Exhibit 99.1

FOR IMMEDIATE RELEASE

Ironwood Pharmaceuticals Reports Third Quarter 2023 Results

– LINZESS® (Iinaclotide) EUTRx prescription demand growth increased 8% year-over-year; LINZESS U.S. net sales of $279 million, an increase of 7% year-over-year –

– Reported positive final data from STARS Nutrition, a Phase II study of apraglutide in short bowel syndrome with intestinal failure (SBS-IF) and colon-in-continuity (CIC) –

– Expects topline data for the Phase II study of CNP-104 in primary biliary cholangitis (PBC) in the third quarter of 2024 –

– Maintains Full Year 2023 Guidance –

BOSTON, Mass., November 9, 2023 — Ironwood Pharmaceuticals, Inc. (Nasdaq: IRWD), a GI-focused healthcare company, today reported its third quarter 2023 results and recent business performance.

“We are proud of the progress we have made across our strategic priorities so far this year, as we believe we have strengthened our position to become the leading GI healthcare company in the industry,” said Tom McCourt, chief executive officer of Ironwood. “Our high conviction in the STARS clinical program was augmented by the positive final data from the STARS Nutrition study, reinforcing our belief in apraglutide’s potential to be a best-in-class GLP-2 analog for the whole spectrum of patients with short bowel syndrome with intestinal failure, including those with colon-in-continuity. In addition, we are encouraged to have seen T-cell immune responses in patients treated with CNP-104 for the potential treatment of primary biliary cholangitis and look forward to the topline results in the third quarter of 2024. Our commitment to developing and advancing innovative GI assets is as strong as it has ever been. We believe the positive momentum across our pipeline programs, combined with the continued strong performance of LINZESS, positions us well for success in our mission to be the leader in GI. We are looking forward to a strong finish to the year and meaningful pipeline catalysts ahead in 2024.”

Third Quarter 2023 Financial Highlights1

(in thousands, except for per share amounts)

Third Quarter 2023 Corporate Highlights

U.S. LINZESS

Pipeline Updates

Apraglutide

CNP-104

IW-3300

Third Quarter 2023 Financial Results

1 Adjusted EBITDA is calculated by subtracting mark-to-market adjustments on derivatives related to Ironwood’s 2022 Convertible Notes, restructuring expenses, net interest expense, income taxes, depreciation and amortization, and acquisition-related costs from GAAP net income.

2 2023 adjusted EBITDA guidance includes a one-time charge of approximately $1.1 billion related to acquired in-process research and development from the acquisition of VectivBio in the second quarter of 2023. For purposes of this guidance, Ironwood has assumed that it will not incur material expenses related to additional business development activities in 2023.

Non-GAAP Financial Measures

Ironwood presents non-GAAP net income and non-GAAP net income per share to exclude the impact, net of tax effects, of net gains and losses on derivatives related to Ironwood’s 2022 Convertible Notes that are required to be marked-to-market, amortization of acquired intangible assets, restructuring expenses, and acquisition-related costs. Non-GAAP adjustments are further detailed below:

Ironwood also presents adjusted EBITDA, a non-GAAP measure, as well as guidance on adjusted EBITDA. Adjusted EBITDA is calculated by subtracting mark-to-market adjustments on derivatives related to Ironwood’s 2022 Convertible Notes, restructuring expenses, net interest expense, income taxes, depreciation and amortization, and acquisition-related costs from GAAP net income. The adjustments are made on a similar basis as described above related to non-GAAP net income, as applicable.

Management believes this non-GAAP information is useful for investors, taken in conjunction with Ironwood’s GAAP financial statements, because it provides greater transparency and period-over-period comparability with respect to Ironwood’s operating performance. These measures are also used by management to assess the performance of the business. Investors should consider these non-GAAP measures only as a supplement to, not as a substitute for or as superior to, measures of financial performance prepared in accordance with GAAP. In addition, these non-GAAP financial measures are unlikely to be comparable with non-GAAP information provided by other companies. For a reconciliation of non-GAAP net income and non-GAAP net income per share to GAAP net income and GAAP net income per share, respectively, and for a reconciliation of adjusted EBITDA to GAAP net income, please refer to the tables at the end of this press release.

Ironwood does not provide guidance on GAAP net income or a reconciliation of expected adjusted EBITDA to expected GAAP net income because, without unreasonable efforts, it is unable to predict with reasonable certainty the non-GAAP adjustments used to calculate adjusted EBITDA. These adjustments are uncertain, depend on various factors and could have a material impact on GAAP net income for the guidance period.

Conference Call Information

Ironwood will host a conference call and webcast at 8:30 a.m. Eastern Time on Thursday, November 9, 2023 to discuss its third quarter 2023 results and recent business activities. Individuals interested in participating in the call should dial (888) 330-2384 (U.S. and Canada) or (240) 789-2701 (international) using conference ID number and event passcode 4671230. To access the webcast, please visit the Investors section of Ironwood’s website at www.ironwoodpharma.com at least 15 minutes prior to the start of the call to ensure adequate time for any software downloads that may be required. The call will be available for replay via telephone starting at approximately 11:30 a.m. Eastern Time on November 9, 2023, running through 11:59 p.m. Eastern Time on November 23, 2023. To listen to the replay, dial (800) 770-2030 (U.S. and Canada) or (647) 362-9199 (international) using conference ID number 4671230. The archived webcast will be available on Ironwood’s website for 14 days beginning approximately one hour after the call has completed.

About Ironwood Pharmaceuticals

Ironwood Pharmaceuticals (Nasdaq: IRWD), an S&P SmallCap 600® company, is a leading global gastrointestinal (GI) healthcare company on a mission to advance the treatment of GI diseases and redefine the standard of care for GI patients. We are pioneers in the development of LINZESS® (linaclotide), the U.S. branded prescription market leader for adults with irritable bowel syndrome with constipation (IBS-C) or chronic idiopathic constipation (CIC). LINZESS is also approved for the treatment of functional constipation in pediatric patients ages 6-17 years-old. Ironwood is also advancing apraglutide, a next-generation, long-acting synthetic GLP-2 analog being developed for rare gastrointestinal diseases, including short bowel syndrome with intestinal failure (SBS-IF) as well as several earlier stage assets. Building upon our history of GI innovation, we keep patients at the heart of our R&D and commercialization efforts to reduce the burden of GI diseases and address significant unmet needs.

Founded in 1998, Ironwood Pharmaceuticals is headquartered in Boston, Massachusetts, and has additional operations in Basel, Switzerland.

We routinely post information that may be important to investors on our website at www.ironwoodpharma.com. In addition, follow us on X and on LinkedIn.

About LINZESS (Linaclotide)

LINZESS® is the #1 prescribed brand in the U.S. for the treatment of adult patients with irritable bowel syndrome with constipation (“IBS-C”) or chronic idiopathic constipation (“CIC”), based on IQVIA data. LINZESS is a once-daily capsule that helps relieve the abdominal pain, constipation, and overall abdominal symptoms of bloating, discomfort and pain associated with IBS-C, as well as the constipation, infrequent stools, hard stools, straining, and incomplete evacuation associated with CIC. LINZESS relieves constipation in children and adolescents aged 6 to 17 years with functional constipation. The recommended dose is 290 mcg for IBS-C patients and 145 mcg for CIC patients, with a 72 mcg dose approved for use in CIC depending on individual patient presentation or tolerability. In children with functional constipation aged 6 to 17 years, the recommended dose is 72 mcg.

LINZESS is not a laxative; it is the first medicine approved by the FDA in a class called GC-C agonists. LINZESS contains a peptide called linaclotide that activates the GC-C receptor in the intestine. Activation of GC-C is thought to result in increased intestinal fluid secretion and accelerated transit and a decrease in the activity of pain-sensing nerves in the intestine. The clinical relevance of the effect on pain fibers, which is based on nonclinical studies, has not been established.

In the United States, Ironwood and AbbVie co-develop and co-commercialize LINZESS for the treatment of adults with IBS-C or CIC. In Europe, AbbVie markets linaclotide under the brand name CONSTELLA® for the treatment of adults with moderate to severe IBS-C. In Japan, Ironwood's partner, Astellas, markets linaclotide under the brand name LINZESS for the treatment of adults with IBS-C or CIC. Ironwood also has partnered with AstraZeneca for development and commercialization of LINZESS in China, and with AbbVie for development and commercialization of linaclotide in all other territories worldwide.

LINZESS Important Safety Information

INDICATIONS AND USAGE

LINZESS® (linaclotide) is indicated for the treatment of both irritable bowel syndrome with constipation (IBS-C) and chronic idiopathic constipation (CIC) in adults and functional constipation (FC) in children and adolescents 6 to 17 years of age. It is not known if LINZESS is safe and effective in children with FC less than 6 years of age or in children with IBS-C less than 18 years of age.

IMPORTANT SAFETY INFORMATION

Contraindications

Warnings and Precautions

Diarrhea

Common Adverse Reactions (incidence ≥2% and greater than placebo)

Please see full Prescribing Information including Boxed Warning:

https://www.rxabbvie.com/pdf/linzess_pi.pdf

LINZESS® and CONSTELLA® are registered trademarks of Ironwood Pharmaceuticals, Inc. Any other trademarks referred to in this press release are the property of their respective owners. All rights reserved.

Forward-Looking Statements

This press release contains forward-looking statements. Investors are cautioned not to place undue reliance on these forward-looking statements, including statements about Ironwood’s ability to execute on its mission; Ironwood’s strategy, business, financial position and operations; Ironwood’s ability to drive growth and profitability; the demand, development, commercial availability and commercial potential of linaclotide, including pursuing highly differentiated GI assets to add to our portfolio, and the drivers, timing, impact and results thereof; the potential indications for, and benefits of, linaclotide; our financial performance and results, and guidance and expectations related thereto; LINZESS prescription demand growth, LINZESS U.S. net sales growth, total revenue and adjusted EBITDA in 2023; our ability to develop apraglutide and the expected timing of receiving data from the apraglutide clinical trials; the potential of apraglutide to become the standard of care for patients with SBS-IF; the potential of CNP-104 to be the first PBC disease modifying therapy and the expected timing of receiving topline data from the clinical study for CNP-104 in PBC patients; and our plan to advance IW-3300 including the timing and results thereof. These forward-looking statements speak only as of the date of this press release, and Ironwood undertakes no obligation to update these forward-looking statements. Each forward-looking statement is subject to risks and uncertainties that could cause actual results to differ materially from those expressed or implied in such statement. Applicable risks and uncertainties include those related to the effectiveness of development and commercialization efforts by us and our partners; preclinical and clinical development, manufacturing and formulation development of linaclotide, apraglutide, CNP-104, IW-3300, and our product candidates; the risk that clinical programs and studies, including for the linaclotide pediatric program, apraglutide, IW-3300 and CNP-104, may not progress or develop as anticipated, including that studies are delayed or discontinued for any reason, such as safety, tolerability, enrollment, manufacturing, economic or other reasons; the risk that findings from our completed nonclinical and clinical studies may not be replicated in later studies; the risk that peripheral T-cell immune responses evidenced in patients treated with CNP-104 may neither support the mechanistic rationale for CNP-104 nor be predictive of the topline data from the clinical study for CNP-104 in PBC patients since the clinical relevance of such T-cell immune response has not been adequately established; the risk that we or our partners are unable to obtain, maintain or manufacture sufficient LINZESS or our product candidates, or otherwise experience difficulties with respect to supply or manufacturing; the efficacy, safety and tolerability of linaclotide and our product candidates; the risk that the commercial and therapeutic opportunities for LINZESS or our product candidates are not as we expect; decisions by regulatory and judicial authorities; the risk we may never get additional patent protection for linaclotide and other product candidates, that patents for linaclotide or other products may not provide adequate protection from competition, or that we are not able to successfully protect such patents; the risk that we are unable to manage our expenses or cash use, or are unable to commercialize our products as expected; the risk that the development of any of our linaclotide pediatric programs, apraglutide, CNP-104 and/or IW-3300 are not successful or that any of our product candidates is not successfully commercialized; outcomes in legal proceedings to protect or enforce the patents relating to our products and product candidates, including abbreviated new drug application litigation; the risk that financial and operating results may differ from our projections; developments in the intellectual property landscape; challenges from and rights of competitors or potential competitors; the risk that our planned investments do not have the anticipated effect on our company revenues; developments in accounting guidance or practice; Ironwood’s or AbbVie’s accounting practices, including reporting and settlement practices as between Ironwood and AbbVie; the risk that we are unable to manage our expenses or cash use, or are unable to commercialize our products as expected; the impact of the COVID-19 pandemic; and the risks listed under the heading “Risk Factors” and elsewhere in our Annual Report on Form 10-K for the year ended December 31, 2022, in our Quarterly Report on Form 10-Q for the second quarter ended June 30, 2023, and in our subsequent Securities and Exchange Commission filings.

Investors:

Greg Martini, 617-374-5230

gmartini@ironwoodpharma.com

Matt Roache, 617-621-8395

mroache@ironwoodpharma.com

Media:

Beth Calitri, 978-417-2031

bcalitri@ironwoodpharma.com

Condensed Consolidated Balance Sheets

(In thousands)

(unaudited)

Condensed Consolidated Statements of Income

(In thousands, except per share amounts)

(unaudited)

Reconciliation of GAAP Results to Non-GAAP Financial Measures

(In thousands, except per share amounts) (unaudited)

A reconciliation between net income (loss) on a GAAP basis and on a non-GAAP basis is as follows:

A reconciliation between basic net income (loss) per share on a GAAP basis and on a non-GAAP basis is as follows:

A reconciliation between diluted net income (loss) per share on a GAAP basis and on a non-GAAP basis is as follows:

1 GAAP and non-GAAP net loss for nine months ended September 30, 2023 include a one-time charge of approximately $1.1 billion related to acquired in-process research and development from the acquisition of VectivBio in the second quarter of 2023.

Reconciliation of GAAP Net Income to Adjusted EBITDA

(In thousands)

(unaudited)

A reconciliation of GAAP net income (loss) to adjusted EBITDA:

1 GAAP net loss and adjusted EBITDA for nine months ended September 30, 2023 includes a one-time charge of approximately $1.1 billion related to acquired in-process research and development from the acquisition of VectivBio in the second quarter of 2023.

U.S. LINZESS Commercial Collaboration1

Revenue/Expense Calculation

(In thousands)

(unaudited)

1 Ironwood collaborates with AbbVie on the development and commercialization of linaclotide in North America. Under the terms of the collaboration agreement, Ironwood receives 50% of the net profits and bears 50% of the net losses from the commercial sale of LINZESS in the U.S. The purpose of this table is to present calculations of Ironwood’s share of net profit (loss) generated from the sales of LINZESS in the U.S. and Ironwood’s collaboration revenue/expense; however, the table does not present the research and development expenses related to LINZESS in the U.S. that are shared equally between the parties under the collaboration agreement. Please refer to the table at the end of this press release for net profit for the U.S. LINZESS brand collaboration with AbbVie.

2 LINZESS net sales are recognized using AbbVie’s revenue recognition accounting policies and reporting conventions. As a result, certain rebates and discounts are classified as LINZESS U.S. commercial costs, expenses and other discounts within Ironwood’s calculation of collaborative arrangements revenue.

3 Includes certain discounts recognized and cost of goods sold incurred by AbbVie; also includes commercial costs incurred by AbbVie and Ironwood that are attributable to the cost-sharing arrangement between the parties.

4 Commercial margin is defined as commercial profit on sales of LINZESS as a percent of total LINZESS U.S. net sales.

US LINZESS Full Brand Collaboration1

Revenue/Expense Calculation

(In thousands)

(unaudited)

1 Ironwood collaborates with AbbVie on the development and commercialization of linaclotide in North America. Under the terms of the collaboration agreement, Ironwood receives 50% of the net profits and bears 50% of the net losses from the commercial sale of LINZESS in the U.S. The purpose of this table is to present calculations of the total net profit (loss) generated from the sales of LINZESS in the U.S., including the commercial costs and expenses and the research and development expenses related to LINZESS in the U.S. that are shared equally between the parties under the collaboration agreement.

2 LINZESS net sales are recognized using AbbVie’s revenue recognition accounting policies and reporting conventions. As a result, certain rebates and discounts are classified as LINZESS U.S. commercial costs, expenses and other discounts within Ironwood’s calculation of collaborative arrangements revenue.

3 Includes certain discounts recognized and cost of goods sold incurred by AbbVie; also includes commercial costs incurred by AbbVie and Ironwood that are attributable to the cost-sharing arrangement between the parties.

4 R&D expenses related to LINZESS in the U.S. are shared equally between Ironwood and AbbVie under the collaboration agreement.