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Organization and Significant Accounting Policies (Policies) | 12 Months Ended
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Dec. 31, 2018
Organization and Significant Accounting Policies [Abstract] |
Basis of Presentation | Basis of Presentation In our consolidated financial statements we included the accounts of Ionis Pharmaceuticals, Inc. (“we”, “us” or “our”) and the consolidated results of our majority-owned affiliate, Akcea Therapeutics, Inc., which we formed in December 2014. In July 2017, Akcea completed an initial public offering, or IPO, and therefore beginning in July 2017, we no longer own 100 percent of Akcea. From the closing of Akcea’s IPO in July 2017 through mid-April 2018, we owned approximately 68 percent of Akcea. In the second, third and fourth quarters of 2018, we received additional shares of Akcea’s stock related to our license of TEGSEDI and AKCEA-TTR-LRx to Akcea, increasing our ownership percentage to approximately 75 percent. We reflected the increase in our ownership in these financial statements. In the first quarter of 2019, Akcea will pay us a $75 million sublicense fee in Akcea common stock, as a result of Novartis’ license of AKCEA-APO(a)-LRx in February 2019. We will receive 2.8 million shares of Akcea common stock for the sublicense fee. Refer to the noncontrolling interest in Akcea section in this note for further information related to our accounting for our investment in Akcea.
Basic and Diluted Net Income (Loss) per Share | Basic and Diluted Net Income (Loss) per Share Basic net income (loss) per share We compute basic net income (loss) per share by dividing the total net income (loss) attributable to our common stockholders by our weighted-average number of common shares outstanding during the period. The calculation of total net income (loss) attributable to our common stockholders for 2018 and 2017 considered our net income for Ionis on a stand-alone basis plus our share of Akcea’s net loss for the period. During 2016, we owned 100 percent of Akcea. To calculate the portion of Akcea’s net loss attributable to our ownership for 2018 and 2017, we multiplied Akcea’s loss per share by the weighted average shares we owned in Akcea during the period. As a result of this calculation, our total net income (loss) available to Ionis common stockholders for the calculation of net income (loss) per share is different than net income (loss) attributable to Ionis Pharmaceuticals, Inc. common stockholders in our consolidated statements of operations for 2018 and 2017. Our basic net income per share for 2018, was calculated as follows (in thousands, except per share amounts):
Year Ended December 31, 2018 |  | Weighted Average Shares Owned in Akcea |  |  | Akcea’s Net Income (Loss) Per Share |  |  | Ionis’ Portion of Akcea’s Net Loss |
Common shares |  |  | 59,812 |  |  | $ | (2.74 | ) |  | $ | (163,938 | )
Akcea’s net loss attributable to our ownership |  |  |  |  |  |  |  |  |  | $ | (163,938 | )
Ionis’ stand-alone net income |  |  |  |  |  |  |  |  |  |  | 440,806 |
Net income available to Ionis common stockholders |  |  |  |  |  |  |  |  |  | $ | 276,868 |
Weighted average shares outstanding |  |  |  |  |  |  |  |  |  |  | 132,320 |
Basic net income per share |  |  |  |  |  |  |  |  |  | $ | 2.09 |
Prior to Akcea’s IPO in July 2017, we owned Akcea series A convertible preferred stock, which included a six percent cumulative dividend. Upon completion of Akcea’s IPO in July 2017, our preferred stock was converted into common stock on a 1:1 basis. The preferred stock dividend was not paid at the IPO because the IPO was not a liquidation event or a change in control. During 2017, Akcea used a two-class method to compute its net income (loss) per share because it had both common and preferred shares outstanding during the periods. The two-class method required Akcea to calculate its net income (loss) per share for each class of stock by dividing total distributable losses applicable to preferred and common stock, including the six percent cumulative dividend contractually due to series A convertible preferred shareholders, by the weighted-average of preferred and common shares outstanding during the requisite period. Since Akcea used the two-class method, accounting rules required us to include our portion of Akcea’s net income (loss) per share for both Akcea’s common and preferred shares that we owned in our calculation of basic and diluted net income (loss) per share for year ended December 31, 2017. We calculated our basic net income per share for 2017 as follows (in thousands, except per share amounts):
Year Ended December 31, 2017 |  | Weighted Average Shares Owned in Akcea |  |  | Akcea’s Net Loss Per Share |  |  | Ionis’ Portion of Akcea’s Net Loss |
Common shares |  |  | 20,669 |  |  | $ | (3.08 | ) |  | $ | (63,638 | )
Preferred shares |  |  | 15,748 |  |  |  | (1.80 | ) |  |  | (28,346 | )
Akcea’s net loss attributable to our ownership |  |  |  |  |  |  |  |  |  | $ | (91,984 | )
Ionis’ stand-alone net income |  |  |  |  |  |  |  |  |  |  | 110,776 |
Net income available to Ionis common stockholders |  |  |  |  |  |  |  |  |  | $ | 18,792 |
Weighted average shares outstanding |  |  |  |  |  |  |  |  |  |  | 124,016 |
Basic net income per share |  |  |  |  |  |  |  |  |  | $ | 0.15 |
Dilutive net income (loss per share) For 2018 and 2017, we had net income available to Ionis common stockholders. As a result, we computed diluted net income per share using the weighted-average number of common shares and dilutive common equivalent shares outstanding during those periods. We calculated our diluted net income per share for 2018 as follows (in thousands except per share amounts):
Year Ended December 31, 2018 |  | Income (Numerator) |  |  | Shares (Denominator) |  |  | Per-Share Amount |
Net income available to Ionis common stockholders |  | $ | 276,868 |  |  |  | 132,320 |  |  | $ | 2.09 |
Effect of dilutive securities: |  |  |  |  |  |  |  |  |  |  |  |
Shares issuable upon exercise of stock options |  |  | — |  |  |  | 1,216 |  |  |  |  |
Shares issuable upon restricted stock award issuance |  |  | — |  |  |  | 514 |  |  |  |  |
Shares issuable related to our ESPP |  |  | — |  |  |  | 6 |  |  |  |  |
Income available to Ionis common stockholders, plus assumed conversions |  | $ | 276,868 |  |  |  | 134,056 |  |  | $ | 2.07 |
We calculated our diluted net income per share for 2017 as follows (in thousands except per share amounts):
Year Ended December 31, 2017 |  | Income (Numerator) |  |  | Shares (Denominator) |  |  | Per-Share Amount |
Net income available to Ionis common stockholders |  | $ | 18,792 |  |  |  | 124,016 |  |  | $ | 0.15 |
Effect of dilutive securities: |  |  |  |  |  |  |  |  |  |  |  |
Shares issuable upon exercise of stock options |  |  | — |  |  |  | 1,619 |  |  |  |  |
Shares issuable upon restricted stock award issuance |  |  | — |  |  |  | 459 |  |  |  |  |
Shares issuable related to our ESPP |  |  | — |  |  |  | 4 |  |  |  |  |
Income available to Ionis common stockholders, plus assumed conversions |  | $ | 18,792 |  |  |  | 126,098 |  |  | $ | 0.15 |
For 2018 and 2017, the calculation excluded our convertible notes because the effect on diluted earnings per share was anti-dilutive. For 2016, we incurred a net loss; therefore, we did not include dilutive common equivalent shares in the computation of diluted net loss per share because the effect would have been anti-dilutive. Common stock from the following would have had an anti-dilutive effect on net loss per share:
| ● | 1 percent convertible senior notes;
| ● | 2¾ percent convertible senior notes;
| ● | Dilutive stock options;
| ● | Unvested restricted stock units; and
| ● | Employee Stock Purchase Plan, or ESPP.
Revenue Recognition | Revenue Recognition Adoption of New Revenue Recognition Accounting Standard (Topic 606) In May 2014, the FASB issued accounting guidance on the recognition of revenue from customers. This guidance supersedes the revenue recognition requirements we previously followed in Accounting Standards Codification, or ASC, Topic 605, Revenue Recognition, or Topic 605, and created a new Topic 606, Revenue from Contracts with Customers, or Topic 606. Under Topic 606, an entity will recognize revenue when it transfers control of promised goods or services to customers in an amount that reflects what the entity expects to receive in exchange for the goods or services. Further, an entity will recognize revenue upon satisfying the performance obligation(s) under the related contract. We adopted Topic 606 on January 1, 2018 under the full retrospective approach, which required us to revise our prior period revenue. Under Topic 606, we were required to review all of our ongoing collaboration agreements in which we recognized revenue after January 1, 2016. We were required to assess what our revenue would have been for the period from January 1, 2016 to December 31, 2017 under Topic 606. As a result of this analysis, we determined that the cumulative revenue we would have recognized under Topic 606 decreased by $86.1 million. We recorded this amount as a cumulative adjustment to our accumulated deficit as of January 1, 2016 on our revised statement of stockholders’ equity. We have labeled our prior period financial statements “as revised” to indicate the change required under the accounting rules. The following tables summarize the adjustments we were required to make to amounts we originally reported in 2017 and 2016 to adopt Topic 606 (in thousands, except per share amounts): Consolidated Balance Sheet
|  | At December 31, 2017 |
|  | As Previously Reported under Topic 605 |  |  | Topic 606 Adjustment |  |  | As Revised |
Current portion of deferred contract revenue |  | $ | 106,465 |  |  | $ | 18,871 |  |  | $ | 125,336 |
Long-term portion of deferred contract revenue |  | $ | 72,708 |  |  | $ | 35,318 |  |  | $ | 108,026 |
Accumulated deficit |  | $ | (1,187,398 | ) |  | $ | (53,636 | ) |  | $ | (1,241,034 | )
Noncontrolling interest in Akcea Therapeutics, Inc. |  | $ | 87,847 |  |  | $ | (3,580 | ) |  | $ | 84,267 |
Total stockholders’ equity |  | $ | 418,719 |  |  | $ | (53,439 | ) |  | $ | 365,280 |
Consolidated Statements of Operations
|  | Year Ended December 31, 2017 |
|  | As Previously Reported under Topic 605 |  |  | Topic 606 Adjustment |  |  | As Revised |
Revenue: |  |  |  |  |  |  |  |  |
Commercial revenue: |  |  |  |  |  |  |  |  |
SPINRAZA royalties |  | $ | 112,540 |  |  | $ | - |  |  | $ | 112,540 |
Licensing and other royalty revenue |  |  | 9,519 |  |  |  | (2,045 | ) |  |  | 7,474 |
Total commercial revenue |  |  | 122,059 |  |  |  | (2,045 | ) |  |  | 120,014 |
Research and development revenue under collaborative agreements |  |  | 385,607 |  |  |  | 8,558 |  |  |  | 394,165 |
Total revenue |  | $ | 507,666 |  |  | $ | 6,513 |  |  | $ | 514,179 |
Income from operations |  | $ | 24,534 |  |  | $ | 6,513 |  |  | $ | 31,047 |
Net income (loss) |  | $ | (17,296 | ) |  | $ | 6,513 |  |  | $ | (10,783 | )
Net income (loss) attributable to Ionis Pharmaceuticals, Inc. common stockholders |  | $ | (5,970 | ) |  | $ | 6,316 |  |  | $ | 346 |
Net income per share, basic and diluted |  | $ | 0.08 |  |  | $ | 0.07 |  |  | $ | 0.15 |
|  | Year Ended December 31, 2016 |
|  | As Previously Reported under Topic 605 |  |  | Topic 606 Adjustment |  |  | As Revised |
Revenue: |  |  |  |  |  |  |  |  |
Commercial revenue: |  |  |  |  |  |  |  |  |
SPINRAZA royalties |  | $ | 883 |  |  | $ | — |  |  | $ | 883 |
Licensing and other royalty revenue |  |  | 19,839 |  |  |  | 2,045 |  |  |  | 21,884 |
Total commercial revenue |  |  | 20,722 |  |  |  | 2,045 |  |  |  | 22,767 |
Research and development revenue under collaborative agreements |  |  | 325,898 |  |  |  | 24,111 |  |  |  | 350,009 |
Total revenue |  | $ | 346,620 |  |  | $ | 26,156 |  |  | $ | 372,776 |
Income (loss) from operations |  | $ | (46,316 | ) |  | $ | 26,156 |  |  | $ | (20,160 | )
Net income (loss) |  | $ | (86,556 | ) |  | $ | 26,156 |  |  | $ | (60,400 | )
Net income (loss) attributable to Ionis Pharmaceuticals, Inc. common stockholders |  | $ | (86,556 | ) |  | $ | 26,156 |  |  | $ | (60,400 | )
Net income (loss) per share, basic and diluted |  | $ | (0.72 | ) |  | $ | 0.22 |  |  | $ | (0.50 | )
Consolidated Statements of Cash Flows
|  | Year Ended December 31, 2017 |
|  | As Previously Reported under Topic 605 |  |  | Topic 606 Adjustment |  |  | As Revised |
Net income (loss) |  | $ | (17,296 | ) |  | $ | 6,513 |  |  | $ | (10,783 | )
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities: |  |  |  |  |  |  |  |  |  |  |  |
Deferred contract revenue |  | $ | 36,695 |  |  | $ | (6,513 | ) |  | $ | 30,182 |
Cash and cash equivalents at beginning of year |  | $ | 84,685 |  |  | $ | — |  |  | $ | 84,685 |
Cash and cash equivalents at end of year |  | $ | 129,630 |  |  | $ | — |  |  | $ | 129,630 |
|  | Year Ended December 31, 2016 |
|  | As Previously Reported under Topic 605 |  |  | Topic 606 Adjustment |  |  | As Revised |
Net income (loss) |  | $ | (86,556 | ) |  | $ | 26,156 |  |  | $ | (60,400 | )
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities: |  |  |  |  |  |  |  |  |  |  |  |
Deferred contract revenue |  | $ | (59,150 | ) |  | $ | (26,156 | ) |  | $ | (85,306 | )
Cash and cash equivalents at beginning of year |  | $ | 128,797 |  |  | $ | — |  |  | $ | 128,797 |
Cash and cash equivalents at end of year |  | $ | 84,685 |  |  | $ | — |  |  | $ | 84,685 |
Under Topic 606, compared to Topic 605, our total revenue increased $6.5 million for 2017 and $26.2 million for 2016. The change in our revenue was primarily due to:
| ● | A change in how we recognize milestone payments: Topic 606 requires us to amortize more of the milestone payments we achieve, rather than recognizing the milestone payments in full in the period in which we achieved the milestone event as we did under Topic 605. This change resulted in an increase in R&D revenue recognized for 2017 and 2016 of $23.7 million and $24.1 million, respectively.
| ● | A change in how we calculate revenue for payments we are recognizing into revenue over time: Under Topic 605, we amortized payments into revenue evenly over the period of our obligations. When we made a change to our estimated completion period, we recognized that change on a prospective basis. Under Topic 606, we are required to use an input method to determine the amount we amortize each reporting period. Each period we review our “inputs” such as our level of effort expended, including the time we estimate it will take us to complete the activities or costs incurred, relative to the total expected inputs to satisfy the performance obligation. For certain collaborations, such as Bayer and Novartis, the input method resulted in a change to the revenue we had previously recognized using a straight-line amortization method. This change resulted in a decrease in our R&D revenue of $15.1 million for 2017. This change did not result in an impact to our 2016 R&D revenue.
Our updated revenue recognition policy reflecting Topic 606 is as follows: Our Revenue Sources We generally recognize revenue when we have satisfied all contractual obligations and are reasonably assured of collecting the resulting receivable. We are often entitled to bill our customers and receive payment from our customers in advance of recognizing the revenue. In the instances in which we have received payment from our customers in advance of recognizing revenue, we include the amounts in deferred revenue on our consolidated balance sheet. Commercial Revenue: SPINRAZA royalties and Licensing and other royalty revenue We earn commercial revenue primarily in the form of royalty payments on net sales of SPINRAZA. We will also recognize as commercial revenue future sales milestone payments and royalties we earn under our partnerships. Commercial Revenue: TEGSEDI Product Sales, net We began adding product sales from TEGSEDI to our commercial revenue in the fourth quarter of 2018. In the U.S., TEGSEDI is distributed through an exclusive distribution agreement with a third-party logistics company, or 3PL, that takes title to TEGSEDI. The 3PL is our sole customer in the U.S. The 3PL then distributes TEGSEDI to a specialty pharmacy and a specialty distributor, which we collectively refer to as wholesalers, who then distribute TEGSEDI to health care providers and patients. In Germany, TEGSEDI is distributed through a non-exclusive distribution model with a 3PL that takes title to TEGSEDI. The 3PL is our sole customer in Germany. The 3PL in Germany then distributes TEGSEDI to hospitals and pharmacies. Research and development revenue under collaborative agreements We often enter into collaboration agreements to license and sell our technology on an exclusive or non-exclusive basis. Our collaboration agreements typically contain multiple elements, or performance obligations, including technology licenses or options to obtain technology licenses, research and development, or R&D, services, and manufacturing services. Our collaboration agreements are detailed in Note 6, Collaborative Arrangements and Licensing Agreements. Under each collaboration note we discuss our specific revenue recognition conclusions, including our significant performance obligations under each collaboration. Steps to Recognize Revenue We use a five step process to determine the amount of revenue we should recognize and when we should recognize it. The five step process is as follows:
| 1. | Identify the contract
Accounting rules require us to first determine if we have a contract with our partner, including confirming that we have met each of the following criteria:
| ● | We and our partner approved the contract and we are both committed to perform our obligations;
| ● | We have identified our rights, our partner’s rights and the payment terms;
| ● | We have concluded that the contract has commercial substance, meaning that the risk, timing, or amount of our future cash flows is expected to change as a result of the contract; and
| ● | We believe collectability is probable.
| 2. | Identify the performance obligations
We next identify the distinct goods and services we are required to provide under the contract. Accounting rules refer to these as our performance obligations. We typically have only one performance obligation at the inception of a contract, which is to perform R&D services. Often times we enter into a collaboration agreement in which we provide our partner with an option to license a medicine in the future. We may also provide our partner with an option to request that we provide additional goods or services in the future, such as active pharmaceutical ingredient, or API. We evaluate whether these options are material rights at the inception of the agreement. If we determine an option is a material right, we will consider the option a separate performance obligation. Historically, we have concluded that the options we grant to license a medicine in the future or to provide additional goods and services as requested by our partner are not material rights. These items are contingent upon future events that may not occur. When a partner exercises its option to license a medicine or requests additional goods or services, then we identify a new performance obligation for that item. In some cases, we deliver a license at the start of an agreement. If we determine that our partner has full use of the license and we do not have any additional performance obligations related to the license after delivery, then we consider the license to be a separate performance obligation.
| 3. | Determine the transaction price
We then determine the transaction price by reviewing the amount of consideration we are eligible to earn under the collaboration agreement, including any variable consideration. Under our collaboration agreements, consideration typically includes fixed consideration in the form of an upfront payment and variable consideration in the form of potential milestone payments, license fees and royalties. At the start of an agreement, our transaction price usually consists of only the upfront payment. We do not typically include any payments we may receive in the future in our initial transaction price because the payments are not probable. We reassess the total transaction price at each reporting period to determine if we should include additional payments in the transaction price. Milestone payments are our most common type of variable consideration. We recognize milestone payments using the most likely amount method because we will either receive the milestone payment or we will not, which makes the potential milestone payment a binary event. The most likely amount method requires us to determine the likelihood of earning the milestone payment. We include a milestone payment in the transaction price once it is probable we will achieve the milestone event. Most often, we do not consider our milestone payments probable until we or our partner achieve the milestone event because the majority of our milestone payments are contingent upon events that are not within our control and are usually based on scientific progress. For example, in the first quarter of 2019, we earned a $35 million milestone payment from Roche when it dosed the first patient in the Phase 3 study of IONIS-HTTRx. At December 31, 2018, we determined it was not probable that we could earn this milestone payment. As such, we did not recognize any revenue associated with it in 2018.
| 4. | Allocate the transaction price
Next, we allocate the transaction price to each of our performance obligations. When we have to allocate the transaction price to more than one performance obligation, we make estimates of the relative stand-alone selling price of each performance obligation because we do not typically sell our goods or services on a stand-alone basis. We then allocate the transaction price to each performance obligation based on the relative stand-alone selling price. We may engage a third party, independent valuation specialist to assist us with determining a stand-alone selling price for collaborations in which we deliver a license at the start of an agreement. We estimate the stand-alone selling price of these licenses using valuation methodologies, such as the relief from royalty method. Under this method, we estimate the amount of income, net of taxes, for the license. We then discount the projected income to present value. The significant inputs we use to determine the projected income of a license could include:
| ● | Estimated future product sales;
| ● | Estimated royalties on future product sales;
| ● | Contractual milestone payments;
| ● | Expenses we expect to incur;
| ● | Income taxes; and
| ● | A discount rate.
We typically estimate the selling price of R&D services by using our internal estimates of the cost to perform the specific services. The significant inputs we use to determine the selling price of our R&D services include:
| ● | The number of internal hours we estimate we will spend performing these services;
| ● | The estimated cost of work we will perform;
| ● | The estimated cost of work that we will contract with third parties to perform; and
| ● | The estimated cost of API we will use.
For purposes of determining the stand-alone selling price of the R&D services we perform and the API we will deliver, accounting guidance requires us to include a markup for a reasonable profit margin. We do not reallocate the transaction price after the start of an agreement to reflect subsequent changes in stand-alone selling prices.
| 5. | Recognize revenue
We recognize revenue in one of two ways, over time or at a point in time. We recognize revenue over time when we are executing on our performance obligation over time and our partner receives benefit over time. For example, we recognize revenue over time when we provide R&D services. We recognize revenue at a point in time when our partner receives full use of an item at a specific point in time. For example, we recognize revenue at a point in time when we deliver a license or API to a partner. For R&D services that we recognize over time, we measure our progress using an input method. The input methods we use are based on the effort we expend or costs we incur toward the satisfaction of our performance obligation. We estimate the amount of effort we expend, including the time we estimate it will take us to complete the activities, or costs we incur in a given period, relative to the estimated total effort or costs to satisfy the performance obligation. This results in a percentage that we multiply by the transaction price to determine the amount of revenue we recognize each period. This approach requires us to make numerous estimates and use significant judgement. If our estimates or judgements change over the course of the collaboration, they may affect the timing and amount of revenue that we recognize in the current and future periods. The following are examples of when we typically recognize revenue based on the types of payments we receive. Commercial Revenue: SPINRAZA royalties and Licensing and other royalty revenue We recognize royalty revenue in the period in which the counterparty sells the related product, which in certain cases may require us to estimate our royalty revenue. We recognize royalties from SPINRAZA sales in the period Biogen records the sale of SPINRAZA. Our accounting for SPINRAZA royalties did not change as a result of adopting Topic 606. Commercial Revenue: TEGSEDI Product Sales, net We recognize TEGSEDI product sales in the period when our customer obtains control of TEGSEDI, which occurs at a point in time upon transfer of title to the customer. We classify payments to customers or other parties in the distribution channel for services that are distinct and priced at fair value as selling, general and administrative expenses in our consolidated statements of operations. Otherwise payments to customers or other parties in the distribution channel that do not meet those criteria are classified as a reduction of revenue, as discussed further below. We exclude from revenues, taxes collected from customers relating to product sales and remitted to governmental authorities. Reserves for TEGSEDI Product Sales We record TEGSEDI product sales at our net sales price, or transaction price. We include in our transaction price estimated reserves for discounts, returns, chargebacks, rebates, co-pay assistance and other allowances that we offer within contracts between us and our customers, wholesalers, health care providers and other indirect customers. We estimate our reserves using the amounts we have earned or what we can claim on the associated sales. We classify our reserves as reductions of accounts receivable when the amount is payable to our customer or a current liability when the amount is payable to a party other than our customer in our consolidated balance sheet. In certain cases, our estimates include a range of possible outcomes that are probability-weighted for relevant factors such as our historical experience, current contractual and statutory requirements, specific known market events and trends, industry data and forecasted customer buying and payment patterns. Overall, our reserves reflect our best estimates under the terms of our respective contracts. When calculating our reserves and related product sales, we only recognize amounts to the extent that we consider it probable that we would not have to reverse in a future period a significant amount of the cumulative sales we previously recognized. The actual amounts we receive may ultimately differ from our reserve estimates. If actual amounts in the future vary from our estimates, we will adjust these estimates, which would affect our net TEGSEDI product sales in the respective period. The following are the components of variable consideration related to TEGSEDI product sales: Chargebacks: In the U.S., we estimate obligations resulting from contractual commitments with the government and other entities to sell products to qualified healthcare providers at prices lower than the list prices charged to our U.S. customer. Our U.S. customer charges us for the difference between what it pays for the product and the selling price to the qualified healthcare providers. We record reserves for these chargebacks related to TEGSEDI product sales to our U.S. customer during the reporting period. We also estimate the amount of product remaining in the distribution channel inventory at the end of the reporting period that we expect our customer to sell to wholesalers in future periods. Government rebates: We are subject to discount obligations under government programs, including Medicaid programs and Medicare in the U.S. We estimate Medicaid and Medicare rebates based on a range of possible outcomes that are probability-weighted for the estimated payer mix. We record these reserves as an accrued liability on our consolidated balance sheet with a corresponding offset reducing our TEGSEDI product sales in the same period we recognize the related sale. For Medicare rebates, we also estimate the number of patients in the prescription drug coverage gap for whom we will owe an additional liability under the Medicare Part D program. On a quarterly basis, we update our estimates and record any adjustments in the period that we identify the adjustments. In Germany, pharmaceutical companies must grant a specified rebate percentage to the German government. We include this rebate in the same period we recognize the related TEGSEDI product sales, resulting in a reduction of product sales. Trade discounts and allowances: We provide customary invoice discounts on TEGSEDI product sales to our U.S. customer for prompt payment. We record this discount as a reduction of TEGSEDI product sales in the period in which we recognize the related product revenue. In addition, we receive and pay for various distribution services from our U.S. customer and wholesalers in our U.S. distribution channel. For services we receive that are either not distinct from the sale of TEGSEDI or for which we cannot reasonably estimate the fair value, we classify such fees as a reduction of TEGSEDI product sales. Product Returns: Our U.S. customer has return rights and the wholesalers have limited return rights primarily related to the expiration date of the TEGSEDI product. We estimate the amount of TEGSEDI product sales that our customer may return. We record our return estimate as an accrued refund liability on our consolidated balance sheet with a corresponding offset reducing our TEGSEDI product sales, in the same period we recognize the related sale. Based on our distribution model for TEGSEDI, contractual inventory limits with our customer and wholesalers and the price of TEGSEDI, we believe we will have minimal returns. Our customer in Germany only takes title to the product once it receives an order from a hospital or pharmacy and therefore does not maintain any inventory of TEGSEDI, as such we do not estimate returns in Germany. Other incentives: In the U.S., we estimate reserves for other incentives including co-payment assistance we provide to patients with commercial insurance who have coverage and reside in states that allow co-payment assistance. We record a reserve for the amount we estimate we will pay for co-payment assistance. We base our reserve on the number of estimated claims and our estimate of the cost per claim related to TEGSEDI product sales that we have recognized as revenue. We record our other incentive reserve estimates as an accrued liability on our consolidated balance sheet with a corresponding offset reducing our TEGSEDI product sales, in the same period we recognize the related sale. Research and development revenue under collaboration agreements: Upfront Payments When we enter into a collaboration agreement with an upfront payment, we typically record the entire upfront payment as deferred revenue if our only performance obligation is for R&D services we will provide in the future. We amortize the upfront payment into revenue as we perform the R&D services. For example, under our new collaboration agreement with Roche to develop IONIS-FB-LRx for the treatment of complement-mediated diseases, we received a $75 million upfront payment in the fourth quarter of 2018. We allocated the upfront payment to our single performance obligation, R&D services. We are amortizing the $75 million upfront payment using an input method over the estimated period of time we are providing R&D services. Refer to Note 6, Collaborative Arrangements and Licensing Agreements, for further discussion. Under Topic 605, we amortized upfront payments evenly over the period of our obligation. Milestone Payments We are required to include additional consideration in the transaction price when it is probable. We typically include milestone payments for R&D services in the transaction price when they are achieved. We include these milestone payments when they are achieved because there is considerable uncertainty in the research and development processes that trigger these payments under our collaboration agreements. Similarly, we include approval milestone payments in the transaction price once the medicine is approved by the applicable regulatory agency. We will recognize sales based milestone payments in the period we achieve the milestone under the sales-based royalty exception allowed under accounting rules. We recognize milestone payments that relate to an ongoing performance obligation over our period of performance. For example, in the third quarter of 2017, we initiated a Phase 1/2a clinical study of IONIS-MAPTRx in patients with mild Alzheimer’s disease. We earned a $10 million milestone payment from Biogen related to the initiation of this study. Under Topic 606, we added this payment to the transaction price and allocated it to our R&D services performance obligation. We are recognizing revenue from this milestone payment over our estimated period of performance. Under Topic 605, this milestone payment was recognized in full in the third quarter of 2017, which was the period in which we achieved the milestone event. Conversely, we recognize in full those milestone payments that we earn based on our partners’ activities when our partner achieves the milestone event. For example, in the third quarter of 2018, we recognized a $10 million milestone payment when AstraZeneca initiated a Phase 1 study of IONIS-AZ4-2.5-LRx. We concluded that the milestone payment was not related to our R&D services performance obligation. Therefore, we recognized this milestone payment in full in the third quarter of 2018 because we do not have any performance obligations related to this milestone payment. Our revenue recognition of milestone payments we earn based on our partners’ activities did not change as a result of adopting Topic 606. License Fees We generally recognize as revenue the total amount we determine to be the stand-alone selling price of a license when we deliver the license to our partner. This is because our partner has full use of the license and we do not have any additional performance obligations related to the license after delivery. For example, in the fourth quarter of 2018, we earned a $35 million license fee when Biogen licensed IONIS-SOD1Rx from us. Our recognition of license fees did not change as a result of adopting Topic 606. Amendments to Agreements From time to time we amend our collaboration agreements. When this occurs, we are required to assess the following items to determine the accounting for the amendment:
| 1) | If the additional goods and/or services are distinct from the other performance obligations in the original agreement; and
| 2) | If the goods and/or services are at a stand-alone selling price.
If we conclude the goods and/or services in the amendment are distinct from the performance obligations in the original agreement and at a stand-alone selling price, we account for the amendment as a separate agreement. If we conclude the goods and/or services are not distinct and at their stand-alone selling price, we then assess whether the remaining goods or services are distinct from those already provided. If the goods and/or services are distinct from what we have already provided, then we allocate the remaining transaction price from the original agreement and the additional transaction price from the amendment to the remaining goods and/or services. If the goods and/or services are not distinct from what we have already provided, we update the transaction price for our single performance obligation and recognize any change in our estimated revenue as a cumulative adjustment. For example, in May 2015, we entered into an exclusive license agreement with Bayer to develop and commercialize IONIS-FXIRx for the prevention of thrombosis. As part of the agreement, Bayer paid us a $100 million upfront payment. At the onset of the agreement, we were responsible for completing a Phase 2 study of IONIS-FXIRx in people with end-stage renal disease on hemodialysis and for providing an initial supply of API. In February 2017, we amended our agreement with Bayer to advance IONIS-FXIRx and to initiate development of IONIS-FXI-LRx, which Bayer licensed. As part of the 2017 amendment, Bayer paid us $75 million. We are also eligible to receive milestone payments and tiered royalties on gross margins of IONIS-FXIRx and IONIS-FXI-LRx. Under the 2017 amendment, we concluded we had a new agreement with three performance obligations. These performance obligations were to deliver the license of IONIS-FXI-LRx, to provide R&D services and to deliver API. We allocated the $75 million transaction price to these performance obligations. Refer to Note 6, Collaborative Arrangements and Licensing Agreements, for further discussion of our accounting treatment for our Bayer collaboration. Our allocation of the consideration we received for the Bayer amendment did not change as a result of adopting Topic 606. However, the method in which we are recognizing revenue related to our R&D services performance obligation did change. We are amortizing revenue related to our R&D services performance obligation using the input method under Topic 606. Multiple Agreements From time to time, we may enter into separate agreements at or near the same time with the same partner. We evaluate such agreements to determine whether we should account for them individually as distinct arrangements or whether the separate agreements should be combined and accounted for together. We evaluate the following to determine the accounting for the agreements:
| ● | Whether the agreements were negotiated together with a single objective;
| ● | Whether the amount of consideration in one contract depends on the price or performance of the other agreement; or
| ● | Whether the goods and/or services promised under the agreements are a single performance obligation.
Our evaluation involves significant judgment to determine whether a group of agreements might be so closely related that accounting guidance requires us to account for them as a combined arrangement. For example, in the second quarter of 2018, we entered into two separate agreements with Biogen at the same time: a new strategic neurology collaboration agreement and a stock purchase agreement, or SPA. We evaluated the Biogen agreements to determine whether we should treat the agreements separately or combine them. We considered that the agreements were negotiated concurrently and in contemplation of one another. Based on these facts and circumstances, we concluded that we should evaluate the provisions of the agreements on a combined basis. Refer to Note 6, Collaborative Arrangements and Licensing Agreements for further discussion of the accounting treatment for the 2018 strategic neurology collaboration with Biogen. Contracts Receivable Our contracts receivable balance represents the amounts we have billed our partners for goods we have delivered or services we have performed that are due to us unconditionally. When we bill our partners with payment terms based on the passage of time, we consider the contract receivable to be unconditional. We typically receive payment within one quarter of billing our partner. Our contracts receivable balance as of December 31, 2017 did not change when we adopted Topic 606. Unbilled SPINRAZA Royalties Our unbilled SPINRAZA royalties represent our right to receive consideration from Biogen in advance of when we are eligible to bill Biogen for SPINRAZA royalties. We include these unbilled amounts in other current assets on our consolidated balance sheet. Our unbilled SPINRAZA royalties as of December 31, 2017 did not change when we adopted Topic 606. Deferred Revenue We are often entitled to bill our customers and receive payment from our customers in advance of our obligation to provide services or transfer goods to our partners. In these instances, we include the amounts in deferred revenue on our consolidated balance sheet. During the years ended December 31, 2018 and 2017, we recognized $105.3 million and $95.1 million of revenue from amounts that were in our beginning deferred revenue balances for those periods, respectively. Refer to our revenue recognition policy above detailing how we recognize revenue for further discussion. The following table summarizes the adjustments we were required to make to our deferred revenue amounts to adopt Topic 606 (in thousands):
|  | At December 31, 2017 |
|  | As Previously Reported under Topic 605 |  |  | Topic 606 Adjustment |  |  | As Revised |
Current portion of deferred contract revenue |  | $ | 106,465 |  |  | $ | 18,871 |  |  | $ | 125,336 |
Long-term portion of deferred contract revenue |  |  | 72,708 |  |  |  | 35,318 |  |  |  | 108,026 |
Total deferred revenue |  | $ | 179,173 |  |  | $ | 54,189 |  |  | $ | 233,362 |
Our deferred revenue balance increased $54.2 million at December 31, 2017 under Topic 606, compared to Topic 605. The increase was primarily related to the change in the accounting for certain milestone payments and the way in which we amortize payments. Under Topic 605, we previously recognized the majority of the milestone payments we earned in the period we achieved the milestone event, which did not impact our deferred revenue balance. Under Topic 606 we are now amortizing more milestone payments over the period of our performance obligation, which adds to our deferred revenue balance. Additionally, under Topic 605 we amortized payments evenly over the period of our obligation. Under Topic 606, we are required to use an input method to determine the amount we amortize each reporting period. The increase in deferred revenue relates to agreements with the following partners:
| ● | $24.2 million from Biogen;
| ● | $15.9 million from AstraZeneca;
| ● | $11.8 million from Novartis; and
| ● | $ 2.3 million from other partners.
Cost of Products Sold | Cost of Products Sold We obtained the first regulatory approval for TEGSEDI in July 2018, as a result we began recognizing cost of products sold expenses related to TEGSEDI. Our cost of products sold includes manufacturing costs, transportation and freight costs and indirect overhead costs associated with the manufacturing and distribution of TEGSEDI. We also may include certain period costs related to manufacturing services and inventory adjustments in cost of products sold. Prior to obtaining regulatory approval, we expensed a significant portion of the costs we incurred to produce the TEGSEDI supply we are using in the commercial launch as research and development expense. We previously recognized $0.1 million of costs to produce TEGSEDI related to the TEGSEDI commercial revenue we recognized in 2018.
Research and Development Expenses | Our research and development expenses include wages, benefits, facilities, supplies, external services, clinical trial and manufacturing costs and other expenses that are directly related to our research and development operations. We expense research and development costs as we incur them. When we make payments for research and development services prior to the services being rendered, we record those amounts as prepaid assets on our consolidated balance sheet and we expense them as the services are provided. For the years ended December 31, 2018, 2017 and 2016, research and development expenses were $411.9 million, $372.5 million and $340.4 million, respectively. A portion of the costs included in research and development expenses are costs associated with our partner agreements. For the years ended December 31, 2018, 2017 and 2016, research and development costs of approximately $58.7 million, $59.5 million and $187.1 million, respectively, were related to our partner agreements.
Patent Expenses | We capitalize costs consisting principally of outside legal costs and filing fees related to obtaining patents. We amortize patent costs over the useful life of the patent, beginning with the date the U.S. Patent and Trademark Office, or foreign equivalent, issues the patent. The weighted average remaining amortizable life of our issued patents was 10.1 years at December 31, 2018. The cost of our patents capitalized on our consolidated balance sheet at December 31, 2018 and 2017 was $32.7 million and $30.8 million, respectively. Accumulated amortization related to patents was $8.7 million and $8.8 million at December 31, 2018 and 2017, respectively. Based on our existing patents, we estimate amortization expense related to patents in each of the next five years to be the following:
Years Ending December 31, |  | Amortization (in millions) |
2019 |  | $ | 1.7 |
2020 |  | $ | 1.6 |
2021 |  | $ | 1.5 |
2022 |  | $ | 1.4 |
2023 |  | $ | 1.3 |
We review our capitalized patent costs regularly to ensure that they include costs for patents and patent applications that have future value. When we identify patents and patent applications that we are not actively pursuing, we write off any associated costs. In 2018, 2017 and 2016, patent expenses were $2.6 million, $2.1 million and $3.9 million, respectively, and included non-cash charges related to the write-down of our patent costs to their estimated net realizable values of $0.8 million, $0.4 million and $2.3 million, respectively.
Noncontrolling Interest in Akcea Therapeutics, Inc. | Noncontrolling Interest in Akcea Therapeutics, Inc. Prior to Akcea’s IPO in July 2017, we owned 100 percent of Akcea. From the closing of Akcea’s IPO in July 2017 through mid-April 2018, we owned approximately 68 percent of Akcea. In the second, third and fourth quarters of 2018, we received additional shares of Akcea’s stock related to our license of TEGSEDI and AKCEA-TTR-LRx to Akcea, increasing our ownership percentage to approximately 75 percent. We reflected this increase in our ownership percentage in these financial statements as an adjustment to noncontrolling interest. The shares third parties own represent an interest in Akcea’s equity that is not controlled by us. However, as we continue to maintain overall control of Akcea through our voting interest, we reflect the assets, liabilities and results of operations of Akcea in our consolidated financial statements. We reflect the noncontrolling interest attributable to other owners of Akcea’s common stock in a separate line on the statement of operations and a separate line within stockholders’ equity in our consolidated balance sheet. In addition, we record a noncontrolling interest adjustment to account for the stock options Akcea grants, which if exercised, will dilute our ownership in Akcea. This adjustment is a reclassification within stockholders’ equity from additional paid-in capital to noncontrolling interest in Akcea equal to the amount of stock-based compensation expense Akcea had recognized.
Concentration of Credit Risk | Concentration of Credit Risk Financial instruments that potentially subject us to concentrations of credit risk consist primarily of cash equivalents, short-term investments and receivables. We place our cash equivalents and short-term investments with reputable financial institutions. We primarily invest our excess cash in commercial paper and debt instruments of the U.S. Treasury, financial institutions, corporations, and U.S. government agencies with strong credit ratings and an investment grade rating at or above A-1, P-1 or F-1 by Moody’s, Standard & Poor’s, or S&P, or Fitch, respectively. We have established guidelines relative to diversification and maturities that maintain safety and liquidity. We periodically review and modify these guidelines to maximize trends in yields and interest rates without compromising safety and liquidity.
Cash, Cash Equivalents and Investments | Cash, Cash Equivalents and Short-Term Investments We consider all liquid investments with maturities of three months or less when we purchase them to be cash equivalents. Our short-term investments have initial maturities of greater than three months from date of purchase. We classify our short-term debt investments as “available-for-sale” and carry them at fair market value based upon prices on the last day of the fiscal period for identical or similar items. We record unrealized gains and losses on debt securities as a separate component of comprehensive income (loss) and include net realized gains and losses in gain (loss) on investments. We use the specific identification method to determine the cost of securities sold. We also have equity investments of less than 20 percent ownership in publicly and privately held biotechnology companies that we received as part of a technology license or partner agreement. At December 31, 2018, we held equity investments in two publicly held companies, ProQR Therapeutics N.V., or ProQR, and Antisense Therapeutics Limited, or ATL. We also held equity investments in four privately-held companies, Atlantic Pharmaceuticals Limited, Dynacure SAS, Seventh Sense Biosystems and Suzhou Ribo Life Science Co, Ltd. In January 2018, we adopted the amended accounting guidance related to the recognition, measurement, presentation, and disclosure of certain financial instruments. The amended guidance requires us to measure and record our equity investments at fair value. Additionally, the amended accounting guidance requires us to recognize the changes in fair value in our consolidated statement of operations, instead of through accumulated other comprehensive income. Prior to 2018, we accounted for our equity investments in privately held companies under the cost method of accounting. Under the amended guidance we account for our equity investments in privately held companies at their cost minus impairments, plus or minus changes resulting from observable price changes in orderly transactions for the identical or similar investment of the same issuer. Our adoption of this guidance did not have an impact on our results.
Inventory Valuation | Inventory Valuation We reflect our inventory on our consolidated balance sheet at the lower of cost or market value under the first-in, first-out method, or FIFO. We capitalize the costs of raw materials that we purchase for use in producing our medicines because until we use these raw materials they have alternative future uses. We include in inventory raw material costs for medicines that we manufacture for our partners under contractual terms and that we use primarily in our clinical development activities and drug products. We can use each of our raw materials in multiple products and, as a result, each raw material has future economic value independent of the development status of any single medicine. For example, if one of our medicines failed, we could use the raw materials for that medicine to manufacture our other medicines. We expense these costs as R&D expenses when we begin to manufacture API for a particular medicine if the medicine has not been approved for marketing by a regulatory agency. We obtained the first regulatory approval for TEGSEDI in July 2018. At December 31, 2018, our physical inventory for TEGSEDI included API that we produced prior to when we obtained regulatory approval and accordingly has no cost basis as we had previously expensed the costs as R&D expenses. We review our inventory periodically and reduce the carrying value of items we consider to be slow moving or obsolete to their estimated net realizable value based on forecasted demand compared to quantities on hand. We consider several factors in estimating the net realizable value, including shelf life of our inventory, alternative uses for our medicines in development and historical write-offs. We did not record any inventory write-offs for the years ended December 31, 2018, 2017 or 2016. Total inventory was $8.6 million and $10.0 million as of December 31, 2018 and 2017, respectively.
Property, Plant and Equipment | Property, Plant and Equipment We carry our property, plant and equipment at cost and depreciate it on the straight-line method over its estimated useful life, which consists of the following (in thousands):
|  | Estimated Useful Lives |  |  | December 31, |
|  | (in years) |  |  | 2018 |  |  | 2017 |
Computer software, laboratory, manufacturing and other equipment |  | 3 to 10 |  |  | $ | 53,496 |  |  | $ | 66,558 |
Building, building improvements and building systems |  | 15 to 40 |  |  |  | 97,528 |  |  |  | 92,770 |
Land improvements |  |  | 20 |  |  |  | 2,853 |  |  |  | 2,853 |
Leasehold improvements |  | 5 to 15 |  |  |  | 18,981 |  |  |  | 26,748 |
Furniture and fixtures |  | 5 to 10 |  |  |  | 6,283 |  |  |  | 6,161 |
|  |  |  |  |  |  | 179,141 |  |  |  | 195,090 |
Less accumulated depreciation |  |  |  |  |  |  | (61,474 | ) |  |  | (87,676 | )
|  |  |  |  |  |  | 117,667 |  |  |  | 107,414 |
Land |  |  |  |  |  |  | 14,493 |  |  |  | 14,493 |
Total |  |  |  |  |  | $ | 132,160 |  |  | $ | 121,907 |
We depreciate our leasehold improvements using the shorter of the estimated useful life or remaining lease term.
Fair Value of Financial Instruments | Fair Value of Financial Instruments We have estimated the fair value of our financial instruments. The amounts reported for cash, accounts receivable, accounts payable and accrued expenses approximate the fair value because of their short maturities. We report our investment securities at their estimated fair value based on quoted market prices for identical or similar instruments.
Long-Lived Assets | Long-Lived Assets We evaluate long-lived assets, which include property, plant and equipment and patent costs, for impairment on at least a quarterly basis and whenever events or changes in circumstances indicate that we may not be able to recover the carrying amount of such assets. We recorded charges of $0.8 million, $0.8 million and $2.3 million for the years ended December 31, 2018, 2017 and 2016, respectively, related primarily to the write-down of intangible assets.
Use of Estimates | Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the U.S. requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates.
Stock-Based Compensation Expense | Stock-Based Compensation Expense We measure stock-based compensation expense for equity-classified awards, principally related to stock options, restricted stock units, or RSUs, and stock purchase rights under our ESPP based on the estimated fair value of the award on the date of grant. We recognize the value of the portion of the award that we ultimately expect to vest as stock-based compensation expense over the requisite service period in our Consolidated Statements of Operations. We reduce stock-based compensation expense for estimated forfeitures at the time of grant and revise in subsequent periods if actual forfeitures differ from those estimates. We use the Black-Scholes model as our method of valuing option awards and stock purchase rights under our ESPP. On the grant date, we use our stock price and assumptions regarding a number of highly complex and subjective variables to determine the estimated fair value of stock-based payment awards. These variables include, but are not limited to, our expected stock price volatility over the term of the awards, and actual and projected employee stock option exercise behaviors. Option-pricing models were developed for use in estimating the value of traded options that have no vesting or hedging restrictions and are fully transferable. Because our employee stock options have certain characteristics that are significantly different from traded options, and because changes in the subjective assumptions can materially affect the estimated value, in management’s opinion, the existing valuation models may not provide an accurate measure of the fair value of our employee stock options. Although we determine the estimated fair value of employee stock options using an option-pricing model, that value may not be indicative of the fair value observed in a willing buyer/willing seller market transaction. We recognize compensation expense for option awards and RSUs using the accelerated multiple-option approach. Under the accelerated multiple-option approach (also known as the graded-vesting method), we recognize compensation expense over the requisite service period for each separately vesting tranche of the award as though the award were in substance multiple awards, which results in the expense being front-loaded over the vesting period. The fair value of RSUs is based on the market price of our common stock on the date of grant. The RSUs we have granted vest annually over a four-year period. See Note 4, Stockholders’ Equity, for additional information regarding our stock-based compensation plans.
Accumulated Other Comprehensive Loss | Accumulated Other Comprehensive Loss Accumulated other comprehensive loss is primarily comprised of unrealized gains and losses on investments, net of taxes and adjustments we made to reclassify realized gains and losses on investments from other accumulated comprehensive loss to our Consolidated Statement of Operations. The following table summarizes changes in accumulated other comprehensive loss for the years ended December 31, 2018, 2017 and 2016 (in thousands):
|  | Year Ended December 31, |
|  | 2018 |  |  | 2017 |  |  | 2016 |
Beginning balance accumulated other comprehensive loss |  | $ | (31,759 | ) |  | $ | (30,358 | ) |  | $ | (13,565 | )
Unrealized losses on securities, net of tax (1) |  |  | (280 | ) |  |  | (960 | ) |  |  | (17,219 | )
Amounts reclassified from accumulated other comprehensive loss |  |  | — |  |  |  | (374 | ) |  |  | 447 |
Currency translation adjustment |  |  | 23 |  |  |  | (67 | ) |  |  | (21 | )
Net other comprehensive loss for the period |  |  | (257 | ) |  |  | (1,401 | ) |  |  | (16,793 | )
Ending balance accumulated other comprehensive loss |  | $ | (32,016 | ) |  | $ | (31,759 | ) |  | $ | (30,358 | )
(1) | A tax benefit of $0.3 million was included in other comprehensive loss for the year ended December 31, 2018. There was no tax benefit or expense for other comprehensive loss for the years ended December 31, 2017 or 2016.
Convertible Debt | Convertible Debt We account for convertible debt instruments, including our 1 percent and 2¾ percent notes that may be settled in cash upon conversion (including partial cash settlement) by separating the liability and equity components of the instruments in a manner that reflects our nonconvertible debt borrowing rate. We determine the carrying amount of the liability component by measuring the fair value of similar debt instruments that do not have the conversion feature. If no similar debt instrument exists, we estimate fair value by using assumptions that market participants would use in pricing a debt instrument, including market interest rates, credit standing, yield curves and volatilities. We use accounting estimates and assumptions when we determine the fair value of the debt component. These estimates and assumptions we use are judgmental in nature and could have a significant impact on the determination of the debt component, and the associated non-cash interest expense. We assigned a value to the debt component of our convertible notes equal to the estimated fair value of similar debt instruments without the conversion feature, which resulted in us recording our debt at a discount. We are amortizing our debt issuance costs and debt discount over the life of the convertible notes as additional non-cash interest expense utilizing the effective interest method. For additional information, see Note 3, Long-Term Obligations and Commitments.
Segment Information | Segment Information We have two operating segments, our Ionis Core segment and Akcea Therapeutics, our majority-owned affiliate. Akcea is a biopharmaceutical company focused on developing and commercializing medicines to treat patients with rare and serious diseases. We provide segment financial information and results for our Ionis Core segment and our Akcea Therapeutics segment based on the segregation of revenues and expenses that our chief decision maker reviews to assess operating performance and to make operating decisions. We allocate a portion of Ionis’ development, R&D support and general and administrative expenses to Akcea for work Ionis performs on behalf of Akcea.
Fair Value Measurements | Fair Value Measurements We use a three-tier fair value hierarchy to prioritize the inputs used in our fair value measurements. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets for identical assets, which includes our money market funds and treasury securities classified as available-for-sale securities and our investment in equity securities in publicly-held biotechnology companies; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable, which includes our fixed income securities and commercial paper classified as available-for-sale securities; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore requiring us to develop our own assumptions. We classify the majority of our securities as Level 2. We obtain the fair value of our Level 2 investments from our custodian bank or from a professional pricing service. We validate the fair value of our Level 2 investments by understanding the pricing model used by the custodian banks or professional pricing service provider and comparing that fair value to the fair value based on observable market prices. During 2018 and 2017, there were no transfers between our Level 1 and Level 2 investments. When we recognize transfers between levels of the fair value hierarchy, we recognize the transfer on the date the event or change in circumstances that caused the transfer occurs. The following tables present the major security types we held at December 31, 2018 and 2017 that are regularly measured and carried at fair value. At December 31, 2018, our ProQR investment was subject to trading restrictions through the fourth quarter of 2019, as a result we included a lack of marketability discount in valuing this investment, which is a Level 3 input. At December 31, 2017, we did not have any financial instruments that we valued using Level 3 inputs. The tables segregate each security type by the level within the fair value hierarchy of the valuation techniques we utilized to determine the respective securities’ fair value (in thousands):
|  | At December 31, 2018 |  |  | Quoted Prices in Active Markets (Level 1) |  |  | Significant Other Observable Inputs (Level 2) |  |  | Significant Unobservable Inputs (Level 3) |
Cash equivalents (1) |  | $ | 146,281 |  |  | $ | 146,281 |  |  | $ | — |  |  | $ | — |
Corporate debt securities (2) |  |  | 1,252,960 |  |  |  | — |  |  |  | 1,252,960 |  |  |  | — |
Debt securities issued by U.S. government agencies (3) |  |  | 276,612 |  |  |  | — |  |  |  | 276,612 |  |  |  | — |
Debt securities issued by the U.S. Treasury (4) |  |  | 260,154 |  |  |  | 260,154 |  |  |  | — |  |  |  | — |
Debt securities issued by states of the U.S. and political subdivisions of the states (3) |  |  | 79,942 |  |  |  | — |  |  |  | 79,942 |  |  |  | — |
Investment in ProQR Therapeutics N.V. (5) |  |  | 1,349 |  |  |  | — |  |  |  | — |  |  |  | 1,349 |
Total |  | $ | 2,017,298 |  |  | $ | 406,435 |  |  | $ | 1,609,514 |  |  | $ | 1,349 |
|  | At December 31, 2017 |  |  | Quoted Prices in Active Markets (Level 1) |  |  | Significant Other Observable Inputs (Level 2) |
Cash equivalents (1) |  | $ | 86,262 |  |  | $ | 86,262 |  |  | $ | — |
Corporate debt securities (6) |  |  | 647,461 |  |  |  | — |  |  |  | 647,461 |
Debt securities issued by U.S. government agencies (3) |  |  | 136,325 |  |  |  | — |  |  |  | 136,325 |
Debt securities issued by the U.S. Treasury (3) |  |  | 30,818 |  |  |  | 30,818 |  |  |  | — |
Debt securities issued by states of the U.S. and political subdivisions of the states (7) |  |  | 93,932 |  |  |  | — |  |  |  | 93,932 |
Total |  | $ | 994,798 |  |  | $ | 117,080 |  |  | $ | 877,718 |
(1) | Included in cash and cash equivalents on our consolidated balance sheet.
(2) | $50.2 million included in cash and cash equivalents on our consolidated balance sheet, with the difference included in short-term investments on our consolidated balance sheet.
(3) | Included in short-term investments on our consolidated balance sheet.
(4) | $14.2 million included in cash and cash equivalents on our consolidated balance sheet, with the difference included in short-term investments on our consolidated balance sheet.
(5) | Included in other current assets on our consolidated balance sheet.
(6) | $11.9 million included in cash and cash equivalents on our consolidated balance sheet, with the difference included in short-term investments on our consolidated balance sheet.
(7) | $3.5 million included in cash and cash equivalents on our consolidated balance sheet, with the difference included in short-term investments on our consolidated balance sheet.
Novartis Future Stock Purchase In January 2017, we and Akcea entered into a SPA with Novartis. As part of the SPA, Novartis was required to purchase $50 million of Akcea’s common stock at the IPO price or our common stock at a premium if an IPO did not occur by April 2018. Therefore, at the inception of the SPA, we recorded a $5.0 million asset representing the fair value of the potential future premium we could have received if Novartis purchased our common stock. We determined the fair value of the future premium by calculating the value based on the stated premium in the SPA and estimating the probability of an Akcea IPO. We also included a lack of marketability discount when we determined the fair value of the premium because we would have issued unregistered shares to Novartis if they had purchased our common stock. We measured this asset using Level 3 inputs and recorded it in other assets on our consolidated balance sheet. Because Akcea completed its IPO before April 2018, Novartis will not purchase additional shares of Ionis stock. Therefore, this asset no longer had any value and we wrote-off the remaining balance to other expenses on our third quarter 2017 consolidated statement of operations. The following is a reconciliation of the potential premium we would have received if Akcea had not completed its IPO, measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for 2017 (in thousands):
|  | Year Ended December 31, 2017 |
Beginning balance of Level 3 instruments |  | $ | — |
Value of the potential premium we will receive from Novartis at inception of the SPA (January 2017) |  |  | 5,035 |
Write-off of premium to other expenses |  |  | (5,035 | )
Ending balance of Level 3 instruments |  | $ | — |
Income Taxes | Income Taxes We account for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in our financial statements or tax returns. In addition, deferred tax assets are recorded for the future benefit of utilizing net operating losses and research and development credit carryforwards. We record a valuation allowance when necessary to reduce deferred tax assets to the amount we expect to realize. We apply the authoritative accounting guidance prescribing a threshold and measurement attribute for the financial recognition and measurement of a tax position taken or expected to be taken in a tax return. We recognize liabilities for uncertain tax positions based on a two-step process. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained on audit, including resolution of related appeals or litigation processes, if any. The second step requires us to estimate and measure the tax benefit as the largest amount that is more than 50 percent likely to be realized upon ultimate settlement. We are required to use significant judgment in evaluating our uncertain tax positions and determining our provision for income taxes. Although we believe our reserves are reasonable, no assurance can be given that the final tax outcome of these matters will not be different from that which is reflected in our historical income tax provisions and accruals. We adjust these reserves for changing facts and circumstances, such as the closing of a tax audit or the refinement of an estimate. To the extent that the final tax outcome of these matters is different than the amounts recorded, such differences may impact the provision for income taxes in the period in which such determination is made. We are also required to use significant judgment in determining any valuation allowance recorded against our deferred tax assets. In assessing the need for a valuation allowance, we consider all available evidence, including scheduled reversal of deferred tax liabilities, past operating results, the feasibility of tax planning strategies and estimates of future taxable income. We base our estimates of future taxable income on assumptions that are consistent with our plans. The assumptions we use represent our best estimates and involve inherent uncertainties and the application of our judgment. Should actual amounts differ from our estimates, the amount of our tax expense and liabilities we recognize could be materially impacted. We record a valuation allowance to reduce the balance of our net deferred tax assets to the amount we believe is more-likely-than-not to be realized. For U.S. federal income tax purposes, we are required to file separate U.S. federal income tax returns for Ionis and Akcea. We began deconsolidating Akcea for U.S. federal income tax purposes upon Akcea’s initial public offering. As a result, we are required to assess our Ionis stand-alone and Akcea’s valuation allowances separately even though we consolidate Akcea’s financial results in our consolidated financial statements. We continue to file combined state tax returns in most jurisdictions. As a result, we continue to assess the state portion of our valuation allowance for those jurisdictions on a consolidated basis. We have historically recorded a valuation allowance against all our net deferred tax assets due to cumulative financial statement losses. However, in the fourth quarter of 2018, we reversed the valuation allowance previously recorded against our Ionis stand-alone U.S. federal net deferred tax assets, resulting in a one-time non-cash tax benefit of $332.1 million. Given our current stand-alone Ionis pre-tax income, and assuming we maintain this current level of Ionis stand-alone pre-tax income, we expect to generate income before taxes in the U.S. in future periods at a level that would result in us fully utilizing our U.S. federal net operating loss carryforwards and most of our Research and Development and Orphan Drug tax credit carryforwards over the next three years. We continue to maintain a full valuation allowance of $234.2 million against all of Akcea’s net deferred tax assets and the net state deferred tax assets of Ionis at December 31, 2018 due to uncertainties related to our ability to realize the tax benefits associated with these assets. We evaluate our deferred tax assets regularly to determine whether adjustments to the valuation allowance are appropriate due to changes in facts or circumstances, such as changes in expected future pre-tax earnings, tax law, interactions with taxing authorities and developments in case law. In making this evaluation, we rely on our recent history of pre-tax earnings. Our material assumptions are our forecasts of future pre-tax earnings and the nature and timing of future deductions and income represented by the deferred tax assets and liabilities, all of which involve the exercise of significant judgment. Although we believe our estimates are reasonable, we are required to use significant judgment in determining the appropriate amount of valuation allowance recorded against our deferred tax assets. We do not provide for a U.S. income tax liability and foreign withholding taxes on undistributed foreign earnings of our foreign subsidiaries.
Impact of Recently Issued Accounting Standards | Impact of Recently Issued Accounting Standards In February 2016, the FASB issued amended accounting guidance related to lease accounting, which will require us to record all leases with a term longer than one year on our balance sheet. When we record leases on our balance sheet under the new guidance, we will record a liability with a value equal to the present value of payments we will make over the life of the lease (lease liability) and an asset representing the underlying leased asset (right of use asset). The new accounting guidance requires us to determine if our leases are operating or financing leases. We will record expense for operating leases on a straight-line basis as an operating expense. If we determine a lease is a financing lease, we will record both interest and amortization expense and generally the expense will be higher in the earlier periods of the lease. We adopted this guidance on January 1, 2019 and adjusted our opening balance sheet on that date. We elected the available practical expedients. The most significant impact was the recognition of right of use assets and lease liabilities for our operating leases. We are in the process of finalizing the impact of the adoption. The adoption will not have an impact on our consolidated statement of operations or statement of cash flows. In June 2016, the FASB issued guidance that changes the measurement of credit losses for most financial assets and certain other instruments. If we have credit losses, this updated guidance requires us to record allowances for these instruments under a new expected credit loss model. This model requires us to estimate the expected credit loss of an instrument over its lifetime, which represents the portion of the amortized cost basis we do not expect to collect. The new guidance requires us to remeasure our allowance in each reporting period we have credit losses. The new standard is effective for annual and interim periods beginning after December 15, 2019. Early adoption is permitted for periods beginning after December 15, 2018. When we adopt the new standard, we will make any adjustments to beginning balances through a cumulative-effect adjustment to accumulated deficit on that date. We plan to adopt this guidance on January 1, 2020. We are currently assessing the effects it will have on our consolidated financial statements and disclosures. In February 2018, the FASB issued updated guidance for reclassification of tax effects from accumulated other comprehensive income (loss). The updated guidance gives entities an option to reclassify amounts included in accumulated other comprehensive income (loss) that under the Tax Act do not have a way to be relieved, and allows a one-time reclassification to retained earnings. The updated guidance is effective for all entities for fiscal years beginning after December 31, 2018, and interim periods within those fiscal years. We have decided not to record the reclassification adjustments provided by this guidance. In June 2018, the FASB issued updated guidance to simplify the accounting for stock-based compensation expense for nonemployees. Specifically, we are now expensing grants to nonemployees in a similar manner as grants to employees. Previously, we had to re-value these grants at each reporting period to reflect the current fair value. Under the amended guidance, we value grants to nonemployees when we grant them and we will not adjust their value for future changes. We adopted this guidance in the second quarter of 2018. The updated guidance did not have a material impact to our financial results. In November 2018, the FASB issued clarifying guidance of the interaction between the collaboration accounting guidance and the new revenue recognition guidance we adopted on January 1, 2018 (Topic 606). The clarifying guidance included the following:
| 1) | When a participant is considered a customer in a collaborative arrangement, all of the associated accounting under Topic 606 should be applied;
| 2) | Adds “unit of account” concept to collaboration accounting guidance to align with Topic 606. This is used to determine if revenue is recognized or if a contra expense is recognized from consideration received under a collaboration; and
| 3) | Precludes revenue from being recognized under Topic 606 when a transaction with a collaborative partner is determined not be a customer and is not directly related to the sales to third parties.
The updated guidance is effective for public entities for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted. We plan to adopt this guidance on January 1, 2020. We are currently assessing the effects it will have on our consolidated financial statements and disclosures.

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