FDA Approves SKYSONA, Second Lentiviral Vector Gene Therapy in the U.S.

Hans-Peter Kiem, MD, PhD - September 20, 2022

The approval of SKYSONA® comes one month after the first lentiviral vector gene therapy, Zynteglo, was approved for use in the U.S.

The FDA granted accelerated approved to the gene therapy elivaldogene autotemcel (eli-cel) to slow the progression of the neurodegenerative dysfunction early, active cerebral adrenoleukodystrophy (CALD) in boys 4-17. Eli-cel, which will be marketed as SKYSONA®, is now the second lentiviral vector gene therapy for patients with severe genetic diseases in the U.S. and the first for CALD.

Eli-cel, developed by bluebird bio, uses ex-vivo transduction with the Lenti-D lentiviral vector to add functional copies of the ABCD1 gene into a patient’s own hematopoietic stem cells. The functional gene enables production of the ALD protein in the patient’s brain that can help break down fatty acids. Without the working protein, the nervous system can’t function properly, which can impair walking, speech, and vision. Nearly half of patients who do not receive treatment die within five years of symptom onset. Bluebird bio confirmed the previous clinical hold on the eli-cel clinical development program has been lifted.

This approval is a significant advancement for the field because it gives patients an alternative to allogeneic hematopoietic stem cell transplantation, which can be associated with serious complications, especially in patients without a human leukocyte antigen (HLA) matched donor.

As a condition of the accelerated approval, bluebird bio has agreed to provide confirmatory long-term clinical data to the FDA. bluebird anticipates that this will include data from commercially treated patients as well as data from an ongoing long-term follow-up study that will follow patients treated in clinical trials for 15 years.

Patients treated with SKYSONA had an estimated 72 percent likelihood of surviving for two years without any of six major functional disabilities associated with CALD, according to clinical trial data. The gene therapy will likely be available by the end of this year through qualified treatment centers including Boston Children’s Hospital and the Children’s Hospital of Philadelphia.

Dr. Kiem is president of ASGCT. He is also a professor of medicine and pathology and director of the stem cell and gene therapy program at the University of Washington, and the Stephanus Family Endowed Chair for Cell and Gene Therapy at the Fred Hutchinson Cancer Center.