The Tetraphase Pharmaceuticals Inc. shares had fallen in late trading Tuesday to 80%.  This is after a study discovered that its manufactured experimental antibiotic was no better than a standard generic treatment.

The pharmaceutical company developed eravacycline to combat deadly drug-resistant infections.  In a conducted study of 908 with complicated UTI, the said drug didn't prove that is better or even equal with levofloxacin, a generic drug, said Tetraphase in a statement Tuesday.

Tetraphase is a clinical-stage biopharmaceutical company that uses its proprietary chemistry technology to produce novel antibiotics to cure serious and life-threatening multidrug-resistant (MDR) infections.  The company has developed an antibiotics platform that offers the potential to dramatically improve the treatment of both broad-spectrum and MDR bacterial infections.

Eravacycline, the company's lead drug, cures infections produced by gram-negative bacteria called superbugs, a class of antibiotic-resistant pathogens.  Although eravacycline is no match to Johnson & Johnson's antibiotic, levofloxacin, it is far better than Merck & Co's antibiotic, ertapenem. It was proven at an earlier late-stage study.

"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."

The drug maker had said it expected to apply for U.S. regulatory approval for eravacycline by the end of this year.  The drug is also expected to contend with the new superbug-fighting antibiotics, including Merck's Zerbaxa that was recently approved.

Tetraphase shares had more than doubled in the previous years, raised by positive trial data, inclusive of one study released in December showing eravacycline's success in treating intra-abdominal infections.  It has been aided by active market deals that had made small drug and biotechnology companies targets.  One example is that Merck & Co. spent $9.5 billion on a takeover of another antibiotics maker, Cubist Pharmaceuticals Inc.

But the company's share has now fell at $11.23 in extended trading after closing at $44.78.  They had gained about 45% since the company announced results from the first late-stage study in December.