US drug giant Merck & Co has kicked off a mid-stage study of an experimental drug designed to treat patients with Alzheimer's disease.

The Whitehouse Station, New Jersey-based group said this week that it has started a Phase II/III clinical trial to assess the safety and efficacy of MK-8931 in patients with mild-to-moderate forms of the illness.

The global, multicenter study, called EPOCH, will first look at the safety of the drug in 200 patients before advancing into the full-scale Phase III trial, which aims to enrol around 1,700.

The company will be hoping that EPOCH meets its primary efficacy targets of significant changes from baseline in the Alzheimer's Disease Assessment Scale Cognitive Subscale and Alzheimer's Disease Cooperative Study – Activities of Daily Living scores.

BACE inhibition

MK-8931 is novel drug that inhibits the enzyme BACE, which is believed to play a key role in the production of the amyloid beta that accumulates in the brain to form amyloid plaques in patients with the disease.

According to Merck, evidence suggests that inhibiting BACE could reduce amyloid plaque formation and modify the progression of Alzheimer's disease.

Earlier this year a Phase I study showed that MK-8931 decreased cerebral spinal fluid beta-amyloid by more than 90% in healthy volunteers, raising hopes of a new treatment for this disease.