Among people with hemophilia A or B (PwHA/B), fitusiran appears to be both safe and effective for reducing bleeding risk, according to research presented at the EHA 2023 Hybrid Congress.

Fitusiran is a subcutaneously administered investigational drug that targets antithrombin, with the potential to rebalance homeostasis regardless of patient inhibitor status. Previous work suggested that fitusiran may reduce the annualized bleeding rate (ABR) compared with episodic/on-demand treatment.

For this open-label phase 3 ATLAS-PPX study ( Identifier: NCT03549871), researchers compared the safety and efficacy of fitusiran with that of prior clotting factor concentrate (CFC)/bypassing agent (BPA) prophylaxis among PwHA/B, with or without inhibitors.

Continue Reading

Overall, 80 patients were enrolled, of whom 65 were eligible for analysis. Of these, 19 had inhibitors, 50 had hemophilia A, and 15 had hemophilia B.

Analysis showed that the median ABRs were 0 with fitusiran vs 4.4 with CFC/BPA. Moreover, 63.1% of patients in the fitusiran group had 0 bleeds; the ABR reduction rate with fitusiran was, furthermore, 61.1% (P =.0008).

Patients who received fitusiran also had improved health-related quality of life scores compared with CFC/BPA.

Nine (13.4%) patients in the fitusiran group, however, had serious adverse events, compared with 7.7% in the CFC/BPA group (n=5). Alanine aminotransferase or aspartate transaminase elevations to more than 3 times the upper limit of normal were observed in 25.4% of patients in the fitusiran group. Suspected or confirmed thromboembolic events, furthermore, occurred in 3% of patients who received fitusiran.

Disclosures: This research was supported by Sanofi. Some study authors declared affiliations with biotech, pharmaceutical, or device companies. Please see the original reference for a full list of disclosures.


Kenet G, Nolan B, Zulfikar B, et al. A phase 3 study (ATLAS-PPX) to evaluate efficacy and safety of fitusiran in people with haemophilia A or B who have switched from prior clotting factor concentrate or bypassing agent prophylaxis. EHA 2023. June 8-11, 2023. Abstract S303.