Vibegron is a beta-3 adrenergic agonist the treatment of overactive bladder (OAB) with symptoms of urge urinary incontinence, urgency, and urinary frequency in adults. It can be found under the brand name Gemtesa and it relaxes the detrusor smooth muscle of the bladder, thereby increasing bladder capacity. β3AR is stimulated and undergoes a conformation change and activates adenylyl cyclases (AC), which promotes the formation of cyclic adenosine monophosphate (cAMP). Increased intracellular cAMP concentration leads to the activation of cAMP-dependent protein kinase A (PKA), which subsequently phosphorylates myosin light chains that are responsible for inhibiting the interaction of actin with myosin dependent on calcium – calmodulin complex. Once vibegron is administered and it binds to the beta-3 adrenergic receptor, the G protein signalling cascade begins. The alpha and beta/gamma subunits of the G protein separate and GDP is replaced with GTP on the alpha subunit. This alpha subunit then activates adenylyl cyclase which converts ATP to cAMP. cAMP then activates protein kinase A (PKA) which in turn phosphorylates targets and inhibits MLCK through decreased calcium levels causing muscle relaxation. PKA can phosphorylate certain Gq-coupled receptors as well as phospholipase C (PLC) and thereby inhibit G protein-coupled receptor (GPCR) -PLC-mediated phosphoinositide (PI) generation, and thus calcium flux. PKA phosphorylates the inositol 1,4,5-trisphosphate (IP3) receptor to reduce its affinity for IP3 and further limit calcium mobilization. PKA phosphorylates myosin light chain kinase (MLCK) and decreases its affinity to calcium calmodulin, thus reducing activity and myosin light chain (MLC) phosphorylation. PKA also phosphorylates KCa++ channels in ASM, increasing their open-state probability (and therefore K+ efflux) and promoting hyperpolarization. Since myosine light chain kinase is not activated, Serine/threonine-protein phosphatase continues to dephosphorylate myosin LC-P, and more cannot be synthesized so myosin remains unbound from actin causing muscle relaxation. This relaxation of the smooth muscles in the bladder causes the bladder to expand to relax, making the sense of urgency for urination lesser. Some side effects of using vibegron may include headache, nausea, fever, and diarrhea.

Vibegron Pathway References