Alzheimer’s disease (AD) continues to be the most prominent cause of dementia for millions of sufferers worldwide. With no effective cure on the market and only one FDA-approved therapy in the last 18 years, Alzheimer’s disease research proves notoriously complex where the development of effective therapeutics is concerned. In light of World Alzheimer’s Month, this analysis examines the landscape of AD clinical trials spanning the last five years and the effect the Covid-19 pandemic has had on research.

The greatest proportion of clinical trials are in Phase I (42.9%), followed by Phase II trials with 38.4%, and only 13.6% and 5.1% of studies in Phase III and Phase IV, respectively. With the overwhelming majority of research efforts in early-phase studies, we observe the difficulty in clinical trial progression to later stages. During this period, as shown in Figure 1, the highest number of trials were observed in 2018, with the lowest numbers obtained in 2017. Unsurprisingly, the greatest single-year rise in the number of trials was observed between 2017 and 2018. During this period, North America had the highest proportion of trials (37%) and proves to be the most popular region for clinical trial conduct. Asia-Pacific follows closely in second place with 36.6%, with Europe in third place with 23.2% of trials. Where country-wise distribution is concerned, the US assumes lead position throughout.

Over the last five years, industry-sponsored trials have dominated the AD research landscape with 66.4% of studies relative to their non-industry counterparts holding 33.6% of trials. Industry focus on AD is expected given the lack of effective therapeutics. Any potential breakthrough candidates will monopolise a market with a relatively large patient population. In June 2021, the FDA granted Biogen ’s Aduhelm accelerated approval, the first AD treatment to receive approval since 2003. Aduhelm has a unique status as the first therapy to target the AD disease pathway via reduction of amyloid-beta plaques, a hallmark of AD. However, the approval has been met with some disapproval, with critics arguing that the data presented from pivotal clinical trials fail to display sufficient efficacy, with fears that the drug may be administered to a large patient population with minimal benefit. Nevertheless, Aduhelm may serve to determine whether the amyloid-beta reduction is a suitable surrogate endpoint for the determination of efficacy in AD research.

Owing to the Covid-19 pandemic and consequent clinical trial disruption, we would have expected the number of trial initiations in 2020 to be significantly lower than that of previous years. However, the variation is minor with a proportional difference of 0.3%, as shown in Figure 1. Fewer trial terminations and withdrawals were listed in 2020 as compared with 2019 and sponsors may have therefore been able to minimise the disruptive effects of the pandemic on the conduct of trials. As AD is a debilitating chronic disease with no cure, the continuation of research is vital in validating insight gained from clinical trials. The increased uptake of decentralised trials and virtual technologies is a key method utilized to mitigate the disruptive effects of the pandemic, with a 60% increase in the use of these strategies observed from 2019 to 2020. AD trials are well suited to adapting to pandemic challenges as many of the endpoints are related to cognitive assessments that can be assessed virtually or through decentralized means. During the pandemic, mobile healthcare and telemedicine proved to be the most widely utilized decentralized/virtual trial technique and can be of real benefit to trial participants. The more flexible schedule reduces the transport burden for participants and caregivers, making trials more accessible to a wider population. The increased uptake of decentralized trials may ultimately allow for increased research participation, making progress in the field all the more likely.