bluebird bio Receives FDA Accelerated Approval for SKYSONA® Gene Therapy for Early, Active Cerebral Adrenoleukodystrophy (CALD)

SKYSONA is the first FDA approved therapy shown to slow the progression of neurologic dysfunction in boys with this devastating and fatal neurodegenerative disease

SOMERVILLE, MA, USA I September 16, 2022 I bluebird bio, Inc. (Nasdaq: BLUE) today announced the U.S. Food and Drug Administration (FDA) has granted Accelerated Approval of SKYSONA® (elivaldogene autotemcel), also known as eli-cel, to slow the progression of neurologic dysfunction in boys 4-17 years of age with early, active cerebral adrenoleukodystrophy (CALD). The Company also confirmed that the previous clinical hold on the eli-cel clinical development program has been lifted.

CALD is a rare, progressive, neurodegenerative disease that primarily affects young boys and causes irreversible, devastating neurologic decline, including major functional disabilities such as loss of communication, cortical blindness, requirement for tube feeding, total incontinence, wheelchair dependence, or complete loss of voluntary movement. Nearly half of patients who do not receive treatment die within five years of symptom onset. Prior to the approval of SKYSONA treatment, effective options were limited to allogeneic hematopoietic stem cell transplant (allo-HSCT), which is associated with the risk of serious potential complications including death, that can increase dramatically in patients without a human leukocyte antigen (HLA) matched donor.

“Children with CALD and their families have been at the heart of bluebird’s mission since the company was founded more than a decade ago,” said Andrew Obenshain, chief executive officer, bluebird bio. “For the ALD community, this long-awaited approval represents significant hope and offers families a new option where, for many, there had been none. We are grateful to every individual who was involved in the development of SKYSONA and are committed to working with providers and payers to make this important treatment option available to patients and their families.”

“The agony of watching your child slip away is something no parent should have to bear,” said Elisa Seeger, co-founder, ALD Alliance. “We have made significant strides in providing children diagnosed with CALD the best chance at life with early identification of ALD through expanded newborn screening. Yet with limited treatment options, early diagnosis is still cause for despair instead of hope for many families. Today, parents whose boys receive a CALD diagnosis can have renewed hope for the future.”

“CALD strikes young boys in the prime of their development, robbing them of core neurologic functions necessary for survival. That is an unimaginable reality for any parent, and as a clinician, it is heartbreaking to have limited treatment options for these children and their families,” said David A. Williams, MD, Chief, Division of Hematology/Oncology, Boston Children’s Hospitali. “After supporting the clinical development of SKYSONA for nearly a decade as a study site, Boston Children’s Hospital is extremely pleased that an FDA-approved therapy is now available for children who urgently need new therapies.”

“As one of the largest and most experienced pediatric gene therapy and stem cell transplant programs in the world, the University of Minnesota is committed to expanding access and advancing care and research for patients with rare diseases like ALD,” said Paul Orchard, MD, a pediatric blood and marrow transplant physician at the University of Minnesota Medical School and M Health Fairview Masonic Children’s Hospital. “It’s crucial for these patients and families to have another therapeutic option for cerebral ALD beyond blood stem cell transplantation utilizing cells from another donor, and we’ve seen firsthand the impact that gene therapy has on our patients. We are encouraged by progress we’re making to treat these rare and devastating diseases.”

As a condition of the SKYSONA Accelerated Approval, bluebird has agreed to provide confirmatory long-term clinical data to the FDA. bluebird anticipates that this will include data from the ongoing long-term follow-up study (LTF-304), which follows patients treated in clinical trials for 15 years, and from commercially treated patients.

bluebird anticipates that commercial product will be available by the end of 2022 through a limited number of Qualified Treatment Centers (QTCs) in the United States, including Boston Children’s Hospital and Children’s Hospital of Philadelphia.

bluebird has set the wholesale acquisition cost of SKYSONA in the U.S. at $3.0M. Additional information is available through bluebird’s patient support program, my bluebird support, which will provide personalized support for patients and their families related to all aspects of the gene therapy journey. Caregivers of patients with CALD can visit or call 833-888-NEST (833-888-6378) Monday-Friday between 8 a.m. and 8 p.m. ET to ask questions and enroll.

The SKYSONA Biologics License Application (BLA) was reviewed by the U.S. FDA under Priority Review, and bluebird received a rare pediatric priority review voucher upon approval. SKYSONA was previously granted Orphan Drug designation, Rare Pediatric Disease designation, and Breakthrough Therapy designation.

SKYSONA Clinical Data

The approval of SKYSONA is based on data from bluebird bio’s Phase 2/3 study ALD-102 (Starbeam) (N=32) and Phase 3 ALD-104 (N=35) study.

Both open-label, single-arm studies enrolled patients with early, active CALD who had elevated very long chain fatty acid (VLCFA) values, a Loes score between 0.5 and 9 (inclusive), and gadolinium enhancement on magnetic resonance imaging (MRI) of demyelinating lesions. Additionally, patients were required to have a neurologic function score (NFS) of ≤ 1, indicating limited changes in neurologic function. The efficacy of SKYSONA was compared to a natural history population.

Per protocol, patients treated with SKYSONA were assessed using the NFS and monitored for the emergence of six Major Functional Disabilities (MFDs) associated with CALD progression including loss of communication, cortical blindness, requirement for tube feeding, total incontinence, wheelchair dependence, or complete loss of voluntary movement.

The Accelerated Approval of SKYSONA is based on 24-month MFD-free survival. A post-hoc enrichment analysis in symptomatic patients assessed MFD-free survival from onset of symptoms (NFS ≥ 1) in SKYSONA treated (N=11) and untreated patients (N=7). SKYSONA treated patients had an estimated 72 percent likelihood of MFD-free survival at 24 months from time of first NFS ≥ 1, compared to untreated patients who had only an estimated 43 percent likelihood of MFD-free survival.

The most common non-laboratory adverse reactions (incidence ≥ 20%) are mucositis, nausea, vomiting, febrile neutropenia, alopecia, decreased appetite, abdominal pain, constipation, pyrexia, diarrhea, headache, and rash. The most common Grade 3 or 4 laboratory abnormalities (≥40%) include leukopenia, lymphopenia, thrombocytopenia, neutropenia, anemia, and hypokalemia. Please see SKYSONA Important Safety Information below, including a Boxed Warning for Hematologic Malignancy.

Enrollment is complete and all patients have been treated in both studies; follow-up in ALD-104 is ongoing. All patients who complete 24 months of follow-up in studies ALD-102 or ALD-104 are encouraged to participate in a long-term follow-up study (LTF-304) to continue monitoring safety and efficacy outcomes in boys treated with SKYSONA through 15 years post-treatment. On September 15, 2022, the FDA lifted the clinical hold that was put in place August 2021, prior to the completion of its review of the SKYSONA Biologics License Application.

About Cerebral Adrenoleukodystrophy (CALD)

CALD is a progressive and irreversible neurodegenerative disease that primarily affects young boys. The disorder is caused by mutations in the ABCD1 gene that affect the production of adrenoleukodystrophy protein (ALDP) and subsequently leads to accumulation of very long-chain fatty acids (VLCFAs), primarily in the white matter of the brain and spinal cord. This accumulation leads to the breakdown of myelin, the protective sheath that nerve cells need to function effectively, especially for thinking and muscle control. The onset of symptoms of CALD typically occurs in childhood (median age 7). Early diagnosis and treatment of CALD is essential, as nearly half of patients who do not receive treatment die within five years of symptom onset.


SKYSONA is indicated to slow the progression of neurologic dysfunction in boys 4-17 years of age with early, active cerebral adrenoleukodystrophy (CALD). Early, active cerebral adrenoleukodystrophy refers to asymptomatic or mildly symptomatic (neurologic function score, NFS ≤ 1) boys who have gadolinium enhancement on brain magnetic resonance imaging (MRI) and Loes scores of 0.5-9.

This indication is approved under accelerated approval based on 24-month Major Functional Disability (MFD)- free survival. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial(s).

Limitations of Use

SKYSONA does not prevent the development of or treat adrenal insufficiency due to adrenoleukodystrophy.

An immune response to SKYSONA may limit the persistence of descendent cells of SKYSONA, causing rapid loss of efficacy of SKYSONA in patients with full deletions of the human adenosine triphosphate binding cassette, sub family D, member 1 (ABCD1) transgene.

SKYSONA has not been studied in patients with CALD secondary to head trauma.

Given the risk of hematologic malignancy with SKYSONA, and unclear long-term durability of SKYSONA and human adrenoleukodystrophy protein (ALDP) expression, careful consideration should be given to the appropriateness and timing of treatment for each boy, especially for boys with isolated pyramidal tract disease based on available treatment options since their clinical symptoms do not usually occur until adulthood.

Please see full Prescribing Information for SKYSONA, including BOXED WARNING and Medication Guide.

Investor Conference Call Information

bluebird bio will host a call for analysts and investors on Monday, September 19, 2022, at 8:00 a.m. ET. Please note that there is a new process to access the call via telephone. To register online and receive a dial in number and unique PIN to access the live conference call, please follow this link

The live webcast of the call may be accessed by visiting the “Events & Presentations” page within the Investors & Media section of the bluebird website at A replay of the webcast will be available on the bluebird website for 90 days following the event.

About SKYSONA® (elivaldogene autotemcel), also known as eli-cel

SKYSONA is a one-time gene therapy custom-designed to treat the underlying cause of cerebral adrenoleukodystrophy (CALD). SKYSONA uses ex-vivo transduction with the Lenti-D lentiviral vector (LVV) to add functional copies of the ABCD1 gene into a patient’s own hematopoietic stem cells (HSCs). The addition of the functional ABCD1 gene allows patients to produce the ALD protein (ALDP), which can then participate in the local degradation of very long-chain fatty acids (VLCFAs). This degradation of VLCFAs is believed to slow or possibly prevent further inflammation and demyelination.

About bluebird bio, Inc.

bluebird bio is pursuing curative gene therapies to give patients and their families more bluebird days. With a dedicated focus on severe genetic diseases, bluebird has industry-leading clinical and research programs for sickle cell disease, beta-thalassemia and cerebral adrenoleukodystrophy and is advancing research to apply new technologies to these and other diseases. We custom design each of our therapies to address the underlying cause of disease and have developed in-depth and effective analytical methods to understand the safety of our lentiviral vector technologies and drive the field of gene therapy forward.

Founded in 2010, bluebird has the largest and deepest ex-vivo gene therapy data set in the world—setting the standard for industry. Today, bluebird continues to forge new paths, combining our real-world experience with a deep commitment to patient communities and a people-centric culture that attracts and grows a diverse flock of dedicated birds. ​

For more information, visit or follow us on social media at @bluebirdbio, LinkedIn, Instagram and YouTube.

SKYSONA and bluebird bio are trademarks of bluebird bio, Inc.

i Dr. David Williams, Chief of Hematology/Oncology at Boston Children's Hospital served as a Principal Investigator for SKYSONA clinical studies. He has consulted for bluebird bio but has not consulted for the SKYSONA (also known as eli-cel) technology.

SOURCE: bluebird bio

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