Astellas Overactive Bladder Drug Raises Risks, FDA Says

Astellas Pharma Inc.’s drug to treat overactive bladder has side effects including increased blood pressure that need to be considered when weighing whether the medicine should be approved, U.S. regulators said.

The medicine, mirabegron, also increased heart rate and was associated with hypersensitivity reactions ranging from painful rash to anemia, the Food and Drug Administration said today in a report ahead of an April 5 meeting of advisers on the drug.

Overactive bladder -- the strong, sudden urge to urinate -- affects 42 million people in the U.S., Nancy Martin, medical director of scientific and medical affairs for Tokyo-based Astellas, said by telephone. Mirabegron is the first in a new class for the condition, according to Astellas.

“Although the safety results from the clinical trials database appear generally reasonable, the special safety concerns, especially the increases in blood pressure and pulse” need additional consideration, FDA staff wrote.

There were 11 deaths in trials that “appear unlikely to be related to mirabegron,” according to the report.

Reduced Incontinence

The drug reduced the number of times patients were incontinent, or involuntarily urinated, in a 24-hour period, the staff wrote.

Mirabegron eliminated baseline incontinence in 32 percent of patients taking 50 milligrams and reduced incidents of incontinence by half in 54 percent of those in final-phase studies of 862 patients taking the medicine, compared to 878 people on placebo, Martin said.

The treatment also was linked to tests revealing potential liver disease, a small number of urinary tract infections and malignant tumors, FDA staff wrote. The reason mirabegron would lead to tumor formation is unknown.

Drugs on the market to treat overactive bladder block a receptor that causes contractions that make someone feel the urge to urinate though they also can affect the ability to empty the bladder, Martin said. Mirabegron enhances bladder storage without affecting patients’ ability to urinate.

Current treatments include Pfizer Inc.’s Detrol, Warner Chilcott Plc’s Enablex and Astellas’s Vesicare. Vesicare generated $1 billion in sales last year, according to data compiled by Bloomberg.

Patients also often stop taking drugs on the market because of dry mouth, according to Martin. She said incidents of dry mouth with mirabegron were similar to placebo.

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