A new drug called verubecestat produced by Merck has passed an initial clinical hurdle, leading to ongoing Phase 3 trials
Current Alzheimer's treatment is fairly paltry, with little ability to slow disease progression or alleviate symptoms. However, a drug that targets BACE1, an enzyme that produces beta amyloid, may represent a small breakthrough in treatment.
Passing a hurdle
In a trial involving 32 people, verubecestat has proven able to reduce amyloid build up in the cerebrospinal fluid within a 1 or 2 week period. At the doses used in the study, it also appeared to have little negative side effects. This was initially a major concern, as previous attempts to silence BACE1 activity have had damaging consequences such as serious liver toxicity. Because the drug doesn't entirely block BACE1, it appears to lower production without triggering some more unpleasant side effects.
Targeting amyloid plaque formation has proved extremely difficult, and it has taken many years of drug development and trials to reach this point. Confounding variables and inaccurate targeting has meant that drug efficacy may have been masked, and it's still not clear the exact role amyloid plays in disease progression. Many scientists believe that it may kickstart the disease, but that once it's begun there are other factors that must be contended with too such as inflammation and tau tangles.
“It's really the first molecule of its kind to combine [amyloid]-lowering potency with a very positive safety profile that allows us to treat patients for the time needed to determine if there will be clinical benefits on cognition”
Now that verubecestat is in 2 long term phase 3 trials involving 3500 patients, we'll eventually see more definitive data. A big question that remains is whether these amyloid limiting treatments can help people in latter stages of the disease or whether they're exclusively a preventative treatment. As it stands that seems the more likely option, and many researchers believe that a successful Alzheimer's therapy will likely have to incorporate multiple drugs targeting amyloid production as well as other pathological processes. We are also awaiting more data on antibody therapies which may actively clear amyloid from the brain rather than inhibiting its production. It could be that these two strategies in conjunction are complementary.
Read more at The Scientific American