Tetraphase shares tumble after late-stage study failure for antibiotic eravacycline

Shares in Tetraphase Pharmaceuticals plunged more than 60 percent after the company announced that a Phase III study of its experimental antibiotic eravacycline for the treatment of patients with complicated urinary tract infections failed to meet its co-primary endpoints. CEO Guy Macdonald said "we are surprised and obviously very disappointed" in the results.

The IGNITE3 trial randomised 1205 patients to receive either eravacycline or Merck & Co.'s Invanz (ertapenem) for a minimum of five days, with subjects then eligible for transition to an appropriate approved oral agent. The study's co-primary endpoints of responder rate in the microbiological intent-to-treat population at the end-of-intravenous (EOI) treatment visit and at the test-of-cure (TOC) visit were evaluated using a 10-percent non-inferiority margin.

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Results showed that responder rates at the EOI visit were 84.8 percent for eravacycline and 94.8 percent for ertapenem, while responder rates at the TOC visit were 68.5 percent and 74.9 percent, respectively. In 2015, Tetraphase reported that the Phase III IGNITE2 trial, which also investigated eravacycline for the treatment of complicated urinary tract infections, failed to hit its main endpoint of statistical non-inferiority versus Johnson & Johnson's Levaquin (levofloxacin).

Macdonald said that despite the latest results "we continue to move forward with our registration strategy for eravacycline in complicated intra-abdominal infections." Tetraphase submitted an application in Europe seeking approval of the fully-synthetic fluorocycline antibiotic in this indication in August last year, with a filing made in the US last month. "We are actively preparing for the commercialisation of eravacycline as a treatment in [complicated intra-abdominal infections] in both the US and in Europe," Macdonald added.

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