The neurokinin NK2 receptor is known to pre-exist in equilibrium between at least three states: resting-inactive, calcium-triggering, and cAMP-producing. Its endogeneous ligand, NKA, mainly induces the calcium response. Using a FRET-based assay, we have previously discovered an allosteric modulator of the NK2 receptor that has the unique ability to discriminate among the two signaling pathways: calcium-signaling is not affected while cAMP signaling is significantly decreased. A series of compounds have been prepared and studied in order to better understand the structural determinants of this allosteric functional switch of a GPCR. Most of them display the same allosteric profile, with smooth pharmacomodulation. One compound however exhibits significantly improved modulatory properties of NKA induced signaling when compared to the original modulator.