Achaogen Inc said on Tuesday U.S. health regulators cleared its antibiotic Zemdri (plazomicin) to treat adults with complicated urinary tract infections but declined approval for treating bloodstream infections

The U.S. Food and Drug Administration cited lack of evidence of the effectiveness of the drug in a clinical study to treat bloodstream infections, the company said in a statement.

A urinary tract infection (UTI) is an infection from microbes. These are organisms that are too small to be seen without a microscope. Most UTIs are caused by bacteria, but some are caused by fungi and in rare cases by viruses. UTIs are among the most common infections in humans.

A UTI can happen anywhere in your urinary tract. Your urinary tract is made up of your kidneys, ureters, bladder, and urethra. Most UTIs only involve the urethra and bladder, in the lower tract. However, UTIs can involve the ureters and kidneys, in the upper tract. Although upper tract UTIs are rarer than lower tract UTIs, they’re also usually more severe.

"We see limited impact on future revenues if plazomicin's label does not include (bloodstream infections)," Wedbush analyst Robert Driscoll said in an interview last week.

FDA decision on the drug follows similar recommendations by an independent panel 

The drug is approved for complicated urinary tract infections, including pyelonephritis, caused by Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, or Enterobacter cloacae, in patients who have limited or no alternative treatment options. Zemdri is an intravenous infusion, administered once daily.

The condition has other approved treatments in the market, including Vabomere (meropenem and vaborbactam), developed by Medicines Co unit Rempex Pharmaceuticals and approved for complicated urinary tract infections caused by E. coli, K. pneumoniae, and Enterobacter cloacae species complex.