Tetraphase Pharmaceuticals Inc (NASDAQ:TTPH) had a rough day today as shares fell 17%, after the antibiotic drug-maker announced that the FDA is requiring one more successful Phase 3 trial of the company’s lead drug eravacycline, an antibiotic with potent activity against drug-resistant bacteria, for regulatory approval.

In reaction, Needham analyst Alan Carr maintained a Hold rating on the stock given extended timelines to commercialization and risks around the oral eravacycline program.

Carr commented, “We had believed the FDA might be open to approval of the IV formulation based on just the completed Phase 2 and Phase 3 trials in complicated Intra-Abdominal Infections (cIAI). This would have allowed for commercial launch as early as 2017. To address FDA requirements and minimize the delay to market, the company now plans to conduct another Phase 3 IV cIAI trial (results 4Q17E) and submit an NDA shortly thereafter. A Phase 3 IV complicated Urinary Tract Infections (cUTI) trial will also be run, as previously planned, but because results are not likely until 2018, data will be submitted separately as an sNDA.”

According to TipRanks.com, which measures analysts’ and bloggers’ success rate based on how their calls perform, analyst Alan Carr has a yearly average return of 9.1% and a 43% success rate. Carr has a -3.9% average return when recommending TTPH, and is ranked #262 out of 3913 analysts.