Provided herein are neuropeptide-2 receptor agonists of the formula (I): as well as pharmaceutically acceptable salts, derivatives and fragments thereof, wherein the substituents are as those disclosed in the specification. X is 4-oxo-6-(1-piperazinyl)-3(4H)-quinazoline-acetic acid (Pqa). These compounds, and the pharmaceutical compositions containing them, are useful for the treatment of diseases such as, for example, obesity and diabetes.