The emergence of gene therapy for rare diseases

Introduction: Gene therapy is emerging from a checkered past to success in several diseases, most of them are rare. Currently, the goal of most gene therapy trials is gene replacement, gene correction or knockdown of gene products for monogenetic diseases via viral vectors that cure or slow disease progression. The definition can be broadened to include nonviral vectors, such as antisense oligonucleotides and small interfering RNA, to control too much gene expression. Gene modification of stem cells is also a gene therapy and works by providing cells with corrected genes.Areas covered: Diseases that have been shown to benefit from gene therapy in clinical trials include adenosine deaminase-severe combined immunodeficiency (ADA-SCID), X-linked SCID, homozygous familial hypercholesterolemia, lipoprotein lipase deficiency, Leber’s congenital amaurosis and adrenoleukodystrophy. There is reason for the optimism that gene therapies will eventually provide treatments and perhaps cures for disease that currently have no or inadequate therapies. Many rare diseases may benefit.Expert opinion: This resurgence of hope for gene therapy applications is based on several recent positive approvals and ongoing trials for gene therapy with positive results. Here we consider orphan drugs and orphan status/designations that are currently being tested.