Study of lentiviral gene therapy for X-linked CGD underway

A Phase I/II clinical trial that involves using a lentiviral vector as a curative treatment for X-linked chronic granulomatous disease is underway in the U.S., with four patients out of five doing well after the procedure. The trial is based on studies currently in progress in the United Kingdom, where four patients have been treated, with three surviving.

The gene therapy process uses a patient’s own blood-forming stem cells, which are removed and modified to correct the genetic defect that causes X-linked CGD. The lentiviral delivery system is used to insert a normal copy of the missing gene into the blood stem cells. Once treated, the modified blood stem cells are transplanted back into the patient, where they produce functional white blood cells.

Lentiviral vector gene therapy treatment is similar to a bone marrow transplant (BMT), in that patients must undergo a full dose of chemotherapy to remove their remaining blood stem cells to “make space” for the gene-corrected ones to grow. However, unlike traditional BMT, or hematopoietic stem cell transplantation (HSCT), the cells being inserted back into the patient are their own, rather than donor cells.

“The advantage is that there's no chance of graft vs. host [disease] because we use the patient's own cells,” said Dr. Donald Kohn, professor of pediatrics in the UCLA David Geffen School of Medicine, professor of microbiology, immunology and molecular genetics in Life Sciences at UCLA, member of the UCLA Children’s Discovery and Innovation Institute at Mattel Children’s Hospital and the principal investigator on the trial. “This means there is also less risk of infection because we do not need to give immunosuppressant drugs.”

While the therapy holds great potential, it is still in the clinical trial phase and is not yet approved by the Food and Drug Administration (FDA). As a result, the trial is only open to patients who lack a fully matched bone marrow or cord blood donor and have had a serious infection.

In the meantime, clinical trials are ongoing at three U.S. locations, including Boston Children’s Hospital, UCLA, and the National Institutes of Health (NIH). The trial at the NIH is led by Dr. Elizabeth Kang and Dr. Harry Malech, two well-known experts in the CGD community.

“Hopefully, this treatment will be approved in the next two to four years,” said Dr. Kohn.