Pharmacological characterization of olodaterol, a novel inhaled beta2-adrenoceptor agonist exerting a 24-hour-long duration of action in preclinical models.

The preclinical pharmacological profile of 6-hydroxy-8-[(1R)-1-hydroxy-2-[[2-(4-methoxyphenyl)-1,1-dimethylethyl]amino]ethyl]-2H-1,4-benzoxazin-3(4H)-one monohydrochloride (olodaterol, previously known as BI 1744 CL), a novel, enantiomeric pure, inhaled human beta(2)-adrenoceptor (hbeta(2)-AR) agonist, was compared with marketed drugs, such as salmeterol and formoterol. In vitro, olodaterol showed a potent, nearly full agonistic response at the hbeta(2)-AR (EC(50) = 0.1 nM; intrinsic activity = 88% compared with isoprenaline) and a significant selectivity profile (241- and 2299-fold [corrected] against the hbeta(1)- and hbeta(3)-ARs, respectively). Likewise, olodaterol was able to potently reverse contraction induced by different stimuli in isolated human bronchi. In vivo, antagonistic effects of single doses of olodaterol and formoterol were measured against acetylcholine challenges in anesthetized guinea pigs and dogs for up to 24 h by using the Respimat Soft Mist inhaler. Heart rate and metabolic parameters (serum potassium, lactate, and glucose) were monitored to evaluate systemic pharmacodynamic effects in the dog model. In both models, olodaterol provided bronchoprotection over 24 h. Formoterol applied at an equally effective dose did not retain efficacy over 24 h. In both models olodaterol showed a rapid onset of action comparable with formoterol. Taken together, the preclinical behavior of olodaterol suggests that this novel beta(2)-AR agonist has the profile for once-daily dosing in humans concomitant with a fast onset of action and a favorable systemic pharmacodynamic profile.

Virally encoded G protein-coupled receptors: targets for potentially innovative anti-viral drug development.

Various herpes- and poxviruses contain DNA sequences encoding proteins with homology to cellular chemokine receptors, which belong to the family of G protein-coupled receptors (GPCRs). Since GPCRs play a crucial role in cellular communication and chemokine receptors play a prominent role in the immune system, the virally encoded GPCRs may be crucial determinants of viral action. The Kaposi's sarcoma-associated herpesvirus (KSHV, or human herpesvirus 8), implicated in the pathogenesis of Kaposi's sarcoma (KS), a highly vascularized tumor, encodes a GPCR, referred to as ORF74. This virally encoded receptor was found to induce tumorigenesis and transgenic expression of ORF74 induces an angioproliferative disease resembling KS. Cytomegalovirus (CMV), suggested to play a role in atherosclerosis, encodes four GPCRs, among which US28. This virally encoded GPCR is able to induce migration of smooth muscle cells, a feature essential for the development of atherosclerosis. Remarkably, the KSHV and some CMV-encoded GPCRs display constitutive activity, while their cellular homologs do not. It remains to be determined whether this phenomenon contributes to the pathogenesis of viral action. Also, the family of poxviruses encodes GPCRs of which the function is not clear yet. In this review we will give an overview of the different virally encoded GPCRs, and discuss their putative role in viral action and potential as drug target.

Constitutive signaling of the human cytomegalovirus-encoded chemokine receptor US28.

Previously it was shown that the HHV-8-encoded chemokine receptor ORF74 shows considerable agonist-independent, constitutive activity giving rise to oncogenic transformation (Arvanitakis, L., Geras-Raaka, E., Varma, A., Gershengorn, M. C., and Cesarman, E. (1997) Nature 385, 347-350). In this study we report that a second viral-encoded chemokine receptor, the human cytomegalovirus-encoded US28, also efficiently signals in an agonist-independent manner. Transient expression of US28 in COS-7 cells leads to the constitutive activation of phospholipase C and NF-kappaB signaling via G(q/11) protein-dependent pathways. Whereas phospholipase C activation is mediated via Galpha(q/11) subunits, the activation of NF-kappaB strongly depends on betagamma subunits with a preference for the beta(2)gamma(1) dimer. The CC chemokines RANTES (regulated on activation, normal T cell expressed and secreted) and MCP-1 (monocyte chemotactic protein-1) act as neutral antagonists at US28, whereas the CX(3)C chemokine fractalkine acts as a partial inverse agonist with IC(50) values of 1-5 nm. Our data suggest that a high level of constitutive activity might be a more general characteristic of viral G protein-coupled receptors and that human cytomegalovirus might exploit this G protein-coupled receptor property to modulate the homeostasis of infected cells via the early gene product US28.