On October 23, 2012, Ironwood Pharmaceuticals, Inc. ("Ironwood") and AstraZeneca AB ("AstraZeneca") entered into a collaboration agreement (the "Collaboration Agreement") whereby Ironwood granted to AstraZeneca a license to co-develop and co-commercialize Ironwood's linaclotide in the People's Republic of China. The parties are jointly responsible for the development and commercialization of linaclotide in China, with AstraZeneca having primary responsibility for the local operational execution.

Pursuant to the terms of the Collaboration Agreement, AstraZeneca will make an upfront payment of $25 million to Ironwood and will share the net profits and losses associated with linaclotide in China, with AstraZeneca carrying 55 percent of each until a certain specified milestone is achieved, moving to a 50/50 percent split thereafter. Ironwood is also eligible for $125 million in additional commercial milestone payments, contingent on the achievement of certain sales targets in China.

Subject to customary termination provisions, the Collaboration Agreement will continue as long as there is an agreed upon development plan or commercialization plan in effect.

The foregoing summary is qualified in its entirety by reference to the Collaboration Agreement, which Ironwood expects to file as an exhibit to its Annual Report on Form 10-K for the year ending December 31, 2012.

A copy of the press release issued by the parties on October 23, 2012 announcing the transaction is attached to this Current Report on Form 8-K as Exhibit 99.1.

(d) Exhibits.

Exhibit No.        Description

99.1               Ironwood Pharmaceuticals, Inc. and AstraZeneca Press Release dated
                   October 23, 2012