On the heels of last summer's phase IIb failure of TC-5214 in overactive bladder – a disappointment that pushed shares to a then-52-week low of $2.76 – and a string of other duds with neuronal nicotinic receptors (NNRs), Targacept Inc. said top-line results from a phase I/II exploratory study of TC-6499 as a treatment for diabetic gastroparesis also missed its primary endpoint and the program will be discontinued.