Therapeutic development approaches to treat haploinsufficiency diseases: restoring protein levels.

Rare diseases affect one in ten people but only a small fraction of these diseases have an FDA-approved treatment. Haploinsufficiency, caused by a dominant loss-of-function mutation, is a unique rare disease group because patients have one normal allele of the affected gene. This makes rare haploinsufficiency diseases promising candidates for drug development by increasing expression of the normal gene allele, decreasing the target protein degradation and enhancing the target protein function. This review summarizes recent progresses and approaches used in the translational research of therapeutics to treat haploinsufficiency diseases including gene therapy, nucleotide-based therapeutics and small-molecule drug development. We hope that these drug development strategies will accelerate therapeutic development to treat haploinsufficiency diseases.