Item 1.01. Entry into a Material Definitive Agreement.

On October 30, 2012, Ironwood Pharmaceuticals, Inc. ("Ironwood") and BMR-Rogers Street LLC (the "Landlord") entered into a Seventh Amendment to Lease (the "Amendment"). Ironwood and the Landlord are parties to a Lease dated as of January 12, 2007, as previously amended on April 9, 2009, February 9, 2010, July 1, 2010, February 3, 2011, October 18, 2011 and July 19, 2012 (the "Lease"), under which Ironwood leases office and laboratory space at 301 Binney Street, Cambridge, Massachusetts (the "Facility") from the Landlord.

The Amendment provides that, among other things, as of October 30, 2012, Ironwood leases from the Landlord an additional 93,000 rentable square feet of the Facility. Ironwood will occupy the additional space in four stages of approximately 23,250 square feet per stage. Ironwood will pay Landlord rent for each stage beginning no later than December 1, 2013, June 1, 2014, June 1, 2015 and June 1, 2016, respectively; however, Ironwood may occupy, and therefore pay rent for, each of the four stages at any time before these dates. The initial rent for the additional space will be $43.00 per rentable square foot per year, and such rent will increase annually by $0.50 per rentable square foot.

The Amendment also extends the term of the entire Lease by 24 months, with an expiration date of January 31, 2018. Ironwood will continue to pay for its utility services in the Facility.

Item 2.03. Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant.

The information set forth above in Item 1.01 of this Current Report on Form 8-K regarding the Lease and the Amendment is incorporated into this Item 2.03 by reference.

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