Rib-X Pharmaceuticals has postponed its IPO after cutting its expected price range in half. The antibiotics developer had been planning to raise $65 million by offering 10 million shares at a price range between $6 and $7. Previously, the expected offering range was $12 to $14. The company had filed to go public on the NASDAQ under the ticker symbol of RIBX on November 28, 2011. Rib-X has raised a hefty $180.5 million in venture financing since 2002, and its three biggest backers are Warburg Pincus, Saints Capital and Oxford Bioscience Partners.