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Results Announced for Clotting Factor Candidate in Hemophilia B

Drug prevents and controls bleeding in phase III trial (Sept. 26)

On September 26, Biogen Idec, based in Weston, Mass., announced positive results from its phase III B-LONG clinical study of a new recombinant clotting factor candidate — Factor IX Fc (rFIXFc) — in patients with hemophilia B. Hemophilia B is a rare inherited disorder that impairs blood coagulation.

The study showed that rFIXFc was effective in the prevention and control of bleeding, in routine prophylaxis, and in perioperative management. Recombinant FIXFc was generally well-tolerated. Additional analyses of the B-LONG study are ongoing, and Biogen anticipates presenting further data at a future scientific meeting. The company plans to submit a biologics license application (BLA) to the FDA in the first half of 2013.

The B-LONG trial was a global, open-label, multicenter phase III study that evaluated the efficacy, safety, and pharmacokinetics of intravenously injected rFIXFc. The study was designed to evaluate rFIXFc in the control and prevention of bleeding, in routine prophylaxis, and in perioperative management in patients with hemophilia B.

The study had four treatment arms. In arm 1 (weekly prophylaxis; n = 63), patients were treated weekly with a starting dose of 50 IU/kg, which was adjusted to maintain trough factor levels sufficient to prevent bleeding. In arm 2 (individualized-interval prophylaxis; n = 29), patients were treated with 100 IU/kg at an initial interval of 10 days, which was subsequently individualized to maintain trough factor levels sufficient to prevent bleeding. In arm 3 (episodic treatment; n = 27), patients received rFIXFc episodic treatment as needed for bleeding. In arm 4 (perioperative management; n = 12 patients), rFIXFc was evaluated in the surgical setting; 8 patients in the surgery arm were also enrolled in other treatment arms.

The primary efficacy and safety measures were the annualized bleeding rate and the incidence of adverse events and of inhibitor development in patients studied for up to 77 weeks. Secondary endpoints included the response to treatment of rFIXFc and the pharmacokinetics of rFIXFc versus BeneFIX (coagulation Factor IX, recombinant).

A total of 123 male patients aged 12 years and older were enrolled, and 93.5% of the participants completed the study.

Recombinant FIXFc was generally well-tolerated. No inhibitors of rFIXFc were detected, and no cases of anaphylaxis were reported in any patients, all of whom switched from commercially available Factor IX products. One serious adverse event was possibly related to the drug. The patient experienced obstructive uropathy in the setting of hematuria; he continued rFIXFc treatment, and the event resolved with medical management.

The most common adverse events (incidence of 5% or greater) occurring outside of the perioperative management arm (i.e., arms 1, 2, and 3, but not arm 4) were nasopharyngitis, influenza, arthralgia (joint pain), upper respiratory infection, hypertension, and headache.

The overall median annualized bleeding rates (including spontaneous and traumatic bleeds) were 2.95 in the weekly-prophylaxis arm, 1.38 in the individualized-interval prophylaxis arm, and 17.69 in the episodic-treatment arm. In the individualized-interval prophylaxis arm, the median dosing interval during the last 6 months of the study was 14 days.

Control of bleeding was assessed in all patients who experienced a bleeding episode during the study. Overall, 90.4% of bleeding episodes were controlled by a single injection of rFIXFc.

Recombinant FIXFc was assessed in the perioperative management of 12 patients undergoing 14 major surgical procedures. The treating physicians rated the hemostatic efficacy of rFIXFc as good or excellent in all of these surgeries.

The B-LONG trial included a pharmacokinetic (PK) analysis. In a protocol-defined subset of patients with extensive PK sampling, the approximate terminal half-life of rFIXFc was 82 hours compared with 34 hours for BeneFIX.

For more information, visit the Biogen Idec Web site.

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