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Apitegromab

Phase 3

Spinal Muscular Atrophy | Small molecule | Neurology |Scholar Rock Holding Corporation|Last Updated: May 1, 2026

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Trial Design
RandomizedDouble-BlindPLACEBO_CONTROLLEDDMC
Total Trials3
Total Enrollment478
FDA Designations
PRIORITY_REVIEW
Clinical trial landscape

Apitegromab · 5 trials · 13 indications

Phase 3 2Phase 2 3
NCT05626855Long-Term Safety & Efficacy of Apitegromab in Patients With SMA Who Completed Previous Trials of ApitegromabSpinal Muscular Atrophy
ACTIVE NOT_RECRUITING238 Analytics
NCT05156320Efficacy and Safety of Apitegromab in Patients With Later-Onset Spinal Muscular Atrophy Treated With Nusinersen or RisdiplamSpinal Muscular Atrophy
COMPLETED188 Analytics
PHASE3ACTIVE NOT_RECRUITING
Long-Term Safety & Efficacy of Apitegromab in Patients With SMA Who Completed Previous Trials of Apitegromab
Spinal Muscular AtrophyUnlock trial analytics
PHASE3COMPLETED
Efficacy and Safety of Apitegromab in Patients With Later-Onset Spinal Muscular Atrophy Treated With Nusinersen or Risdiplam
Spinal Muscular AtrophyUnlock trial analytics
Study Endpoints
Primary Endpoints
Evaluate the long-term safety and tolerability of apitegromab in patients with Type 2 and Type 3 SMA
Up to 6 years

Incidence of TEAEs and SAEs by severity

Main Efficacy Population: Change from Baseline in Hammersmith Functional Motor Scale Expanded (HFMSE) total score.
Baseline up to 12 months.

The HFMSE assesses the physical abilities of patients with Type 2 and Type 3 SMA. It comprises of 33 items graded on a scale of 0, 1, or 2, where 0 denotes unable, 1 denotes performed with modification or adaptation, and 2 denotes performed without modification or adaptation. The overall score is the sum of the scores for all activities with a maximum achievable score of 66. Higher scores indicate increased motor function.

Assess the efficacy of apitegromab compared with placebo in participants with FSHD
52 Weeks

Percent change from baseline in total lean muscle volume (LMV) as measured by full body magnetic resonance imaging (MRI) at week 52

Evaluate the PK of apitegromab in subjects <2 years old with SMA
52 Weeks

Apitegromab concentrations in serum

Evaluate the PD of apitegromab in subjects <2 years old with SMA
52 Weeks

Total latent myostatin concentrations in serum

Evaluate the motor function outcomes (ie, efficacy) due to apitegromab treatment
48 Weeks

Change from baseline in the raw score of the Bayley Scale of Infant and Toddler Development, Fourth Edition - Gross Motor Subscale (BSID-4 GMS) at 48 weeks. BSID-4 GMS is a standardized assessment commonly used to evaluate development across 5 domains in infants and young children. It consists of 58 items, scored from 0 to 2 for each item, with higher scores indicating better gross motor development.

Change from Baseline in total Lean Body Mass (kg) at 24 weeks
Baseline and 24 weeks

Dual-energy X-ray absorptiometry was used to evaluate body composition

Secondary Endpoints
Evaluate the long-term efficacy of apitegromab by assessing changes in motor function outcome measures at prespecified time points
Up to 6 years
Further evaluate the immunogenicity of apitegromab
Up to 6 years
Main Efficacy Population: Change from Baseline in Revised Upper Limb Module (RULM) total score.
Baseline up to 12 months.
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Study Design & Arms
AllocationNA
MaskingNONE
ModelSINGLE_GROUP
PurposeTREATMENT
Treatment Arms
ArmTypeDescription
Treatment PeriodEXPERIMENTALPatients who are ≥2 years of age with Type 2 and Type 3 SMA will receive apitegromab 20 mg/kg every 4 weeks by intravenous (IV) infusion during the 104-week Treatment Period
Main Efficacy Population (Apitegromab 10 mg/kg)EXPERIMENTALAged 2-12 years at Screening. Participants were randomized to receive apitegromab 10 mg/kg for up to 52 weeks.
Main Efficacy Population (Apitegromab 20 mg/kg)EXPERIMENTALAged 2-12 years at Screening. Participants were randomized to receive apitegromab 20 mg/kg for up to 52 weeks.
Main Efficacy Population (Placebo)PLACEBO_COMPARATORAged 2-12 years at Screening. Participants were randomized to receive placebo for up to 52 weeks.
Exploratory Subpopulation (Apitegromab)EXPERIMENTALAged 13-21 years at Screening. Participants were randomized to receive apitegromab 20 mg/kg for up to 52 weeks.
Exploratory Subpopulation (Placebo)PLACEBO_COMPARATORAged 13-21 years at Screening. Participants were randomized to receive placebo for up to 52 weeks.
ApitegromabEXPERIMENTAL10 mg/kg IV
PlaceboPLACEBO_COMPARATORPlacebo IV
Apitegromab low dose + SMN TherapyEXPERIMENTALPatients who are less than 2 years of age with SMA will receive apitegromab every 4 weeks by intravenous (IV) infusion during the 48-week Treatment Period. Patients must have been treated with an approved SMN1-targeted therapy (ie, onasemnogene abeparvovec-xioi) or are continuing to be treated with an approved SMN2-targeted therapy (ie, nusinersen or risdiplam).
Apitegromab high dose + SMN TherapyEXPERIMENTALPatients who are less than 2 years of age with SMA will receive apitegromab every 4 weeks by intravenous (IV) infusion during the 48-week Treatment Period. Patients must have been treated with an approved SMN1-targeted therapy (ie, onasemnogene abeparvovec-xioi) or are continuing to be treated with an approved SMN2-targeted therapy (ie, nusinersen or risdiplam).
Cohort 1EXPERIMENTALApitegromab + incretin mimetic
Cohort 2PLACEBO_COMPARATORPlacebo + incretin mimetic
Interventions
NameTypeDescription
ApitegromabDRUGApitegromab (SRK-015) is an investigational, fully human immunoglobulin G4 monoclonal antibody that specifically binds to human proforms (i.e., inactive precursor forms) of myostatin, pro- and latent- myostatin, with high affinity, inhibiting activation of myostatin, a negative regulator of muscle growth and strength.
PlaceboDRUGPlacebo was administered every 4 weeks by intravenous (IV) infusion.
NusinersenDRUGNusinersen is a current standard-of-care SMN therapy that targets the SMN2 gene. It will be administered intrathecally per the prescribing information.
RisdiplamDRUGRisdiplam is a current standard-of-care SMN therapy that targets the SMN2 gene. It will be administered orally per the prescribing information.
TirzepatideDRUGGlucose-dependent insulinotropic polypeptide (GIP) receptor and glucagon-like peptide-1 (GLP-1) receptor agonist. Tirzepatide was administered every week by subcutaneous injection.
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Eligibility Criteria
Age Range2 Years to N/A
SexALL
Healthy VolunteersNo
Study Sites49

Inclusion Criteria: * Patients have completed the Phase 2 TOPAZ (Study SRK-015-002) trial or the Phase 3 SAPPHIRE (Study SRK-015-003) trial. (For TOPAZ, completed is defined as completion of Visit EC14 in Extension Period C or participating in TOPAZ at the time the trial is ended. For SAPPHIRE, com...

Countries:United StatesBelgiumFranceGermanyItalyNetherlandsPolandSpainUnited Kingdom
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Recent Changes (Last 90 Days)
LOWMay 26, 2026NCT07047144primaryCompletionDate: changed
LOWMay 26, 2026NCT07435129primaryCompletionDate: changed
LOWMay 26, 2026NCT05626855primaryCompletionDate: changed
LOWMay 24, 2026NCT07047144studyFirstPostDate: changed
LOWMay 24, 2026NCT07435129studyFirstPostDate: changed
LOWMay 24, 2026NCT05626855studyFirstPostDate: changed