• Shares of drug developer fall 80 percent in late trading
  • Drug failed to beat generic medicine in 908-person trial

Tetraphase Pharmaceuticals Inc. fell 80 percent in late trading Tuesday after a study found that its experimental antibiotic wasn’t better than a standard generic treatment.

The drug, eravacycline, is being developed for deadly, drug-resistant infections. In a study of 908 patients with complicated urinary tract infections, eravacycline didn’t show that it was equal or better than levofloxacin, a generic drug, Tetraphase said in a statement Tuesday. The shares fell to $9.11 during late trading in New York, after closing at $44.78.

"We plan to further analyze the data and provide an update after we have discussed the data and our plans for a path forward with the regulatory agencies," Chief Executive Officer Guy Macdonald said in the statement. "We continue to believe that eravacycline can benefit patients with serious infections."

Tetraphase shares had more than doubled in the past year, pushed up by positive trial data, including one study released in December that showed eravacycline’s success in treating intra-abdominal infections. It had also been helped by an active deals market that has made small drug and biotechnology companies targets. For example, Merck & Co. spent $9.5 billion on a takeover of another antibiotics maker, Cubist Pharmaceuticals Inc.

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