What’s Next in Hemophilia Treatment: Gene Therapy
Hemophilia is a genetic bleeding disorder which reduces the blood’s ability to clot properly, leading to spontaneous bleeding or excessive bleeding after injury.1 There are two main types of hemophilia – A and B. Hemophilia almost exclusively affects males, and it’s estimated between 20,000 and 33,000 people in the United States have the disease.1-3 Signs and symptoms include bleeding in joints or muscles, bruising, and frequent nosebleeds.1 You can learn more about hemophilia in our patient condition guide.
According to the Centers for Disease Control and Prevention, the best way to treat hemophilia is to replace the missing blood clotting factor so that the blood can clot properly.4 This is typically done by injecting treatment products, called clotting factor concentrates, into a person's vein. Since the mid-1990s, these intravenous (IV) therapies have been the mainstay of hemophilia treatment, with patients requiring infusions as frequently as 2 to 3 times each week.
Fortunately, the need for this lifelong therapy may soon change with the advent of gene therapies for hemophilia. There currently are three gene therapies for hemophilia A and two gene therapies for hemophilia B in late-phase development, and it’s expected the first gene therapy for hemophilia could be approved as soon as 2022.
Five Things To Know About Hemophilia Gene Therapy
1. The underlying nature of hemophilia makes it a perfect candidate for gene therapy. Currently, gene therapy can only treat diseases caused by a mutation of a single gene. Hemophilia fits this bill, with the F8 or F9 gene being responsible for clotting factor deficiency. It’s also easier to cure disease by replacing a gene, which is the case with hemophilia, rather than silencing or repairing one. Even small increases in protein production (in this case, clotting factor) resulting from gene therapy can have a significant effect on the course of disease.
2. A single treatment could cure a patient. Gene therapies for hemophilia are intended to be one-time IV infusions. In gene therapy, a functional version of the F8 or F9 gene is delivered to a patient’s liver cells, which should allow the patient to begin producing enough clotting factor on his or her own to prevent bleeding episodes without the need for IV factor replacement. Data from clinical trials suggests these therapies can increase natural factor production in patients for several years after administration, resulting in significantly reduced annualized bleed rates and a decrease or total elimination of factor infusions.5
3. Not all hemophilia patients will be good candidates for gene therapy. Clinical trials so far have been limited to patients who have moderate or severe disease and no inhibitors or autoantibodies (immune-mediated complications that can arise in some people with hemophilia). If real-world use is similar to those included in the trials, that could mean up to 30% of hemophilia A patients and 3% of hemophilia B patients would be ineligible for gene therapy.5 Even if a patient’s disease characteristics seem suitable for gene therapy, it is difficult to predict to what extent they will respond and produce factor even after receiving a functional replacement gene.6
4. Treatment will be very expensive. It has been estimated that the per-patient price for hemophilia gene therapy could be in the range of $2-3 million.6 Although this price seems astronomical, a $2 million price tag for a gene therapy that could eliminate the need for routine factor replacement may actually be more cost-effective given the high cost of factor products.
5. Specialty pharmacists could still play an important role in the care of hemophilia patients even after gene therapy. There is potential for specialty pharmacies to participate in the distribution chain for gene therapy. Additionally, specialty pharmacists could serve as a vital resource for patients by providing ongoing disease management and education, as well as long-term outcomes monitoring.
It is an exciting time for patients affected by hemophilia, with the dream of a cure potentially becoming a reality very soon.
Sources:
1 Centers for Disease Control and Prevention. What is Hemophilia? Accessed on June 29, 2021 from cdc.gov/ncbddd/hemophilia/facts.htmll.
2 National Hemophilia Foundation. Hemophilia A. Accessed on June 29, 2021 from hemophilia.org/bleeding-disorders-a-z/types/hemophilia-a.
3 National Hemophilia Foundation. Hemophilia B. Accessed on June 29, 2021 from hemophilia.org/bleeding-disorders-a-z/types/hemophilia-b.
4 Centers for Disease Control and Prevention. Treatment of Hemophilia. Accessed on June 30, 2021 from cdc.gov/ncbddd/hemophilia/treatment.html.
5 ASH Clinical News. Gene therapy for hemophilia: progress and setbacks. November 1, 2020. Accessed July 2, 2021 from ashclinicalnews.org/spotlight/feature-articles/gene-therapy-hemophilia-progress-setbacks/.
6 Perrin GQ, Herzog RW, Markusic DM. Update on clinical gene therapy for hemophilia. Blood. 2019;133(5):407-414.
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