What should I consider if I am interested in participating in an investigational gene therapy clinical trial for hemophilia?
First, let’s take a look at what investigational means. This is a term that refers to a potential treatment that is being studied in clinical trials, but not approved by regulatory agencies, such as the Food and Drug Administration, or FDA. In clinical trials, scientists are studying to see if the investigational therapy is safe and effective, how much is needed, and how it may be used for that disease. Please consult with your doctor if you want to know more about participating in a clinical trial.
Your doctor and healthcare team will explain the different clinical trial designs, the screening and eligibility criteria, and the potential benefits and risks of participating in gene therapy research. There are multiple types of investigational gene therapies in clinical trials. For now, we’ll focus on explaining the adeno-associated virus, or AAV, clinical trials for hemophilia.
First, a little background on AAV: AAV vectors are commonly chosen for investigational hemophilia gene therapy clinical trials for many reasons, such as they are not known to cause human disease and they have a natural ability to travel to the liver, where factor is typically produced. Once the vector reaches its destination, it delivers a new functional gene to the liver cells that are intended to make factor VIII or factor IX clotting protein.
The type of AAV vector used may differ in each clinical trial. There are a variety of naturally occurring AAVs that can be modified or bioengineered for use as vectors. Another potential difference between investigational gene therapy clinical trials is amount, or dose, of vector given. How a gene therapy dose is measured is different than what you may be used to for currently available hemophilia treatments.
A gene therapy dose is measured by number of vectors. Typically, a dose can contain billions, trillions, or even quadrillions of vectors! While that may sound like a lot, let’s look at it another way. Did you know that there are 240 billion cells in the liver? With so many cells in the liver, there needs to be billions or trillions of vectors to reach as many of those cells as possible.
When dosing involves such large numbers of vectors, the amount of vector given may be different between clinical trials. In the case of hemophilia, researchers are searching to find potential doses that may be safe and effective for the treatment of certain patients with hemophilia.
Finally, the outcomes, or endpoints, used to measure safety and efficacy may be different in clinical trials. Some examples of endpoints in investigational gene therapy hemophilia clinical trials include measuring how much of a specific blood clotting factor is produced and for how long, how many bleeding episodes occur, and the number of factor infusions needed after gene therapy administration.
These are just a few key considerations in evaluating investigational gene therapy clinical trials for hemophilia—it’s a lot to consider!
That’s why it's important to discuss clinical trials and any results with your doctor to understand the differences.
You can also find information on websites like this one, and also at ClinicalTrials.gov, the National Hemophilia Foundation, the Hemophilia Federation of America, and the World Federation of Hemophilia. Many advocacy groups also offer both live and virtual educational programs.
Wherever you are in your hemophilia journey, discuss your questions about clinical trials for hemophilia with your doctor so you can be informed and feel empowered.