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This trial will study the efficacy and safety of taldefgrobep alfa as an adjunctive therapy for participants who are already taking a stable dose of nusinersen or risdiplam or have a history of onasemnogene abeparvovec-xioi, compared to placebo.


Spinal Muscular Atrophy, Neuromuscular Diseases, SMA

Recruitment Status

Active, not recruiting

Detailed Description

Myostatin is a negative regulator of muscle growth. Blocking myostatin activity has been shown to increase muscle size and function. Taldefgrobep alfa directly blocks myostatin activity and was well tolerated in other clinical studies. In combination with medications that increase the amount of SMN protein in the body, taldefgrobep alfa has the potential to further improve motor function and clinical measures for people living with SMA.

Eligibility Criteria

Key Inclusion Criteria:

Spinal Muscular Atrophy confirmed by genetic diagnosis of 5q-autosomal recessive SMA as well as SMN2 copy number
Ambulant or Non-Ambulant
Treated with an SMA disease-modifying therapy and anticipated to remain on that same treatment regimen and dose throughout the trial including nusinersen, risdiplam, and/or a history of onasemnogene abeparvovec

Key Exclusion Criteria:

Cannot have previously taken anti-myostatin therapies
Must weigh at least 15kg
Respiratory insufficiency, defined by the medical necessity for invasive or non-invasive ventilation for daytime treatment while awake (use overnight or during daytime naps is acceptable)
History of Spinal Fusion within 6 months of Screening. MAGEC rod nonsurgical adjustments are allowed during the study
Presence of an implanted shunt for the drainage of CSF or an implanted central nervous system (CNS) catheter


Intervention Type

Intervention Name


taldefgrobep alfa




taldefgrobep alfa


Phase 3



Min Age

4 Years

Max Age

21 Years

Download Date

November 7, 2023

Principal Investigator

Leslie Hayes, MD

This field has been modified from to show a contact specific to Boston Children's.

Primary Contact Information

Kristina Nedeljkovic

This field has been modified from to show a contact specific to Boston Children's.

For more information on this trial, visit


For more information and to contact the study team:

A Study to Evaluate the Efficacy and Safety of Taldefgrobep Alfa in Participants With Spinal Muscular Atrophy NCT05337553 Kristina Nedeljkovic