Add-on or switch to vibegron in patients with overactive bladder insufficiently responding to initial 4-week...

Overactive bladder (OAB) is a condition characterised by urinary urgency, often accompanied by frequency and nocturia. Antimuscarinics and β3 receptor agonists are first-line therapies that improve urinary symptoms and the quality of life. For insufficient antimuscarinic response, options include dose increase, switching medications or combination therapy. However, evidence for these strategies, especially combinations with vibegron, is limited and needs further study.

The study is designed as a randomised, open-label, parallel-group, multicentre trial conducted in Japan. A total of 110 patients with OAB who met the OAB criteria and did not respond adequately to the initial 4-week antimuscarinic treatment will be randomised in a 1:1 ratio into two groups: an add-on group in which vibegron 50 mg/day is added to the current antimuscarinic drug and a switch group in which the current antimuscarinics are discontinued and replaced with vibegron 50 mg/day⁠. The primary endpoint is the intergroup comparison of changes in daily urinary frequency between the add-on group and the switch group at 12 weeks after the initiation of protocol treatment. The primary analysis aims to confirm the non-inferiority of the switch group compared with the add-on group using a Bayesian mixed model for repeated measures. Non-inferiority will be confirmed if the posterior probability that the difference in the change in urinary frequency at 12 weeks between the two groups falls within the non-inferiority margin of one-time is 80% or greater.

The trial has been reviewed and approved by the Institute of Science Tokyo Certified Clinical Research Review Board (approval number: NR2024-001)⁠. Participants will provide informed consent to participate before taking part in the study. Results will be reported in a separate publication.

Japan Registry of Clinical Trials (jRCT) (jRCTs031240134)⁠.