UPDATED: Bankers Reveal Top Biotech IPO Contenders; New Filer Ironwood Among Them

(MoneyWatch)  Ironwood Pharmaceuticals filed for an initial public offering today, a move that several biotech investors had previously predicted.

Ironwood, formerly known as Microbia, reported good data earlier this month from two Phase III trials of linaclotide for chronic constipation. The drug, which is in two more pivotal trials for irritable bowel syndrome, has attracted partnering deals with Forest Laboratories for in the U.S. and Laboratorios Almirall in Europe. Analysts predict peak annual sales upward of $500 million.

Looking to raise $173 million, Ironwood is the sixth biotech to join the U.S. IPO queue in the current window. Ready and waiting are antibiotic company Trius Therapeutics, ophthalmology player Alimera Sciences, cardiovascular company Anthera Pharmaceuticals, stem cell developer Aldagen, and diagnostic/specialty firm Prometheus Laboratories. Also, Johnson & Johnson spin-out Movetis is planning an IPO in Europe.

Who's up next? A few bankers and venture capitalists picked the following as likely biotech IPO filers (they picked Ironwood too, and they were right on that one):

• Portola Pharmaceuticals ?€" a well-funded biotech boasting a $575 million deal with Novartis for the Phase II antiplatelet drug elinogrel and a $470 million deal with Merck for the Phase II anticoagulant betrixaban
• Pacific Biosciences ?€" made a big splash last year with a $100 million venture round for its DNA sequencing technology
• Regulus Therapeutics ?€" the mRNA love-child of Alnylam Pharmaceuticals and Isis Pharmaceuticals
• Concert Pharmaceuticals ?€" signed a billion-dollar deal with summer with GlaxoSmithKline for deuterium-modified compounds
• Macrogenics ?€" its own antibodies are nearing late-stage, and it picked up some hot cancer stem cell technology by acquiring Raven Biotechnologies
• AVEO Pharmaceuticals - its next-gen VEGF inhibitor for kideny cancer is said to be stirring partnership interest (thanks to reader Kingrim for the tip)

Anyone else have predictions?