Australian CSL's US biotherapeutics subsidiary CSL Behring has reported positive results from its Phase III PROLONG-9FP clinical development programme of IDELVION to treat haemophilia B.

IDELVION is characterised by a long-acting, coagulation factor IX (Recombinant), Albumin Fusion Protein (rFIX-FP) and is intravenously administered into the bloodstream, and can also be self-administered or administered by a caregiver.

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After being administered, the rIX-FP remains in the blood circulation until the Factor IX is activated. The albumin is cleaved from Factor IX by releasing activated Factor IX during coagulation.

The Phase III is part of the PROLONG-9FP clinical development programme, which includes five phases designed as open-label, multicentre studies intended to test the safety and efficacy, as well as determine the pharmacokinetics profile of IDELVION in children and adults with haemophilia B.

"Results suggested adult patients achieving 5% to 10% of sustained factor IX activity levels experienced an almost 80% lower risk of bleeding events over one year."

Haemophilia B is a congenital bleeding disorder that occurs due to lack of or a defective factor IX. It may cause prolonged or spontaneous bleeding, especially into the muscles, joints, or internal organs.

A pooled analysis of the clinical programme tested the relationship between estimated factor IX activity levels and clinical bleeding risk in adult haemophilia B patients treated with IDELVION using prophylaxis or on-demand (episodic) treatment.

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Results suggested adult patients achieving 5% to 10% of sustained factor IX activity levels experienced an almost 80% lower risk of bleeding events over one year.

CSL Behring clinical pharmacology director John Roberts said: "This new analysis of Phase III IDELVION clinical trials shows a strong association between high and prolonged factor IX levels and efficacy of IDELVION in reducing bleeding risk in adult haemophilia B patients.

"These findings provide additional clinical rationale for targeting and maintaining factor IX trough activity levels above 5% or 10% to optimise treatment outcomes, aligning with World Federation of Haemophilia clinical guidelines for the management of haemophilia."