ST-920 gene therapy outcomes in Fabry disease
By Agata Buczak
New data presented across three sessions at WORLDSymposium 2026 (We’re Organizing Research on Lysosomal Diseases) show a consolidated view of clinical, cardiac, and pharmacology outcomes with isaralgagene civaparvovec (ST-920), an investigational gene therapy for adults with Fabry disease. Presenters report durable α-Gal A (α-galactosidase A) expression, sustained reductions in lyso-Gb3, and signals of renal and cardiac stability following single-dose treatment.
John A. Bernat (University of Iowa Health Care, Iowa City, USA), who shared updated findings from the phase 1/2 STAAR study, described the results as showing “elevated expression of α-Gal A and corresponding reductions in plasma lyso-Gb3.” In the 32 adults with one full year of follow-up, the mean annualized estimated glomerular filtration rate (eGFR) slope was positive, with similar patterns observed in those followed for 2 years. All participants receiving enzyme replacement therapy (ERT) at baseline discontinued ERT after treatment, with an average time off therapy of nearly 2 years. Bernat highlighted the “consistency of biomarker and renal trends” across the follow-up period, reinforcing the signal of renal stabilization.
Cardiac outcomes presented by Robert J. Hopkin (Cincinnati Children’s Hospital Medical Center, Ohio, USA) complemented these findings. In 33 adults with varying degrees of baseline cardiac involvement, ventricular wall thickness and left ventricular mass index remained stable at week 52. Hopkin emphasized that “all cardiac endpoints were stable,” including in sex and disease type subgroups. Treatment-emergent cardiac adverse events were infrequent, with palpitations reported as the only event occurring more than once. Data presented also indicate improvements in patient-reported quality of life across the cohort, which Hopkin described as “a meaningful trend observed across assessments.”
Additional mechanistic insight came from pharmacology and immunogenicity data presented by Yanmei Lu (Sangamo Therapeutics, Richmond, California, USA). According to data reported in the abstract, “94% of participants exhibited sustained supraphysiological α-Gal A activity” through long-term follow-up, with some individuals reaching levels 142.9-fold above the mean normal reference. Sustained reductions in plasma lyso-Gb3 were also reported, including decreases of 53% in ERT-naive or pseudo-naive participants with elevated baseline values. No clinically meaningful effects of anti-drug antibodies or capsid-specific T-cell responses were seen, and a single mild liver enzyme elevation resolved with corticosteroid treatment, while enzyme expression was maintained.
The presenters noted that long-term follow-up of ST-920 continues, including extended renal and immunogenicity assessments and additional cardiac characterization. Ongoing analyses from both STAAR and its long-term extension are expected to provide further insight into durability of expression, biomarker trends, and organ-specific outcomes after one-time dosing.
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