Bluebird bio has announced updated results from a clinical development programme evaluating its investigational Lenti-D gene therapy in patients with cerebral adrenoleukodystrophy (CALD).

The primary efficacy endpoint in the study is the proportion of patients who are alive and free of major functional disabilities at month 24. Of those patients who have or would have reached 24 months of follow-up and completed the study, 88% continue to be alive and major functional disabilities-free in a long-term follow-up study.

Further data show that three out of the 32 treated patients did not or will not meet the primary efficacy endpoint; two patients withdrew from the study at “investigator discretion,” and one experienced rapid disease progression early on-study resulting in MFDs and death.

The company also announced that the 14 patients currently on-study have less than 24 months of follow-up and have shown no evidence of MFDs.

“With the longest follow-up from the Phase II/III Starbeam study now up to five years, the data show that all boys with CALD who were treated with Lenti-D and were free of major functional disabilities at 24 months continued to be major functional disabilities -free,” explained David Davidson, chief medical officer of the company.

He continued, “Importantly, there were no reports of graft failure or treatment-related mortality, and adverse events were generally consistent with myeloablative conditioning. These results support the potential of Lenti-D as a treatment for CALD, which we hope may become an option for the boys and their families affected by this devastating disease.”

CALD is the most severe manifestation of adrenoleukodystrophy (ALD), a rare metabolic disorder. Approximately 35-40% of boys diagnosed with ALD will progress to CALD, typically between the ages of three and 12 years. It is characterised by a rapidly progressive neurologic decline leading to severe loss of neurologic function and death, in most untreated patients.