Trial details
In ATLAS-A/B, 80 male patients were randomized to prophylactic fitusiran once monthly and 40 to continue with clotting factors as needed for bleeding. Just over 20% had hemophilia B, the rest hemophilia A. The mean age was 34 years, and subjects had a mean of about 12 bleeds in the 6 months leading up to the study.
Half of the fitusiran group had no treated bleeds during the study period versus only 5% in the control arm.
The five treatment emergent serious adverse events in the fitusiran arm included cholelithiasis in two subjects, plus cholecystitis, lower respiratory tract infection, and asthma in one each. Two fitusiran patients discontinued treatment because of cholecystitis and increased alanine aminotransferase.
ATLAS-INH had the same study design, and investigated patients with inhibitors; again, just over 20% had hemophilia B, the rest A. Mean age was 28 years, and patients had a mean of about 13 bleeds over the 6 months before the study. A total of 38 subjects were randomized to fitusiran, and 19 to bypassing agents as needed.
Almost 66% of fitusiran patients had no treated bleeds versus about 5% in the control arm.
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Dr. Guy Young
There “was far less bleeding both for hemophilia A and B. It’s definitely a clinically meaningful and important” effect, said ATLAS-INH lead investigator Guy Young, MD, director of the hemostasis and thrombosis program at Children’s Hospital Los Angeles.
He said the improved quality of life with fitusiran noted in both trials was “not surprising. If you only have to dose once a month subcutaneously, and you are not bleeding, of course your quality of life is going to improve.”
Both fitusiran thrombotic events occurred in ATLAS-INH. One patient developed deep vein thrombosis, subclavian vein thrombosis, and superficial thrombophlebitis but stayed in the study. Another discontinued after developing suspected spinal vessel thrombosis. Serious adverse events among five other subjects included acute cholecystitis and hematuria.
Fitusiran was associated with liver enzyme elevations in both trials, but they were generally mild to moderate.
The studies were funded by fitusiran maker Sanofi Genzyme. Several investigators were employees. Dr. Pipe is a consultant, Dr. Srivastava is a researcher and adviser, and Dr. Young is a speaker and consultant for the company and disclosed honoraria from it. Dr. Key had no relevant disclosures.