Novel Gene Therapy Better at Targeting the Heart Shows Promise for Fabry Disease, Preclinical Data Suggest

A novel gene therapy developed by 4D Molecular Therapeutics can increase gene delivery to the heart without triggering an immune response, according to preclinical data.

The gene therapy candidate is anticipated to enter human clinical trials in 2020.

The findings were presented in a scientific poster, “A Novel Cardiotropic AAV Variant 4D-C102 Demonstrates: Superior Gene Delivery and Reduced Immunogenicity in Cardiac Tissues Versus Wildtype AAV in Non-Human Primates, and Results in Functional GLA in Cardiomyocytes and Fabry Fibroblasts,” during the 6th International Update on Fabry Disease, May 26–28 in Prague, Czech Republic.

Fabry disease is caused by mutations in the GLA gene, which codes for the alpha-GalA enzyme. These mutations result in the accumulation of fatty molecules known as Gb3 and lyso-Gb3 inside cells, which leads to renal, cardiac, and/or cerebrovascular disease. Cardiovascular disease is the most common cause of mortality for patients with Fabry disease, accounting for 75% of all known deaths.

The current standard treatment for patients with Fabry is enzyme replacement therapy, but it requires lifelong and regular infusions that may not be effective in all tissues.

Adeno-associated viruses (AAV) are naturally occurring, harmless viruses used to deliver gene therapies. However, current AAV vectors in development for Fabry disease “traffic predominantly to the liver and are not targeted to heart tissue,” the researchers wrote.

As such, 4D Molecular Therapeutics (4DMT) developed a new AAV variant (known as 4D-C102) that can efficiently deliver genes to the heart and directly target the cause of heart disease. 4D-C102 carries a luciferase gene — an enzyme that produces bioluminescence — so that researchers can “see” it light up in the organs of interest.

A single injection of 4D-C102 into the veins of mice resulted in a rapid expression of the luciferase gene (within 15 days) which lasted for two months. The vector was expressed in target tissues including the heart and liver in a dose-dependent manner. This means that as the gene therapy dose increased, the level of fluorescence increased accordingly.

Similarly, a single injection of 4D-C102 into non-human primates showed better delivery and lower immune responses in the heart compared with conventional AAV viral constructs. In both of these cases, a 10-fold lower dose of 4D-C102 was used than the dose currently used in AAV-based clinical trials for neuromuscular gene therapy.

Furthermore, 4D-C102 showed a greater ability to deliver the luciferase gene to human heart muscle cells in vitro than conventional AAV constructs.

To evaluate the ability of 4D-C102 to infect human cells that are relevant to Fabry disease, the researchers infected fibroblasts (a type of connective tissue cell) derived from Fabry patients.

This time the 4D-C102 vector carried the healthy version of the GLA gene, and its name was modified to 4D-310. Increasing the dose of 4D-310 delivered to these fibroblasts resulted in an increase of alpha-GalA enzyme expression and function in vitro.

“The data generated using the novel vector, 4D-C102, and the 4D-310 Fabry product candidate using that vector, helps validate 4DMT’s Therapeutic Vector Evolution approach for in vivo cardiac tissue targeting,” Gabriel Brooks, MD, vice-president of clinical research and development at 4DMT, said in a press release. “This data package also provides the basis of a preclinical data package that we believe will enable commencement of clinical development of our Fabry product candidate.”

Peter Francis, MD, PhD, the company’s chief medical officer, added: “4DMT is building upon our Therapeutic Vector Evolution platform with the goal of ultimately bringing gene therapy products to patients with severe genetic diseases. We are pleased to present these data as an early demonstration of our platform’s ability to potentially address neuromuscular diseases.”