My system (Norton) flags the link as hazardous.

Extract from link below:

Gene therapy
Elliot was given an engineered virus that was filled with the instructions for manufacturing the missing factor IX. The virus acts like a microscopic postman that delivers the blueprints to the liver, which then starts producing the clotting protein. It was a one-off infusion that took about an hour to drip into Elliott's body. He recalls being "astonished" to see the amount of factor IX in his blood go from only 1% of normal levels to normal.

[bbc.com]