Australia-based biotechnology company CSL (ASX:CSL)(USOTC:CSLLY) announced on Friday the results from its four year HOPE-B study confirming the long-term durability and safety of a one-time infusion of HEMGENIX (etranacogene dezaparvovec-drlb) for adults living with haemophilia B. study, confirming the long-term durability and safety of a one-time infusion of HEMGENIX (etranacogene dezaparvovec-drlb) for adults living with haemophilia B at the 18th Annual Congress of the European Association for Haemophilia and Allied Disorders (EAHAD).

Data showed that through four years, HEMGENIX continues to deliver elevated and sustained factor IX activity levels, can offer long-term and greater bleed protection compared to prophylactic treatment, can eliminate the need for routine factor IX prophylaxis, and maintains a favourable safety profile.

Approved in 2022 by the US Food and Drug Administration (FDA), HEMGENIX is the first gene therapy for the treatment of adults with haemophilia B who currently use factor IX prophylaxis therapy, or have current or historical life-threatening bleeding, or have repeated, serious spontaneous bleeding episodes. It is also the only approved gene therapy for haemophilia B that can treat adult patients with and without AAV5 neutralising antibodies thereby providing the potential for a greater number of eligible patients to be treated.

In the Phase III, open-label, single-dose, single-arm HOPE-B trial, 54 adult male participants with severe or moderately severe haemophilia B, with or without preexisting AAV5 neutralising antibodies, were infused with a single dose of HEMGENIX. Of the 54 participants who received HEMGENIX, 51 completed four years of follow-up. HEMGENIX produced mean factor IX levels of 41.5 IU/dL (n=50) at year one, 36.7 IU/dL (n=50) at year two, 38.6 IU/dL (n=48) at year three and 37.4 IU/dL (n=47) at year four post-infusion. In addition, mean adjusted annualised bleeding rate (ABR) for all bleeds was reduced by approximately 90% from lead-in (4.16, n=54) as compared to year four (0.40, n=51). Furthermore, joint bleeds were reduced from a mean ABR of 2.34 at lead-in to 0.09 during year four. In year four, 94% of patients remained free of continuous prophylaxis treatment. No patients returned to continuous prophylaxis between year three and year four.