We also aim to leverage our leading capabilities in GI to bring additional treatment options to GI patients; for example, in November 2021, we entered into a collaboration and license option agreement, or the COUR Collaboration Agreement, with COUR Pharmaceutical Development Company, Inc., or COUR, which grants us an option to acquire an exclusive license to research, develop, manufacture and commercialize, in the U.S., products containing CNP-104, a tolerizing immune modifying nanoparticle, for the treatment of primary biliary cholangitis, or PBC. We are also advancing IW-3300, a GC-C agonist, for the potential treatment of visceral pain conditions, such as interstitial cystitis/bladder pain syndrome, or IC/BPS, and endometriosis.
To date, we have dedicated a majority of our activities to the research, development and commercialization of linaclotide, as well as to the research and development of our other product candidates. Prior to the year ended December 31, 2019, we incurred net losses in each year since our inception in 1998. We have generated net income in each year thereafter. For the three and six months ended June 30, 2022, we recorded net income of $37.1 million and $75.9 million, respectively. For the three and six months ended June 30, 2021, we recorded net income of $391.3 million and $431.2 million, respectively. As of June 30, 2022, we had an accumulated deficit of $795.6 million. We are unable to predict the extent of any future losses or guarantee that our company will be able to maintain positive cash flows.
We were incorporated in Delaware on January 5, 1998 as Microbia, Inc. On April 7, 2008, we changed our name to Ironwood Pharmaceuticals, Inc. We operate in one reportable business segment—human therapeutics.
Financial Operations Overview
Revenues. Our revenues are generated primarily through our collaborative arrangements and license agreements related to research and development and commercialization of linaclotide.
The majority of our revenues are generated from the sales of LINZESS in the U.S. We record our share of the net profits and losses from the sales of LINZESS in the U.S. less commercial expenses on a net basis and present the settlement payments to and from AbbVie as collaboration expense or collaborative arrangements revenue, as applicable. Net profits or losses consist of net sales to third-party customers and sublicense income in the U.S. less the cost of goods sold as well as selling, general and administrative expenses. Although we expect net sales to increase over time, the settlement payments between AbbVie and us, resulting in collaborative arrangements revenue or collaboration expense, are subject to fluctuation based on the ratio of selling, general and administrative expenses incurred by each party. In addition, our collaborative arrangements revenue may fluctuate as a result of the timing and amount of license fees and clinical and commercial milestones received and recognized under our current and future strategic partnerships as well as timing and amount of royalties from the sales of linaclotide in the European, Canadian, Mexican, Japanese or Chinese markets or any other markets where linaclotide receives approval and is commercialized.
Research and Development Expense. The core of our research and development strategy is to leverage our demonstrated expertise and capabilities in GI diseases to bring multiple medicines to patients. Research and development expense consists of expenses incurred in connection with the research into and development of products and product candidates. These expenses consist primarily of compensation, benefits and other employee-related expenses, research and development related facility costs, third-party contract costs relating to nonclinical study and clinical trial activities, development of manufacturing processes, regulatory registration of third-party manufacturing facilities, and licensing fees for our product candidates. Research and development expenses include amounts owed to AbbVie in connection with our collaboration agreement.
Linaclotide. Our commercial product, LINZESS, is commercially available in the U.S. for the treatment of IBS-C or CIC in adults. Linaclotide is also available to adult men and women suffering from IBS-C or CIC in certain countries of the world, including China, Japan, and in a number of E.U. countries.
We and AbbVie continue to explore ways to enhance the clinical profile of LINZESS by studying linaclotide in additional indications, populations and formulations to assess its potential to treat various conditions. In September 2020, based on the Phase IIIb data of linaclotide 290 mcg on the overall abdominal symptoms of bloating pain and discomfort in adult patients with IBS-C, the U.S. FDA approved our Supplemental New Drug Application to include a more comprehensive description of the effects of LINZESS in its approved label.
In connection with the U.S. FDA approval of LINZESS, we were required to conduct certain nonclinical and clinical studies including those aimed at further understanding the safety profile of linaclotide. We and AbbVie completed additional studies and determined that: (a) orally administered linaclotide was not detected in breast milk, (b)