WASHINGTON – Repeat treatment with onabotulinumtoxin A provided sustained improvements in the symptoms of overactive bladder and was well tolerated in women who were followed for a median 2.4 years beyond their participation in one of the two large clinical trials that established the agent’s effectiveness and safety for this indication.
"This treatment remains a safe and effective therapeutic option" for patients with overactive bladder, said Dr. Tomasz Rechberger of the Medical University of Lublin (Poland). It’s "an attractive alternative [in the longer term] for patients who were inadequately treated with anticholinergics."
Women who completed either of the placebo-controlled, multicenter phase III studies were given the option of entering a 3-year open-label extension study in which they could receive additional treatments upon request and as needed to maintain symptom control. The intradetrusor injections of 100 U of onabotulinumtoxin A (Botox) needed to be at least 12 weeks apart.
At the scientific meetings of the American Urogynecologic Society and the International Urogynecological Association, Dr. Rechberger reported on an interim analysis of this extension study, which was scheduled to end in August 2014.
As of June 2014, the overall discontinuation rate among the 749 patients who entered the extension study was 38%, but only 4.5% discontinued because of adverse effects or a lack of efficacy. "It was extremely low – much lower than [we expected]," said Dr. Rechberger.
The women had a mean age of 60 and had experienced symptoms of overactive bladder (OAB) for more than 6 years. At the start of the extension study, they had a mean of 5.6 episodes per day of urinary incontinence, 11.6 micturitions per day, and 8.4 urgency episodes per day.
In the original studies, the results after 12 weeks showed that patients treated with Botox experienced urinary incontinence an average of 1.6-1.9 times fewer per day than did patients treated with placebo, and they needed to urinate on average 1.0-1.7 times fewer per day, according to the Food and Drug Administration. In 2013, the FDA approved the use of Botox to treat adults with OAB who cannot use or do not adequately respond to anticholinergics.
Consistent reductions in symptoms were seen after the one to five treatments evaluated as part of the interim analysis of the extension study. Investigators checked all endpoints against the baseline 12 weeks after each treatment. The number of urinary incontinence episodes per day, for instance, was reduced by 3.3 after the first treatment cycle, 3.7 after two treatments, 3.9 after the third treatment, and 3.2 after the fourth and fifth treatment cycles.
Approximately 63%-72% of patients achieved a reduction of incontinence episodes of at least 50% across the treatment cycles.
Additionally, women saw mean reductions in micturition ranging from 2.4 to 3 over the five treatment cycles, and mean reductions in urgency episodes ranging from 3.6 to 4.2. A consistent increase in the volume voided per micturition also was seen.
Urinary tract infection was the most common side effect in each repeat treatment, as was the case in the original studies, but declined slightly with each treatment cycle, from approximately 30% after the first treatment to approximately 20% after the fifth. There were no new safety signals, Dr. Rechberger reported.
Each treatment consisted of 20 cystoscopic injections of 0.5 mL each. The median time between treatments ranged from 24 to 33 weeks – significantly longer than the required 12-week minimum.
Dr. Rechberger is an advisory committee member for Allergan (maker of Botox) and consults for Astellas and Johnson & Johnson. The study was funded by Allergan.