Clinical trials in rare disease: challenges and opportunities.

The neuronal ceroid lipofuscinoses constitute one of many groups of rare childhood diseases for which disease-modifying treatments are nonexistent. Disease-specific barriers to therapeutic success include incomplete understanding of disease pathophysiology and limitations of treatments that cannot adequately cross the blood-brain barrier to access the central nervous system. Therapeutic development in the neuronal ceroid lipofuscinoses shares many challenges with other rare diseases, such as incomplete understanding of natural history to inform trial design, need for alternatives to the randomized controlled clinical trial, requirement for more sensitive outcome measures to quantify disease, limited access to resources required to mount a clinical trial (including funding), and difficulties of recruiting a small sample to participation. Solutions to these barriers will require multicenter collaboration, partnership with patient organizations, training a new generation of researchers interested in rare diseases, and leveraging existing resources.