Dive Brief:

• Merck & Co. announced after market close on Tuesday that it has discontinued another Phase 3 study for its Alzheimer's disease treatment verubecestat (MK-8931).
• The decision to pull the plug was made after an external Data Monitoring Committee deemed it unlikely that there would be a positive risk/benefit profile should the trial continue.
• The APECS study was a late-stage trial in prodromal — or very early — Alzheimer's disease. Nearly a year ago to the day, Merck had discontinued the Phase 3 EPOCH trial of verubecestat in mild-to-moderate patients also due to lack of efficacy. 

Dive Insight:

Verubecestat is just the latest in a long line of Alzheimer's drug failures. Developing a disease-modifying drug for the debilitating neurodegenerative disease has been particularly tricky, and players from the biggest pharma to the smallest biotechs have seen major trial blow-ups in late stages.

What might be the most frustrating part is that many compounds showed promising results in early- and mid-stage studies, only to show no effect in large, expensive Phase 3 trials.

The need for a treatment for Alzheimer's disease is great, and only rising as the population ages and people live longer. Should any company reach the market with a disease-modifying drug it would be a multi-billion dollar blockbuster. 

Verubecestat, like many of the other Alzheimer's drugs that have failed, targets the beta amyloid plaques that form in the brain. One of the prevailing theories is that these plaques accumulate and clump, causing the debilitating neurological symptoms and severe memory loss associated with the disease. Yet, other researchers argue the plaques that form are not the cause, but rather a symptom of the disease. 

Hope remains

Despite the many failures in Alzheimer's disease, there are still a number of big pharma and big biotech companies conducting clinical trials in the space.

Evercore ISI analyst Umer Raffat in a note told investors the Merck failure is not a positive read-through to other candidates in development, but that there are some key differences in patient populations in clinical trials that could potentially impact the outcome.

A candidate from Eisai Inc. and Biogen Inc., aducanumab, has been considered particularly promising by investors and has been closely watched in the clinic.

Data on the drug — and a make-or-break moment for Biogen  — is expected in 2019.