Merck ($MRK) is pressing forward with its controversial Alzheimer's treatment, and now it has signed a deal with Luminex ($LMNX) to develop a companion diagnostic that will screen patients for its ongoing clinical program. The blockbuster hopeful MK-8931 is designed to block an enzyme that helps produce beta amyloid peptide, believed to trigger Alzheimer's. Merck is in the midst of a Phase II/III trial of the drug, and Luminex's job is to craft and get approval for a diagnostic that will track two biomarkers in patients' cerebrospinal fluid, identifying those at risk for Alzheimer's who might benefit from MK-8931. FierceMedicalDevices story