VTX-801 is a novel experimental gene therapy that will be assessed in a phase 1/2 clinical trial evaluating its safety and efficacy when administered as a single intravenous infusion in adults with Wilson disease. Wilson disease is a rare genetic disease that results in the impairment of the liver’s ability to manage copper levels. The disease has the potential to cause serious liver damage, neurological problems, and death.1 

VTX-801 is manufactured by Pfizer in collaboration with Vivet Therapeutics, and it has been granted Orphan Drug designation (ODD) by the US Food and Drug Administration (FDA) and European Commission (EC) as well as Fast Track designation by the FDA. The FDA’s Fast Track program speeds up the evaluation of novel potential medicines that are intended to cure serious illnesses and address unmet medical needs while also facilitating their development.1

Mechanism of Action

Patients with Wilson disease have a defective ATP7B gene. VTX-801 contains a corrected form of the ATP7B gene. An adeno-associated virus (AAV) vector delivers the corrected form of the gene into liver cells without causing infection.2 

This recombinant AAV (rAAV) vector-based gene therapy has been shown to deliver functional protein with the ability to restore copper homeostasis, restore liver damage, and decrease copper buildup in the brain in a mouse model of Wilson disease. The rAAV serotype used in VTX-801 was chosen because of its demonstrated tropism for transducing human liver cells.1

Read more about experimental therapies for Wilson disease

Ongoing Clinical Trial

The GATEWAY trial (NCT04537377)3 is an open-label, multicenter, nonrandomized phase 1/2 clinical trial that will evaluate the safety, tolerability, and efficacy of a single intravenous infusion of VTX-801 in adult patients with Wilson disease, both before and after background Wilson disease therapy withdrawal.4

The study aims to enroll 16 adult patients with Wilson disease, and it will investigate up to 3 doses of VTX-801. Patients will take part in an observational predosing period and receive a prophylactic steroid treatment. The primary endpoint is the safety and tolerability profile of VTX-801 52 weeks after a single infusion. Secondary endpoints include changes in disease-related indicators, such as serum ceruloplasmin activity and free serum copper levels, as well as radiocopper-related parameters and VTX-801 responder status to enable standard-of-care withdrawal.1 

The name “GaTeWay” stands for “Gene Therapy for Wilson Disease.” The study makes an effort to determine the safety and most appropriate dosage of VTX-801 to restore naturally occurring copper excretion in the long term.2 

VTX-801 will be administered as a single dose to patients in a hospital setting. Over the course of the following 12 months, patients will visit their study center on multiple occasions to allow the research team to evaluate their progress. Such visits will happen more frequently in the first year of the study and less frequently in the following years. After the preliminary 1-year trial phase, the study will run for another 4 years. This will be essential to determine the long-term efficacy of VTX-801.2 

More details on the eligibility criteria of the study can be found using the registered clinical trials number: NCT04537377.

References

  1. VTX-801 receives U.S. FDA Fast Track designation for the treatment of Wilson disease. Vivet Therapeutics and Pfizer Inc; August 12, 2021.
  2. Introducing Gateway, a clinical trial for Wilson Disease. Vivet Therapeutics. Accessed September 19, 2022.
  3. A phase I/II study of VTX-801 in adult patients with Wilson’s disease (GATEWAY). ClinicalTrials.gov. September 3, 2020. Updated August 5, 2022. Accessed September 19, 2022.
  4. Vivet Therapeutics’ clinical-stage gene therapy, VTX-801 receives US FDA Fast Track designation to treat Wilson disease. Pharmabiz.com. August 13, 2021. Accessed September 19, 2022.

Reviewed by Kyle Habet, MD, on 9/27/2022.