RICHMOND, Calif. — Sangamo Therapeutics, Inc. (Nasdaq: SGMO), a genomic medicine company, today announced detailed data from the registrational Phase 1/2 STAAR study evaluating isaralgagene civaparvovec, or ST-920, a wholly owned investigational gene therapy for the treatment of adults with Fabry disease.
These data were presented at the International Congress of Inborn Errors of Metabolism 2025 (ICIEM2025) in Kyoto, Japan, on September 4, 2025, in a poster presentation (Poster Ref: P-662). These data are also available on Sangamo’s website on the Presentations page.
“These STAAR study data demonstrate the potential for ST-920 to provide meaningful clinical benefits to Fabry disease patients,” said Dr John Bernat, M.D., Ph.D., University of Iowa and investigator of the Phase 1/2 STAAR study. “The positive mean eGFR slope at both one and two years, which compares favorably to approved Fabry treatments, alongside stable cardiac function, are exciting developments, particularly given the decline in renal and cardiac function traditionally seen with Fabry patients. The ability for patients to discontinue the use of burdensome enzyme replacement therapies further supports the potential of ST-920 as a single-dose, durable treatment option for people living with Fabry disease.”
“Fabry disease is a debilitating and multifaceted condition, for which there is a serious unmet medical need,” said Nathalie Dubois-Stringfellow, Ph. D, Chief Development Officer at Sangamo. “We are excited by the potential of ST-920 to provide long-lasting clinical benefits to a wide range of Fabry disease patients. Improvements in renal function and stable cardiac function, alongside quality of life and additional clinical benefits, show the ability of ST-920 to address the underlying pathology of Fabry disease and provide a potentially transformative treatment for Fabry disease patients. We look forward to sharing these data with health authorities.”
Updated Phase 1/2 STAAR Study Results (as of April 10, 2025 cut-off date)
Efficacy (32 dosed patients followed at least 12 months)
- A positive mean annualized eGFR slope of 1.965 mL/min/1.73m2/year (95% confidence interval (CI): -0.153, 4.083) at 52-weeks was observed across all 32 dosed patients. This compares favorably to a meta-analysis of publications of approved Fabry treatments (Fabrazyme, Replagal and Galafold).
- Furthermore, a mean annualized eGFR slope at Week 104 of 1.747 mL/min/1.73m2/year (95% CI: -0.106, 3.601) was observed for the 19 patients who have achieved 104-weeks of follow-up.
- Supportive mean annualized eGFR slopes were also observed across a variety of patient subgroups, including gender, baseline ERT status, Fabry disease type and baseline eGFR, showing consistency in effect across Fabry patients in the study.
- Stable cardiac function was observed, including left ventricular mass (LVM), left ventricular mass index (LVMI), left ventricular myocardial global longitudinal strain (GLS), T1 and T2 mapping, end-diastolic and end-systolic volumes that remained stable over at least one year.
- Durability of effect was demonstrated with elevated expression of alpha-galactosidase A (α-Gal A) activity maintained for up to 4.5 years for the longest treated patient.
- All 18 patients who began the study on Enzyme Replacement Therapy (ERT) had been withdrawn from ERT and remained off ERT as of the data cutoff date1. Plasma lyso-Gb3 levels in these patients remained generally stable following ERT withdrawal.
- Of the 10 patients who had measurable titers of total antibodies (TAb) or neutralizing antibodies (Nab) against α-Gal A associated with ERT at baseline, TAb or NAb titers decreased markedly in nine patients and became undetectable in eight following treatment.
- Improvements in disease severity were reported in the Fabry Outcome Survey adaptation of the Mainz Severity Score Index (FOS-MSSI) age-adjusted score, with 22 patients showing improvements in their total MSSI score at 12 months and nine patients improving their FOS-MSSI disease category at the last assessment.
- Statistically and clinically significant improvements in the short form-36 (SF-36) quality of life scores were observed including role-physical +14.8 (95% CI: 7.3, 22.4, p=0.0003), vitality +9.6 (95% CI: 3.9, 15.2, p=0.0017), bodily pain +9.0 (95% CI: 2.3, 15.7, p=0.0104), social functioning +7.8 (95% CI: 2.0, 13.6, p=0.0100), general health +7.4 (95% CI: 2.0, 12.8, p=0.0091), and physical component scores +4.2 (95% CI: 1.8, 6.6, p=0.0014), at week 52 compared to baseline.
- Statistically significant improvements were seen in the gastrointestinal symptom rating scale (GSRS) compared to baseline.
Safety (all dosed patients):
- Isaralgagene civaparvovec demonstrated a favorable safety and tolerability profile in the study, without the requirement for preconditioning.
- The majority of adverse events were grade 1-2 in nature. The most common treatment-emergent adverse events (TEAEs) were pyrexia (60.6% of participants), COVID-19 (36.4%), headache (30.3%), and nasopharyngitis (33.3%).
- All TEAEs resolved in response to clinical management and there were no safety-related study discontinuations and no deaths.
Sangamo believes these data support the potential for isaralgagene civaparvovec as a one-time, durable treatment of the underlying pathology of Fabry disease, to provide meaningful clinical benefits above current standards of care and will form the basis for an anticipated BLA submission under the Accelerated Approval pathway as early as the first quarter of 2026.
The STAAR study enrolled male and female patients who were either on ERT, were ERT pseudo-naïve (defined as having been off ERT for six or more months), or were ERT-naïve. The median age of patients enrolled in the study was 42, with a median duration of follow-up of 24 months and the longest treated patient having achieved 4.5 years of follow-up.
Isaralgagene civaparvovec has been granted Orphan Drug, Fast Track and RMAT designations from the FDA, Orphan Medicinal Product designation and PRIME eligibility from the European Medicines Agency and Innovative Licensing and Access Pathway from U.K. Medicines and Healthcare products Regulatory Agency.
Sangamo is advancing BLA preparation activities for isaralgagene civaparvovec, while continuing to engage in business development negotiations for a potential Fabry commercialization agreement.
A Current Report on Form 8-K summarizing the Phase 1/2 STAAR study data will be filed by Sangamo, and this press release is subject to the further detail provided in that Form 8-K.
About the STAAR Study
The Phase 1/2 STAAR study is a global open-label, single-dose, dose-ranging, multicenter clinical study designed to evaluate isaralgagene civaparvovec, or ST-920, a gene therapy product candidate in patients with Fabry disease. Isaralgagene civaparvovec requires a one-time infusion without preconditioning.
About Fabry Disease
Fabry disease is a lysosomal storage disorder caused by mutations in the galactosidase alpha gene (GLA), which leads to deficient alpha-galactosidase A (α-Gal A) enzyme activity, which is necessary for metabolizing globotriaosylceramide (Gb3). The buildup of Gb3 in the cells can cause serious damage to vital organs, including the kidney, heart, nerves, eyes, gut and skin. Symptoms of Fabry disease can include decreased or absent sweat production, heat intolerance, angiokeratoma (skin blemishes), vision problems, kidney disease, heart failure, gastrointestinal disturbance, mood disorders, neuropathic pain and tingling in the extremities.
About Sangamo Therapeutics
Sangamo Therapeutics is a genomic medicine company dedicated to translating ground-breaking science into medicines that transform the lives of patients and families afflicted with serious neurological diseases who do not have adequate or any treatment options. Sangamo believes that its zinc finger epigenetic regulators are ideally suited to potentially address devastating neurological disorders. Moreover, Sangamo’s SIFTER capsid discovery platform is advancing delivery to the central nervous system in preclinical studies. Sangamo is also progressing next generation genome editing through its modular integrase (MINT) platform. Sangamo’s pipeline includes multiple partnered programs and programs with opportunities for partnership and investment. To learn more, visit www.sangamo.com and connect with us on LinkedIn and Twitter/X.
Reference
- Since the data cutoff date, a physician has decided to resume ERT for one of their treated patients who had withdrawn from ERT. This patient, who received ST-920 more than two and a half years ago, maintained supraphysiological levels of a-Gal A activity, and their lyso-Gb3 levels were generally stable as of the data cutoff date
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