A Study to Learn About Salanersen's (BIIB115) Effects on Movement and Its Safety When Given Before Symptoms Appear in Babies With Genetically Diagnosed Spinal Muscular Atrophy (SMA)

Phase

Condition

Spinal Muscular Atrophy

Treatment

Salanersen

Clinical Study ID

NCT07221669

277SM302

2025-523116-37

Ages < 42
All Genders
Accepts Healthy Volunteers

Study Summary

In this study, researchers will learn more about the effects and safety of BIIB115, also known as salanersen.

Specifically, researchers will learn more about how salanersen works in babies who have been diagnosed with SMA through genetic testing but have not yet started showing signs or symptoms. Most people with SMA have changes in a gene called survival motor neuron 1, also known as SMN1. These changes lower the amount of SMN protein in their bodies. Without enough of this protein, motor neurons and muscles cannot work properly. A similar gene called SMN2 can help replace some of the lost SMN protein in the body. Salanersen works by helping the SMN2 gene to make more SMN protein.

In this study, participants will have either 2 SMN2 copies or 3 SMN2 copies. The higher the copy number, the less severe the participant's SMA is.

The main goal of this study is to see if starting salanersen before signs or symptoms appear can prevent signs or symptoms of SMA or make them less severe. Researchers will use different tests to learn if motor symptoms are changing, including the World Health Organization (WHO) motor milestones.

The main questions researchers want to answer in this study are:

How many participants with 2 copies of the SMN2 gene can sit without support at 12 months?
How many participants with 3 copies of the SMN2 gene can walk alone at 18 months?

Researchers will also learn more about:

The effects on participants' motor symptoms and how many new movement milestones participants achieve.
How many participants stay free of SMA symptoms
How much salanersen gets into the fluid surrounding the brain and spinal cord.
How much salanersen gets into the blood.
How many participants have adverse events or serious adverse events. Adverse events are health problems that may or may not be caused by the study drug.

This study will be done as follows:

First, participants will be screened to check if they can join the study. The screening period will be up to 28 days.
This is an "open label" study. This is a study in which the participants, study doctor, and site staff know which study drug participants are receiving. In this study, all participants will receive salanersen through an intrathecal injection, or one that is given into the fluid surrounding the brain and spinal cord.
There will be 2 parts in this study. During Part 1, participants will receive 2 doses of salanersen, about 12 months apart from each other. Part 1 will last up to 25 months.
During Part 2, participants will continue to receive salanersen. They will receive up to 3 doses, 12 months apart from each other. Part 2 will last up to 36 months.
During Part 1, participants will have up to 11 clinic visits and up to 3 phone calls. During Part 2, participants will have up to 7 clinic visits and up to 12 phone calls.

Eligibility Criteria

Inclusion

Key Inclusion Criteria:

-≤42 days of age at first dose of salanersen.

Genetic documentation of 5q SMA homozygous gene deletion or mutation or compoundheterozygous mutation.
Two or three copies of the survival motor neuron 2 (SMN2) gene.
Ulnar compound muscle action potential (CMAP) amplitude ≥2 millivolt (mV) atScreening and Day 1 predose.
Body weight ≥3rd percentile for age based on World Health Organization (WHO) ChildGrowth Standards at the time of informed consent.

Exclusion

Key Exclusion Criteria:

Any clinical signs or symptoms at Screening or Day 1 predose that are, in theopinion of the Investigator, strongly suggestive of SMA.
Areflexia on neurologic examination at biceps, knee, or ankle at Screening or Day 1Predose.
Hypoxemia (oxygen saturation <96% awake or asleep without any supplemental oxygen orrespiratory support, or for altitudes >1000 meters (m), oxygen saturation of <92%awake or asleep without any supplemental oxygen or respiratory support).
Diagnosis of neonatal respiratory distress syndrome necessitating surfactantreplacement therapy or invasive ventilatory support.
Any reason, anatomical or otherwise (including hematology/coagulation laboratoryresults), that presents increased risk of complication from the LP procedures orsafety assessments.
Any prior treatment with an approved SMA disease-modifying therapy (e.g.,nusinersen, onasemnogene abeparvovec-xioi [OA], and/or risdiplam), a myostatininhibitor therapy, or an investigational drug given for the treatment of SMA.

Note: Other protocol-defined inclusion/exclusion criteria will apply.

Study Design

Salanersen

January 30, 2026

May 29, 2032

Study Description

For Part 1 of the study, the primary objective is to evaluate the clinical efficacy of salanersen in participants with genetically diagnosed SMA, and the secondary objective is to evaluate safety and tolerability, pharmacokinetics (PK), and effect on biomarkers after treatment with salanersen in participants with genetically diagnosed SMA.

For Part 2 of the study, the primary objective is to evaluate the long-term clinical efficacy of salanersen in participants with genetically diagnosed SMA, and the secondary objective is to evaluate the long-term safety and tolerability, PK, and effect on biomarkers after treatment with salanersen in participants with genetically diagnosed SMA.

Connect with a study center

Neurology Rare Disease Center
Flower Mound 4691585, Texas 4736286 75028
United States
Active - Recruiting
Childrens Hospital of the Kings Daughter Norfolk
Norfolk 4776222, Virginia 6254928 23507
United States
Active - Recruiting

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