May 11, 2015
An article published in the Orphanet Journal of Rare Diseases identifies the lysosomal diseases for which there is the greatest pressure to develop treatments. The article distinguishes the disorders for which therapies were successfully developed, received approval or orphan drug designation and those for which fewer or no therapies were approved. The authors highlight four factors playing a key role in successful orphan drug development or orphan drug designations: 1) prevalence of disease 2) endpoints 3) regulatory precedent (i.e. past approval), and 4) nature of treatment. Drugs for rare diseases with higher prevalence met with higher regulatory approval rates than treatments for ultra rare diseases or rare diseases with very low prevalence. Out of fourteen drugs for seven lysosomal storage disorders receiving FDA approval, ten were enzyme replacement therapies, one was a substrate reduction therapy and three were small molecular therapies facilitating lysosomal substrate transportation. The authors further reported that generally “drug development focused on more common diseases, (while) primarily neurological diseases were neglected”. They also observed that “small clinical trials with either somatic or biomarker endpoints were successful and that “enzyme replacement therapy was the most successful technology”.