Gene therapy success for X-CGD patients

People with a rare blood disease have been successfully treated using gene therapy of their own stem cells, it has been announced.

American and British research teams found that six of the nine people with X-linked Chronic Granulomatous Disease (X-CGD) treated with the new therapy went into remission and stopped other treatments.

People with CGD have a mutation in the CYBB gene, one of the five genes that white blood cells need to kill bacterial and fungal infections with a burst of chemicals. Without this defensive chemical burst, patients with the disease are susceptible to infections, some of which can be severe to life-threatening.

The only other treatment for CGD is a bone marrow transplant. However, it can be difficult to identify a healthy matched bone marrow donor, and transplant carries risks including graft versus host disease, infection and transplant rejection.

For the trial, senior author Dr Donald Kohn, of University of California Los Angeles (UCLA), worked with collaborators in the NHS, France-based Genethon, the US National Institute of Allergy and Infectious Diseases at the National Institutes of Health, and Boston Children’s Hospital.

The research, published in the journal Nature Medicine, involved restoring the activity of the defective NAPDH oxidase in the patient’s phagocytic cells by gene transfer using a lentiviral vector.

Nine patients aged 2 to 27 years – four in Europe and five in the USA – were treated in clinical trials. Seven, who were followed for 12 to 36 months after treatment, did not contract any new infections. Two patients died during the trial as a result of complications acquired prior to gene therapy treatment.

The seven surviving patients all remained free of new CGD-related infections, and six of them were able to discontinue their normal courses of preventive antibiotics.

“None of the patients had complications that you might normally see from donor cells and the results were as good as you'd get from a donor transplant, or better,” said Dr Kohn.

Since the paper was written, another four patients have been treated, all of whom are currently free of new CGD-related infections, and no complications have arisen.

Source: Kohn DB, Booth C, Kang EM, Pai SY, Shaw KL, Santilli G, Armant M, Buckland KF, Choi U, De Ravin SS, Dorsey MJ, Kuo CY, Leon-Rico D, Rivat C, Izotova N, Gilmour K, Snell K, Dip JX, Darwish J, Morris EC, Terrazas D, Wang LD, Bauser CA, Paprotka T, Kuhns DB, Gregg J, Raymond HE, Everett JK, Honnet G, Biasco L, Newburger PE, Bushman FD, Grez M, Gaspar HB, Williams DA, Malech HL, Galy A, Thrasher AJ; Net4CGD consortium. (2020) “Lentiviral gene therapy for X-linked chronic granulomatous disease”, Nature Medicine, doi: 10.1038/s41591-019-0735-5