Pfizer and its biotech partner Spark Therapeutics have announced the beginning of a Phase III trial of their gene therapy for haemophilia B, fidanacogene elaparvovec. Actually, it’s the pre-beginning phase because this step is a structured evaluation of the efficacy and safety of current factor IX prophylaxis in the usual care setting. The aim is to provide 6 months of data against which gene therapy can be evaluated by within-patient comparisons. Nevertheless, the announcement marks a significant step in the development of gene therapy for haemophilia: Phase III trials are designed to quantify risks and benefits in the final investigational step that provides the evidence on which regulatory approval is decided. In May 2018, Pfizer and Spark announced interim data for 15 people with moderate or severe haemophilia B in a continuing Phase 1/2 trial of fidanacogene elaparvovec. All had discontinued routine infusions of factor IX concentrates with no reported serious adverse events.

Details of the study have been registered at – search for NCT03587116.

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