On Jan. 8, 2025, UC San Diego announced that it is offering a newly Food and Drug Administration-approved gene therapy for hemophilia B, a rare blood disorder that causes excessive bleeding. The therapy entails a single infusion designed to reduce bleeding and increase clotting factor levels in the blood. It provides patients with a potential one-time treatment option that targets the genetic cause of the condition.
Hemophilia B is caused by a mutation in the gene responsible for producing clotting factor IX, a protein essential for blood clotting. Patients with the disorder face long-term risks of excessive bleeding and require regular intravenous infusions of clotting factor concentrates.
Symptoms of hemophilia B include nosebleeds, prolonged bleeding after an injury, unexplained bleeding, large bruises, and blood in urine or stool. If left untreated, hemophilia B can be fatal and lead to life-threatening bleeding episodes.
Dr. Annette von Drygalski, an expert in hemophilia and director of UCSD Health’s Center for Bleeding and Clotting Disorders, said it took years of work to find a potential cure for hemophilia B.
UCSD was involved in Phase I, II, and III clinical trials to evaluate the safety and efficacy of this gene therapy. Its contributions were key in advancing the therapy toward FDA approval
“This represents over 30 years of effort to potentially bring a cure to those affected by hemophilia B, specifically in clotting factors VIII or IX. While it is not yet a cure, it is at least providing long-term expression,” said von Drygalski.
The treatment involves a one-time infusion of Hemgenix, a gene therapy medicine created by Dutch biotechnology company uniQure. This carries a virus holding a functional copy of the factor IX gene. The virus transfers the copy to the patient’s liver cells, where replication begins outside the cells and increases production of the factor IX protein. After the therapy, the body begins clotting normally.
One of the risks associated with the new gene therapy is the liver’s possible rejection of the infusion, requiring patients to take steroids like prednisone for extended periods — sometimes for several months.
“It’s a two-hour infusion,” von Drygalski said. “Some patients may require steroids to prevent the body from rejecting the therapy as it targets the liver, which can recognize it as foreign and attempt to reject it. Others may need immunosuppression for the same reason.”
In May 2024, UCSD’s Center for Bleeding and Clotting Disorders performed its first patient infusion of the gene therapy on a male in his 60s. He no longer requires at-home treatment and is showing significant improvement after years of suffering from bleeding and joint pain.
The potential impact of gene therapy is notable, offering patients hope for a more manageable life.
“This is a breakthrough because, think about it: If you had to self-administer an infusion several times a week to replace the missing factor, it would be incredibly time-consuming,” von Drygalski said. “Imagine having to set aside time every day just to complete the infusion. This therapy can help people lead a more normal life.”
UCSD is actively negotiating with insurance companies to make the therapy more accessible to patients.
