Bluebird’s Rare Childhood Neurodegenerative Gene Therapy Gains Accelerated Approval

A month after gaining FDA approval for Zynteglo, a customized gene therapy for a rare blood disorder, Bluebird is back at the approval table after receiving accelerated approval for Skysona, a bespoke gene therapy to treat cerebral adrenoleukodystrophy (CALD). Skysona’s approval marks the first FDA-approved therapy for treating the rare childhood neurodegenerative disease. 

A Speedy Path to Approval for a Debilitating Disease

CALD is a rare disease primarily in young boys affecting the ABCD1 gene that, through a chain of events, breaks down myelin, the protective layer of nerve cells that help control motor and cognitive function. The median onset age of CALD is seven, and nearly half of patients who do not receive treatment die within five years of diagnosis. 

Bluebird designed Skysona to slow the progression of CALD in boys aged four to 17 with early, active CALD, meaning the patients are either asymptomatic or mildly symptomatic based on standardized diagnostic tests. The FDA reviewed the Biologics License Application (BLA) under its Priority Review program and based the accelerated approval on data from the Phase ⅔ STARBEAM clinical trial. 

The STARBEAM clinical trial started in 2013 and consisted of 32 participants and measured the number of patients without Major Functional Disabilities (MFD) after 24 months. The FDA put the trial on clinical hold in August 2021 after three reports of myelodysplastic syndrome after the gene therapy treatment. The FDA lifted the hold on September 15, just before it approved the drug based on the clinical trials’ data. 

The FDA ultimately deemed the clinical trials convincing after Skysona demonstrated a 72% likelihood of MFD-free survival at 24 months. The study measured six signs of MFD to monitor patients, which included loss of communication, cortical blindness, the requirement for tube feeding, total incontinence, wheelchair dependence, or complete loss of voluntary movement. 

The Accelerated Approval Program requires companies who receive the designation to perform additional confirmatory trials to validate the drug’s safety and efficacy to receive regular approval. Bluebird committed to a 15-year post-treatment follow-up study to evaluate Skysona’s safety and efficacy.

Related Article: Bluebird Bio’s Zynteglo Becomes First FDA-Approved Gene Therapy For Beta-Thalassemia

Rolling the Treatment Out as Soon as Possible

With the FDA’s approval, Bluebird now has the opportunity to administer Skysona to patients in need across America. However, because the treatment is very complex, not every hospital or children’s hospital will have the opportunity to administer the specialized gene therapy. 

Bluebird anticipates that Skysona will be available by the end of 2022 only at a limited number of qualified treatment centers, which include Boston Children’s Hospital and Children’s Hospital of Philadelphia. The one-time treatment will come at a substantial cost of about $3 million, making it slightly more than its predecessor, Zynteglo, which has a price tag of $2.7 million. 

Skysona’s FDA approval is another leap forward in the revolutionary field of gene therapy. Bluebird’s Skysona is the first and only specialized treatment for CALD, which has a devastating impact on families around the globe. The novel treatment could provide reprieve for families and individuals with very few other options, thanks to Bluebird’s concerted effort to treat rare diseases with gene therapy technology.

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Author

Reed Slater