A Study to Assess the Safety, Tolerability, Efficacy, Pharmacokinetics, and Immunogenicity of Intravenous Administration of ARGX-119 in Pediatric Participants Aged 5 to Less Than 18 Years With Spinal Muscular Atrophy (Sparkle)

May 20, 2026 updated by: argenx

A Phase 2 Double-Blinded, Randomized, Placebo-Controlled Study to Assess the Safety, Tolerability, Efficacy, Pharmacokinetics, and Immunogenicity of Intravenous Administration of ARGX-119 in Pediatric Participants Aged 5 to Less Than 18 Years With Spinal Muscular Atrophy

This study aims to find the correct dose of ARGX-119 for children with SMA. The study will also look at how safe the study drug is, how well it works, how it moves through the body, and how the immune system responds to it. The study consists of a double-blinded treatment period (DBTP) where participants will either receive ARGX-119 IV or placebo IV, in addition to disease-modifying therapy (DMT) for 24 weeks. Participants who complete the DBTP will enter the open-label active-treatment extension period (ATEP) during which all participants will receive ARGX-119 IV up to 100 weeks (approximately 2 years).

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Detailed Description

This phase 2 study aims to establish proof of concept with the age-appropriate dose of ARGX-119 in ambulant pediatric patients with spinal muscular atrophy (SMA). Despite available treatments, there remains an unmet medical need for patients with SMA. Neuromuscular junction (NMJ) dysfunction contributes to the pathophysiology of SMA, including muscle weakness and fatigability. Activation of muscle-specific kinase (MuSK) by ARGX-119 may stabilize and improve NMJ function in patients with SMA, reducing muscle weakness and fatigability, and improving quality of life.

Study Type

Interventional

Enrollment (Estimated)

60

Phase

  • Phase 2

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

  • United States
    • Arkansas
      • Little Rock, Arkansas, United States, 72202
        • Recruiting
        • Arkansas Children's Hospital
        • Contact:
        • Principal Investigator:
          • Kapil Arya, Dr.
    • California
      • San Diego, California, United States, 92123
        • Not yet recruiting
        • Rady Childrens Hospital
        • Contact:
        • Principal Investigator:
          • Chamindra Laverty, Dr.
      • Stanford, California, United States, 94305
        • Not yet recruiting
        • Stanford University Medical Center
        • Contact:
        • Principal Investigator:
          • Carolina Tesi Rocha, Dr.
    • Connecticut
      • Hartford, Connecticut, United States, 06106
        • Not yet recruiting
        • Connecticut Children's Medical Center
        • Contact:
        • Principal Investigator:
          • Gyula Acsadi, Dr.
    • Florida
      • Kissimmee, Florida, United States, 34746
    • Illinois
      • Chicago, Illinois, United States, 60611
        • Recruiting
        • Ann & Robert H. Lurie Children's Hospital of Chicago
        • Contact:
        • Principal Investigator:
          • Nancy Kuntz, Dr.
    • Iowa
      • Iowa City, Iowa, United States, 52242
        • Not yet recruiting
        • University of Iowa Stead Family Children's Hospital
        • Contact:
        • Principal Investigator:
          • Katherine Mathews, Dr.
    • Maryland
      • Baltimore, Maryland, United States, 21205
        • Not yet recruiting
        • The Johns Hopkins Hospital
        • Contact:
        • Principal Investigator:
          • Jessica Nance, Dr.
    • Massachusetts
      • Boston, Massachusetts, United States, 02115
        • Not yet recruiting
        • Boston Children's Hospital
        • Contact:
        • Principal Investigator:
          • Basil Darras, Dr.
    • Missouri
      • Columbia, Missouri, United States, 65212
        • Not yet recruiting
        • The Curators of the University of Missouri on behalf of University of Missouri Health Care
        • Contact:
        • Principal Investigator:
          • William Arnold, Dr.
    • New York
      • New York, New York, United States, 10032
        • Not yet recruiting
        • Columbia University Herbert Irving Comprehensive Cancer Center
        • Contact:
        • Principal Investigator:
          • Claudia Chiriboga, Dr.
    • North Carolina
      • Hillsborough, North Carolina, United States, 27278
        • Recruiting
        • Rare Disease Research NC, LLC
        • Contact:
        • Principal Investigator:
          • Edward Smith, Dr.
    • Pennsylvania
      • Philadelphia, Pennsylvania, United States, 19104
        • Not yet recruiting
        • Children's Hospital Philadelphia - Neurology
        • Contact:
        • Principal Investigator:
          • John Brandsema, Dr.
    • Tennessee
      • Memphis, Tennessee, United States, 38105
        • Not yet recruiting
        • St. Jude Children's Research Hospital
        • Contact:
        • Principal Investigator:
          • Richard Finkel, Dr.
    • Texas
      • Flower Mound, Texas, United States, 75028
        • Recruiting
        • Neurology Rare Disease Center
        • Principal Investigator:
          • Diana Castro, Dr.
        • Contact:
      • Houston, Texas, United States, 77030
        • Not yet recruiting
        • Texas Children's Hospital
        • Contact:
        • Principal Investigator:
          • Timothy Lotze, Dr.
    • Virginia
      • Norfolk, Virginia, United States, 23507
        • Not yet recruiting
        • Childrens Hospital of The Kings Daughters
        • Contact:
        • Principal Investigator:
          • Crystal Proud, Dr.

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Child

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Is aged ≥5 to <18 years when completing the informed consent process, defined as providing informed assent according to local regulations and having a parent or guardian sign the ICF, and can comply with protocol
  • requirements.
  • Has documented historical genetic diagnosis of 5q-SMA.
  • Currently receiving a stable SMA treatment regimen (nusinersen or risdiplam) and/or have a history of onasemnogene abeparvovec treatment
  • Must be able to walk at least 50 meters without walking aids in the 6MWT at screening

Exclusion Criteria:

  • Known medical condition that would interfere with an accurate assessment of SMA, confound the results of the study, or put the participant at undue risk, as assessed by the investigator
  • Recent major surgery, except spinal fusion, within 3 months of screening or intends to have major surgery during the study
  • Current or previous administration of antimyostatin therapies in the past 6 months
  • Severe scoliosis (defined as curvature >40°) and/or contractures at screening. o History of spinal fusion within 6 months before screening or planned during the study
  • Respiratory insufficiency, defined by the medical necessity for invasive or noninvasive ventilation for daytime treatment while awake. Ventilation used overnight or during daytime naps is acceptable.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: DBTP - ARGX-119 IV
Participants receive ARGX-119 IV during the DBTP
Biological: ARGX-119 IV
Intravenous infusion of ARGX-119
Placebo Comparator: DBTP - Placebo IV
Participants receive placebo IV during the DBTP
Other: Placebo IV
Intravenous infusion of placebo
Placebo Comparator: ATEP - ARGX-119 IV
Participants receive ARGX-119 IV during the ATEP. Participants from ARGX-119 IV arm in the DBTP will receive placebo once to maintain the DBTP blinding
Other: Placebo IV
Intravenous infusion of placebo
Biological: ARGX-119 IV
Intravenous infusion of ARGX-119

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Incidence of AEs
Time Frame: Up to 124 weeks
Adverse Events
Up to 124 weeks
Incidence of SAEs
Time Frame: Up to 124 weeks
Serious Adverse Events
Up to 124 weeks
Change in RHS total score from baseline to week 24 of the double blinded treatment period (DBTP)
Time Frame: Up to 24 weeks
The RHS (Revised Hammersmith Scale) is a validated 36-item scale developed to evaluate the spectrum of gross motor function. Maximum total score; 69 (optimal motor function)
Up to 24 weeks

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Change from baseline over time for the 6MWT - distance and fatigue index
Time Frame: Up to 124 weeks
In the 6MWT (6-minute walk test) participants will be instructed to walk as fast as possible without jogging or running along a 25- meter linearly marked course for 6 minutes without using walking devices or assistance. Distance walked over the entire 6-minute period, and other parameters, will be determined
Up to 124 weeks
ARGX-119 serum concentrations over time
Time Frame: Up to 124 weeks
ARGX-119 serum concentrations over time
Up to 124 weeks
Incidence of antidrug antibodies (ADA) against ARGX-119
Time Frame: Up to 124 weeks
Incidence of antidrug antibodies (ADA) against ARGX-119
Up to 124 weeks

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

argenx

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

December 19, 2025

Primary Completion (Estimated)

May 28, 2029

Study Completion (Estimated)

May 28, 2029

Study Registration Dates

First Submitted

December 15, 2025

First Submitted That Met QC Criteria

December 15, 2025

First Posted (Actual)

December 17, 2025

Study Record Updates

Last Update Posted (Actual)

May 22, 2026

Last Update Submitted That Met QC Criteria

May 20, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • ARGX-119-24-SMA-2001
  • 2025-523496-32-00 (Ctis)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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