Sangamo Therapeutics Announces Updated Preliminary Phase 1/2 Data in Fabry Disease Showing Continued Tolerability and Sustained Elevated α-Gal A Enzyme Activity in Nine 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 July 21, 2022 cutoff date, the investigational treatment continued to be generally well tolerated, with no treatment-related serious adverse events. The nine patients in the dose escalation phase exhibited elevated alpha-galactosidase A (α-Gal A) activity, sustained for up to 23 months for the patient with the longest follow-up.

These updated data will be shared today via an oral presentation at the 29^th Congress of the European Society of Gene & Cell Therapy – ESGCT 2022 – from 8:30-10:40 a.m. British Summer Time (Ref: OR21). These data are also available on Sangamo’s website on the Events & Presentations page.

“I’m encouraged by these results, showing isaralgagene civaparvovec gene therapy has reassuring safety data to date, with no requirement for corticosteroid therapy,” said Dr Patrick Deegan, MD, Cambridge University Hospitals NHS Foundation Trust, and investigator of the Phase 1/2 study. “ST-920 has the potential to provide an alternative to enzyme replacement therapy for patients with Fabry disease. I look forward to seeing additional data as we continue to progress this important program.”

As of the cutoff date, all nine patients treated in the dose escalation phase across the four dose cohorts (0.5e13 vg/kg, 1e13 vg/kg, 3e13 vg/kg and 5e13 vg/kg), sustained elevated α-Gal A activity ranging from nearly 2-fold to 30-fold of mean normal at the last date of measurement.

Cohort 1

• Patient 1 [began the study on ERT and was subsequently withdrawn from ERT at month 19]: α-Gal A activity was 30.4-fold of mean normal at Month 23.
• Patient 2 [ERT pseudo-naïve]: α-Gal A activity was 1.9-fold of mean normal at Month 18.

Cohort 2

• Patient 3 [ERT pseudo-naïve]: α-Gal A activity was 3.7-fold of mean normal at Month 16.
• Patient 4 [began the study on ERT and was subsequently withdrawn from ERT at week 24]: α-Gal A activity was 7.9-fold of mean normal at Month 12.

Cohort 3

• Patient 5 [began the study on ERT and was subsequently withdrawn from ERT at week 29]: α-Gal A activity was 14.7-fold of mean normal at Week 35.
• Patient 6 [began the study on ERT and was subsequently withdrawn from ERT at week 20]: α-Gal A activity was 4.8-fold of mean normal at Week 26.
• Patient 7 [on ERT]: α-Gal A activity measured at ERT trough was 8.4-fold of mean normal at Week 12.

Cohort 4