Clinical Trials · global
Rare Disease Prevention Extends to Young Children: Andembry Pediatric Trial Reports Positive Results, Key Data Still Awaited
After 22 children ages 2 to 11 received preventive treatment for one year, most had no further hereditary angioedema attacks; CSL is preparing to apply for an expanded indication but has not yet disclosed attack rates or details of adverse events.
Hereditary angioedema swelling can strike the abdomen, face, or even the airways without warning, making it especially difficult for young children and their caregivers. CSL announced preliminary results from a Phase 3 follow-up trial, saying its preventive drug Andembry (garadacimab-gxii) showed a treatment response in children ages 2 to 11, with most participants remaining attack-free over one year. The findings provide the first clinical evidence supporting an extension below the currently approved age range.
This multicenter, open-label, single-arm study enrolled 22 children. Sixteen participants ages 6 to 11 received a 100 mg subcutaneous injection monthly, while six children ages 2 to 5 received 100 mg every two months. The longer dosing interval in the younger group also makes drug exposure and pharmacokinetics important considerations in the regulatory submission.
Andembry is a monoclonal antibody targeting activated factor XII (FXIIa). FXIIa is upstream in the kallikrein–kinin system and promotes the generation of bradykinin; excess bradykinin is the central mechanism behind recurrent tissue swelling in these patients. Blocking the signal upstream is intended not to treat acute swelling that has already occurred, but to reduce the likelihood of attacks over the long term.
CSL said the trial’s safety and tolerability profile was consistent with earlier studies and that treatment responses were observed across age groups. However, the company disclosed only that “most” children remained attack-free, without revealing the exact number, attack rates before and after treatment, serious adverse events, or discontinuations due to side effects. The magnitude of benefit and the risks therefore cannot yet be independently assessed.
ClinicalTrials.gov lists NCT05819775 as a Phase 3 study sponsored by CSL Behring, primarily evaluating safety, pharmacokinetics, pharmacodynamics, and efficacy. Registry data show that the trial ran from May 2023 to November 2025, with one of its primary outcomes tracking treatment-emergent adverse events over 12 months. Because the study had no control group and included only 22 participants, it is better suited to supplementing pediatric dosing and safety data; the preliminary announcement alone cannot resolve questions about rare risks or the relative merits of different treatments.
Andembry is currently approved in more than 40 countries for the prevention of attacks in patients ages 12 and older. CSL plans to begin submitting applications to regulators during the first half of the company’s fiscal year to expand the indication to children ages 2 to 11. Full results are scheduled to be presented at a medical conference and submitted to a peer-reviewed journal. Whether the drug will meaningfully change treatment options for young children will still depend on complete attack data, detailed safety findings, and regulators’ review of the two dosing frequencies.