CSL Behring up as FDA approves hemophilia B gene therapy

With a list price of $3.5 million, Hemgenix (etranacogene dezaparvovec) becomes the most expensive single-dose drug and the first gene therapy approved for hemophilia B.

The US Food and Drug Administration (FDA) gave CSL Behring’s one-time gene therapy the thumbs up yesterday to treat adults with hemophilia B, a rare bleeding disorder caused by a gene defect that results in insufficient production of blood clotting protein factor IX.

“We are thrilled to witness this milestone in hemophilia B treatment,” said Kim Phelan, COO of The Coalition for Hemophilia B. “Over the years we have seen a variety of advancements for the hemophilia community, but gene therapy is the first treatment option to offer those living with hemophilia B – and caregivers – the possibility of freedom from the need for regular, ongoing infusions.”

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Hemgenix is based on a recombinant adeno-associated viral (AAV) vector of serotype 5 (AAV5) gene therapy that contains the Padua variant of a codon-optimized human FIX complementary deoxyribonucleic acid (AAV5-Padua hFIX).

Hemgenix’ global rights were added to Australia-based CSL Behring’s product pipeline in June 2020 through a deal with UniQure that netted the latter $450 million upfront and a potential $1.6 billion depending on progress.

Under terms of the deal, the gene therapy was to continue to be manufactured at uniQure’s Lexington, Massachusetts site. The 80,000 square-foot facility was named in the FDA’s approval letter as the approved source of manufacture for Hemgenix’s drug substance and drug product. The final drug product labeling and packaging takes place at a CSL Behring facility undisclosed in the FDA letter.

Hemgenix has a list price of $3.5 million, making it the most expensive one-time therapy in the world, overtaking bluebird bio’s Skysona (elivaldogene autotemcel, or eli-cel), which had a list price of $3 million following its approval in September.