Guy Young, MD, Director of the Hemostasis and Thrombosis Program at Children’s Hospital Los Angeles, discusses an ATLAS-OLE subgroup analysis of fitusiran in patients with hemophilia.
Hemophilia is a rare bleeding disorder that slows the blood clotting process. People with this disorder experience prolonged bleeding following an injury or surgery. In severe cases, heavy bleeding occurs after minor trauma or in the absence of injury. Serious complications can result from bleeding into the joints, muscles, brain, or other internal organs. The major types of this disorder are hemophilia A and hemophilia B, caused by a deficiency of factor VIII and IX, respectively.
Fitusiran is the first antithrombin (AT)-lowering therapy approved by the FDA for the treatment of patients ages 12 years and older with hemophilia A and B, with or without factor VII or IX inhibitors. Fitusiran is a small interference RNA drug that inhibits antithrombin and promotes thrombin generation, restoring homeostasis and increasing blood clotting. It is administered subcutaneously with a 50mg dose.
A study presented at the 2026 International Society on Thrombosis and Haemostasis (ISTH) Congress aimed to assess the safety and efficacy of fitusiran AT-DR in a subgroup analysis by age group from the phase 3 open-label extension study ATLAS-OLE (NCT03754790).
A total of 286 males aged 12 years and older with severe hemophilia A and B, with and without inhibitors, received the AT-DR and were included in the safety analysis. The proportion of participants with any treatment-emergent (TEAEs) and serious adverse events were similar, irrespective of age. There were no treatment discontinuations due to TEAEs in the adolescent population. One of 60 adolescents, three of 266 adults and none of the three elderly participants experienced a thrombotic event. Additionally, no transaminase elevations greater than 3x ULN were reported in adolescents.
Efficacy analyses included 213 participants. Observed median annualized bleeding rate (ABR) were 3.7 in the adolescent population and 3.7 in both the adult and overall populations. A total of 40% of adolescents had no bleeds compared to 28.9% of adults. ABR and number of bleeds were significantly lower in the elderly population. However, it is noted that the sample size remains too small to support definitive conclusions.
For more information, click here.
To learn more about hemophilia and other rare hematologic disorders, visit https://checkrare.com/diseases/hematologic-disorders/