evaluable for the specified category.

Prothrombin time was evaluated to assess safety. "Shift to low" measured change in normal, high and unknown values of PT at baseline to low values postbaseline. "Shift to high" measured change in normal, low and unknown values of PT at baseline to high values postbaseline.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure. 'Number analysed (n)' signifies number of participants evaluable for the specified category.

INR was evaluated to assess safety. "Shift to low" measured change in normal, high and unknown values of INR at baseline to low values postbaseline. "Shift to high" measured change in normal, low and unknown values of INR at baseline to high values postbaseline. The category with at least one participant with shift from baseline in INR ratio is reported.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study. 'Number analysed (n)' signifies number of participants evaluable for the specified category.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at specified timepoint.

Participants with abnormalities in neurological examinations recorded as AEs were reported.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study.

Part A: Safety set included all participants who received at least one dose of nusinersen. Part C: ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure.

Section 2 of HINE was used to assess motor milestones of participants. It's composed of 8 motor milestone categories: voluntary grasp, ability to kick in supine position, head control, rolling, sitting, crawling, standing, & walking. Motor milestone responder: (i) a participant that demonstrated at least a 2-point increase in category of ability to kick or maximal score on that category or a 1-point increase in category of head control, rolling, sitting, crawling, standing, or walking, (ii) improvement in more categories than worsening, excluding category of voluntary grasp. For category of ability to kick, improvement, as defined in (i), worsening: at least a 2-point decrease or decrease to lowest possible score of no kicking. For other 6 categories, improvement: 1-point increase, worsening: at least 1-point decrease. Participants who died or withdrew from study were considered as non-responders. Difference in percentage of responders reported using Fisher's exact test.

As planned, analysis was performed in the Matched sham set. Matched sham set comprised of sham control participants of CS3B study (NCT02193074) identified by a matching algorithm and all of current study 50/28 mg participants that were included in the ITT set.

Section 2 of the HINE was used to assess motor milestones of the participants. It's composed of 8 motor milestone categories: voluntary grasp, ability to kick in supine position, head control, rolling, sitting, crawling, standing, and walking. Within each category, 3 to 5 levels can be achieved. The total HINE section 2 motor milestones score was calculated as sum of each level & ranged from 0 to 26, higher score indicating improvement in motor milestones. A negative change from baseline indicates decline in motor milestones. Change from baseline in HINE section 2 motor milestones total score was compared to study CS3B (NCT02193074) matched sham control group, and was analysed using joint rank methodology.

As planned, analysis was performed in the Matched sham set. Matched sham set comprised of sham control participants of CS3B study (NCT02193074) identified by a matching algorithm and all of current study 50/28 mg participants that were included in ITT set.

The change from baseline in the plasma concentration of NF-L was compared to the study CS3B (NCT02193074) matched sham control group. Joint rank methodology was used for the analysis to account for mortality. The change from baseline data was reported in terms of least square geometric mean ratio to baseline. Lower ratios to baseline represent greater reductions in concentrations of NF-L from baseline.

As planned, analysis was performed in the Matched sham set. Matched sham set comprised of sham control participants of the CS3B study (NCT02193074) identified by a matching algorithm and all of current study 50/28 mg participants that were included in the ITT set.

The CHOP-INTEND test was designed to evaluate the motor skills of infants with significant motor weakness. It included 16 items (capturing neck, trunk, and proximal and distal limb strength), nine of which were scored 0, 1, 2, 3, or 4, five were scored as 0, 2, or 4, one was scored as 0, 1, 2, or 4, and one as 0, 2, 3, or 4 with higher scores indicating greater muscle strength and function. Total score was calculated as the sum of scores for each item. Total score ranged from 0 (worst possible score) and 64 (best possible score). The change from baseline to Day 302 in the total score was analyzed using the joint-rank methodology to account for mortality.

ITT set included all participants who were randomized and received at least one dose of nusinersen.

Section 2 of the HINE was used to assess motor milestones of the participants. It's composed of 8 motor milestone categories: voluntary grasp, ability to kick in supine position, head control, rolling, sitting, crawling, standing, and walking. Within each of these categories, participants can progress from complete absence of a motor ability (the lowest level in each category) through multiple milestones (2 to 4 levels in each category) to the highest level within the category. The total motor milestones score for HINE section was calculated as the sum of each level and ranged from 0 to a maximum score of 26, higher score indicating improvement in motor milestones.

ITT set included all participants who were randomized and received at least one dose of nusinersen.

The change from baseline in plasma concentration of NF-L was analysed using the joint rank methodology to account for mortality. The change from baseline data was reported in terms of LS geometric mean ratio to baseline. Lower ratios to baseline represent greater reductions in concentrations of NF-L from baseline.

ITT set included all participants who were randomized and received at least one dose of nusinersen.

Permanent ventilation was defined as tracheostomy or ≥ 16 hours of ventilation/day continuously for > 21 days in absence of an acute reversible event. An independent endpoint adjudication committee (EAC) determined date at which a participant was considered to have met protocol-specified criteria of an acute reversible event. Only events that were adjudicated by the EAC as meeting the criteria for permanent ventilation or death were included in analysis. Participants who did not meet the endpoint definition were censored on the last occasion the participant was seen (either in-person visit or by telephone contact), irrespective of whether the participant has completed the full course of treatment and whether the participant has completed the study or permanently withdrawn.

As planned, analysis was performed in the Matched sham set. Matched sham set comprised of sham control participants of the CS3B study (NCT02193074) identified by a matching algorithm and all of current study 50/28 mg participants that were included in the ITT set.

Time to death was determined by an independent EAC. Time to death (overall survival) was compared to the study CS3B (NCT02193074) matched sham control group.

As planned, analysis was performed in the Matched sham set. Matched sham set comprised of sham control participants of the CS3B study (NCT02193074) identified by a matching algorithm and all of current study 50/28 mg participants that were included in the ITT set.

Permanent ventilation was defined as tracheostomy or ≥ 16 hours of ventilation/day continuously for > 21 days in the absence of an acute reversible event. An independent EAC determined the date at which a participant was considered to have met the protocol-specified criteria of an acute reversible event. Only events that were adjudicated by the EAC as meeting the protocol defined criteria for permanent ventilation or death was included in the analysis. Participants who did not meet the endpoint definition were censored on the last occasion the participant was seen (either in-person visit or by telephone contact), irrespective of whether the participant has completed the full course of treatment and whether the participant has completed the study or permanently withdrawn.

ITT set included all participants who were randomized and received at least one dose of nusinersen.

Time to death was determined by an independent EAC. Participants who did not die were censored on the last occasion the participant was seen (either in-person visit or by telephone contact), irrespective of whether the participant has completed the full course of treatment and whether the participant has completed the study or permanently withdrawn.

ITT set included all participants who were randomized and received at least one dose of nusinersen.

HFMSE scale was a tool used to assess motor function in children with later-onset SMA. The original 20 item Hammersmith Functional Motor Scale was expanded to include 13 additional adapted items from the Gross Motor Function Measure to improve sensitivity for the higher functioning ambulant population. Each item is scored 0 (unable), 1 (performs with modification or adaptation) or 2 (able) and the total score was calculated by summing the 33 items and ranged from 0 to 66 with higher scores indicating greater motor function.

ITT set included all participants who were randomized and received at least one dose of nusinersen.

RULM test was developed to assess upper limb functional abilities. RULM test: total 20 items. First item was assessed on 7-point scale (0:No useful function to 6-Can abduct both arms simultaneously, elbows in extension in full circle until they touch above head). This first item did not contribute to total score. For remaining 19 items, 18 items were assessed on 3-point scale: 0-Unable to achieve independently; 1-Modified method but achieves goal independent of physical assistance from another person; 2-Normal -achieves goal without any assistance. One remaining item was assessed as either 0 or 1. For each item, score was collected on left & right side. Derived total score=summing scores from these 19 individual items ranging from 0-if participant fails all activities to 37-if participant achieves all activities. If, for an individual item, response was recorded for both left & right side, highest score was used in calculating total score. Higher scores=increased upper limb function.

ITT set included all participants who were randomized and received at least one dose of nusinersen.

The WHO motor milestones were a set of six milestones in motor development: sitting without support, standing with assistance, hands and knees crawling, walking with assistance, standing alone and walking alone. The examiner recorded an overall rating of the participant's emotional state and then for each milestone one of the following four classifications: no (inability) - child tried but failed to perform the milestone, no (refusal) - child refused to perform despite being calm and alert, yes - child was able to perform the milestone, unable to test - could not be tested because of irritability, drowsiness or sickness. Mean of number of new milestones achieved per participant was calculated and reported in this outcome measure.

ITT set included all participants who were randomized and received at least one dose of nusinersen. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure.

ACEND instrument was designed to quantify caregiver impact experienced by parents/caregivers of children affected with severe neuromuscular diseases, including children with SMA. The ACEND included a total of seven domains assessing physical impact (including feeding/grooming/dressing, sitting/play, transfers, and mobility) and general caregiver impact (including time, emotion, and finance, and each domain comprised several items. The total score for each domain was calculated on a scale of 0 to 100, with a higher score indicating a decreased caregiver burden. A negative change from baseline indicates an increased caregiver burden.

ITT set included all participants who were randomized and received at least one dose of nusinersen.

Participants were evaluated using PedsQL generic core scale & neuromuscular module. PedsQL generic core scale was used to calculate PedsQL inventory total score (PQLI), that included parent & participant's assessment on 4 dimensions: physical, emotional, social, & school functioning & psychosocial health. Each item was scored on 5-point ordinal scale (0=never to 4=almost always). PedsQL neuromuscular module (PQLN) measured HRQOL dimensions specific to with neuromuscular disorders, like SMA. Each item was scored on 5-point ordinal scale (0=never to 4=almost always). Dimensions were reversed scored & were linearly transformed to 0-100 scale (0=100, 1=75, 2=50, 3=25, 4=0) for both PQLI and PQLN, higher scores indicative of better health related quality of life. Total scale scores were calculated as sum of all items over number of items answered on all scales. If more than 50% of items/more within a dimension were missing, scale score was not computed.

ITT set included all participants who were randomized and received at least one dose of nusinersen. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure. 'Number analysed (n)' indicates number of participants evaluable for the specified total score

The change from baseline data was reported in terms of geometric mean ratio to baseline. Lower ratios to baseline represent greater reductions in concentrations of NF-L from baseline.

ITT set included all participants who were randomized and received at least one dose of nusinersen.

The change from baseline data was reported in terms of geometric mean ratio to baseline. Lower ratios to baseline represent greater reductions in concentrations of NF-L from baseline.

ITT set included all participants who were randomized and received at least one dose of nusinersen. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure.

AE was any unfavorable and unintended sign (including an abnormal assessment such as an abnormal laboratory value), symptom, or disease temporally associated with the use of a medicinal (investigational) product, whether or not related to the medicinal (investigational) product. An SAE was any untoward medical occurrence that at any dose resulted in death, in the view of the Investigator, placed the participant at immediate risk of death, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, resulted in a birth defect. AE was regarded as treatment-emergent if it was present prior to receiving the first dose of nusinersen in the current study and subsequently worsened in severity or was not present prior to receiving the first dose of nusinersen and subsequently appeared.

Safety set included all participants who received at least one dose of nusinersen.

Hematology parameters included complete blood cell count, with differential and platelet count, and absolute neutrophil count. These parameters were flagged as low, normal, or high relative to parameter's normal range or as unknown if no result was available, by the Investigator. Here, shift to low indicates values that were normal, high or unknown at baseline and shifted to low values postbaseline. Shift to high indicates values that were normal, low or unknown at baseline and shifted to high values postbaseline. The categories with at least one participant with shift from baseline in these parameters are reported.

Safety set included all participants who received at least one dose of nusinersen. 'Number analysed (n)' signifies number of participants evaluable for analysis of the specified hematology parameter.

Blood chemistry parameters included protein, albumin, creatinine, blood urea nitrogen, bilirubin (total and direct), alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transferase, glucose, calcium, phosphorus, bicarbonate, chloride, sodium, potassium, cystatin C, and creatine kinase. Parameters were flagged as low, normal, or high relative to parameter's normal range or as unknown if no result was available, by the Investigator. Here, shift to low indicates values that were normal, high or unknown at baseline and shifted to low values postbaseline. Shift to high indicates values that were normal, low or unknown at baseline and shifted to high values postbaseline. Categories with at least one participant with shift from baseline in these parameters are reported.

Safety set included all participants who received at least one dose of nusinersen. 'Number analysed (n)' signifies number of participants evaluable for analysis of the specified parameter.

Urinalysis included assessments of urine total protein, specific gravity, pH, protein, glucose, ketones, bilirubin, blood, RBC , WBC, epithelial cells, bacteria, casts and crystals. These parameters were flagged as low, normal, or high relative to parameter's normal range or as unknown if no result was available, by the Investigator. Here, shift to low indicates values that were normal, high, positive, abnormal or unknown at baseline and shifted to low values postbaseline. Shift to high indicates values that were normal, negative, absent, low or unknown at baseline and shifted to high values postbaseline. The categories with at least one participant with shift from baseline in these parameters are reported.

Safety set included all participants who received at least one dose of nusinersen. 'Number analysed (n)' signifies number of participants evaluable for analysis of the specified parameter.

CSF parameters included cell count, total protein, and glucose. These parameters were flagged as low, normal, or high relative to parameter's normal range or as unknown if no result was available, by the Investigator. Here, shift to low indicates values that were normal, high or unknown at baseline and shifted to low values postbaseline. Shift to high indicates values that were normal, low or unknown at baseline and shifted to high values postbaseline. The categories with at least one participant with shift from baseline in these parameters are reported.

Safety set included all participants who received at least one dose of nusinersen. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure. 'Number analysed (n)' signifies number of participants evaluable for analysis of the specified parameter.

The ECGs were assessed by the investigator to be normal, abnormal and abnormal AE. The number of participants with ECG shifts from normal to each of the categorical values denoting an abnormal scan (abnormal not AE, abnormal AE) was assessed. Shift from baseline to worst post-baseline values were reported. The categories with at least one participant with shift from baseline in ECG are reported.

Safety set included all participants who received at least one dose of nusinersen.

Vital sign assessment included temperature, pulse rate systolic blood pressure, diastolic blood pressure, and respiratory rate. As pre-specified in protocol, the criteria for determining potentially clinically relevant abnormalities in vital signs included: temperature < 36.0 and > 38.0 degrees C, pulse rate < 60 and > 100 bpm, systolic blood pressure < 90, > 140 and > 160 mmHg, diastolic blood pressure < 50, > 90 and > 100 mmHg and respiratory rate < 12 and > 20 breaths per minute. The categories with at least one participant with clinically relevant vital sign abnormalities are reported.

Safety set included all participants who received at least one dose of nusinersen. 'Number analysed (n)' signifies number of participants evaluable for analysis of the specified parameter.

Body height was measured for all participants (infantile-onset and later-onset SMA).

Safety set included all participants who received at least one dose of nusinersen. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

Head circumference was measured in participants with infantile-onset SMA.

Safety set included all participants who received at least one dose of nusinersen. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

Chest circumference was measured in participants with infantile-onset SMA.

Safety set included all participants who received at least one dose of nusinersen. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

Arm circumference was measured in participants with infantile-onset SMA.

Safety set included all participants who received at least one dose of nusinersen. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

Ulnar length was measured in participants with later-onset SMA.

Safety set included all participants who received at least one dose of nusinersen. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

WHO child growth standards (2006) was used to calculate the weight for age percentile in the infantile-onset participants. The 2000 CDC Growth Charts was used to calculate the weight for age percentile for later-onset participants. Negative change from baseline indicates reduction in weight for age percentile

Safety set included all participants who received at least one dose of nusinersen. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

As pre-specified in the protocol, weight for length percentile was assessed only for the participants with infantile-onset SMA. Negative change from baseline indicates reduction in weight for length percentile.

Safety set included all participants who received at least one dose of nusinersen. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

As pre-specified in the protocol, head to chest circumference ratio was assessed only for the participants with infantile-onset SMA. Negative change from baseline indicates reduction in head-to-chest circumference ratio.

Safety set included all participants who received at least one dose of nusinersen. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure at the specified time point.

aPTT was evaluated to assess safety. "Shift to low" measured change in normal, high and unknown values of aPTT at baseline to low values postbaseline. "Shift to high" measured change in normal, low and unknown values of aPTT at baseline to high values postbaseline.

Safety set included all participants who received at least one dose of nusinersen. 'Number analysed (n)' signifies number of participants evaluable for the specified category.

Prothrombin time was evaluated to assess safety. "Shift to low" measured change in normal, high and unknown values of PT at baseline to low values postbaseline. "Shift to high" measured change in normal, low and unknown values of PT at baseline to high values postbaseline.

Safety set included all participants who received at least one dose of nusinersen. 'Number analysed (n)' signifies number of participants evaluable for the specified category.

INR was evaluated to assess safety. "Shift to low" measured change in normal, high and unknown values of INR at baseline to low values postbaseline. "Shift to high" measured change in normal, low and unknown values of INR at baseline to high values postbaseline.

Safety set included all participants who received at least one dose of nusinersen. 'Number analysed (n)' signifies number of participants evaluable for the specified category.

Safety set included all participants who received at least one dose of nusinersen. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure.

Participants with abnormalities in neurological examinations recorded as AEs were reported.

Safety set included all participants who received at least one dose of nusinersen.

Safety set included all participants who received at least one dose of nusinersen.

Safety set included all participants who received at least one dose of nusinersen. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure.

Parts A, B and C: ITT set included all participants who received at least one dose of nusinersen in the current study.

Parts A, B and C: ITT set included all participants who received at least one dose of nusinersen in the current study.

The CGIC scale was a 7 point scale that required the clinician to assess how much the participant's illness had changed relative to a baseline state at the beginning of the intervention, where 1=very much improved, 2=much improved, 3=minimally improved, 4=no change, 5=minimally worse, 6=much worse, 7=very much worse. Higher rating indicates worsening of the condition. A separate CGIC assessment was performed by the Investigator (I) and caregiver (C). The categories with at least one participant having a CGIC score was reported.

ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure. 'Number analyzed' indicates the number of participants evaluable for the specified category.

ITT set included all participants who received at least one dose of nusinersen in the current study.

ITT set included all participants who were randomized and received at least one dose of nusinersen.

ITT set included all participants who received at least one dose of nusinersen in the current study.

PASA was assessed using a questionnaire. Caregivers were asked a series of questions regarding the mealtime behavior of the participant. The PASA questionnaire was developed to assess the signs and symptoms of dysphagia. It included 33 items across 4 domains: general feeding, drinking liquids, eating solid foods, & assessment of swallowing concerns. Items in domains general feeding, drinking liquids, & eating solid foods are assessed with 5 levels of response scored as 4-Never, 3-Rarely, 2-Sometimes, 1-Often, & 0-Always. Domain for assessing swallowing concerns has 4 levels of responses scored as: 3-Strongly Disagree, 2-Disagree, 1-Agree, 0-Strongly Agree. Higher score= improvement. A negative change from baseline=decrease in swallowing ability. From domains 'drinking liquids' and 'eating solid foods', 2 items (attempted to drink liquids and eat solid foods) were assessed as "Yes"/"No", which are reported in another outcome measure.

ITT set included all participants who received at least one dose of nusinersen. 'Number analysed (n)' signifies the number of participants evaluable for the specified parameter.

PASA was assessed using a questionnaire. Caregivers were asked a series of questions regarding the mealtime behavior of the participant. The PASA questionnaire was developed to assess the signs and symptoms of dysphagia. It included 33 items across 4 domains that cover general feeding, drinking liquids, eating solid foods, and assessment of swallowing concerns. The 2 items of domains drinking liquids (attempted to drink liquids), eating solid foods (attempted to eat solid foods) were assessed as "Yes"/"No". Data for the 2 items were summarized in terms of the shift from baseline.

ITT set included all participants who received at least one dose of nusinersen.

PASA was assessed using a questionnaire. Caregivers were asked a series of questions regarding the mealtime behavior of the participant. The PASA questionnaire was developed to assess the signs and symptoms of dysphagia. It included 33 items across 4 domains that cover general feeding, drinking liquids, eating solid foods, and assessment of swallowing concerns. Items in domains of general feeding, drinking liquids, & eating solid foods are assessed with 5 levels of response scored as 4-Never, 3-Rarely, 2-Sometimes, 1-Often, & 0-Always. Domain for assessing swallowing concerns has 4 levels of responses scored as: 3-Strongly Disagree, 2-Disagree, 1-Agree, 0-Strongly Agree. Higher score= improvement. A negative change from baseline=decrease in swallowing ability. As planned, for part B of the study, the PASA scale was assessed for the domain general feeding only.

ITT set included all participants who were randomized and received at least one dose of nusinersen. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure. 'Number analysed (n)', signifies the number of participants evaluable for the specified parameter.

The change from baseline data was reported in terms of geometric mean ratio to baseline. Lower ratios to baseline represent greater reductions in concentrations of NF-L from baseline.

ITT set included all participants who were randomized and received at least one dose of nusinersen.

HFMSE scale was a tool used to assess motor function in children with SMA. The original 20 item Hammersmith Functional Motor Scale was expanded to include 13 additional adapted items from the Gross Motor Function Measure to improve sensitivity for the higher functioning ambulant population. Each item is scored 0 (unable), 1 (performs with modification or adaptation) or 2 (able) and the total score was calculated by summing the 33 items and ranged from 0 to 66 with higher scores indicating greater motor function. Negative change from baseline indicates decrease in motor function.

ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure.

RULM test was developed to assess upper limb functional abilities. RULM test: total 20 items. First item was assessed on 7-point scale (0:No useful function to 6-Can abduct both arms simultaneously, elbows in extension in full circle until they touch above head). This first item did not contribute to total score. For remaining 19 items, 18 items were assessed on 3-point scale: 0-Unable to achieve independently; 1-Modified method but achieves goal independent of physical assistance from another person; 2-Normal -achieves goal without any assistance. One remaining item was assessed as either 0 or 1. For each item, score was collected on left & right side. Derived total score=summing scores from these 19 individual items ranging from 0-if participant fails all activities to 37-if participant achieves all activities. If, for an individual item, response was recorded for both left & right side, highest score was used in calculating total score. Higher scores=increased upper limb function.

ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure.

The WHO motor milestones were a set of six milestones in motor development: sitting without support, standing with assistance, hands and knees crawling, walking with assistance, standing alone and walking alone. The examiner recorded an overall rating of the participant's emotional state and then for each milestone one of the following four classifications: no (inability) - child tried but failed to perform the milestone, no (refusal) - child refused to perform despite being calm and alert, yes - child was able to perform the milestone, unable to test - could not be tested because of irritability, drowsiness or sickness.

ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure.

ACEND instrument was designed to quantify caregiver impact experienced by parents/caregivers of children affected with severe neuromuscular diseases, including children with SMA. The ACEND included a total of seven domains assessing physical impact (including feeding/grooming/dressing, sitting/play, transfers, and mobility) and general caregiver impact (including time, emotion, and finance, and each domain comprised several items. The total score for each domain was calculated on a scale of 0 to 100, with a higher score indicating a decreased caregiver burden. A negative change from baseline indicates an increased caregiver burden.

ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure.

Participants were evaluated using PedsQL generic core scale & neuromuscular module. PedsQL generic core scale was used to calculate PedsQL inventory total score (PQLI), that included parent & participant's assessment on 4 dimensions: physical, emotional, social, & school functioning & psychosocial health. Each item was scored on 5-point ordinal scale (0=never to 4=almost always). PedsQL neuromuscular module (PQLN) measured HRQOL dimensions specific to with neuromuscular disorders, like SMA. Each item was scored on 5-point ordinal scale (0=never to 4=almost always). Dimensions were reversed scored & were linearly transformed to 0-100 scale (0=100, 1=75, 2=50, 3=25, 4=0) for both PQLI and PQLN, higher scores indicative of better health related quality of life. Total scale scores were calculated as sum of all items over number of items answered on all scales. If more than 50% of items/more within a dimension were missing, scale score was not computed.

ITT set included all participants who received at least one dose of nusinersen in the current study. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure. 'Number analysed (n)' signifies number of participants evaluable for the specified total score.

The CHOP-INTEND test was designed to evaluate the motor skills of infants with significant motor weakness. It included 16 items (capturing neck, trunk, and proximal and distal limb strength), nine of which were scored 0, 1, 2, 3, or 4, five were scored as 0, 2, or 4, one was scored as 0, 1, 2, or 4, and one as 0, 2, 3, or 4 with higher scores indicating greater muscle strength and function. Total score was calculated as the sum of scores for each item. Total score ranged from 0 (worst possible score) and 64 (best possible score).

ITT set included all participants who received at least one dose of nusinersen in the current study. It was planned to be assessed in infantile-onset SMA participants. 'Overall number of participants analyzed' signifies number of participants with data available for outcome measure analysis.

Section 2 of the HINE was used to assess motor milestones of the infantile-onset SMA participants. It's composed of 8 motor milestone categories: voluntary grasp, ability to kick in supine position, head control, rolling, sitting, crawling, standing, and walking. Within each of these categories, participants can progress from complete absence of a motor ability (the lowest level in each category) through multiple milestones (2 to 4 levels in each category) to the highest level within the category. The 8 categories of HINE Section 2 can be summed to give a total score that ranges from 0 to 26.

ITT set included all participants who received at least one dose of nusinersen in the current study. It was planned to be assessed in infantile-onset SMA participants. 'Overall number of participants analyzed' signifies number of participants evaluable for this outcome measure.