First hemophilia B gene therapy approved: More than two decades in the making.

Competing Interests: Declaration of interests T.V. received funding from Takeda, Pfizer, and Catalyst Biosciences and speaker honoraria from Takeda, Pfizer, BioMarin, and Biotest; research grants for gene therapy (European Union Horizon 2020 UPGRADE project under grant agreement N°825825 and Vrije Universiteit Brussel – IOF GEAR). M.C.O. received funding from BioMarin, Novo Nordisk, Pfizer, Roche, Sanofi, and Takeda; speaker honoraria from BioMarin, Bayer, Biotest, Pfizer, Roche, and Takeda; and consulting payments from Bayer, BioMarin, Novo Nordisk, Pfizer, Roche, Sanofi, and Takeda. R.W.H. received grant funding from Spark Therapeutics and serves on scientific advisory boards or consultant for Intellia, Regeneron, Pfizer, BioMarin, and Prevail Therapeutics.