An experimental antidepressant from AstraZeneca and Targacept failed to meet the goal of changing a key depression rating score in the first of a number of late-stage clinical trials, the companies said on Tuesday.

The results relate to the so-called Renaissance 3 Phase III study into TC-5214, a flexible dose trial conducted in Europe.

TC-5214 is designed to work by modulating neuronal nicotinic receptors in the brain. Over-stimulation of these receptors is thought to be associated with depression.

(Reporting by Ben Hirschler)