Results of a safety review have led to the discontinuation of phase 3 clinical studies of elenbecestat, an investigational oral BACE (beta amyloid cleaving enzyme) inhibitor, which was being assessed for early Alzheimer disease (AD) treatment. 

The decision to halt the trials was made after the Data Safety Monitoring Board found an unfavorable risk-benefit ratio. The phase 3 program consisted of two studies, MISSION AD1 and MISSION AD2

Both studies randomized a total of ~2100 patients with mild cognitive impairment or mild AD who had confirmed amyloid pathology in the brain, to receive either elenbecestat 50mg or placebo daily during the treatment period of 24 months; Clinical Dementia Rating-Sum of Boxes score was designated as the primary end point in both trials.

Additional data from the studies will be presented at  future medical meetings, according to the Companies. A long-term extension trial evaluating elenbecestat will also be discontinued.

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Over the past year, several clinical trials investigating other BACE inhibitors have been discontinued due to safety issues (atabecestat, umibecestat, verubecestat) or futility (lanabecestat).

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