As a result of the factors discussed above, as well as the factors discussed under “Note Regarding Forward-Looking Statements” in this Quarterly Report on Form 10-Q and under “Part I, Item 1A – Risk Factors” in our 2021 Annual Report on Form 10-K, we are unable to determine the duration and costs to complete current or future nonclinical and clinical stages of our product candidates or when, or to what extent, we will generate revenues from the commercialization and sale of our product candidates. Development timelines, probability of success and development costs vary widely. We anticipate that we will make determinations as to which additional programs to pursue and how much funding to direct to each program on an ongoing basis in response to the data of each product candidate, the competitive landscape and ongoing assessments of such product candidate’s commercial potential.
We expect to invest in our development programs for the foreseeable future. We will continue to invest in linaclotide, including the investigation of ways to enhance the clinical profile within its currently approved indications, and the exploration of its potential utility in other indications, populations and formulations. We will continue to invest in our GI-focused product candidates as we advance them through pre-clinical and clinical trials, in addition to funding research and development activities under our external collaboration and license agreements.
Selling, General and Administrative Expense. Selling, general and administrative expense consists primarily of compensation, benefits and other employee-related expenses for personnel in our administrative, finance, legal, information technology, business development, commercial, sales, marketing, communications and human resource functions. Other costs include legal costs of pursuing patent protection of our intellectual property, general and administrative related facility costs, insurance costs and professional fees for accounting, tax, consulting, legal and other services. As we continue to invest in the commercialization of LINZESS, we expect our selling, general and administrative expenses will be substantial for the foreseeable future.
We include AbbVie’s collaboration-related commercial costs, expenses, and other discounts in the calculation of the net profits and net losses from the sale of LINZESS in the U.S. and present the net payment to or from AbbVie as collaboration expense or collaborative arrangements revenue, respectively.
Restructuring Expenses. Restructuring expenses pertain to a workforce reduction and restructuring initiative and are more fully described in Note 17, Workforce Reductions and Restructuring, to our consolidated financial statements in our 2021 Annual Report on Form 10-K.
Interest Expense. Interest expense consists primarily of cash and non-cash interest costs related to our convertible senior notes. Prior to the adoption of ASU 2020-06 on January 1, 2022, non-cash interest expense consisted of amortization of the debt discount and debt issuance costs. Following the adoption of ASU 2020-06 on January 1, 2022, non-cash interest expense consists solely of amortization of the debt issuance costs. The adoption of ASU 2020-06 is more fully described in Note 2, Summary of Significant Accounting Policies, to our condensed consolidated financial statements appearing elsewhere in this Quarterly Report on Form 10-Q.
Interest and Investment Income. Interest and investment income consists of interest earned on our cash and cash equivalents, as well as significant financing components of payments due from collaboration partners.
Gain (Loss) on Derivatives. In June 2015, we issued 2.25% Convertible Senior Notes due June 15, 2022, or the 2022 Convertible Notes, and in August 2019, we issued 0.75% Convertible Senior Notes due 2024, or the 2024 Convertible Notes, and 1.50% Convertible Senior Notes due 2026, or the 2026 Convertible Notes (together with the 2022 Convertible Notes and the 2024 Convertible Notes, the Convertible Senior Notes). In connection with the issuance of our 2022 Convertible Notes, we entered into convertible note hedge transactions, or the Convertible Note Hedges, and separate note hedge warrant transactions, or the Note Hedge Warrants, with certain financial institutions. Gain (loss) on derivatives consists of the change in fair value of the Convertible Note Hedges and Note Hedge Warrants, which are recorded at fair value at each reporting date and changes in fair value are recorded in our condensed consolidated statements of income. The Convertible Note Hedges and Note Hedge Warrants are more fully described in Note 8, Notes Payable, to our condensed consolidated financial statements appearing elsewhere in this Quarterly Report on Form 10-Q.
Income Taxes. We prepare our income tax provision based on our interpretation of the income tax accounting rules and each jurisdiction’s enacted tax laws and regulations and record our income tax provision by applying our estimated annual effective tax rate to year-to-date pre-tax income, plus adjustments for significant unusual or infrequently occurring items.