(Bloomberg) -- England’s thrifty drug-cost regulator endorsed one of the world’s most expensive medicines — a one-time infusion that frees hemophilia patients from regular  treatments — for a limited period while the product’s effectiveness remains under scrutiny. 

The agreement uses an outcomes-based payment model and is the first of its kind that will give patients access to CSL Behring’s hemophilia B treatment. The drug, Hemgenix, is also the first to get a recommendation under the Innovative Medicines Fund, an arrangement that pays for new treatments while more efficacy data is collected. 

The payment model gives the NHS the “necessary assurances of value and financial protection,” said Sujan Sivasubramaniyam, head of medical affairs and patient advocacy in the UK & Ireland at CSL Behring. 

Hemophilia B is a genetic bleeding disorder where a key clotting protein is either missing or not working properly. Over 2,000 people in the UK live with the condition, with roughly over 200 of those eligible for the new gene therapy. Hemgenix is a one-time infusion that corrects the gene that isn’t working as it should. It’s not intended for patients with the more common hemophilia A. 

Hemgenix was granted a conditional marketing authorization in the UK in 2023, and is one of the world’s most expensive drugs with a list price of $3.5 million — the same cost as Pfizer Inc.’s competing gene therapy. The UK usually negotiates steep discounts before rolling out new medicines on the NHS. 

The drug-cost regulator recommended against the use of Hemgenix in draft guidance last year, saying there was a need for more long-term evidence on how well it works. At the time, the cost effectiveness was also deemed above what the National Institute for Health and Care Excellence considers “an acceptable use of NHS resources.”

There has been reluctance to use the Innovative Medicines Fund because if the data on its efficacy isn’t convincing, its manufacturer has to keep paying for patients to stay on the treatment. Because Hemgenix is used only once, CSL Behring doesn’t run that risk. 

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