Novel Drug for Overactive Bladder Works Even If Antimuscarinics Do Not

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PARIS—Mirabegron, an experimental drug for overactive bladder (OAB), can effectively treat the condition in patients whether or not they failed previous antimuscarinic therapy, according to findings presented at the 27th Annual Congress of the European Association of Urology.

The findings are from a post-hoc analysis of a randomized, double-blind phase 3 trial comparing mirabegron, the first in a new class of OAB agents with a distinct mechanism of action, with tolterodine slow release (SR) or placebo. The study, which included 1,978 patients in 26 European countries and Australia, found that mirabegron at daily doses of 50 or 100 mg reduced the mean number of micturitions and incontinence episodes compared with placebo in OAB patients with and without prior antimuscarinic therapy.

Investigators led by Vikram Khullar, MBBS, of Imperial College in London, U.K., randomized 493 patients to receive mirabegron 50 mg, 496 to receive mirabegron 100 mg, 495 to receive tolterodine SR 4 mg, and 494 to receive placebo orally once a day for 12 weeks. Among patients who had no prior treatment with antimuscarinics, the mean number of micturitions per 24 hours decreased significantly from baseline by a mean of 0.52, 0.37, and 0.29 in the mirabegron 50 and 100 mg groups and the tolterodine group, respectively, compared with placebo. Among patients who had discontinued prior antimuscarinic therapy because of insufficient effect, the mean number of micturitions per 24 hours decreased significantly by a mean of 0.59 and 0.58 in the mirabegron 50 and 100 mg groups, respectively, whereas it declined nonsignificantly by only 0.08 in the tolterodine group.

The mean number of incontinence episodes per 24 hours in antimuscarinic-naïve patients decreased by 0.29, 0.15, and 0.08 in the mirabegon 50 and 100 mg groups and the tolterodine group, respectively, compared with placebo. Among the patients who discontinued prior antimuscarinic therapy because of insufficient effect, the mean number of incontinence episodes decreased significantly by 0.76 and 0.62 in the mirabegon 50 and 100 mg groups, and nonsignificantly by only 0.06 in the tolterodine group.

“Patients who had previously not found antimuscarinics efficacious found that mirabegron 50 [or] 100 mg gave them greater efficacy over placebo, whereas the tolterodine group did not find such an effect,” Dr. Khullar said.

Mirabegron was well tolerated at both doses, the study found. The number of patients with treatment-emergent adverse effects was similar in all study arms (42.8%, 40.1%, 46.7% and 43.3% of the mirabegron 50 and 100 mg groups, tolterodine group, and placebo group, respectively), the researchers reported.

The study was funded by Astellas Pharma, which is developing mirabegron.

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