Trial Outcomes & Findings for A Phase 2 Study to Evaluate the Safety, Efficacy, Pharmacokinetics and Pharmacodynamics of PF-06252616 in Duchenne Muscular Dystrophy (NCT NCT02310763)

A total of 162 participants were screened, 121 participants were enrolled in the study and assigned to 1 of 3 sequences. Only 120 participants received the study treatment and 1 participant withdrew prior to dosing.

A Phase 2 Study to Evaluate the Safety, Efficacy, Pharmacokinetics and Pharmacodynamics of PF-06252616 in Duchenne Muscular Dystrophy

An adverse event (AE) was any untoward medical occurrence in a clinical investigation participant administered a product; the event did not need to have a causal relationship with the treatment. A serious adverse event (SAE) was any untoward medical occurrence at any dose that resulted in death; was life threatening; required inpatient hospitalization or prolongation of existing hospitalization; resulted in persistent or significant disability/incapacity; resulted in congenital anomaly/birth defect. AEs included both SAEs and AEs. TEAEs were AEs occurred following the start of treatment or AEs increasing in severity during treatment. Severe TEAEs were TEAEs that interfered significantly with participants' usual function. Treatment-related TEAEs were determined by the investigator.

An AE was any untoward medical occurrence in a clinical investigation participant administered a product; the event did not need to have a causal relationship with the treatment. TEAEs were AEs occurred following the start of treatment or AEs increasing in severity during treatment. Treatment-related TEAEs were determined by the investigator.

An AE was any untoward medical occurrence in a clinical investigation participant administered a product; the event did not need to have a causal relationship with the treatment. TEAEs were AEs occurred following the start of treatment or AEs increasing in severity during treatment. Treatment-related TEAEs were determined by the investigator.

Hematology evaluation included: hemoglobin, hematocrit, red blood cell (RBC) count, platelets, RBC morphology, white blood cell (WBC) count, absolute lymphocytes, absolute atypical lymphocytes, absolute total neutrophils, absolute total neutrophils count, absolute band cells, absolute basophils, absolute eosinophils, absolute monocytes and absolute myelocytes.

Coagulation evaluation included activated partial thromboplastin time (aPTT) and prothrombin time (PT).

Liver function evaluation included: total/direct/indirect bilirubin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT), alkaline phosphatase, total protein, albumin and glutamate dehydrogenase.

Renal function evaluation included: blood urea nitrogen (BUN), creatinine and uric acid.

Electrolytes evaluation included: sodium, potassium, chloride, calcium, phosphate, bicarbonate, ferritin, transferrin saturation, iron, iron binding capacity and unsaturated iron binding capacity. Number of participants with iron abnormalities was reported in different age groups.

Hormone evaluations included free thyroxine (T4), thyroid stimulating hormone (TSH), lutenizing hormone (LH), follicle stimulating hormone (FSH), and androstenedione. Numbers of participants with abnormalities of LH, FSH and androstenedione were reported in different age groups.

Clinical chemistry evaluation included glucose, creatine kinase (CK), troponin I, and amylase.

Urinalysis included: urine pH, qualitative urine glucose, qualitative urine ketones, qualitative urine protein, qualitative blood/hemoglobin, urine nitrite, urine leukocytes, urine RBC, urine WBC, urine granular casts, urine hyaline casts, urine urate (uric acid) acidic crystal, urine calcium oxalate crystals, urine amorphous crystals, urine bacteria, urine microscopic exam.

Number of participants with blood detected in fecal samples is presented.

Magnetic resonance imaging (MRI) of Liver was obtained to quantify liver iron accumulation for safety monitoring. MRIs were sent to an independent central radiology imaging facility for calculation of the average transverse relaxation rate (R2\*) value which was used to monitor for iron accumulation in the liver. Number of participants meeting the following criteria is presented as follows: 1) normal: R2\*\<=75Hz at 1.5T or \<=139 Hz at 3.0T; 2) above normal: R2\*\>75Hz and \<=190Hz at 1.5T or R2\* \>139Hz and \<=369Hz at 3.0T; 3) mild overload: R2\*\>190Hz at 1.5T or R2\*\>360Hz at 3.0T.

Physical examination included head, ears, eyes, nose, mouth, skin, heart and lung examinations, lymph nodes, gastrointestinal, musculoskeletal, and neurological systems. A targeted nose and throat mucosal exam were also performed to monitor for any signs of mucosal telangiectasias. An SAE was any untoward medical occurrence at any dose that resulted in death; was life threatening; required inpatient hospitalization or prolongation of existing hospitalization; resulted in persistent or significant disability/incapacity; resulted in congenital anomaly/birth defect. Investigators determined which physical examination findings were reported as SAEs.

Tanner staging was performed before the first dose of each dose escalation to monitor for signs of accelerated sexual development. The physical changes in pubertal development (pubic hair, penis and testes) were assessed using the system described by Marshall and Tanner. Stage 1 is preadolescent, Stages 2, 3, and 4 are initiation of puberty and Stage 5 is mature adult. Details about the system can be referred to Tanner JM. Growth at Adolescence. Blackwell Scientific Publications 1962; 2nd edition.

Vital signs evaluation included supine systolic and diastolic blood pressure (BP), pulse rate, and respiratory rate. An SAE was any untoward medical occurrence at any dose that resulted in death; was life threatening; required inpatient hospitalization or prolongation of existing hospitalization; resulted in persistent or significant disability/incapacity; resulted in congenital anomaly/birth defect. Investigators determined which vital signs findings were reported as SAEs.

Number of participants with ECG data meeting the following criteria are presented: 1) corrected QT interval using Fridericia's formula (QTcF interval) \<450msec; 2) QTcF interval \>=450 and \<480msec; 3) QTcF interval \>=480 and \<500msec; 4) QTcF interval\>=500msec; 5) QTcF interval increase from baseline\<30msec; 6) QTcF interval increase from baseline \>=30 and \<60msec; 7) QTcF interval increase from baseline \>=60msec.

The LVEF was the ratio of blood ejected during systole to blood in the ventricle at the end of diastole. LVEF was measured by cardiac magnetic resonance image (MRI) or echocardiogram. The same method of cardiac imaging was used consistently within a single participant. Cardiac MRIs were read by a central imaging vendor and echocardiograms were read locally at each site. The LVEF values measured by cardiac MRI and echocardiogram are combined in the following presentation. The analysis of covariance (ANCOVA) model was used to analyze the change from baseline for domagrozumab compared to placebo on LVEF. The baseline result, age, use of angiotensin receptor blocker (ARB)/beta blocker/angiotensin converting enzyme (ACE) inhibitor and treatment were included as fixed effects in the model.

Bone mineral density (BMD) was evaluated by Dual energy X-ray Absorptiometry (DXA). The height adjusted Z-score presented below is the number of standard deviations which compares the BMD of the participant to the average BMD matched for their age, sex and ethnicity. If the Z-score was -2 standard deviations or lower, the result was "below the expected range for age". If the Z-score was above -2 standard deviations, the result was "within the expected range for age".

Bone age assessment was evaluated by the ratio of the bone age to the chronological age using the X rays of the hand and wrist. Ratio of bone age to chronological age was calculated by bone age/chronological age at scan date. Chronological age at scan date was calculated by (scan date-date of birth+1)/365.25.

An AE was any untoward medical occurrence in a clinical investigation participant administered a product; the event did not need to have a causal relationship with the treatment. The Columbia Suicide Severity Rating Scale (C-SSRS) was performed to identify the risk of suicide ideation or behavior. AEs of suicide ideation or behavior were determined by the investigator.

The 4SC quantified the time required for a participant to ascend 4 standard steps. Mixed effect model for repeated measures (MMRM) was used to analyze the change from baseline on 4SC for domagrozumab compared to placebo. The baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

FVC was measured by spirometry to evaluate respiratory muscle function. MMRM was used to analyze the change from baseline on FVC for domagrozumab compared to placebo. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

The NSAA is a 17-item test that measured gross motor function. Each individual item received a score of 0-unable to perform independently, 1-able to perform with assistance, or 2-able to perform without assistance. A total score was achieved by summing all the individual items. The total score could range from 0 to 34 (fully-independent function). MMRM was used to analyze the change from baseline for domagrozumab compared to placebo. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

ROM was evaluated by using goniometry to evaluate the loss of motion in the ankles. MMRM was used to analyze the change from baseline on ROM for domagrozumab compared to placebo. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

The PUL was used to assess motor performance of the upper limb. The PUL scale includes 22 items; an entry item defining the starting functional level, and 21 items subdivided into three levels: shoulder (4 items), middle (9 items) and distal (8 items). Scoring options per item may not be uniform and may vary from 0-1 and 0-6, according to the performance, with higher values corresponding to better performance. A total maximum score of 74 is achieved by adding the individual level scores. MMRM was used to analyze the change from baseline for domagrozumab compared to placebo. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

6MWD evaluated ambulation ability by measuring the distance walked in 6 minutes. MMRM was used to analyze the change from baseline on 6MWD for domagrozumab compared to placebo. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

Muscle strength was quantified by means of a handheld dynamometer. The following muscle groups were evaluated: knee extension, elbow flexion, hip abduction, elbow extension and shoulder abduction. MMRM was used to analyze the change from baseline on muscle strength for domagrozumab compared to placebo. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

Muscle strength was quantified by means of a handheld dynamometer. The following muscle groups were evaluated: knee extension, elbow flexion, hip abduction, elbow extension and shoulder abduction. MMRM was used to analyze the change from baseline on muscle strength for domagrozumab compared to placebo. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

Muscle strength was quantified by means of a handheld dynamometer. The following muscle groups were evaluated: knee extension, elbow flexion, hip abduction, elbow extension and shoulder abduction. MMRM was used to analyze the change from baseline on muscle strength for domagrozumab compared to placebo. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

Muscle strength was quantified by means of a handheld dynamometer. The following muscle groups were evaluated: knee extension, elbow flexion, hip abduction, elbow extension and shoulder abduction. MMRM was used to analyze the change from baseline on muscle strength for domagrozumab compared to placebo. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

Muscle strength was quantified by means of a handheld dynamometer. The following muscle groups were evaluated: knee extension, elbow flexion, hip abduction, elbow extension and shoulder abduction. MMRM was used to analyze the change from baseline on muscle strength for domagrozumab compared to placebo. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

The 4SC quantified the time required for a participant to ascend 4 standard steps. MMRM was used to analyze the change from baseline on 4SC for the natural history control group compared to placebo group (Sequence 3). This MMRM was established to assess the appropriateness on using the natural history control group as a comparator. The natural history control group was established by filtering the CINRG (Cooperative International Neuromuscular Research Group) natural history database. Participants who met the following requirements at baseline and had evaluable 4SC data on Week 49 were included in this group: 1) age: 6 to \<16 years; 2)treatment of glucocorticoid steroids \>=6 months prior to baseline and continuous use until the latest visit week; 3) 4SC: 2-15.9 seconds; 4) participants who were ambulatory at baseline; 5) LVEF: \>=55% or missing.

The 4SC quantified the time required for a participant to ascend 4 standard steps. MMRM was used to analyze the change from baseline on 4SC for domagrozumab compared to the natural history control group. The natural history control group was established by filtering the CINRG natural history database. Participants who met the following requirements at baseline and had evaluable 4SC data on Week 97 were included in this group: 1) age: 6 to \<16 years; 2) treatment of glucocorticoid steroids \>=6 months prior to baseline and continuous use until the latest visit week; 3) 4SC: 2-15.9 seconds; 4 participants who were ambulatory at baseline; 5) LVEF: \>=55% or missing.

FVC was measured by spirometry to evaluate respiratory muscle function. MMRM was used to analyze the change from baseline on FVC for the natural history control group compared to placebo group (Sequence 3). MMRM was used to analyze the change from baseline on FVC for the natural history control group compared to placebo group (Sequence 3). This MMRM was established to assess the appropriateness on using the natural history control group as a comparator. The natural history control group was established by filtering the CINRG natural history database. Participants who met the following requirements at baseline and had evaluable FVC data on Week 49 were included in this group: 1) age: 6 to \<16 years; 2)treatment of glucocorticoid steroids \>=6 months prior to baseline and continuous use until the latest visit week; 3) 4SC: 2-15.9 seconds; 4) participants who were ambulatory at baseline; 5) LVEF: \>=55% or missing.

FVC was measured by spirometry to evaluate respiratory muscle function. MMRM was used to analyze the change from baseline on FVC for domagrozumab compared to the natural history control group. The natural history control group was established by filtering the CINRG natural history database. Participants who met the following requirements at baseline and had evaluable FVC data on Week 97 were included in this group: 1) age: 6 to \<16 years; 2) treatment of glucocorticoid steroids \>=6 months prior to baseline and continuous use until the latest visit week; 3) 4SC: 2-15.9 seconds; 4 participants who were ambulatory at baseline; 5) LVEF: \>=55% or missing.

The NSAA is a 17-item test that measured gross motor function. A total score could range from 0 to 34 (fully-independent function). MMRM was used to analyze the change from baseline on NSAA for the natural history control group compared to placebo group (Sequence 3). This MMRM was established to assess the appropriateness on the using natural history control group as a comparator. The natural history control group was established by filtering the CINRG natural history database. Participants who met the following requirements at baseline and had evaluable NSAA data on Week 49 were included in this group: 1) age: 6 to \<16 years; 2)treatment of glucocorticoid steroids \>=6 months prior to baseline and continuous use until the latest visit week; 3) 4SC: 2-15.9 seconds; 4) participants who were ambulatory at baseline; 5) LVEF: \>=55% or missing.

The NSAA is a 17-item test that measured gross motor function. The total score could range from 0 to 34 (fully-independent function). MMRM was used to analyze the change from baseline on NSAA for domagrozumab compared to the natural history control group. The natural history control group was established by filtering the CINRG natural history database. Participants who met the following requirements at baseline and had evaluable NSAA data on Week 97 were included in this group: 1) age: 6 to \<16 years; 2) treatment of glucocorticoid steroids \>=6 months prior to baseline and continuous use until the latest visit week; 3) 4SC: 2-15.9 seconds; 4 participants who were ambulatory at baseline; 5) LVEF: \>=55% or missing.

6MWD evaluated ambulation ability by measuring the distance walked in 6 minutes. MMRM was used to analyze the change from baseline on 6MWD for the natural history control group compared to placebo group (Sequence 3). This MMRM was established to assess the appropriateness on using the natural history control group as a comparator. The natural history control group was established by filtering the CINRG natural history database. Participants who met the following requirements at baseline and had evaluable 6MWD data on Week 49 were included in this group: 1) age: 6 to \<16 years; 2)treatment of glucocorticoid steroids \>=6 months prior to baseline and continuous use until the latest visit week; 3) 4SC: 2-15.9 seconds; 4) participants who were ambulatory at baseline; 5) LVEF: \>=55% or missing.

6MWD evaluated ambulation ability by measuring the distance walked in 6 minutes. MMRM was used to analyze the change from baseline on 6MWD for domagrozumab compared to the natural history control group. The natural history control group was established by filtering the CINRG natural history database. Participants who met the following requirements at baseline and had evaluable 6MWD data on Week 97 were included in this group: 1) age: 6 to \<16 years; 2)treatment of glucocorticoid steroids \>=6 months prior to baseline and continuous use until the latest visit week; 3) 4SC: 2-15.9 seconds; 4) participants who were ambulatory at baseline; 5) LVEF: \>=55% or missing.

The 4SC quantified the time required for a participant to ascend 4 standard steps. A subset analysis was performed by categorizing participants into 3 subsets according to the baseline 4SC time: 1) \<3.5 seconds, 2)\>=3.5 seconds and \<=8 seconds, 3) \>8 seconds. MMRM was used to analyze the change from baseline for domagrozumab compared to placebo in subsets. The baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

The 4SC quantified the time required for a participant to ascend 4 standard steps. A subset analysis was performed by categorizing participants into 3 subsets according to the baseline 4SC time: 1) \<3.5 seconds, 2)\>=3.5 seconds and \<=8 seconds, 3) \>8 seconds.MMRM was used to analyze the change from baseline for domagrozumab compared to placebo in subsets. The baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

The 4SC quantified the time required for a participant to ascend 4 standard steps. A subset analysis was performed by categorizing participants into 3 subsets according to the baseline 4SC time: 1) \<3.5 seconds, 2)\>=3.5 seconds and \<=8 seconds, 3) \>8 seconds. MMRM was used to analyze the change from baseline for domagrozumab compared to placebo in subsets. The baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

FVC was measured by spirometry to evaluate respiratory muscle function. A subset analysis was performed by categorizing participants into 3 subsets according to the baseline 4SC time: 1) \<3.5 seconds, 2)\>=3.5 seconds and \<=8 seconds, 3) \>8 seconds. MMRM was used to analyze the change from baseline on FVC for domagrozumab compared to placebo in subsets. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

FVC was measured by spirometry to evaluate respiratory muscle function. A subset analysis was performed by categorizing participants into 3 subsets according to the baseline 4SC time: 1) \<3.5 seconds, 2)\>=3.5 seconds and \<=8 seconds, 3) \>8 seconds. MMRM was used to analyze the change from baseline on FVC for domagrozumab compared to placebo in subsets. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

FVC was measured by spirometry to evaluate respiratory muscle function. A subset analysis was performed by categorizing participants into 3 subsets according to the baseline 4SC time: 1) \<3.5 seconds, 2)\>=3.5 seconds and \<=8 seconds, 3) \>8 seconds. MMRM was used to analyze the change from baseline on FVC for domagrozumab compared to placebo in subsets. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

The NSAA is a 17-item test that measured gross motor function. Each individual item received a score of 0-unable to perform independently, 1-able to perform with assistance, or 2-able to perform without assistance. A total score was achieved by summing all the individual items. The total score could range from 0 to 34 (fully-independent function). A subset analysis was performed by categorizing participants into 3 subsets according to the baseline 4SC time: 1) \<3.5 seconds, 2)\>=3.5 seconds and \<=8 seconds, 3) \>8 seconds. MMRM was used to analyze the change from baseline for domagrozumab compared to placebo in subsets. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

The NSAA is a 17-item test that measured gross motor function. Each individual item received a score of 0-unable to perform independently, 1-able to perform with assistance, or 2-able to perform without assistance. A total score was achieved by summing all the individual items. The total score could range from 0 to 34 (fully-independent function). A subset analysis was performed by categorizing participants into 3 subsets according to the baseline 4SC time: 1) \<3.5 seconds, 2)\>=3.5 seconds and \<=8 seconds, 3) \>8 seconds. MMRM was used to analyze the change from baseline for domagrozumab compared to placebo in subsets. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

The NSAA is a 17-item test that measured gross motor function. Each individual item received a score of 0-unable to perform independently, 1-able to perform with assistance, or 2-able to perform without assistance. A total score was achieved by summing all the individual items. The total score could range from 0 to 34 (fully-independent function). A subset analysis was performed by categorizing participants into 3 subsets according to the baseline 4SC time: 1) \<3.5 seconds, 2)\>=3.5 seconds and \<=8 seconds, 3) \>8 seconds. MMRM was used to analyze the change from baseline for domagrozumab compared to placebo in subsets. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

The PUL was used to assess motor performance of the upper limb. The PUL scale includes 22 items; an entry item defining the starting functional level, and 21 items subdivided into three levels: shoulder (4 items), middle (9 items) and distal (8 items). Scoring options per item may not be uniform and may vary from 0-1 and 0-6, according to the performance, with higher values corresponding to better performance. A total maximum score of 74 is achieved by adding the individual level scores. A subset analysis was performed by categorizing participants into 3 subsets according to the baseline 4SC time. MMRM was used to analyze the change from baseline .The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

The PUL was used to assess motor performance of the upper limb. The PUL scale includes 22 items; an entry item defining the starting functional level, and 21 items subdivided into three levels: shoulder (4 items), middle (9 items) and distal (8 items).Scoring options per item may not be uniform and may vary from 0-1 and 0-6, according to the performance, with higher values corresponding to better performance. A total maximum score of 74 is achieved by adding the individual level scores. A subset analysis was performed by categorizing participants into 3 subsets according to the baseline 4SC time. MMRM was used to analyze the change from baseline.The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

The PUL was used to assess motor performance of the upper limb. The PUL scale includes 22 items; an entry item defining the starting functional level, and 21 items subdivided into three levels: shoulder (4 items), middle (9 items) and distal (8 items).Scoring options per item may not be uniform and may vary from 0-1 and 0-6, according to the performance, with higher values corresponding to better performance. A total maximum score of 74 is achieved by adding the individual level scores. A subset analysis was performed by categorizing participants into 3 subsets according to the baseline 4SC time. MMRM was used to analyze the change from baseline.The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

6MWD evaluated ambulation ability by measuring the distance walked in 6 minutes. A subset analysis was performed by categorizing participants into 3 subsets according to the baseline 4SC time: 1) \<3.5 seconds, 2)\>=3.5 seconds and \<=8 seconds, 3) \>8 seconds. MMRM was used to analyze the change from baseline on 6MWD for domagrozumab compared to placebo in subsets. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

6MWD evaluated ambulation ability by measuring the distance walked in 6 minutes. A subset analysis was performed by categorizing participants into 3 subsets according to the baseline 4SC time: 1) \<3.5 seconds, 2)\>=3.5 seconds and \<=8 seconds, 3) \>8 seconds. MMRM was used to analyze the change from baseline on 6MWD for domagrozumab compared to placebo in subsets. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

6MWD evaluated ambulation ability by measuring the distance walked in 6 minutes. A subset analysis was performed by categorizing participants into 3 subsets according to the baseline 4SC time: 1) \<3.5 seconds, 2)\>=3.5 seconds and \<=8 seconds, 3) \>8 seconds. MMRM was used to analyze the change from baseline on 6MWD for domagrozumab compared to placebo in subsets. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

Muscle strength was quantified by means of a handheld dynamometer. The following muscle groups were evaluated: knee extension, elbow flexion, hip abduction, elbow extension and shoulder abduction. Change from baseline on muscle strength in all participants with baseline 4SC \<3.5 seconds are presented below.

Muscle strength was quantified by means of a handheld dynamometer. The following muscle groups were evaluated: knee extension, elbow flexion, hip abduction, elbow extension and shoulder abduction. Change from baseline on muscle strength in all participants with baseline 4SC \>=3.5 seconds and \<=8 seconds are presented below.

Muscle strength was quantified by means of a handheld dynamometer. The following muscle groups were evaluated: knee extension, elbow flexion, hip abduction, elbow extension and shoulder abduction. Change from baseline on muscle strength in all participants with baseline 4SC \>8 seconds are presented below.

The whole thigh muscle volume was measured by the proton density weighted sequence with magnetic resonance imaging (MRI) which was used to segment the entire thigh region into 3 primary regions for volumetric measure including 1) muscle; 2) inter/intra-muscular fat, 3) subcutaneous fat. MMRM was used to analyze the percent change from baseline for domagrozumab compared to placebo. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

The thigh muscle volume index was derived from the thigh muscle volume measurements as the fraction of total thigh tissue that was the lean muscle. MMRM was used to analyze the percent change from baseline for domagrozumab compared to placebo. The stratification factor, baseline result, treatment, time and treatment by time interaction were included as fixed effects in the model. Participants were included as a random effect and the model was fit with an unstructured covariance for the repeated measures.

The whole thigh muscle volume was measured by the proton density weighted sequence with magnetic resonance imaging (MRI) which was used to segment the entire thigh region into 3 primary regions for volumetric measure including 1) muscle; 2) inter/intra-muscular fat, 3) subcutaneous fat.

The thigh muscle volume index was derived from the thigh muscle volume measurements as the fraction of total thigh tissue that was the lean muscle.

GDF-8, also called myostatin, is the target of domagrozumab. C0(GDF-8) was observed directly from data.