A responder was defined as a participant with a TIS >= 20 points at Week 25 and at least 1 of the previous scheduled visits (Week 17 or 21), who completes 24 weeks of randomized IMP treatment without the use of rescue corticosteroid treatment. The TIS was a sum response criterion which incorporates 6 weighted international myositis assessment and clinical studies (IMACS) core set measures (CSMs) including Physician and Patient Global Disease Activity (PGA), Manual Muscle Testing-8 (MMT-8), Health Assessment Questionnaire, Muscle Enzyme, and Extramuscular Global Activity (EGA). Thresholds for minimal, moderate, and major improvement were >= 20, >= 40, and >= 60 points, respectively on the TIS. Percentage of responders at Week 25 based on TIS are reported here. Multiple imputation (MI) was used to impute missing values for participants who discontinued due to the military activities in Ukraine.

Analysis was performed on the modified intent-to-treat (mITT) analysis set. The mITT analysis set comprises all participants who underwent study screening procedures, were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP or the lack of any post randomization efficacy data lead to the exclusion of the participant from the mITT.

The TIS was a sum response criterion which incorporates 6 weighted IMACS CSMs including Physician and PGA, MMT-8, Health Assessment Questionnaire, Muscle Enzyme, and EGA. A total improvement score (range 0 to 100; higher the score, better the condition), determined by summing scores for each CSM, was based on improvement in and relative weight of each CSM. Thresholds for minimal, moderate, and major improvement were >= 20, >= 40, and >= 60 points, respectively on the TIS. Least squares (LS) means were estimated using a mixed model repeated measures (MMRM) including treatment, visit, the interaction between treatment and visit, region, and baseline MMT-8 (<=142 points vs >142 points) as fixed effects, participant as a random effect.

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT.

The MMT-8 was a set of 8 designated muscles which were tested bilaterally (potential score ranging from 0 to 150): 7 biaxial muscles with a potential score 0 to 140 and 1 axial (neck flexors) with a potential score of 0 to 10. Improvement is documented with an increase in score. LS means were estimated using a MMRM including treatment, visit, the interaction between treatment and visit, and region as fixed effects, baseline MMT-8 as a continuous covariate and participant as a random effect.

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT.

The CDASI in its modified version 2 (V2) is a validated tool of skin disease activity (3 items) and damage (3 items) assessment. Scores range from 0-100 for activity and from 0-32 for damage. Improvement is documented with a decrease in score. LS means were estimated using a MMRM including treatment, visit, the interaction between treatment and visit, region, and baseline MMT-8 (<=142 points vs >142 points) as fixed effects, baseline CDASI-A as a continuous covariate, and participants as a random effect.

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT.

Reduction in corticosteroid dose.

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT.

The TIS was a sum response criterion which incorporates 6 weighted IMACS CSMs including Physician and PGA, MMT-8, Health Assessment Questionnaire, Muscle Enzyme, and EGA. A total improvement score (range 0 to 100), determined by summing scores for each CSM, was based on improvement in and relative weight of each CSM. Thresholds for minimal, moderate, and major improvement were >= 20, >= 40, and >= 60 points on the TIS.

Analysis was performed on the mITT analysis set. Here, overall number of participants analyzed (N) = participants evaluable for this outcome measure, and number analyzed (n) = participants with evaluable data for each specified timepoint.

The TIS was a sum response criterion which incorporates 6 weighted IMACS CSMs including Physician and PGA, MMT-8, Health Assessment Questionnaire, Muscle Enzyme, and EGA. A total improvement score (range 0 to 100), determined by summing scores for each CSM, was based on improvement in and relative weight of each CSM. Thresholds for minimal, moderate, and major improvement were >= 20, >= 40, and >= 60 points on the TIS.

Analysis was performed on the mITT analysis set extended (mITT-Ex) that comprised all participants in mITT who completed the first 24 weeks of SP1 and received any amount of the IMP in SP2. The documented failure to take any amount of randomized IMP in SP2 led to the exclusion of the participant from mITT-Ex. Here, overall number of participants analyzed (N) = participants evaluable for this outcome measure, and number analyzed (n) = participants with evaluable data for each specified timepoint.

Participants were considered and reported in more than one category (TIS >= 20, >= 40 and >= 60 Points).

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT.

Participants were considered and reported in more than one category (TIS >= 20, >= 40 and >= 60 Points).

Analysis was performed on the mITT-Ex analysis set. The mITT-Ex comprised all participants in mITT who completed the first 24 weeks of SP1 and received any amount of the IMP in SP2. The documented failure to take any amount of randomized IMP in SP2 led to the exclusion of the participant from mITT-Ex.

The observation was censored if no improvement was observed before the intake of rescue/increased doses of oral corticosteroids in SP1 or before the end of the period.

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT.

The observation was censored if no improvement was observed before the intake of rescue/increased doses of oral corticosteroids in SP1 or before the end of the period.

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT.

Individual CSMs included following: Myositis Disease Activity Assessment Tool (MDAAT) Physician global disease activity (PGDA), PGA assessment, MMT-8, health assessment questionnaire-disability index (HAQ-DI), and MDAAT-EGA. Higher values were associated with a better state of health for the MMT-8 (range 0 -150) assessment, while lower values were associated with a better state of health for: MDAAT-PGDA (range 0 -100), PGA (range 0-100), HAQ-DI (range 0-3), MDAAT-EGA (range 0 -100), and CDASI-A (range 0-100).

Analysis was performed on the mITT analysis set. Here, overall number of participants analyzed (N) = participants evaluable for this outcome measure, and number analyzed (n) = participants with evaluable data for each specified timepoint.

Individual CSMs included following: MDAAT-PGDA, PGA assessment, MMT-8, HAQ-DI, and MDAAT extramacular global assessment. Higher values were associated with a better state of health for the MMT-8 (range 0 -150) assessment, while lower values were associated with a better state of health for: MDAAT-PGDA (range 0 -100), PGA (range 0-100), HAQ-DI (range 0-3), MDAAT-EGA (range 0 -100), and CDASI-A (range 0-100).

Analysis was performed on the mITT-Ex analysis set. The mITT-Ex comprised all participants in mITT who completed the first 24 weeks of SP1 and received any amount of the IMP in SP2. The documented failure to take any amount of randomized IMP in SP2 led to the exclusion of the participant from mITT-Ex. Here, overall number of participants analyzed (N) = participants evaluable for this outcome measure, and number analyzed (n) = participants with evaluable data for each specified timepoint.

The DOW consists of meeting 1 of the following criteria on 2 consecutive visits at least 2 weeks apart: PGA Assessment Visual Analog Scale (VAS) worsening >= 2 cm* and MMT-8 worsening >= absolute 10%, or EGA worsening >= 2 cm on the MDAAT VAS, or Any 3 of 6 CSM worsening by >= absolute 20%. (*If baseline PGA VAS is 8 to 10, then any worsening on Physician Global VAS was acceptable as long as MMT-8 criterion was met.)

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT.

The DOW consists of meeting 1 of the following criteria on 2 consecutive visits at least 2 weeks apart: PGA Assessment VAS worsening >= 2 cm* and MMT-8 worsening >= absolute 10%, or EGA worsening >= 2 cm on the MDAAT VAS, or Any 3 of 6 CSM worsening by >= absolute 20%. (*If baseline PGA VAS is 8 to 10, then any worsening on Physician Global VAS was acceptable as long as MMT-8 criterion was met.)

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT.

The DOW consists of meeting 1 of the following criteria on 2 consecutive visits at least 2 weeks apart: PGA Assessment VAS worsening >= 2 cm* and MMT-8 worsening >= absolute 10%, or EGA worsening >= 2 cm on the MDAAT VAS, or Any 3 of 6 CSM worsening by >= absolute 20%. (*If baseline PGA VAS is 8 to 10, then any worsening on Physician Global VAS was acceptable as long as MMT-8 criterion was met.)

Analysis was performed on the mITT-Ex analysis set. The mITT-Ex comprised all participants in mITT who completed the first 24 weeks of SP1 and received any amount of the IMP in SP2. The documented failure to take any amount of randomized IMP in SP2 led to the exclusion of the participant from mITT-Ex.

The DOW consists of meeting 1 of the following criteria on 2 consecutive visits at least 2 weeks apart: PGA Assessment VAS worsening >= 2 cm* and MMT-8 worsening >= absolute 10%, or EGA worsening >= 2 cm on the MDAAT VAS, or Any 3 of 6 CSM worsening by >= absolute 20%. (*If baseline PGA VAS is 8 to 10, then any worsening on Physician Global VAS was acceptable as long as MMT-8 criterion was met.)

Analysis was performed on the mITT-Ex analysis set. The mITT-Ex comprised all participants in mITT who completed the first 24 weeks of SP1 and received any amount of the IMP in SP2. The documented failure to take any amount of randomized IMP in SP2 led to the exclusion of the participant from mITT-Ex.

The DOW consists of meeting 1 of the following criteria on 2 consecutive visits at least 2 weeks apart: PGA Assessment VAS worsening >= 2 cm* and MMT-8 worsening >= absolute 10%, or EGA worsening >= 2 cm on the MDAAT VAS, or Any 3 of 6 CSM worsening by >= absolute 20%. (*If baseline PGA VAS is 8 to 10, then any worsening on Physician Global VAS was acceptable as long as MMT-8 criterion was met.) The observation was censored if no DOW was observed before the intake of rescue treatment or before the end of the period.

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT.

The DOW consists of meeting 1 of the following criteria on 2 consecutive visits at least 2 weeks apart: PGA Assessment VAS worsening >= 2 cm* and MMT-8 worsening >= absolute 10%, or EGA worsening >= 2 cm on the MDAAT VAS, or Any 3 of 6 CSM worsening by >= absolute 20%. (*If baseline PGA VAS is 8 to 10, then any worsening on Physician Global VAS was acceptable as long as MMT-8 criterion was met.) The Number of participants meeting DOW and who received rescue steroid treatment are reported here.

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT.

The DOW consists of meeting 1 of the following criteria on 2 consecutive visits at least 2 weeks apart: PGA Assessment VAS worsening >= 2 cm* and MMT-8 worsening >= absolute 10%, or EGA worsening >= 2 cm on the MDAAT VAS, or Any 3 of 6 CSM worsening by >= absolute 20%. (*If baseline PGA VAS is 8 to 10, then any worsening on Physician Global VAS was acceptable as long as MMT-8 criterion was met.) The percentage of participants meeting DOW and who received rescue steroid treatment are reported here.

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT.

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT. Here, overall number of participants analyzed (N) = participants with oral concomitant corticosteroid treatment at Week 1.

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT. Here, overall number of participants analyzed (N) = participants with oral concomitant corticosteroid treatment at Week 1.

Analysis was performed on the mITT-Ex analysis set. The mITT-Ex comprised all participants in mITT who completed the first 24 weeks of SP1 and received any amount of the IMP in SP2. The documented failure to take any amount of randomized IMP in SP2 led to the exclusion of the participant from mITT-Ex. Here, overall number of participants analyzed (N) = all participants with oral concomitant corticosteroid treatment at Week 1 who were part of mITT Ex.

Analysis was performed on the mITT-Ex analysis set. The mITT-Ex comprised all participants in mITT who completed the first 24 weeks of SP1 and received any amount of the IMP in SP2. The documented failure to take any amount of randomized IMP in SP2 led to the exclusion of the participant from mITT-Ex. Here, overall number of participants analyzed (N) = all participants with oral concomitant corticosteroid treatment at Week 1 who were part of mITT Ex.

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT.

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT. Here, overall number of participants analyzed (N) = participants receiving oral rescue corticosteroid treatment up to Week 25.

The observation was censored if no Rescue was observed before the last day of the last week with IMP intake or before the end of the period.

Analysis was performed on the mITT analysis set. The mITT analysis set comprises all participants who underwent study screening procedures and were randomized to receive any amount of randomized IMP. The documented failure to take any amount of randomized IMP, or the lack of any post-randomization efficacy data, led to the exclusion of the participant from the mITT.

EQ-5D-5L was assessed across 5 levels, with participants selecting the option that best described their health on that day, ranging from "no problems" to "unable to" walk, wash/dress, or perform usual activities. Out of total participants of each arm, only participants having at least 1 Level, 2 Levels, and more than 2 Levels of improvement from baseline in Mobility, Self-care, and Usual Activities Domains of EQ-5D-5L are reported in this outcome measure.

Analysis was performed on the mITT analysis set. Here, overall number of participants analyzed (N) = participants evaluable for this outcome measure, and number analyzed (n) = participants with evaluable data for each specified timepoint.

EQ-5D-5L was assessed across 5 levels, with participants selecting the option that best described their health on that day, ranging from "no problems" to "unable to" walk, wash/dress, or perform usual activities. Out of total participants of each arm, only participants having at least 1 Level, 2 Levels, and more than 2 Levels of improvement from baseline in Mobility, Self-care, and Usual Activities Domains of EQ-5D-5L are reported in this outcome measure.

Analysis was performed on the mITT analysis set. Here, overall number of participants analyzed (N) = participants evaluable for this outcome measure, and number analyzed (n) = participants with evaluable data for each specified category.

EQ-5D-5L was assessed across 5 levels, with participants selecting the option that best described their health on that day, ranging from "no problems" to "unable to" walk, wash/dress, or perform usual activities. Out of total participants of each arm, only participants having no reduction, at least 1 Level, 2 Levels, and more than 2 Levels of improvement from baseline in Mobility, Self-care, and Usual Activities Domains of EQ-5D-5L are reported in this outcome measure.

Analysis was performed on the mITT-Ex analysis set. The mITT-Ex comprised all participants in mITT who completed the first 24 weeks of SP1 and received any amount of the IMP in SP2. The documented failure to take any amount of randomized IMP in SP2 led to the exclusion of the participant from mITT-Ex. Here, overall number of participants analyzed (N) = participants evaluable for this outcome measure, and number analyzed (n) = participants with evaluable data for each specified category.

EQ-5D-5L was assessed across 5 levels, with participants selecting the option that best described their health on that day, ranging from "no problems" to "unable to" walk, wash/dress, or perform usual activities. Out of total participants of each arm, only participants having no reduction, at least 1 Level, 2 Levels, and more than 2 Levels of improvement from baseline in Mobility, Self-care, and Usual Activities Domains of EQ-5D-5L are reported in this outcome measure.

Analysis was performed on the mITT-Ex analysis set. The mITT-Ex comprised all participants in mITT who completed the first 24 weeks of SP1 and received any amount of the IMP in SP2. The documented failure to take any amount of randomized IMP in SP2 led to the exclusion of the participant from mITT-Ex. Here, overall number of participants analyzed (N) = participants evaluable for this outcome measure, and number analyzed (n) = participants with evaluable data for each specified category.

Period 1: Safety analysis set (SAF): All randomized participants who received any IMP, analyzed by actual treatment. Period 2: SAF extended (SAF-EX): Participants from SAF who completed 24 weeks in Period 1 and received any IMP in Period 2. Period 3: SAF for SP3 (SAF-P3): Participants from SAF-EX who completed 52 weeks in Periods 1 and 2 and received any IMP after Week 52.

Period 1: SAF: All randomized participants who received any IMP, analyzed by actual treatment. Period 2: SAF-EX: Participants from SAF who completed 24 weeks in Period 1 and received any IMP in Period 2. Period 3: SAF-P3: Participants from SAF-EX who completed 52 weeks in Periods 1 and 2 and received any IMP after Week 52.

Period 1: SAF: All randomized participants who received any IMP, analyzed by actual treatment. Period 2: SAF-EX: Participants from SAF who completed 24 weeks in Period 1 and received any IMP in Period 2. Period 3: SAF-P3: Participants from SAF-EX who completed 52 weeks in Periods 1 and 2 and received any IMP after Week 52.