The primary objective is to determine whether daily dosing with NYX-2925 changes markers of central pain processing in subjects with fibromyalgia by evaluating changes in evoked pain, and visual stimulation, functional magnetic resonance imaging (fMRI), resting state function connectivity magnetic resonance imaging (rs-fcMRI) and proton magnetic resonance spectroscopy (H-MRS) in fibromyalgia subjects on active drug versus placebo.