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US approval for haemophilia drug derived from genetically engineered rabbit's milk

Published on 02/04/20 at 11:00am
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The FDA has announced the approval of Sevenfact, a haemophilia therapy the active ingredient from which is expressed in genetically engineered rabbits – a first for the US regulator.

The product, developed by Laboratoire Francais du Fractionnement et des Biotechnologies, is indicated in the treatment and control of bleeding episodes in patients of at least 12 years old with haemophilia A or B with inhibitors.

The active ingredient in the drug is a recombinant analogue of human Factor VII, one of the clotting factors deficient or dysfunctional in patients with haemophilia A. The ingredient is expressed in the mammary gland of genetically altered rabbits and is secreted in their milk. By processing and purifying the milk, the ingredient is converted into activated FVII, or FVIIa.

While introduction of appropriate clotting factors may treat continuous or uncontrolled bleeding in affected patients, those who have developed antibodies, or inhibitors, to these factors may become resistant to their beneficial effects. Products like Sevenfact bypass the reaction to Factors VIII and IX in these patients and promotes clotting and controls bleeding.

It is estimated that around 20,000 people in the US live with a form of haemophilia today.

The recombinant DNA construct was given the go-ahead by the FDA’s Center for Veterinary Medicine. Steven M Solomon, Director at the Center, commented: "Based on a comprehensive analysis of the scientific evidence, the FDA determined that the rDNA construct inserted in the rabbit's genomic DNA is safe for the animal and for the people handling the rabbits, and is effective in causing Human Factor VII (hFVII) protein to be expressed in the rabbits' milk. The FDA has also determined under the National Environmental Policy Act that approval of the application will have no significant impact on the environment."

The approval was based on data drawn from 27 patients with haemophilia A or B with inhibitors, covering treatment of a total of 465 mild or moderate and three severe bleeding episodes.

It was found that around 86% of these mild or moderate cases were deemed to have been successfully treated 12 hours after the initial dose in both the lower 75mcg/kg dose and the higher 225mcg/kg dose. Furthermore, the three severe episodes were also successfully treated with the higher dose.

Matt Fellows

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