Recruiting
Phase 3

Salanersen

Sponsor:

Biogen

Code:

NCT07444450

Conditions

Muscular Atrophy, Spinal

Eligibility Criteria

Sex: All

Age: 0

Healthy Volunteers: Not accepted

Interventions

Salanersen

Sham Procedure

Study Details

Brief summary:

In this study, researchers will learn more about the safety and effects of BIIB115, also known as salanersen. Specifically, researchers will learn more about how salanersen works in babies who have already been treated with onasemnogene abeparvovec (OA) after being diagnosed with SMA.

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.

OA works by replacing the missing or abnormal SMN1 gene. Sometimes, OA treatment may not work as well as expected. As a result, researchers are exploring whether giving another drug after OA could lead to better outcomes for people with SMA.

In this study, participants will have 2 SMN2 copies. The higher the copy number, the less severe the participant's SMA is. They will also have received treatment with OA by the time they were 42 days old and before showing any symptoms of SMA.

The main goal of the study is to learn more about the safety of giving salanersen to babies after OA treatment. Researchers will also learn more about whether salanersen can help make SMA symptoms less serious.

The main question researchers want to answer in this study is:

• How many participants have adverse events and serious adverse events after treatment?

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 neurofilament protein is found in the blood after treatment.
  • How much salanersen gets into the fluid surrounding the brain and spinal cord.
  • How much salanersen gets into the blood. Researchers will use different tests to learn if motor symptoms are changing, including the World Health Organization (WHO) motor milestones and Hammersmith Infant Neurological Examination (HINE) Section 2 motor milestones.

The study will be done in 2 parts. Part A will last 1 year while Part B will last up to 4 years.

The 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 6 months. Participants must have received OA treatment before the age of 42 days and started screening within 6 months of the OA dose.
  • Participants will be assigned to 1 of 2 treatment groups by chance. This is a "double blind" study which means neither the participants, study doctor, nor site staff will know which treatment group the participants are assigned to.
  • In this study, salanersen will be given as an intrathecal injection, which is an injection into the fluid surrounding the spine. This is done by a procedure called a lumbar puncture (LP) which involves inserting a needle into the lower back into the space around the spinal cord.
  • During Part A, one group will receive 80 milligrams (mg) of salanersen while another group receives a sham (fake) procedure. This means that a small needle prick will be done, but no injection will be given.
  • For each participant, the first visit of Part A will be 6 months after they receive OA treatment.
  • Part A will have up to 6 clinic visits and 2 phone calls and last up to 1 year.
  • During Part B, both groups of participants will receive 80 mg of salanersen once a year.
  • Part B will have up to 12 clinic visits and 14 phone calls and last up to 4 years.
  • In total, participants will be in the study for up to 5 and a half years.

Conditions

Muscular Atrophy, Spinal

Study ID

NCT07444450

Start date

Sep 4, 2026

Status verified date

Aug, 2026

Completion date

Jul 26, 2033

Anticipated

Primary completion date

Jul 27, 2029

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 0

Healthy Volunteers: Not accepted

Key Inclusion Criteria:

  • Genetic documentation of 5q spinal muscular atrophy (SMA) homozygous gene deletion or mutation or compound heterozygous mutation.
  • 2 copies of the survival motor neuron 2 (SMN2) gene.
  • Onasemnogene Abeparvovec (OA) dose given at ≤ 42 days of age and screening initiated less than 6 months from OA dosing.
  • OA dose given while participant was presymptomatic, per Investigator attestation. For this study, presymptomatic is defined as follows:

  • No clinical signs or symptoms at the time of OA dosing that are, in the opinion of the Investigator, strongly suggestive of SMA.
  • No absence of tendon reflexes (i.e., absence of all of biceps, knee and ankle tendons) at the time of OA dosing (e.g., Hammersmith Infant Neurological Examination (HINE) Section 1 or equivalent).
  • If Compound Muscle Action Potential (CMAP) data is available at the time of dosing, ulnar CMAP amplitude ≥ 2 millivolt (mV).

Key Exclusion Criteria:

  • Any unresolved post-OA laboratory abnormalities defined as follows:

  • Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) must be less than 2 × Upper Limit of Normal (ULN) while not receiving corticosteroids within 30 days prior to dosing with salanersen or sham procedure (repeat testing may be performed if necessary).
  • Evidence of thrombocytopenia, indicated by the platelet count being lower than the normal range for the laboratory.
  • Evidence of elevated troponin-I levels, identified as elevated post-OA, and has not returned to the normal range.
  • Confirmed demonstration of corrected QT interval, using Fridericia's correction method, of > 450 milliseconds (ms).
  • Other than OA, any prior treatment with an approved SMA disease modifying therapy (e.g. nusinersen and/or risdiplam), a myostatin inhibitor therapy, or an investigational drug given for the treatment of SMA.
  • Steroid treatment administered for the purpose of treating complications following OA within 14 days prior to dosing with salanersen or sham procedure on Day 1.

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

Study Design

Enrollment

42 participants

Anticipated

Allocation

Randomized

Intervention Model

Parallel Assignment

Primary purpose

Treatment

Interventions and Outcome Measures

Arms

experimental: Salanersen

Participants will receive a single dose of salanersen, 80 milligrams (mg) administered intrathecally on Day 1 in Part A. In Part B, participants will continue to receive four additional intrathecal doses of salanersen, 80 mg administered on Days 365, 730, 1095, and 1460.

sham comparator: Sham Procedure

Participants will undergo a sham procedure on Day 1 in Part A. In Part B, participants will receive four intrathecal doses of salanersen, 80 mg administered on Days 365, 730, 1095, and 1460.

Interventions

Salanersen

Administered intrathecally

Sham Procedure

A sham lumbar puncture is a skin-only needle prick at the usual lumbar puncture site. The needle does not enter the spinal canal.

Primary outcome measure

  • Parts A: Number of Participants with Adverse Events (AEs) and Serious Adverse Events (SAEs) [ Time Frame: Part A: Up to Day 365 ]

Central Contacts and Locations

Central contacts

US Biogen Clinical Trial Center

866-633-4636clinicaltrials@biogen.com

Global Biogen Clinical Trial Center

clinicaltrials@biogen.com

Locations

Neurology Rare Disease Center

Recruiting

Flower Mound, Texas, United States, 75028

Contacts

972-999-1011

Principal Investigator:

Diana Castro

More Information

Sponsor

Biogen

Last update posted

Aug 11, 2026

Last verified

Aug, 2026

Trial information was received from ClinicalTrials.gov and was last updated on 2026-09-09. This information was provided to ClinicalTrials.gov by Biogen on 2026-08-11.