Vibegron (Gemtesa) is a selective beta-3 adrenergic receptor agonist. It treats OAB, including urge urinary incontinence and urinary frequency by relaxing the detrusor smooth muscle during bladder filling. Thus, increasing bladder capacity. Vibegron is dosed once daily at 75mg tablet. Mirabegron (Myrbetriq) was the first and only other beta-3 agonist currently used for OAB. It too is dosed once daily, as a 25mg or 50mg tablet. In this article, we compare vibegron versus mirabegron in the management of OAB.
Vibegron does appear to have some advantages versus mirabegron. First, and most notably, Vibegron does not interact with the CYP2D6 enzyme whereas mirabegron is a significant inhibitor of CYP2D6. This is important as approximately 25% of all drugs are metabolized by CYP2D6 and studies have shown that about 43% of patients with OAB take drugs that are metabolized by this enzyme. Being able to avoid dosing complications with comorbid conditions gives a significant advantage of vibegron versus mirabegron.
Further, in the EMPOWUR phase 3 clinical trial and subsequent extension study, vibegron was shown to be more effective and better tolerated than placebo and tolterodine. It is possible that as the benefits of beta-3 agonists are seen in practice and market competition drives down the price, vibegron will gain significant market share in OAB treatment.
It is important to highlight the fact that both vibegron and mirabegron are not associated with cognitive decline unlike antimuscarinic agents (anticholinergic). This is definitely a benefit in our geriatric population.
Beta-3 agonists are not typically preferred as a first-line option for patients and likely won’t be for some time. Due to still being brand name, they are a much more expensive option compared to traditional antimuscarinics (ie. oxybutynin, tolterodine, solifenacin, and trospium) used in OAB treatment. Facility formularies and prescription insurance plans typically require multiple trials of these antimuscarinic agents before approving mirabegron/vibegron. Often, a prior authorization will also need to be completed and documented before dispensing.
In conclusion, there are a couple of modest advantages of vibegron versus mirabegron. A demonstration of possible increased efficacy over an anticholinergic (tolterodine) and less CYP2D6 interaction potential make vibegron slightly more appealing than mirabegron. However, in my opinion, it is unlikely that vibegron will significantly change the current approach to OAB treatment soon. Any potential clinical improvements do not appear to be enough to offset the cost factor in making it a first-line option at this time. With that said, vibegron represents an option in patients who have failed traditional antimuscarinic OAB therapy or where anticholinergics may be contraindicated due to cognitive impairment or dementia.
This article was written by Joseph Nelson, PharmD Candidate in collaboration with Eric Christianson, PharmD
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