Rib-X Pharmaceuticals, which is mounting an $80 million IPO effort, is touting positive midstage data from the Phase IIb study of its antibiotic delafloxacin. "Delafloxacin met or exceeded primary and secondary efficacy endpoints evaluated to date in comparison to Zyvox (linezolid), with and without aztreonam, and vancomycin, with and without aztreonam, including endpoints based on the draft guidance" from the FDA, the biotech says. The positive outcome positions Rib-X--a 2011 Fierce 15 company--to take the antibiotic into Phase III. The biotech has burned through $238 million in its quest to develop new antibiotics and recently signed a development pact with Sanofi ($SNY). Release