Sangamo Therapeutics Announces Updated Preliminary Phase 1/2 Data in Fabry Disease Clinical Study Showing Continued Tolerability and Sustained Elevated α-gal A Enzyme Activity in Five Longest Treated Patients

Sangamo Therapeutics, Inc. (Nasdaq: SGMO), a genomic medicine company, today announced updated preliminary results from the Phase 1/2 STAAR clinical study evaluating isaralgagene civaparvovec, or ST-920, a wholly owned gene therapy product candidate for the treatment of Fabry disease. These latest data show that, as of the February 14, 2022 cutoff date, the investigational treatment continued to be generally well tolerated, with no treatment-related adverse events above Grade 1 (mild). The five longest treated patients continued to exhibit elevated alpha-galactosidase A (α-Gal A) activity, sustained up to 15 months as of the last date of measurement. The sixth patient exhibited elevated α-Gal A activity to within normal range at two weeks post dosing.

These updated data will be presented at the Society for the Study of Inborn Errors of Metabolism (SSIEM) Annual Meeting on August 31, 2022, from 6:45pm-8:15pm Central European Time (Ref: SSIEM22-2517). These data are also available on Sangamo’s website on the Events & Presentations page.

“These updated preliminary results continue to demonstrate the potential of isaralgagene civaparvovec gene therapy to safely address the most challenging symptoms of Fabry disease,” said Jaya Ganesh, MD, Division of Medical Genetics and Genomic Sciences at the Icahn School of Medicine at Mount Sinai and investigator of the Phase 1/2 study. “I am excited to see whether these encouraging trends continue into the next dose cohort and beyond, as we progress this potential treatment for a very challenging illness.”

As of the cutoff date, the first five patients treated, across three dose cohorts (0.5e13 vg/kg, 1e13 vg/kg and 3e13 vg/kg), sustained elevated α-Gal A activity ranging from nearly 3-fold to nearly 17-fold above mean normal at the last date of measurement.

• Cohort 1, Patient 1 [on ERT at the cutoff date]: α-Gal A activity measured at ERT trough was 12.4-fold above mean normal at Month 15
• Cohort 1, Patient 2 [not on ERT]: α-Gal A activity was 2.7-fold above mean normal at Month 15
• Cohort 2, Patient 1 [not on ERT]: α-Gal A activity was 3.5-fold above mean normal at Week 48
• Cohort 2, Patient 2 [began the study on ERT and was subsequently withdrawn from ERT at week 24]: α-Gal A activity was 10.3-fold above mean normal at Week 36. This represents a sustained α-Gal A expression compared with the 10-fold above mean normal levels previously exhibited as of November 9, 2021, with α-Gal A expression one week post ERT withdrawal.
• Cohort 3, Patient 1 [on ERT at the cutoff date]: α-Gal A activity measured at ERT trough was 16.7-fold above mean normal at Week 16
• Cohort 3, Patient 2 [on ERT at the cutoff date]: α-Gal A activity measured at ERT trough increased to within normal range at Week 2

“We are excited by the strong progress of our wholly owned Fabry program, which we believe places us in a leading position to offer patients a compelling potential therapy for their underlying disease,” said Nathalie Dubois-Stringfellow, Ph.D, Sangamo’s newly appointed Senior Vice President, Chief Development Officer. “We look forward to sharing an update on the additional patients dosed and continue to actively prepare for a potential Phase 3 trial.”