Updated Follow-up of the Alta Study, a Phase 1/2 Study of Giroctocogene Fitelparvovec (SB-525) Gene Therapy in Adults With Severe Hemophilia

Updated Follow-up of the Alta Study, a Phase 1/2 Study of Giroctocogene Fitelparvovec (SB-525) Gene Therapy in Adults With Severe Hemophilia
Highlights From the 62nd ASH Annual Meeting and Exposition

Updated Follow-up of the Alta Study, a Phase 1/2 Study of Giroctocogene Fitelparvovec (SB-525) Gene Therapy in Adults With Severe Hemophilia A

Andrew D. Leavitt, MD1, Barbara A. Konkle, MD2,3, Kimo Stine, MD4, Nathan Visweshwar, MD5, Thomas J. Harrington, MD6, Adam Giermasz, MD, PhD7, Steven Arkin, MD8, Annie Fang, MD, PhD9, Frank Plonski, RN, MA8, Lynne Smith, MBA10, Li-Jung Tseng, PhD, MBA9, Gregory Di Russo, MD8, Bettina M Cockroft, MD11, Jeremy Rupon, MD10 and Didier Rouy, MD, PhD11

1University of California, San Francisco, CA

2University of Washington, Seattle, WA

3University of Washington, Washington Center for Bleeding Disorders, Seattle, WA

4UAMS at Arkansas Children's Hospital, Little Rock, AR

5University of South Florida, Tampa, FL

6University of Miami Miller School of Medicine, Miami, FL

7University of California Davis, Sacramento, CA

8Pfizer Inc, Cambridge, MA

9Pfizer Inc, New York, NY

10Pfizer Inc, Collegeville, PA

11Sangamo Therapeutics, Brisbane, CA

Key Data Points

STUDY DESIGN

The phase 1/2 study for SB-525 was a dose escalation, 4-dose cohort design, with 2 participants at each of the lower doses and 5 participants at the highest dose, 3 x 1013 vg/kg. Follow-up durations range from 1 to 3 years post-infusion except for 1 participant in cohort 3 (1 x 1013 vg/kg) who prematurely discontinued the study (lost to follow-up).

ALT ELEVATION IN COHORT 4 (3 x 1013 vg/kg)

ALT elevations were the most common adverse event, occurring in 5 of the 11 participants and 4 of the 5 participants at the highest dose in cohort 4. These 4 participants were treated with steroids for durations ranging from 6 to 16 weeks. A second ALT elevation was seen in 3 of these 4 participants.

EFFICACY FOR COHORT 4

FVIII activity using the chromogenic assay for the 5 participants in cohort 4, the highest dose cohort. Post-infusion follow up ranges from 52 to 82 weeks. For weeks 9-52, the median FVIII activity was 56.9% and the mean was 70.4% (as determined for 4 of 5 cohort 4 participants with assessment at 52 weeks).

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