Historically, market authorisations for neurological diseases have had significantly lower rates of success compared with other indications.
Between 2000 to 2015, the likelihood of approval for neurological drugs that entered phase 1 trials (8.4%) was below the mean across all indications (9.6%) and far below haematology (26.1%) and infectious diseases (19.1%). When considering neurodegenerative diseases and specifically Alzheimer’s disease (AD), the rate is even lower with only four drugs: donepezil; galantamine; memantine, and rivastigmine approved between 1996 and 2020.
These drugs, however, only treat the disease’s symptoms rather than the causes. This has largely been due to a lack of understanding of the mechanisms behind disease pathogenesis, with advances in AD happening at a significantly slower rate relative to other diseases. Despite being first discovered over 100 years ago, the complexity of the brain and limitations surrounding research/diagnostic methods and models have acted as barriers for AD drug development.
Recently, however, this trend has begun to shift. In 2021, while cancer drugs accounted for 30% of all new FDA approvals, neurology saw the second most approvals for the third time in a row (10%). The AD pipeline in particular saw major advancements with the (controversial) FDA accelerated approval of Biogen’s Aduhelm (aducanumab) in 2021, the first amyloid-targeting antibody for AD. The FDA approval of Eisai’s Leqembi (lecanemab) in July 2023 – with Lilly’s donanemab submitted but awaiting a currently delayed advisory committee meeting in 2024 (both of which also target amyloid) – continue to highlight the advancements happening in AD therapeutics.
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