(Reuters) - Tetraphase Pharmaceuticals Inc said on Tuesday its lead experimental antibiotic to treat serious infections did not meet the main goals in a late-stage study, sending its shares plunging more than 60 percent in after-market trading.

The antibiotic, eravacycline, was being studied in a pivotal 1,205 patient study for the treatment of complicated urinary tract infections.

Tetraphase said the drug did not achieve the main goal of non-inferiority compared to patients who were treated with Merck’s drug, ertapenem.

Eravacycline is a synthetic tetracycline derivative for drug-resistant bacterial infections administered intravenously in hospital.

The company in January filed a marketing application for eravacycline with the U.S. Food and Drug Administration to treat intra-abdominal infections.

Tetraphase Chief Executive Guy Macdonald said last year annual sales of the company’s lead drug for serious bacterial infections could climb as high as $700 million, if approved.

The company’s shares were down 58 percent at $2.27.