Drug can prevent bleeding in hemophilia A and B
In addition, there was preliminary evidence of reduced bleeding, with a 49% to 100% reduction in estimated ABR during the observation period compared with pre-study values.
Safety results
As of July 11, 2016, fitusiran appears to be generally well tolerated in hemophilia patients, with or without inhibitors (n=31, with 5 patients participating in both Parts B and C).
There have been no serious adverse events related to the drug and no thromboembolic events or laboratory evidence of pathologic clot formation.
One non-inhibitor patient in Part C treated with the 80 mg fixed dose discontinued treatment due to an adverse event that was considered severe and possibly related to the study drug.
This event was described as non-cardiac chest pain and was accompanied by transient elevations of ALT (10x upper limit of normal), AST (8x upper limit of normal), C-reactive protein, and D-dimer, without an increase in total bilirubin. The event resolved with symptomatic management, including antacids and analgesics.
Eleven patients (35%) reported mild, drug-related injection site reactions, which were mostly pain or erythema at the injection site.
Additional adverse events reported in at least 10% of patients included upper respiratory tract infection (10%) and arthralgia (10%). The majority of these events were mild or moderate in severity. 
