Tetraphase Pharmaceuticals saw its stock plummet after revealing that a Phase III study of its experimental antibiotic eravacycline missed key targets in a late stage trial.

The US biopharma said that a Phase III trial assessing the drug in patients with complicated urinary tract infections did not achieve its co-primary endpoints.

The IGNITE3 study failed to show non-inferiority of eravacycline versus ertapenem in responder rate in the microbiological intent-to-treat population at the end-of-IV treatment visit and at the test-of-cure (TOC) visit.

On the plus side, the drug was well tolerated, with a safety profile consistent with prior studies, the firm noted.

“We are surprised and obviously very disappointed that the IGNITE3 trial did not achieve its co-primary endpoints and are fully analysing the data to understand this outcome,” said Guy Macdonald, Tetraphase’s president and chief executive.

“Independent of this outcome, we continue to move forward with our registration strategy for eravacycline in complicated intra-abdominal infections (cIAI).”

The drug is currently under review on both sides of the Atlantic in this setting, with submissions based on the positive outcomes demonstrating high cure rates and favorable tolerability in the IGNITE1 and IGNITE4 Phase III clinical trials of IV eravacycline in cIAI.

“There is a clear unmet need for patients with serious infections, particularly those caused by difficult-to-treat Gram-negative bacteria, and we continue to believe that eravacycline can benefit those patients and we are excited to be getting closer to delivering that potential to patients in need," Mr Macdonald stressed.