Specific β2AR Positive Allosteric Modulator

Example 11

The PAM activity of Cmpd-6 is specific for the β2AR. The specificity of Cmpd-6 for the β2AR was evaluated through in vitro agonist competition radioligand binding to the β1AR, the most closely related subtype of adrenergic receptors. In this assay, Cmpd-6 induces a minimal shift of the ISO competition curve for binding to the β1AR against the ¹²⁵I—CYP radiolabeled antagonist (FIG. 21A) unlike the robust ISO curve shift by Cmpd-6 observed with the β2AR. This displays that Cmpd-6 specifically induces the high affinity binding of the orthosteric agonist ISO to the β2AR but not to the β1AR. Marginal changes were promoted by Cmpd-6 in the ISO dose response pattern of β1AR-mediated cAMP production (FIG. 21B), which is markedly different from that of the β2AR-mediated response. These findings clearly demonstrate that the PAM activity of Cmpd-6 is specific for the β2AR.