Aratana Therapeutics, which is developing 6 new treatments for cats and dogs, joined the biotech queue on Wall Street, filing an S-1 indicating a desire to raise $57.5 million in an IPO. The company was founded just a few years ago and has since licensed three programs. It's planning to trade shares under the symbol PETX. In related news, Tetraphase launched its IPO, raising $75 million for its work on antibiotics. The biotech had to slash its price to $7, after offering a range of $10 to $12, and raised the number of shares being sold. Enanta, which is developing hep C drugs, is also expected to go public this week. Story