The Internal Monitoring Committee (IMC) was responsible for selecting the dose for Part 2 of the study (pivotal dose). An external Independent Data Monitoring Committee (iDMC) reviewed data from Part 1 and confirmed the dose-selection decision of the IMC. The dose for Part 2 selected by the IMC was a dose that: 1.Was judged to be safe and well-tolerated, based on all available safety data from Part 1 and as confirmed by the iDMC; 2. Resulted in an exposure at steady-state below the exposure cap (mean value) of AUC0-24h,ss 2000 ng*h/mL (adjusted for free-fraction, if required); 3. Resulted in an SMN protein increase that was expected to be clinically relevant.

All participants in Part 1.

The Internal Monitoring Committee (IMC) was responsible for selecting the dose for Part 2 of the study (pivotal dose). An external Independent Data Monitoring Committee (iDMC) reviewed data from Part 1 and confirmed the dose-selection decision of the IMC. The dose for Part 2 selected by the IMC was a dose that: 1.Was judged to be safe and well-tolerated, based on all available safety data from Part 1 and as confirmed by the iDMC; 2. Resulted in an exposure at steady-state below the exposure cap (mean value) of AUC0-24h,ss 2000 ng*h/mL (adjusted for free-fraction, if required); 3. Resulted in an SMN protein increase that was expected to be clinically relevant.

All participants in Part 1.

The Motor Function Measure 32 (MFM32) is a scale constructed for use in neuromuscular disorders. It comprises 32 items that evaluate physical function in three dimensions: D1 function related to standing and transfer; D2 axial and proximal function; D3 distal motor function. Tasks are scored with a 4-point Likert scale: 0 - cannot initiate the task or maintain the starting position; 1 - performs the task partially; 2 - performs the task incompletely or imperfectly; 3 - performs the task fully and "normally". The 32 scores are summed and expressed on a 0-100 scale for the MFM32 total score. Higher scores indicate increased motor function. A positive change from Baseline indicates improvement. MMRM analysis was performed based on primary efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing MFM32 total score at Baseline were not included in the analysis.

The MFM32 comprises 32 items that evaluate physical function. The scoring of each task uses a 4-point Likert scale: 0 - cannot initiate the task or maintain the starting position; 1 - performs the task partially; 2 - performs the task incompletely or imperfectly; 3 - performs the task fully and "normally". The 32 scores are summed and expressed on a 0-100 scale for the MFM32 total score. A change in MFM32 total score of threshold >/=3 represents marked improvement in this measure. Logistic regression analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing MFM32 total score at Baseline were not included in the analysis. Missing results at Month 12 are considered as non-responders.

The RULM is a 20 items scale that assesses the proximal and distal motor functions of the arm. There is an entry item and the remaining 18 items are scored on the 3 point scale of: 0: cannot complete task independently; 1: modified method but can complete task independently; 2: completes task without any assistance, and with 1 item scored on a 2 point scale of as a can/cannot score with 1 as the highest score. The RULM total score is the sum of 19 items scores with range of 0-37, and the entry item does not contribute to the total score. Higher scores indicate greater upper limb function. A positive change from Baseline indicates improvement. MMRM analysis was performed based on the efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing RULM total score at Baseline were not included in the analysis.

The HFMSE scale contains 33 items, which are scored on a 3-point Likert-type scale (0-2) and summed to derive the total score, with lower scores indicating greater impairment. The HFMSE contains a series of assessments designed to assess important functional abilities, including standing, transfers, ambulation, and proximal and axial function. The overall score is the sum of the scores for all activities with a maximum achievable score of 66. Higher scores indicate greater motor function. A positive change from Baseline indicates improvement. MMRM analysis was performed based on the efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2.

Spirometry is a pulmonary function test that assesses how the lungs work by measuring how much air moves through the airways. Spirometry was performed by all participants aged 6 or older. Forced vital capacity (FVC) is the total volume that can be exhaled after inhaling maximally. The best % predicted value out of all attempts were used for the analysis. MMRM analysis was performed based on the efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing FVC data at Baseline were not included in the analysis.

The SMA Independence Scale (SMAIS) was developed specifically for SMA participants in order to assess function-related independence. The SMAIS contains 29 items, assessing the amount of assistance required from another individual to perform daily activities such as eating, or bathing. Each item is scored on a 0-4 scale (with an additional option to indicate that an item is non-applicable). The SMAIS total score ranging from 0-44 is obtained based on 22 items with each item on the 0-2 scale. Lower scores indicate greater dependence on another individual. The SMAIS was completed by participants aged 12 years or older and caregivers of participants aged 2-25 years. MMRM analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing SMAIS total score at Baseline were not included in the analysis.

The Clinical Global Impression of Change (CGI-C) is used to score a clinician's impression of a participant's change in global health. The CGI-C is a single item measure of change in global health, using seven response options: "very much improved", "much improved", "minimally improved", "no change", "minimally worse", "much worse", and "very much worse". Participants considered as "improved" included responses of "very much improved, "much improved" and "minimally improved". Logistic regression analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Missing results at Month 12 are considered as non-responders.

The MFM32 comprises 32 items that evaluate physical function in three dimensions: D1 function related to standing and transfer; D2 axial and proximal function; D3 distal motor function. Tasks are scored with a 4-point Likert scale: 0 - cannot initiate the task or maintain the starting position; 1 - performs the task partially; 2 - performs the task incompletely or imperfectly; 3 - performs the task fully and "normally". The 32 scores are summed and expressed on a 0-100 scale for the MFM32 total score. Higher scores indicate increased motor function. Logistic regression analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing MFM32 total score at Baseline were not included in the analysis. Missing results at Month 12 are considered as non-responders.

The MFM32 comprises 32 items that evaluate physical function in three dimensions: D1 standing and transfer; D2 axial and proximal function; D3 distal motor function. Tasks are scored with a 4-point Likert scale: 0-cannot initiate the task or maintain the starting position; 1-performs the task partially; 2-performs the task incompletely or imperfectly; 3-performs the task fully and "normally". The 32 scores are summed and expressed on a 0-100 scale for the total score. Higher scores indicate increased motor function. Standard error of measurement (SEM) is derived using 32 items scores and total scores at baseline. Change from baseline > = one SEM is equivalent to a change >= 4. Logistic regression analysis was performed based on efficacy hypothetical estimand included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing MFM32 total score at Baseline were not included in the analysis.

The MFM32 comprises 32 items that evaluate physical function in three dimensions: D1 function related to standing and transfer; D2 axial and proximal function; D3 distal motor function. Tasks are scored with a 4-point Likert scale: 0 - cannot initiate the task or maintain the starting position; 1 - performs the task partially; 2 - performs the task incompletely or imperfectly; 3 - performs the task fully and "normally". The D1 items score are summed and expressed on 0-100 scale for the MFM D1 total score. Higher scores indicate increased motor function. A positive change from Baseline indicates improvement. MMRM analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing MFM32 D1 score at Baseline were not included in the analysis.

The MFM32 comprises 32 items that evaluate physical function in three dimensions: D1 function related to standing and transfer; D2 axial and proximal function; D3 distal motor function. Tasks are scored with a 4-point Likert scale: 0 - cannot initiate the task or maintain the starting position; 1 - performs the task partially; 2 - performs the task incompletely or imperfectly; 3 - performs the task fully and "normally". The D2 items score are summed and expressed on 0-100 scale for the MFM D2 total score. Higher scores indicate increased motor function. A positive change from Baseline indicates improvement. MMRM analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing MFM32 D2 score at Baseline were not included in the analysis.

The MFM32 comprises 32 items that evaluate physical function in three dimensions: D1 function related to standing and transfer; D2 axial and proximal function; D3 distal motor function. Tasks are scored with a 4-point Likert scale: 0 - cannot initiate the task or maintain the starting position; 1 - performs the task partially; 2 - performs the task incompletely or imperfectly; 3 - performs the task fully and "normally". The D3 items score are summed and expressed on 0-100 scale for the MFM D3 total score. Higher scores indicate increased motor function. A positive change from Baseline indicates improvement. MMRM analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing MFM32 D3 score at Baseline were not included in the analysis.

The MFM32 comprises 32 items that evaluate physical function in three dimensions: D1 function related to standing and transfer; D2 axial and proximal function; D3 distal motor function. Tasks are scored with a 4-point Likert scale: 0 - cannot initiate the task or maintain the starting position; 1 - performs the task partially; 2 - performs the task incompletely or imperfectly; 3 - performs the task fully and "normally". The D1+D2 items score are summed and expressed on 0-100 scale for the MFM D1+D2 total score. Higher scores indicate increased motor function. A positive change from Baseline indicates improvement. MMRM analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing MFM32 D1+D2 scores at Baseline were not included in the analysis.

The MFM32 comprises 32 items that evaluate physical function in three dimensions: D1 function related to standing and transfer; D2 axial and proximal function; D3 distal motor function. Tasks are scored with a 4-point Likert scale: 0 - cannot initiate the task or maintain the starting position; 1 - performs the task partially; 2 - performs the task incompletely or imperfectly; 3 - performs the task fully and "normally". The D2+D3 items score are summed and expressed on 0-100 scale for the MFM D2+D3 total score. Higher scores indicate increased motor function. A positive change from Baseline indicates improvement. MMRM analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing MFM32 D2+D3 scores at Baseline were not included in the analysis.

Spirometry is a pulmonary function test that assesses how the lungs work by measuring how much air moves through the airways. Spirometry was performed by all participants aged 6 or older. Forced expiratory volume (FEV1) is the volume forcefully exhaled in the first second of the forced vital capacity test. The best % predicted value out of all attempts were used for the analysis. MMRM analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing FEV1 data at Baseline were not included in the analysis.

Spirometry is a pulmonary function test that assesses how the lungs work by measuring how much air moves through the airways. Spirometry was performed by all participants aged 6 or older. Peak cough flow (PCF) is an assessment of cough strength. The best % predicted value out of all attempts were used for the analysis MMRM analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing PCF data at Baseline were not included in the analysis.

The Sniff Nasal Inspiratory Pressure (SNIP) is a volitional, non-invasive test of inspiratory muscle strength that has been successfully applied to children > 2 years of age. Advantages include the simplicity of the maneuver and the absence of a mouthpiece, which is particularly helpful for participants with SMA, who may have bulbar weakness. SNIP also has the advantage of measuring inspiratory pressure during a natural maneuver that is easily performed even by young children with neuromuscular disorders. The best % predicted value out of all attempts were used for the analysis. MMRM analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing SNIP data at Baseline were not included in the analysis.

The maximal inspiratory pressure (MIP) is a non-invasive test of muscle strength, which measures the maximum strength of the diaphragm and other inspiratory muscles. MIP was measured in participants aged 6 or older. Participants were asked to perform a forceful inspiration against an occluded mouth piece. The best % predicted value out of all attempts were used for the analysis. MMRM analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing MIP data at Baseline were not included in the analysis.

The maximal expiratory pressure (MEP) is a non-invasive test of muscle strength, which measures the maximum strength of the abdominal muscles and other expiratory muscles. MEP was measured in participants aged 6 or older. Participants were asked to perform a forceful inspiration against an occluded mouth piece. The best % predicted value out of all attempts were used for the analysis. MMRM analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing MEP data at Baseline were not included in the analysis.

The SMAIS was developed specifically for SMA participants in order to assess function-related independence. It contains 29 items, assessing the amount of assistance required from another individual to perform daily activities such as eating, or bathing. Each item is scored on a 0-4 scale (with an additional option to indicate that an item is non-applicable). The SMAIS total score ranging from 0-44 is obtained based on 22 items with each item on the 0-2 scale. Lower scores indicate greater dependence on another individual. The SMAIS was completed by participants aged 12 years or older and caregivers of participants aged 2-25 years. MMRM analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Participants with missing SMAIS total score at Baseline were not included in the analysis.

The CGI-C is used to score a clinician's impression of a participant's change in global health. It is a single item measure of change in global health, using seven response options: "very much improved", "much improved", "minimally improved", "no change", "minimally worse", "much worse", and "very much worse". Participants considered as "no change or improved" included responses of "no change", "very much improved", "much improved" and "minimally improved". Logistic regression analysis was performed based on efficacy hypothetical estimand, which included participants data assuming no prohibited medication intended for treatment of SMA was received and participants continued on their randomized treatment until the analysis time point at Month 12.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Missing results at Month 12 are considered as non-responders.

Disease-related adverse events (AEs) were identified by applying two different types of baskets to the AE dataset: Narrow prospectively defined baskets of MedDRA lowest level terms. This basket was defined based on a group of CDC terms selected from an age and gender matched case control study comparing CDC code rates observed in participants with and without SMA using commercially available insurance claim data (CLAIMS and Market scan data). The lowest level terms included in each basket, coded using the latest version of MedDRA; Broad prospectively defined basket with events selected at preferred term level from all AEs reported in ongoing clinical trials up to January 2019, i.e., prior to unblinding of Part 2 of Study BP39055.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2.

Disease-related AEs were collected through the AE reporting of the study, and the disease-related AE rate was adjusted for patient years (AE rate per 100 patient-years). They were identified by applying two different types of baskets to the AE dataset: Narrow prospectively defined baskets of MedDRA lowest level terms and Broad prospectively defined basket with events selected at preferred term level from all AEs reported in ongoing clinical trials up to January 2019, i.e., prior to unblinding of Part 2 of Study BP39055.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2.

An adverse event (AE) is any untoward medical occurrence in a subject administered a pharmaceutical product and which does not necessarily have to have a causal relationship with the treatment. An adverse event can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding, for example), symptom, or disease temporally associated with the use of a pharmaceutical product, whether or not considered related to the pharmaceutical product. Preexisting conditions which worsen during a study are also considered as adverse events.

All participants in Part 2 who receive at least one dose of study medication (risdiplam or placebo) were included in the safety population.

An adverse event (AE) is any untoward medical occurrence in a subject administered a pharmaceutical product and which does not necessarily have to have a causal relationship with the treatment. An adverse event can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding, for example), symptom, or disease temporally associated with the use of a pharmaceutical product, whether or not considered related to the pharmaceutical product. Preexisting conditions which worsen during a study are also considered as adverse events.

All participants in Part 2 who received at least one dose of study medication (risdiplam or placebo) were included in the safety population.

The Columbia Suicide Severity Rating Scale (C-SSRS) is used to assess the lifetime suicidality of a participant (C-SSRS baseline) as well as any new instances of suicidality (C-SSRS since last visit). The structured interview prompts recollection of suicidal ideation, including the intensity of the ideation, behavior, and attempts with actual/potential lethality. The C-SSRS assessments results were collected for participants aged 6 years and older.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Data was collected for participants aged 6-25 years.

The Columbia Suicide Severity Rating Scale (C-SSRS) is used to assess the lifetime suicidality of a participant (C-SSRS baseline) as well as any new instances of suicidality (C-SSRS since last visit). The structured interview prompts recollection of suicidal ideation, including the intensity of the ideation, behavior, and attempts with actual/potential lethality. The C-SSRS assessments results were collected for participants aged 6 years and older.

The intent-to-treat (ITT) population defined as all randomized participants in Part 2. Data was collected for participants aged 6-25 years.

All participants with at least one time point with a protein measurement were included in the pharmacodynamic (PD) analysis data set.

Reported here is the maximum observed concentration throughout the observation period.

All participants with at least one time point with a risdiplam concentration measurement were included in the pharmacokinetic (PK) analysis data set.

All participants with at least one time point with a risdiplam concentration measurement were included in the PK analysis data set.

All participants with at least one time point with a risdiplam concentration measurement were included in the PK analysis data set.