Expanded access: opening doors to personalized medicine for rare disease patients and patients with neurodegenerative diseases.

In neurodegenerative diseases, a select set of neuron population displays early vulnerability and undergoes progressive degeneration. The heterogeneity of the cerebral cortex and the heterogeneity of patient populations diagnosed with the same disease offer many challenges for developing effective and long-term treatment options. Currently, patients who are considered to have a 'rare' disease are left with no hopes for cure, and many of the neurodegenerative diseases progress fast without any effective solutions. However, as our understanding of disease mechanisms evolve, we begin to realize that the boundaries between diseases are not as sharp as once believed. There are many patients who develop disease due to common underlying causes and mechanisms. As we move forward with drug discovery effort, it becomes obvious that we will have to shift our focus from finding a cure for a disease, to finding solutions to the disease-causing cellular mechanisms so that patients can be treated by mechanism-based strategies. This paradigm shift will lay the foundation for personalized medicine approaches for neurodegenerative disease patients and patients diagnosed with a rare disease.