Alzheimer's Disease and the "Valley of Death": Not Enough Guidance from Human Brain Tissue?

Medical science is currently perceived as underperforming. This is because of the relatively slow recent rate of development of new disease treatments. This has been blamed on cultural, regulatory, and economic factors that generate a so-called "Valley of Death", hindering new drug candidates from being moved into clinical trials and eventually approved for use. We propose, however, that for neurodegenerative diseases, a relative decline of human brain tissue research is also a contributor. The present pharmacological agents for treating Alzheimer's disease (AD) were identified through direct examination of postmortem human brain tissue more than 30 years ago. Since that time the percentage of research grants awarded to human brain tissue-using projects has dropped precipitously and publication rates have stagnated. As human brain tissue research has played a central and often initiating role in identifying most of the targets that have gone to AD clinical trials, it is proposed that the rate of discovery of new targets has been curtailed. Additionally, the continued rejection of cortical biopsy as a diagnostic method for AD has most probably depressed the perceived effect sizes of new medications and contributed to the high Phase II clinical trial failure rates. Despite the relative lack of funding, human brain discovery research has continued to make important contributions to our understanding of neurodegenerative disease, and brain banks have played an essential role. It is likely that the pace of discovery will dramatically accelerate over the coming decades as increasingly powerful tools including genomics, epigenetics, transcriptomics, regulatory RNA, gene expression profiling, proteomics, and metabolomics are applied. To optimize the promise of these new technologies, however, it is critical that brain banks are rejuvenated by enhanced governmental and/or private support.