Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations

The following discussion of our financial condition and results of operations should be read in conjunction with our consolidated financial statements and related notes included elsewhere in this report. Some of the information contained in this discussion and analysis and set forth elsewhere in this report, including information with respect to our plans and strategy for our business, includes forward-looking statements that involve risks and uncertainties. You should review the section entitled “Risk Factors” in Part I - Item 1A of this report for a discussion of important factors that could cause actual results to differ materially from the results described in or implied by the forward-looking statements contained in the following discussion and analysis.

Overview

We are a commercial-stage pharmaceutical company pioneering novel cancer therapies and dedicated to the discovery, development and commercialization of first-in-class drugs directed against nuclear export for the treatment of cancer and other diseases. Our scientific expertise is based upon an understanding of the regulation of intracellular communication between the nucleus and the cytoplasm. We have discovered and are developing and commercializing novel, small molecule Selective Inhibitor of Nuclear Export (“SINE”) compounds that inhibit the nuclear export protein exportin 1 (“XPO1”). These SINE compounds represent a new class of drug candidates with a novel mechanism of action that have the potential to treat a variety of diseases with high unmet medical need. Our lead asset, XPOVIO® (selinexor), was the first oral XPO1 inhibitor to receive marketing approval, receiving its initial U.S. approval from the U.S. Food and Drug Administration (“FDA”) in July 2019, and is currently approved and marketed in the U.S. for the following indications:

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In combination with bortezomib and dexamethasone for the treatment of adult patients with multiple myeloma who have received at least one prior therapy. Approval in this indication was based on the results from the BOSTON (Bortezomib, Selinexor and Dexamethasone) study;

•

In combination with dexamethasone for the treatment of adult patients with relapsed or refractory multiple myeloma who have received at least four prior therapies and whose disease is refractory to at least two proteasome inhibitors, at least two immunomodulatory agents, and an anti-CD38 monoclonal antibody. Approval in this indication was based on the results from the STORM (Selinexor Treatment of Refractory Myeloma) study; and

•

For the treatment of adult patients with relapsed or refractory diffuse large B-cell lymphoma (“DLBCL”), not otherwise specified, including DLBCL arising from follicular lymphoma, after at least two lines of systemic therapy. This indication was approved under accelerated approval based on response rate and was based on the results from the SADAL (Selinexor Against Diffuse Aggressive Lymphoma) study. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial.

The commercialization of XPOVIO in the U.S. is currently supported by sales representatives, nurse liaisons, and a market access team, as well as KaryForwardTM, an extensive patient and healthcare provider support program. Our commercial efforts are also supplemented by patient support initiatives coordinated by our dedicated network of participating specialty pharmacy providers. We plan to continue to educate physicians, other healthcare providers and patients about XPOVIO’s clinical profile and unique mechanism of action as we continue to expand XPOVIO use.

The commercialization of XPOVIO and NEXPOVIO® (selinexor) (the brand name for selinexor in Europe and the United Kingdom (“UK”)) outside of the U.S. is managed by our partners in their respective territories. XPOVIO/NEXPOVIO has received regulatory approval in various indications in over 40 countries outside the U.S. and is commercially available in a growing number of countries as our partners continue to secure reimbursement approvals.

Our primary focus is on marketing XPOVIO in its currently approved indications as well as developing and seeking the regulatory approval of selinexor as an oral agent targeting multiple high unmet need cancer indications, including our core programs in endometrial cancer, multiple myeloma, and myelofibrosis. We plan to continue to conduct clinical trials and to seek additional approvals for the use of selinexor as a single agent or in combination with other oncology therapies to expand the patient populations that are eligible for treatment with selinexor. In January 2024, we announced that further clinical development of our eltanexor program is on hold in an effort to focus our resources on our prioritized late-stage programs.

As of December 31, 2023, we had an accumulated deficit of $1.5 billion. We had net losses of $143.1 million, $165.3 million, and $124.1 million for the years ended December 31, 2023, 2022 and 2021, respectively. We recognized total revenue of $146.0 million in 2023, including $112.0 million of XPOVIO net product revenue and $34.0 million of license revenue. License revenue included $15.0 million of revenue for the reimbursement of development related expenses from the Menarini Group (“Menarini”). As of December 31, 2023, we had $191.4 million in cash, cash equivalents and investments.

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Critical Accounting Estimates

Our discussion and analysis of our financial condition and results of operations are based on our consolidated financial statements, which we have prepared in accordance with U.S. generally accepted accounting principles. The preparation of these consolidated financial statements requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements, as well as the reported amounts of revenues and expenses during the reporting periods. We believe that the estimates and assumptions involved in the accounting policies described below may have the greatest potential impact on our consolidated financial statements and, therefore, consider these to be our critical accounting estimates. We evaluate our estimates and assumptions on an ongoing basis. Actual results may differ from these estimates under different assumptions and conditions. See Note 2 “Summary of Significant Accounting Policies” to the consolidated financial statements included under Part II, Item 8 of this Annual Report on Form 10-K for information about our significant accounting policies.

Product Revenue Reserves

We recognize product revenue, net of variable consideration related to certain allowances and accruals, when the customer takes control of the product, which is typically upon delivery to the customer. Revenue from product sales is recorded at the net sales price, which includes estimates of variable consideration for which reserves are reported. These reserves are based on the amounts earned, or to be claimed on the related sales, and are generally classified as reductions of accounts receivable (if the amount is payable to the customer) or a current liability (if the amount is payable to a party other than a customer). Certain amounts are known at the time of sale based on contractual terms and are recorded pursuant to the most likely amount method, which is the single most likely amount in a range of possible considerations. Other amounts are estimated pursuant to the expected value method, which is the sum of probability-weighted amounts in a range of possible considerations. Relevant factors used in the expected value method include: current contractual and statutory requirements, specific known market events and trends, industry data, and forecasted customer buying and payment patterns. These reserves reflect our best estimates of the variable consideration based on the terms of the respective underlying contracts.

The estimates for our product revenue allowances and accruals are most significantly affected by chargebacks, which are contractual commitments to provide products to qualified healthcare entities at prices lower than the list prices charged to our customers who purchase XPOVIO directly from us, and rebates that represent discount obligations under government programs, including Medicaid, Medicare, the Department of Veterans Affairs, the Department of Defense, and others.

A 10% increase or decrease in these estimates would impact net product revenue by a corresponding increase or decrease of less than $3.0 million.

License and Asset Purchase Agreements

We generate revenue from license or similar agreements with pharmaceutical companies for the development and commercialization of certain of our products and product candidates.

At contract inception, we evaluate all goods or services in the agreement to determine if they are distinct. If they are not distinct, they are combined with other promised goods or services to create a bundle of promised goods or services that are distinct. Distinct goods or services and distinct bundles of goods or services are considered performance obligations. Optional future services where any additional consideration paid to us reflects their standalone selling prices do not provide the customer with a material right and, therefore, are not considered performance obligations. Optional future services that are priced in a manner which provides the customer with a significant or incremental discount are considered performance obligations because they provide the customer with a material right.

We utilize judgment to estimate the transaction price at contract inception. We evaluate contingent milestones to determine if they should be included in the transaction price using the most likely amount method. Milestone payments that are not within our control, such as regulatory approvals, are not considered likely of being achieved until those approvals are received and are excluded from the transaction price using the most likely amount method. The transaction price is then allocated to each performance obligation on a relative standalone selling price basis, for which we recognize revenue as or when the performance obligations are satisfied. At the end of each reporting period, we re-evaluate our estimate of the transaction price including the probability of achieving milestone payments that may not be subject to a material reversal and adjust the transaction price if necessary. Any such adjustments are recorded on a cumulative catch-up basis, which would affect license and other revenue in the period of adjustment.

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Accrued Research and Development Costs

We estimate our accrued research and development costs by reviewing quotes and contracts, identifying services that have been performed on our behalf, and estimating the associated cost incurred for services performed when we have not yet been invoiced or otherwise notified of the actual cost. Most of our service providers invoice us monthly in arrears for services performed or when contractual milestones are met. We make estimates of our accrued research and development costs at each balance sheet date in our financial statements based on facts and circumstances known to us at that time. We periodically confirm the accuracy of our estimates with the service providers and make adjustments if necessary. The significant estimates in our accrued research and development costs include fees to be paid to contract research organizations (“CROs”) and contract manufacturing organizations (“CMOs”) in connection with research and development activities as well as fees to be paid to investigative sites in connection with clinical studies, for which we have not yet been invoiced.

We base our expenses related to CROs and CMOs on our estimates of the services performed and efforts expended pursuant to quotes and contracts with CROs and CMOs that conduct research and development activities on our behalf. The payment terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows. There may be instances in which payments made to our service providers will exceed the level of services performed and result in a prepayment. In accruing service fees, we estimate the time period over which the services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from our estimates, we adjust the accrual or prepayment accordingly. Although we do not expect our estimates to be materially different from amounts actually incurred, if our estimates of the status and timing of services performed differ from the actual status and timing of services performed, it could result in us reporting amounts that are too high or too low in any particular period. To date, our estimates have not been materially different than amounts actually incurred.

Results of Operations

The following table summarizes our results of operations (in thousands):

For the Years Ended December 31,

Operating expenses:

Product Revenue, net (in thousands, except for percentages)

Net product revenue from U.S. commercial sales of XPOVIO for the year ended December 31, 2023 decreased 7% as compared to the year ended December 31, 2022. A number of myeloma foundations that help support Medicare Part D patients with their out-of-pocket costs for multiple myeloma oral oncolytics, including XPOVIO, closed during the first quarter of 2023 and some remained closed throughout 2023. During the foundation closures, we provided XPOVIO to these patients at no charge through our Patient Assistance Program (“PAP”), which adversely impacted our 2023 revenues by approximately $5.8 million as patients who entered our PAP earlier in the year remained in the program through the calendar year and received their refills during the course of their treatment. We believe this trend will be mainly limited to 2023 since, beginning in 2024, changes in the design of Medicare Part D

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under the Inflation Reduction Act eliminated the patient burden of the 5% Beneficiary Coinsurance requirement and we expect less need for Medicare Part D patients to utilize PAP for co-pay assistance in 2024 compared to 2023.

License and Other Revenue (in thousands, except for percentages)

License and other revenue for the year ended December 31, 2023 decreased by $2.6 million as compared to the year ended December 31, 2022 primarily due to a decrease in milestone-related revenue and royalty revenue from Antengene Therapeutics Limited (“Antengene”), partially offset by an increase in milestone-related revenue, license-related revenue, and royalty revenue from Menarini. The license agreements with Menarini and Antengene are each defined and described in Note 5 “License and Asset Purchase Agreements”, to the consolidated financial statements included under Part II, Item 8 of this Annual Report on Form 10-K.

We expect license and other revenue to increase in 2024 as compared to 2023 primarily due to expected milestone achievements.

Operating Costs and Expenses (in thousands, except for percentages)

Cost of Sales

We expect cost of sales to remain relatively consistent in 2024 as compared to 2023.

Research and Development Expenses (in thousands, except for percentages)

In-process research and development — — 7,355 — — (7,355 ) (100 )%

Research and development expenses for the year ended December 31, 2023 decreased by $9.9 million as compared to the year ended December 31, 2022, primarily due to a decrease in personnel costs of $9.2 million and a decrease in stock-based compensation of $7.8 million, which was primarily because of a reduction in headcount and contractors, including severance-related expenses

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incurred in 2022. These decreases were partially offset by an increase in clinical trial and related costs of $9.2 million, primarily due to the advancement of our three pivotal Phase 3 trials and the timing of purchases of comparator drug used in our clinical trials.

We expect our research and development expenses to increase slightly in 2024 as compared to 2023 as we continue to advance our three pivotal Phase 3 trials.

Selling, General and Administrative Expenses (in thousands, except for percentages)

Selling, general and administrative expenses for the year ended December 31, 2023 decreased by $13.5 million as compared to the year ended December 31, 2022, primarily due to a decrease in stock-based compensation and a decrease in consulting, professional and other costs. The decrease in stock-based compensation of $6.0 million was primarily due to severance-related expenses incurred during 2022. The decrease in consulting, professional and other costs was primarily due to lower commercial-related activities.

We expect our selling, general and administrative expenses to decrease slightly in 2024 as compared to 2023 due to cost optimization efforts.

Other Expense, net(in thousands, except for percentages)

Other expense, net for the year ended December 31, 2023 decreased by $9.5 million as compared to the year ended December 31, 2022, primarily due to an increase in interest income resulting from higher interest rates on our investments.

We expect other expense, net to remain relatively consistent in 2024 as compared to 2023.

Results of Operations - Years Ended December 31, 2022 and 2021

Discussion and analysis of the results of operations for the year ended December 31, 2022 as compared to the results of operations for the year ended December 31, 2021 is included under the heading “Item 7.Management’s Discussion and Analysis of Financial Condition and Results of Operations” in our Annual Report on Form 10-K for the year ended December 31, 2022 as filed with the SEC on February 17, 2023 (“2022 Form 10-K”).

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Liquidity and Capital Resources

Cash flows

To date, we have financed our operations primarily through a combination of product revenue sales, private placements of our common stock, proceeds from public offerings of our common stock, proceeds from the issuance of convertible debt, proceeds pursuant to the deferred royalty obligation, and cash generated from our business development activities.

As of December 31, 2023, our principal source of liquidity was $191.4 million of cash, cash equivalents and investments. We have had recurring losses since inception and incurred a loss of $143.1 million for the year ended December 31, 2023. We expect that our cash, cash equivalents and investments at December 31, 2023 will be sufficient to fund our current operating plans and capital expenditure requirements for at least twelve months from the date of issuance of the financial statements contained in this Annual Report on Form 10-K.

The following table provides information regarding our cash flows (in thousands):

Net Cash Used in Operating Activities

The $56.8 million decrease in net cash used in operating activities during the year ended December 31, 2023 as compared to the year ended December 31, 2022 was primarily driven by a decrease in expenses and $27.3 million of milestone payments we received from Antengene in 2023.

Net Cash Provided by (Used in) Investing Activities

The $112.2 million increase in net cash provided by investing activities during the year ended December 31, 2023 as compared to the year ended December 31, 2022 was primarily driven by a $66.9 million decrease in purchases of investments and a $45.2 million increase in proceeds from the sales and maturities of investments.

Net Cash Provided by Financing Activities

The $192.6 million decrease in net cash provided by financing activities during the year ended December 31, 2023 as compared to the year ended December 31, 2022 was primarily driven by net proceeds of approximately $154.7 million from a private placement offering of our common stock in 2022 and $35.1 million in net proceeds received from the sale of common stock under our “at the market offering” program in 2022.

A discussion of changes in our financial condition for the year ended December 31, 2022 as compared to the year ended December 31, 2021 is included under the heading “Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations” in the 2022 Form 10-K.

Sources of Liquidity

On December 5, 2022, we entered into a securities purchase agreement with certain institutional investors pursuant to which we issued and sold, in a private placement offering of securities, an aggregate of (i) 31,791,908 shares of common stock and (ii) accompanying warrants to purchase up to 9,537,563 shares of common stock at an exercise price of $6.36 per share. We received aggregate net proceeds of approximately $154.7 million.

During the year ended December 31, 2023, we received $32.0 million in milestone and upfront payments under our license and distribution arrangements pursuant to which we are entitled to receive additional milestone payments, if certain development goals and sales milestones are achieved, as well as royalties on future net sales of the licensed and sold products in the territories under such arrangements. In addition, under the Menarini Agreement, Menarini will reimburse us for 25% of all development related expenses we

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incur for selinexor from 2022 through 2025, provided that such reimbursements shall not exceed $15.0 million per calendar year. We received $15.0 million of reimbursements for development related expenses under the Menarini Agreement during the year ended December 31, 2023.

In September 2019, we entered into the Revenue Interest Financing Agreement (the “Revenue Interest Agreement”) with HealthCare Royalty Partners III, L.P. and HealthCare Royalty Partners IV, L.P. (“HCR”) which was amended in June 2021 (the “Amended Revenue Interest Agreement”). Pursuant to the Revenue Interest Agreement, HCR paid us $75.0 million, less certain transaction expenses, on September 27, 2019 and pursuant to the Amended Revenue Interest Agreement, HCR paid us $60.0 million on June 23, 2021. For additional information on the Amended Revenue Interest Agreement, see Note 10, “Long-Term Obligations”, to the consolidated financial statements included under Part II, Item 8 of this Annual Report on Form 10-K.

On February 17, 2023, we entered into an Open Market Sale Agreement (the “2023 Open Market Sale Agreement”) with Jefferies LLC, as agent (“Jefferies”). Under the 2023 Open Market Sale Agreement, we may issue and sell shares of our common stock having an aggregate offering price of up to $100.0 million (the “Shares”) from time to time through Jefferies (the “2023 Open Market Offering”). Upon entry into the 2023 Open Market Sale Agreement, we terminated our previous Open Market Sale Agreement with Jefferies, as agent, which we had entered into in August 2018 (the “2018 Open Market Sale Agreement”), pursuant to which we could issue and sell shares of our common stock having an aggregate offering price of up to $175.0 million (the “Open Market Shares”). During the year ended December 31, 2022, we sold an aggregate of 3,991,652 Open Market Shares under the 2018 Open Market Sale Agreement, for net proceeds of approximately $35.1 million.

We did not sell any Open Market Shares under the 2018 Open Market Sale Agreement nor any Shares under the 2023 Open Market Sales Agreement during the year ended December 31, 2023. As of December 31, 2023, $100.0 million of Shares was available for issuance and sale under the 2023 Open Market Sale Agreement.

Commitments, Contingencies and Contractual Obligations

Operating Leases

We are party to an operating lease of 98,502 square feet of office and research space in Newton, Massachusetts with a term through September 30, 2025 (the “Newton, MA Lease”). Pursuant to the Newton, MA Lease, we have provided a security deposit in the form of a cash-collateralized letter of credit in the amount of $0.3 million which is classified in long-term restricted cash on our consolidated balance sheets. We expect to incur total lease costs of $6.7 million from December 31, 2023 to September 30, 2025.

In addition, we are party to certain short-term leases having a term of twelve months or less at the commencement date. We recognize short-term lease expense on a straight-line basis and do not record a related right-of use asset or lease liability for such leases. These costs were insignificant for the years ended December 31, 2023, 2022 and 2021.

Contractual Obligations

We have contractual obligations under our 3.00% Convertible Senior Notes due 2025 and under our Revenue Interest Financing Agreement as disclosed in Note 10, “Long-Term Obligations”, to the consolidated financial statements included under Part II, Item 8 of this Annual Report on Form 10-K.

Funding Requirements

We expect our expenses to remain relatively consistent in 2024 as compared to 2023. We expect to continue to incur costs related to our clinical development programs as we rapidly advance three pivotal Phase 3 trials, as well as commercialization expenses related to sales, marketing, manufacturing and distribution of any of our products, to the extent that these functions are not the responsibility of our collaborators.

Identifying potential product candidates and conducting preclinical studies and clinical trials is a time-consuming, expensive and uncertain process that takes years to complete. In addition, our product candidates for which we receive marketing approval may not achieve commercial success. Our ability to become and remain profitable depends on our ability to generate revenue. There can be no assurance as to the amount or timing of any such revenue, and we may not achieve profitability for several years, if at all, as described more fully in the risk factor entitled “We have incurred significant losses since inception, expect to continue to incur significant losses, and may never achieve or maintain profitability,” under the heading “Risk Factors” in this Annual Report on Form 10-K. Accordingly, we will need to continue to rely on additional financing to achieve our business objectives. Adequate additional financing may not be available to us on acceptable terms, or at all. We may seek additional capital due to favorable market conditions or strategic considerations, even if we believe we have sufficient funds for our current or future operating plans. If we are unable to

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raise capital when needed or on attractive terms, we would be forced to delay, reduce or eliminate our research and development programs or commercialization efforts.

We currently expect that cash, cash equivalents and investments at December 31, 2023 will be sufficient to fund our current operating plans and capital expenditure requirements for at least twelve months from the date of issuance of the financial statements contained in this Annual Report on Form 10-K while we continue to commercialize XPOVIO in the U.S. and continue the clinical trials of our product candidates. Our future long-term capital requirements will depend on many factors, as described more fully in the risk factor entitled “We will need additional funding to achieve our business objectives. If we are unable to raise capital when needed or on acceptable terms, we would be forced to delay, reduce or eliminate our research and development programs and/or commercialization efforts,” under the heading “Risk Factors” in this Annual Report on Form 10-K.

In addition to the expenses required to fund our operations described above, our funding requirements also include the following:

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Lease costs for our headquarters in Newton, Massachusetts with a term through September 30, 2025, which totaled $3.7 million in 2023 and increase annually; we expect total future lease costs to be approximately $6.7 million;

•

Future long-term debt obligations related to the 3.00% Convertible Senior Notes due 2025 of $182.9 million over the next three years; and

•

Future royalty obligations to HCR under our Revenue Interest Financing Agreement of approximately $201.6 million.

Item 7A. Quantitative and Qualitative Disclosures about Market Risk

We are exposed to market risk related to changes in interest rates. We had cash, cash equivalents and investments of $191.4 million as of December 31, 2023. Our primary exposure to market risk is interest rate sensitivity, which is affected by changes in the general level of U.S. interest rates. Due to the short-term duration of our investment portfolio and the low risk profile of our investments, an immediate 100 basis point shift in interest rates would not have a material effect on the fair market value of our investment portfolio.

We do not believe our cash, cash equivalents and investments have significant risk of default or illiquidity. While we believe our cash, cash equivalents and investments do not contain excessive risk, we cannot provide absolute assurance that in the future our investments will not be subject to adverse changes in securities at one or more financial institutions that are in excess of federally insured limits. Given the potential instability of financial institutions, we cannot provide assurance that we will not experience losses on these deposits and investments.

We are also exposed to market risk related to changes in foreign currency exchange rates. We contract with contract research organizations and contract manufacturing organizations that are located in Canada, the United Kingdom and Europe, which are denominated in foreign currencies. We also contract with a number of clinical trial sites outside of the U.S., and our budgets for those studies are frequently denominated in foreign currencies. We are subject to fluctuations in foreign currency rates in connection with these agreements. We do not currently hedge our foreign currency exchange rate risk.

Item 8. Financial Statements and Supplementary Data

The financial statements required to be filed pursuant to this Item 8 are appended to this Annual Report on Form 10-K and are incorporated herein by reference. An index of those financial statements is found in Item 15 of Part IV of this Annual Report on Form 10-K.

Item 9A. Controls and Procedures

Evaluation of Disclosure Controls and Procedures

We have established disclosure controls and procedures designed to ensure that information required to be disclosed in the reports that we file or submit under the Exchange Act is recorded, processed, summarized and reported within the time periods specified in the rules and forms prescribed by the Securities and Exchange Commission and is accumulated and communicated to management, including the principal executive officer (our President and Chief Executive Officer) and principal financial officer (our Executive Vice President, Chief Financial Officer and Treasurer), to allow timely decisions regarding required disclosure.

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Our management, under the supervision and with the participation of our President and Chief Executive Officer and Executive Vice President, Chief Financial Officer and Treasurer, has evaluated the effectiveness of our disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act) as of the end of the period covered by this Annual Report on Form 10-K. Management recognizes that any disclosure controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving their objectives. Our disclosure controls and procedures have been designed to provide reasonable assurance of achieving their objectives. Based on such evaluation, our President and Chief Executive Officer and Executive Vice President, Chief Financial Officer and Treasurer concluded that our disclosure controls and procedures were effective at the reasonable assurance level as of December 31, 2023.

Management’s Annual Report on Internal Control Over Financial Reporting

Our management is responsible for establishing and maintaining adequate internal control over financial reporting, as such term is defined in Rules13a-15(f) and15d-15(f) of the Exchange Act. Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with policies or procedures may deteriorate. Our internal control over financial reporting is a process designed under the supervision of our principal executive officer and principal financial officer to provide reasonable assurance regarding the reliability of financial reporting and the preparation of our financial statements for external reporting purposes in accordance with U.S. generally accepted accounting principles.

Under the supervision and with the participation of management, including our principal executive officer and principal financial officer we conducted an evaluation of the effectiveness of our internal control over financial reporting based on the 2013 framework in Internal Control – Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission. Based on our evaluation under that framework, management concluded that our internal control over financial reporting was effective as of December 31, 2023.

Our independent registered public accounting firm that audited the financial statements included in this Annual Report on Form 10-K has issued an attestation report on our internal control over financial reporting, which is included below.

Changes in Internal Control over Financial Reporting

There were no changes in our internal control over financial reporting identified in connection with the evaluation required by Rule 13a-15(d) and 15d-15(d) of the Exchange Act that occurred during the quarter ended December 31, 2023 that have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

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Report of Independent Registered Public Accounting Firm

To the Shareholders and the Board of Directors of Karyopharm Therapeutics Inc.

Opinion on Internal Control Over Financial Reporting

We have audited Karyopharm Therapeutics Inc.’s internal control over financial reporting as of December 31, 2023, based on criteria established in Internal Control—Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (2013 framework), (the COSO criteria). In our opinion, Karyopharm Therapeutics Inc. (the Company) maintained, in all material respects, effective internal control over financial reporting as of December 31, 2023, based on the COSO criteria.

We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the 2023 consolidated financial statements of the Company and our report dated February 29, 2024 expressed an unqualified opinion thereon.

Basis for Opinion

The Company’s management is responsible for maintaining effective internal control over financial reporting and for its assessment of the effectiveness of internal control over financial reporting included in the accompanying Management’s Annual Report on Internal Control Over Financial Reporting. Our responsibility is to express an opinion on the Company’s internal control over financial reporting based on our audit. We are a public accounting firm registered with the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audit in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether effective internal control over financial reporting was maintained in all material respects.

Our audit included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, testing and evaluating the design and operating effectiveness of internal control based on the assessed risk, and performing such other procedures as we considered necessary in the circumstances. We believe that our audit provides a reasonable basis for our opinion.

Definition and Limitations of Internal Control Over Financial Reporting

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

/s/ Ernst & Young LLP

Boston, Massachusetts

February 29, 2024

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Item 9B. Other Information

Director and Officer Trading Arrangements

A portion of the compensation of our directors and officers (as defined in Rule 16a-1(f) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”)) is in the form of equity awards and, from time to time, directors and officers engage in open-market transactions with respect to the securities acquired pursuant to such equity awards or other securities of our company, including to satisfy tax withholding obligations when equity awards vest or are exercised, and for diversification or other personal reasons.

Transactions in our securities by directors and officers are required to be made in accordance with our Insider Trading Policy, which requires that the transactions be in accordance with applicable U.S. federal securities laws that prohibit trading while in possession of material nonpublic information. Rule 10b5-1 under the Exchange Act provides an affirmative defense that enables directors and officers to prearrange transactions in our securities in a manner that avoids concerns about initiating transactions while in possession of material nonpublic information.

During the fourth quarter of 2023, none of our directors or officers adopted or terminated a Rule 10b5-1 trading arrangement or a non-Rule 10b5-1 trading arrangement (as defined in Item 408(c) of Regulation S-K).

Item 9C. Disclosure Regarding Foreign Jurisdictions that Prevent Inspections

Not applicable.

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PART III

Certain information required by Part III is omitted from this Annual Report on Form 10-K and is incorporated by reference from our definitive proxy statement relating to our 2024 annual meeting of stockholders, pursuant to Regulation 14A of the Exchange Act, which we refer to as our 2024 Proxy Statement. We expect to file our 2024 Proxy Statement with the SEC within 120 days of December 31, 2023.

Item 10. Directors, Executive Officers and Corporate Governance

Information regarding our directors, including the audit committee and audit committee financial experts, and compliance with Section 16(a) of the Exchange Act, if applicable, will be included in our 2024 Proxy Statement and is incorporated herein by reference. Information regarding our executive officers is set forth in “Business - Information about Our Executive Officers” in Part I, Item 1 of this Annual Report on Form 10-K.

We have adopted a Code of Business Conduct and Ethics for all of our directors, officers and employees as required by Nasdaq governance rules and as defined by applicable SEC rules. Stockholders may locate a copy of our Code of Business Conduct and Ethics on our website at www.karyopharm.com or request a copy without charge from:

Karyopharm Therapeutics Inc.

Attention: Investor Relations

85 Wells Avenue, 2nd Floor

Newton, MA 02459

We will post to our website any amendments to the Code of Business Conduct and Ethics and any waivers that are required to be disclosed by the rules of either the SEC or Nasdaq.

Item 11. Executive Compensation

The information required by this Item 11 of Form 10-K regarding executive compensation will be included in our 2024 Proxy Statement and, other than the information required by Item 402(v) of Regulation S-K, is incorporated herein by reference.

Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters

The information required by this Item 12 of Form 10-K regarding security ownership of certain beneficial owners and management and securities authorized for issuance under equity compensation plans will be included in our 2024 Proxy Statement and is incorporated herein by reference.

Item 13. Certain Relationships and Related Transactions, and Director Independence

The information required by this Item 13 of Form 10-K regarding certain relationships and related transactions and director independence will be included in our 2024 Proxy Statement and is incorporated herein by reference.

Item 14. Principal Accountant Fees and Services

The information required by this Item 14 of Form 10-K regarding principal accountant fees and services will be included in our 2024 Proxy Statement and is incorporated herein by reference.

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PART IV

Item 15. Exhibits and Financial Statement Schedules

(a)(1) Financial Statements

The financial statements listed below are filed as a part of this Annual Report on Form 10-K.

Pagenumber

Report of Independent Registered Public Accounting Firm (PCAOB ID 42) 112

Notes to Consolidated Financial Statements 119

(a)(2) Financial Statement Schedules

All financial schedules have been omitted because the required information is either presented in the consolidated financial statements or the notes thereto or is not applicable or required.

(a)(3) Exhibits

The exhibits required by Item 601 of Regulation S-K and Item 15(b) of this Annual Report on Form 10-K are listed in the Exhibit Index immediately preceding the signature page of this Annual Report on Form 10-K and are incorporated herein.

Item 16. Form 10-K Summary

None.

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Report of Independent Registered Public Accounting Firm

To the Shareholders and

the Board of Directors of Karyopharm Therapeutics Inc.

Opinion on the Financial Statements

We have audited the accompanying consolidated balance sheets of Karyopharm Therapeutics Inc. (the Company) as of December 31, 2023 and 2022, the related consolidated statements of operations, comprehensive loss, stockholders’ (deficit) equity and cash flows for each of the three years in the period ended December 31, 2023, and the related notes (collectively referred to as the “consolidated financial statements”). In our opinion, the consolidated financial statements present fairly, in all material respects, the financial position of the Company at December 31, 2023 and 2022, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2023, in conformity with U.S. generally accepted accounting principles.

We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the Company’s internal control over financial reporting as of December 31, 2023, based on criteria established in Internal Control—Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (2013 framework), and our report dated February 29, 2024 expressed an unqualified opinion thereon.

Adoption of ASU No. 2020-06

As discussed in Note 10 to the consolidated financial statements, the Company changed its method of accounting for convertible senior notes in 2021 due to the adoption of Accounting Standards Update No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40).

Basis for Opinion

These financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on the Company’s financial statements based on our audits. We are a public accounting firm registered with the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion.

Critical Audit Matter

The critical audit matter communicated below is a matter arising from the current period audit of the financial statements that was communicated or required to be communicated to the audit committee and that: (1) relates to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective or complex judgments. The communication of the critical audit matter does not alter in any way our opinion on the consolidated financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates.

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Accrued Research and Development Costs

/s/ Ernst & Young LLP

We have served as the Company’s auditor since 2014.

Boston, Massachusetts

February 29, 2024

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Karyopharm Therapeutics Inc.

Consolidated Balance Sheets

(in thousands, except per share amounts)

Assets

Current assets:

Prepaid expenses and other current assets 11,813 19,821

Property and equipment, net 606 1,139

Operating lease right-of-use assets 4,276 6,238

Liabilities and stockholders’ deficit

Current liabilities:

Operating lease liabilities, net of current portion 2,789 6,097

Other liabilities 978 —

Stockholders’ deficit:

Accumulated other comprehensive loss (161 ) (638 )

Total liabilities and stockholders’ deficit $ 240,438 $ 358,172

The accompanying notes are an integral part of these consolidated financial statements.

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Karyopharm Therapeutics Inc.

Consolidated Statements of Operations

(in thousands, except per share amounts)

For the Years Ended December 31,

Revenues:

Operating expenses:

Other income (expense):

Other expense, net (356 ) (83 ) (85 )

Net loss per share—basic and diluted $ (1.25 ) $ (2.02 ) $ (1.65 )

The accompanying notes are an integral part of these consolidated financial statements.

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Karyopharm Therapeutics Inc.

Consolidated Statements of Comprehensive Loss

(in thousands)

For the Years Ended December 31,

Other comprehensive income (loss)

Unrealized gain (loss) on investments 278 (341 ) (286 )

Foreign currency translation adjustment 199 (488 ) (41 )

The accompanying notes are an integral part of these consolidated financial statements.

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Karyopharm Therapeutics Inc.

Consolidated Statements of Stockholders’ (Deficit) Equity

(in thousands)

Shares Amount

Vesting of restricted stock 480 — — — — —

Stock-based compensation expense — — 29,783 — — 29,783

Issuance of common stock for asset purchase 150 — 1,355 — — 1,355

Issuance of common stock, net of issuance costs 638 1 9,902 — — 9,903

Unrealized loss on investments — — — (286 ) — (286 )

Foreign currency cumulative translation adjustment — — — (41 ) — (41 )

Vesting of restricted stock 957 — — — — —

Stock-based compensation expense — — 35,399 — — 35,399

Unrealized loss on investments — — — (341 ) — (341 )

Foreign currency cumulative translation adjustment — — — (488 ) — (488 )

Vesting of restricted stock 1,054 — — — — —

Stock-based compensation expense — — 21,709 — — 21,709

Issuance of common stock warrants — — 239 — — 239

Unrealized gain on investments — — — 278 — 278

Foreign currency cumulative translation adjustment — — — 199 — 199

The accompanying notes are an integral part of these consolidated financial statements.

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Karyopharm Therapeutics Inc.

Consolidated Statements of Cash Flows

(in thousands)

For the Years Ended December 31,

Operating activities

Adjustments to reconcile net loss to net cash used in operating activities:

Amortization of debt issuance costs 814 812 780

Net amortization of premiums and discounts on investments (4,098 ) (825 ) 1,560

Acquired in-process research and development — — 7,355

Changes in operating assets and liabilities:

Investing activities

Purchases of property and equipment — (118 ) (212 )

Acquired in-process research and development — — (5,500 )

Financing activities

Proceeds from issuance of common stock, net of issuance costs — 189,761 9,903

Proceeds from Amended Revenue Interest Agreement — — 60,000

Supplemental disclosures:

Cash paid for interest on convertible debt $ 5,175 $ 5,175 $ 5,175

Cash paid for interest on deferred royalty obligation $ 16,053 $ 29,273 $ 10,361

The accompanying notes are an integral part of these consolidated financial statements.

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Karyopharm Therapeutics Inc.

Notes to Consolidated Financial Statements

1. Organization and Operations

We are a commercial-stage pharmaceutical company pioneering novel cancer therapies and dedicated to the discovery, development and commercialization of first-in-class drugs directed against nuclear export for the treatment of cancer and other diseases. Our scientific expertise is based upon an understanding of the regulation of intracellular communication between the nucleus and the cytoplasm. We have discovered and are developing and commercializing novel, small molecule Selective Inhibitor of Nuclear Export compounds that inhibit the nuclear export protein exportin 1. Our primary focus is on marketing XPOVIO® (selinexor) in its currently approved indications, as well as developing and seeking the regulatory approval of selinexor as an oral agent targeting multiple high unmet cancer indications, including our core programs in endometrial cancer, multiple myeloma, and myelofibrosis. We were incorporated in Delaware on December 22, 2008 and have a principal place of business in Newton, Massachusetts.

Our lead asset, XPOVIO, received its initial U.S. approval from the U.S. Food and Drug Administration (the “FDA”) in July 2019 and is currently approved and marketed for the following indications: (i) in combination with bortezomib and dexamethasone for the treatment of adult patients with multiple myeloma who have received at least one prior therapy; (ii) in combination with dexamethasone for the treatment of adult patients with relapsed or refractory multiple myeloma who have received at least four prior therapies and whose disease is refractory to at least two proteasome inhibitors, at least two immunomodulatory agents, and an anti-CD38 monoclonal antibody; and (iii) for the treatment of adult patients with relapsed or refractory diffuse large B-cell lymphoma (“DLBCL”), not otherwise specified, including DLBCL arising from follicular lymphoma, after at least two lines of systemic therapy. The commercialization of XPOVIO and NEXPOVIO (the brand name for selinexor in Europe and the United Kingdom) outside of the U.S. is managed by our partners in their respective territories. XPOVIO/NEXPOVIO has received regulatory approval in various indications in over 40 countries outside the U.S. and is commercially available in a growing number of countries as our partners continue to secure reimbursement approvals.

To date, we have financed our operations primarily through a combination of product revenue sales, private placements of our common stock, proceeds from our initial public offering and follow-on offerings of our common stock, proceeds from the issuance of convertible debt, proceeds pursuant to a revenue interest financing agreement and subsequent amendment (deferred royalty obligation), proceeds from our “at the market offering” program and cash generated from our business development activities. As of December 31, 2023, we had an accumulated deficit of $1.5 billion. We expect that our cash, cash equivalents and investments at December 31, 2023 will be sufficient to fund our current operating plans and capital expenditure requirements for at least twelve months from the date of issuance of these financial statements.

2. Summary of Significant Accounting Policies

Basis of Presentation and Principles of Consolidation

The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include the accounts of (i) Karyopharm Therapeutics Inc., (ii) Karyopharm Securities Corp. (“KPSC”), our wholly-owned Massachusetts corporation incorporated in December 2013, (iii) Karyopharm Europe GmbH, our wholly-owned German limited liability company, incorporated in September 2014, (iv) Karyopharm Therapeutics (Bermuda) Ltd., a limited liability company, registered in Bermuda in March 2015 and dissolved in January 2022, and (v) Karyopharm Israel Ltd., our wholly-owned Israeli subsidiary formed in June 2018. All intercompany balances and transactions have been eliminated in consolidation.

Segment Information

Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker in deciding how to allocate resources and in assessing performance. We view our operations and manage our business in one operating segment, which is the business of discovering, developing and commercializing drugs to treat cancer and certain other diseases. All of our revenue to date is attributable to the U.S.

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period.

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On an ongoing basis, we evaluate our estimates, including estimates related to our net product revenue, license and other revenue, clinical trial accruals, stock-based compensation expense, interest expense on our deferred royalty obligation, our embedded derivative liability, valuation allowances, and other reported amounts of expenses during the reported period. We base our estimates on historical experience and other market-specific or relevant assumptions that we believe to be reasonable under the circumstances. Although we regularly assess these estimates, actual results could differ from those estimates. Changes in estimates are recorded in the period in which they become known.

Concentrations of Credit Risk and Off-Balance Sheet Risk

Financial instruments which potentially subject us to credit risk consist primarily of cash, cash equivalents and investments. We hold these investments in highly rated financial institutions, and, by policy, limit the amounts of credit exposure to any one financial institution. These amounts at times may exceed federally insured limits. We have not experienced any credit losses in such accounts and do not believe we are exposed to any significant credit risk on these funds. We have no off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements.

The following table summarizes customers that represent 10% or greater of our consolidated total revenue:

For the Years Ended December 31,

Antengene 2 % 9 % 15 %

The following table summarizes customers with amounts due that represent 10% or greater of our consolidated accounts receivable, net balance:

As of December 31,

Customer C 11 % 6 %

Menarini 17 % 2 %

Antengene 3 % 47 %

Fair Value Measurements

Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. We disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. The fair value hierarchy prioritizes valuation inputs based on the observable nature of those inputs. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value and is not a measure of credit quality. The hierarchy defines three levels of valuation inputs:

Level 1 inputs: Quoted prices in active markets for identical assets or liabilities

Level 2 inputs: Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly

Level 3 inputs: Unobservable inputs that reflect our own assumptions about the assumptions market participants would use in pricing the asset or liability.

Cash and Cash Equivalents

Cash and cash equivalents consist primarily of demand deposit accounts and deposits in short-term money market funds. Cash equivalents are stated at cost, which approximates fair value. We consider all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents. We do not hold any money market funds with significant liquidity restrictions that would be required to be excluded from cash equivalents.

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Investments

We determine the appropriate classification of our investments at the time of purchase. All of our investments are reported as short-term as they are available for use during the normal cycle of business. We review any investment when its fair value is less than its amortized cost and when evidence indicates that the investment’s carrying amount is not recoverable within a reasonable period. We evaluate whether the decline in fair value has resulted from credit losses or other factors. In making this assessment, we consider the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency, and adverse conditions specifically related to the security, among other factors. If this assessment indicates that a credit loss exists and if the present value of cash flows expected to be collected is less than the amortized cost basis, an allowance is recorded on our consolidated balance sheet, limited by the amount that the fair value is less than the amortized cost basis. Any impairment that is not related to a credit loss is recognized in other comprehensive income (loss).

Changes in the allowance for credit losses are recorded as a provision for (or reversal of) credit loss expense. Losses are charged against the allowance when we believe the uncollectability of an investment is confirmed or when either of the criteria regarding intent or requirement to sell is met.

Accounts Receivable

Amounts are recorded as accounts receivable when our right to consideration is unconditional other than the passage of time. Accounts receivable consists of amounts due from customers, net of customer allowances for cash discounts and chargebacks. Our contracts with customers have standard payment terms that generally require payment within 30 to 65 days. We analyze accounts for collectability and periodically evaluate the creditworthiness of our customers. We determined an allowance for credit losses was not material as of December 31, 2023 and 2022 as we have had no bad debt write-offs to date and we do not currently have credit issues with any customers.

Accrued Research and Development Costs

We estimate our accrued research and development costs by reviewing quotes and contracts, identifying services that have been performed on our behalf, and estimating the associated cost incurred for services performed when we have not yet been invoiced or otherwise notified of the actual cost. Most of our service providers invoice us monthly in arrears for services performed or when contractual milestones are met. We make estimates of our accrued research and development costs at each balance sheet date in our financial statements based on facts and circumstances known to us at that time. We periodically confirm the accuracy of our estimates with the service providers and make adjustments if necessary. The significant estimates in our accrued research and development costs include fees to be paid to contract research organizations (“CROs”), and contract manufacturing organizations (“CMOs”) in connection with research and development activities as well as fees to be paid to investigative sites in connection with clinical studies, for which we have not yet been invoiced.

Deferred Royalty Obligation

We treat the debt obligation to HealthCare Royalty Partners III, L.P. and HealthCare Royalty Partners IV, L.P. (“HCR”), as discussed further in Note 10, “Long-Term Obligations”, as a deferred royalty obligation, amortized using the effective interest rate method over the estimated life of the revenue streams. We recognize interest expense thereon using the effective rate, which is based on our current estimates of future revenues over the life of the arrangement. We periodically assess our expected revenues using internal projections, impute interest on the carrying value of the deferred royalty obligation, and record interest expense using the imputed effective interest rate. To the extent our estimates of future revenues are greater or less than previous estimates or the estimated timing of such payments is materially different than previous estimates, we will account for any such changes by adjusting the effective interest rate on a prospective basis, which will adjust future interest expense with a corresponding impact to the classification of our deferred royalty obligation. The assumptions used in determining the expected repayment term of the deferred

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royalty obligation and amortization period of the issuance costs requires that we make estimates that could impact the short-term and long-term classification of such costs, as well as the period over which such costs will be amortized.

Common Stock Warrants

We classify our common stock warrants in stockholder’s equity if they only allow for settlement in shares of our common stock, are indexed to our common stock, and meet the criteria for equity classification. See Note 8, “Stockholders’ Equity” for further detail.

Revenue Recognition

To determine revenue recognition, we perform the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) we satisfy a performance obligation. At contract inception, we assess whether the goods or services promised within a contract with a customer are distinct and, therefore, represent a separate performance obligation. Goods or services that are determined not to be distinct are combined with other promised goods and services until a distinct bundle is identified. We then determine the transaction price, which is the total amount of consideration we expect to receive from a customer in exchange for the promised goods or services and includes an estimate of any variable consideration in the contract. We then allocate the transaction price to each performance obligation and recognize the associated revenue when (or as) our customer obtains control of the goods or services within the performance obligation.

Incremental costs of obtaining a contract with a customer are capitalized and amortized consistent with the pattern of transferring the goods or services to which the cost relates when the expected amortization period of the asset is greater than one year. Incremental costs are expensed as incurred if the expected amortization period of the asset that we would have recognized is one year or less.

Product Revenue Recognition

We ship XPOVIO in the U.S. to specialty pharmacies and specialty distributors, collectively referred to as our customers, under a limited number of distribution arrangements with such third parties. Our specialty pharmacy customers resell XPOVIO directly to patients, while our specialty distributor customers resell XPOVIO to healthcare entities, who then resell to patients. We also enter into certain arrangements with group purchasing organizations and/or other payors that provide for government mandated and/or privately negotiated rebates, chargebacks, and discounts with respect to the purchase of our products.

Each unit of XPOVIO that is ordered by our customers represents a distinct performance obligation that is completed when control of the product is transferred to the customer. Accordingly, we recognize product revenue when the customer obtains control of our product, which occurs at a point in time, generally upon delivery pursuant to our agreements with our customers. If taxes are collected from customers relating to product sales and remitted to governmental authorities, they are excluded from revenue.

Revenue from product sales is recorded at the net sales price, which includes estimates of variable consideration for which reserves are reported. These reserves, as detailed below, are based on the amounts earned, or to be claimed on the related sales, and are generally classified as reductions of accounts receivable (if the amount is payable to the customer) or a current liability (if the amount is payable to a party other than a customer). Certain amounts are known at the time of sale based on contractual terms and are recorded pursuant to the most likely amount method, which is the single most likely amount in a range of possible considerations. Other amounts are estimated pursuant to the expected value method, which is the sum of probability-weighted amounts in a range of possible consideration amounts. Relevant factors used in the expected value method include: current contractual and statutory requirements, specific known market events and trends, industry data, and forecasted customer buying and payment patterns. These reserves reflect our best estimates of the variable consideration based on the terms of the respective underlying contracts.

The following are the components of variable consideration related to product revenue:

Cash discounts and distributor fees: We provide customary discounts on XPOVIO sales to our customers for prompt payment, the terms of which are explicitly stated in our contracts with such customers. We also pay fees to our customers for sales order management, data, and distribution services, the terms of which are also explicitly stated in our contracts with such customers. Such fees are not for a distinct good or service and, accordingly, are recorded as a reduction of revenue, as well as a reduction to accounts receivable (cash discounts) or as a component of accrued expenses (distributor fees).

Product returns: Consistent with industry practice, we offer our customers and other indirect purchasers a limited right of return for purchased units of XPOVIO for damage, defect, recall, and/or product expiry (beginning three months prior to the product’s expiration date and ending twelve months after the product’s expiration date). We estimate the amount of product sales that will be returned using quantitative and qualitative considerations, such as visibility into the inventory remaining in the distribution channel.

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Reserves for estimated returns are recorded as a reduction of revenue in the period that the related revenue is recognized, as well as a component of accrued expenses.

Based on the distribution model for XPOVIO, contractual inventory limits with our customers, the price of XPOVIO, and limited contractual return rights, we expect minimal XPOVIO returns. We update our estimated return liability each reporting period based on actual shipments of XPOVIO subject to contractual return rights, changes in expectations about the amount of estimated and/or actual returns, and other qualitative considerations.

Chargebacks: Chargebacks for fees and discounts represent the estimated obligations resulting from our contractual commitments to provide products to qualified healthcare entities at prices lower than the list prices charged to our customers who purchase XPOVIO directly from us. Our customers charge us for the discount provided to the healthcare entities. Chargebacks are generally determined at the time of resale to the qualified healthcare provider by our customers. Accordingly, reserves for chargebacks consist of credits that we expect to issue for units that remain in the distribution channel inventory at the end of the reporting period that we expect will be sold to qualified healthcare entities, as well as chargebacks that customers have claimed, but for which we have not yet issued a credit. We record reserves for chargebacks based on contractual terms in the same period that the related revenue is recognized, resulting in a reduction of product revenue and accounts receivable. We generally issue credits to the customer for such amounts within a few weeks after the customer notifies us of the resale to a discount-eligible healthcare entity.

Government rebates: We are subject to discount obligations under state Medicaid programs, Medicare, the Department of Veterans Affairs, the Department of Defense, and others. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability, which is included as a component of accrued expenses. For Medicare, we estimate the number of patients in the prescription drug coverage gap for whom we will owe an additional liability under Medicare Part D. Our liability for these rebates consists of invoices received for claims from prior and current quarters that have not been paid or for which an invoice has not yet been received, estimates of claims for the current quarter, and estimated future claims that will be made for product that has been recognized as revenue, but which remains in distribution channel inventories at the end of the reporting period.

Other incentives: Other incentives offered by us include co-payment assistance, which we provide as financial assistance to patients with commercial insurance that requires prescription drug co-payments by the patient. We calculate the accrual for co-payment assistance based on estimates of claims and the average co-payment assistance amounts per claim that we expect to receive associated with sales of XPOVIO that have been recognized as revenue but remain in distribution channel inventories at the end of the reporting period. Such estimates are based on industry experience with similar products, as well as actual amounts from our product sales to date. Any adjustments to such estimated liabilities on units in the distribution channel at period end, as well as actual amounts incurred on units sold through the distribution channel during the period, are recorded in the same period that the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability, which is included as a component of accrued expenses.

Product revenue reserves and allowances: As noted above, cash discounts and chargebacks are recorded as reductions of accounts receivable and product returns, distributor fees, government rebates, and other incentives are recorded as a component of accrued expenses. Actual amounts of consideration ultimately received may differ from our estimates. If actual results in the future vary from our estimates, we will adjust these estimates, which would affect product revenue, net and earnings in the period in which such variances become known.

License and Asset Purchase Agreements

We generate revenue from license or similar agreements with pharmaceutical companies for the development and commercialization of certain of our products and product candidates. Such agreements may include the transfer of intellectual property rights in the form of licenses, transfer of technological know-how, delivery of drug substances, research and development services, and participation on certain committees with the counterparty. Payments made by the customer may include non-refundable upfront fees, payments upon the exercise of options, payments based upon the achievement of defined milestones, and royalties on sales of products and product candidates if they are approved and commercialized. Our license and asset purchase agreements are detailed in Note 5, “License and Asset Purchase Agreements”.

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customer with a significant or incremental discount are considered performance obligations because they provide the customer with a material right.

We utilize judgment to estimate the transaction price at contract inception. We evaluate contingent milestones to determine if they should be included in the transaction price using the most likely amount method. Milestone payments that are not within our control, such as regulatory approvals, are not considered likely of being achieved until those approvals are received and are excluded from the transaction price using the most likely amount method. The transaction price is then allocated to each performance obligation on a relative standalone selling price basis, for which we recognize revenue as or when the performance obligations are satisfied. At the end of each reporting period, we re-evaluate our estimate of the transaction price, including the probability of achieving milestone payments that may not be subject to a material reversal, and adjust the transaction price if necessary. Any such adjustments are recorded on a cumulative catch-up basis, which would affect license and other revenue in the period of adjustment.

We then determine whether the performance obligations are satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. We evaluate the measure of progress, as applicable, for each reporting period and, if necessary, adjust the measure of performance and related revenue recognition.

When consideration is received, or such consideration is unconditionally due, from a customer prior to transferring goods or services to the customer under the terms of a contract, a contract liability is recorded within deferred revenue. Contract liabilities within deferred revenue are recognized as revenue after control of the goods or services is transferred to the customer and all revenue recognition criteria have been met.

For arrangements that include a license of intellectual property and sales-based royalties, including sales-based milestone payments, we recognize revenue when the related sales occur because the license of intellectual property is deemed to be the predominant item to which the royalties relate.

We account for asset purchase agreements under the accounting standards for business combinations and research and development, as applicable. In-process research and development acquired in an asset acquisition is expensed immediately unless there is an alternative future use. Subsequent payments made for the achievement of milestones are evaluated to determine whether they have an alternative future use or should be expensed.

Research and Development Expenses

Research and development costs are charged to expense as incurred and include, but are not limited to:

•

employee-related expenses, including salaries, benefits, travel and stock-based compensation expense;

•

expenses incurred under agreements with CROs, CMOs and consultants that help conduct clinical trials and preclinical studies;

•

the cost of acquiring, developing and manufacturing clinical trial materials, including comparator products;

•

facilities, depreciation and other expenses, which include direct and allocated expenses for rent and maintenance of facilities, insurance and other supplies; and

•

costs associated with preclinical activities and regulatory operations.

Costs for certain research and development activities, such as clinical trials, are recognized based on various inputs, including an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, and other information provided to us by our vendors based on their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are accordingly reflected in our financial statements as prepaid or accrued research and development costs.

Selling, General and Administrative Expenses

Selling, general and administrative costs are charged to expense as incurred and consist primarily of salaries, benefits, travel, and other related costs, including stock-based compensation, for personnel in executive, finance, commercial and administrative

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functions. Other significant costs include facility costs not otherwise included in research and development expenses, legal fees relating to patent and corporate matters and fees for accounting and consulting services.

Accounting for Stock-Based Compensation

We grant stock-based awards to employees and non-employees, including stock options, restricted stock units (“RSUs”), performance-based restricted stock units (“PSUs”) and shares issued under our employee stock purchase plan (“ESPP”). We account for all stock-based awards at their fair value as of the grant date and recognize compensation expense on the consolidated statements of operations on a straight-line basis over the vesting period of the award. We use the Black-Scholes option pricing model to determine the fair value of stock options as of the grant date. The fair value of RSUs is the quoted closing market price per share of our common stock on the Nasdaq Global Select Market on the grant date. Forfeitures are recognized as they occur.

PSUs are awards which will vest if certain performance goals are achieved over a certain performance period. Certain portions of certain PSU awards vest based on continuous service to the Company throughout the performance period even if the performance goal is not achieved. Stock-based compensation expense for PSUs is determined using the grant date fair value, which is the quoted closing market price per share of our common stock on the Nasdaq Global Select Market on the grant date. The grant date fair value of PSUs with a market condition also includes a discount that represents the likelihood that the related performance goals will not be achieved. Stock-based compensation expense for PSUs with a market condition is recognized on a straight-line basis over the service period. Market conditions include goals related to the performance of our common stock. Stock-based compensation expense for PSUs without a market condition is not recognized until the achievement of the performance goal is deemed probable (the “Probable Date”). At the Probable Date, we record a cumulative catch-up expense for the portion of the grant date fair value attributable to the period from the grant date to the Probable Date. The remaining expense is recognized over the remaining service period on a straight-line basis.

Foreign Currency Transactions

The functional currency of our subsidiaries in Germany and Israel are the Euro and Shekel, respectively. Foreign currency transaction gains and losses are recorded on the consolidated statements of operations and were immaterial for the years ended December 31, 2023, 2022 and 2021.

Income Taxes

We use the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial reporting and the tax reporting basis of assets and liabilities and are measured using the enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. We provide a valuation allowance against deferred tax assets unless, based upon the available evidence, it is more likely than not that the deferred tax assets will be realized. We have evaluated available evidence and concluded that we may not realize the benefit of our deferred tax assets; therefore, a valuation allowance has been established for the full amount of the net deferred tax assets. We recognize interest and/or penalties related to income tax matters in income tax expense. Our state tax provision pertains to income generated by our KPSC entity. Our foreign tax provision pertains to foreign income taxes due by our German and Israel subsidiaries, both of which operate on a cost-plus profit margin basis.

Net Loss Per Share

Basic and diluted net loss per common share is calculated by dividing net loss by the weighted-average number of common shares outstanding for the periods. Diluted net loss per share is computed by dividing the diluted net loss by the weighted average number of common shares, including potential dilutive common shares assuming the dilutive effect of outstanding stock options and unvested restricted stock units. For periods in which we have reported net losses, diluted net loss per common share is the same as basic net loss per share, since dilutive common shares are not included if their effect is anti-dilutive.

The following potentially dilutive securities were excluded from the calculation of diluted net loss per share due to their anti-dilutive effect (in thousands):

As of December 31,

As discussed further in Note 10, “Long-Term Obligations”, we have the option to settle the conversion obligation for our 3.00% convertible senior notes due 2025 (the “Notes”) in cash, shares or any combination of the two. Based on our net loss position, there was no impact on the calculation of dilutive loss per share during the years ended December 31, 2023, 2022 and 2021.

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As discussed further in Note 8, “Stockholders’ Equity”,there were warrants to purchase up to 9,787,563 shares of our common stock outstanding as of December 31, 2023. These warrants were excluded from the calculation of basic and diluted net loss per common share during the years ended December 31, 2023, 2022 and 2021 as the warrant holders do not have an obligation to share in our losses.

Comprehensive Loss

Comprehensive loss consists of net loss and certain changes in stockholders' deficit that are excluded from net loss, which currently consists of unrealized gains and losses on investments and foreign currency translation adjustments.

3. Product Revenue

To date, our only source of product revenue has been from the U.S. sales of XPOVIO. The following table summarizes activity in each of the product revenue allowance and reserve categories (in thousands):

Discounts andChargebacks Fees, Rebates,and OtherIncentives Returns Total

Discounts and chargebacks are recorded as reductions of accounts receivable, and returns, fees, rebates, and other incentives are recorded as a component of accrued expenses and other liabilities.

As of December 31, 2023 and 2022, net product revenue of $17.8 million and $23.6 million, respectively, was included in accounts receivable, net.

4. Inventory

Prior to regulatory approval, we expense costs relating to the production of inventory as research and development expenses in the period incurred. We capitalize the costs incurred to manufacture our products after regulatory approval when, based on our judgment, future commercialization is considered probable and the future economic benefit is expected to be realized. We value our inventories at the lower of cost or estimated net realizable value. We determine the cost of our inventories, which includes amounts related to materials and manufacturing overhead, on a first-in, first-out basis. Raw materials and work in process includes all inventory costs prior to packaging and labelling, including raw materials, active pharmaceutical ingredient, and drug product. Finished goods include packaged and labelled products.

Raw materials and work in process that may be used for either research and development or commercial sale are classified as inventory until the material is consumed or otherwise allocated for research and development. If the material is intended to be used for research and development, it is expensed as research and development once that determination is made.

We assess the recoverability of our inventory each reporting period and write-down any inventory that has become obsolete, that has a cost basis in excess of its estimated realizable value, or that is not expected to be sold or otherwise consumed before expiry. Inventory write-downs are recorded as cost of sales in the period the impairment is identified.

Cost of sales includes the cost of producing and distributing inventories related to sales of XPOVIO in the U.S. and sales of selinexor to our partners who commercialize our products outside of the U.S. Cost of sales is recognized in the period the related sales occur and includes compensation expense for employees involved with production and distribution, freight, and indirect overhead costs, as well as third-party royalties payable on net product revenue. Cost of sales may also include excess or obsolete inventory adjustment charges, abnormal costs, unabsorbed manufacturing and overhead costs, and manufacturing variances.

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The following table presents our inventory (in thousands), all of which was related to XPOVIO:

As of December 31,

XPOVIO was initially approved by the FDA in July 2019 at which time we began to capitalize costs to manufacture XPOVIO. Prior to FDA approval of XPOVIO, all costs related to the manufacturing of XPOVIO and related material were charged to research and development expense in the period incurred.

5. License and Asset Purchase Agreements

The following license and asset purchase agreements affected the consolidated financial statements during the years ended December 31, 2023, 2022 and 2021:

Antengene License Agreement

In May 2020, we entered into an amendment to our May 2018 license agreement (the “Original Antengene Agreement” and, as amended, the “Amended Antengene Agreement”) with Antengene Therapeutics Limited, a corporation organized and existing under the laws of Hong Kong (“Antengene”) and a subsidiary of Antengene Corporation Co. Ltd., a corporation organized and existing under the laws of the People’s Republic of China, pursuant to which we expanded the territory licensed to Antengene in the Original Antengene Agreement for the exclusive development and commercialization rights of selinexor, eltanexor and KPT-9274, each for the diagnosis, treatment and/or prevention of all human oncology indications, as well as verdinexor for the diagnosis, treatment and/or prevention of certain human non-oncology indications (“Antengene Licensed Compounds”).

Under the terms of the Amended Antengene Agreement, Antengene has the exclusive development and commercialization rights for the Antengene Licensed Compounds in mainland China, Taiwan, Hong Kong, Macau, South Korea, Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, Philippines, Singapore, Thailand, Vietnam, Australia and New Zealand (the “Antengene Territory”). Under the terms of the Original Antengene Agreement, we received an upfront cash payment of $11.7 million in 2018 and in June 2020 we received a one-time upfront cash payment of $11.7 million in connection with the Amended Antengene Agreement. We are also entitled to future milestone payments from Antengene if certain development, regulatory and commercialization goals are achieved. Finally, we are also eligible to receive tiered double-digit royalties based on future net sales of selinexor and eltanexor, and tiered single- to double-digit royalties based on future net sales of verdinexor and KPT-9274 in the Antengene Territory. In addition, upon completion of the manufacturing technology transfer plan, we will grant to Antengene non-exclusive rights to manufacture the Antengene Licensed Compounds solely for their development and commercialization in the Antengene Territory.

As part of the Amended Antengene Agreement, Antengene also has the right to participate in global clinical studies of the Antengene Licensed Compounds and will bear the cost and expense for patients enrolled in such global clinical studies in the Antengene Territory. Antengene is responsible for seeking regulatory and marketing approvals for the Antengene Licensed Compounds in the Antengene Territory, as well as any development of the products necessary to obtain such approvals. Antengene is also responsible for the commercialization of the Antengene Licensed Compounds in the Antengene Territory at its own cost and expense. Until Antengene manufactures its own drug supply, we will furnish clinical and commercial supplies to Antengene pursuant to supply agreements between us and Antengene, the costs of which will be borne by Antengene.

The Amended Antengene Agreement will continue in effect on a product-by-product, country-by-country basis until the later of the tenth anniversary of the first commercial sale of the applicable product in such country or the expiration of specified patent protection and regulatory exclusivity periods for the applicable product in such country. However, the Amended Antengene Agreement may be terminated earlier by (i) either party for breach of the Amended Antengene Agreement by the other party or in the event of the insolvency or bankruptcy of the other party, (ii) Antengene on a product-by-product basis for certain safety reasons or on a product-by-product, country-by-country basis for any reason with 180 days prior notice or (iii) us in the event Antengene challenges or assists with a challenge to certain of our patent rights.

We identified the following performance obligations in the Amended Antengene Agreement: exclusive licenses, initial data transfers, and a stand-ready obligation to provide initial clinical supply for each of the Antengene Licensed Compounds. We also identified as performance obligations the following customer options for each of the Antengene Licensed Compounds that were

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offered at a significant and incremental discount and represent material rights: (i) the material right for additional data transfers; (ii) the material right for additional clinical supply and related substance supply; (iii) the material right for manufacturing technology transfers and licenses; and (iv) the material right for the option for a backup compound, which represents Antengene’s option to select a replacement compound in the event it elects to discontinue the development of the Antengene Licensed Compounds. All of the performance obligations that received an allocation of the initial transaction price of $11.7 million were fully satisfied as of December 31, 2020, except for the performance obligations related to eltanexor, which were fully satisfied during the year ended December 31, 2021. As such, we recognized $0.3 million in revenue when initial clinical supply of eltanexor was delivered to Antengene during the year ended December 31, 2021.

All development and regulatory milestones, which represent variable consideration, will be evaluated each reporting period and included in the transaction price if the milestone is considered likely of achievement and if it is probable that a significant revenue reversal will not occur in future periods. Milestones included in the transaction price will be fully recognized in revenue in the same reporting period because all performance obligations that received an allocation of the transaction price were fully satisfied as December 31, 2021.

Any consideration related to sales-based milestones, as well as royalties on net sales upon commercialization of XPOVIO by Antengene, are recognized when the related sales occur, as they were determined to relate predominantly to the intellectual property licenses granted to Antengene.

Menarini License Agreement

In December 2021, we entered into a license agreement (the “Original Menarini Agreement”) with Berlin-Chemie AG, an affiliate of the Menarini Group (“Menarini”), pursuant to which we granted Menarini a non-exclusive license to develop, and an exclusive license to commercialize, products containing selinexor (the “Product”), for all human oncology indications in the European Economic Area, United Kingdom, Switzerland, Armenia, Azerbaijan, Belarus, Kazakhstan, Kyrgyzstan, Moldova, Russia, Tajikistan, Turkmenistan, Uzbekistan, Ukraine, Turkey, Mexico, all Central America countries and all South America countries (collectively, the “Menarini Territory”). In March 2023, the Original Menarini Agreement was amended (the “Amended Menarini Agreement”) to expand the Menarini Territory to include all countries in the continent of Africa and Saudi Arabia, United Arab Emirates, Kuwait, Oman, Qatar, Bahrain, Lebanon, Jordan, Iraq, and Yemen (together with the Menarini Territory, the “Expanded Menarini Territory”). In addition, we granted to Menarini a non-exclusive license to package and label the Product in or outside of the Expanded Menarini Territory for all human oncology indications solely to enable Menarini to commercialize the Product within the Expanded Menarini Territory.

Under the terms of the Amended Menarini Agreement, we will use commercially reasonable efforts to develop the Product, transfer any marketing approval or authorization with respect to the Product in the Expanded Menarini Territory to Menarini and to complete any post-marketing approval or authorization studies required by a regulatory authority as a condition of maintaining the approval in any country in the Expanded Menarini Territory. Menarini is obligated to use commercially reasonable efforts to apply for and obtain marketing approval or authorization of the Product, and to obtain price or reimbursement approval for the Product after approval of the relevant marketing approval or authorization, in each country of the Expanded Menarini Territory in each indication for which we have conducted a registrational clinical trial. Menarini is also obligated to use commercially reasonable efforts at its sole cost and expense to launch and commercialize the Product in each country of the Expanded Menarini Territory in each indication for which we have conducted a registrational clinical trial.

We received an upfront cash payment of $75.0 million in December 2021 under the Original Menarini Agreement and $3.5 million in April 2023 upon execution of the Amended Menarini Agreement. In addition, we are entitled to receive additional milestone payments from Menarini if certain development and sales performance milestones are achieved. We are further eligible to receive tiered royalties ranging from the mid-teens to mid-twenties based on future net sales of the Product in the Expanded Menarini Territory. The payments owed by Menarini to us are subject to reduction in specified circumstances. Menarini will reimburse us for 25% of all expenses we incur for the development of the Product during 2022 through 2025, provided that such reimbursements shall not exceed $15.0 million per calendar year. These amounts represent variable consideration and will be recognized as earned.

The Amended Menarini Agreement will continue in effect on a country-by-country basis until the last to occur among: (i) the fifteenth anniversary of the first commercial sale of the Product in the applicable country, (ii) the expiration of the last-to-expire of the licensed patent rights in the applicable country or (iii) the expiration of any regulatory exclusivity protection covering the Product in such country. However, the Amended Menarini Agreement may be terminated earlier by either party for (i) an uncured material breach of the Amended Menarini Agreement by the other party (A) on a country-by-country basis with respect to the country to which the breach does not affect the Amended Menarini Agreement as a whole or (B) in its entirety if the breach affects the Amended Menarini Agreement as a whole, or (ii) in the event of the insolvency or bankruptcy of the other party. We may also terminate the Amended Menarini Agreement for certain patent challenges by Menarini.

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We assessed this arrangement and concluded that the contract counterparty, Menarini, is a customer. We identified the following material promises in the arrangement: the granting of a non-exclusive license to develop, and an exclusive license to commercialize, product and label the Product, as well as the initial transfer of know-how and information to Menarini. The Amended Menarini Agreement provides that we will supply to Menarini, and Menarini will purchase from us, all required quantities of Product for the Expanded Menarini Territory in accordance with a supply agreement separately entered into by and between us and Menarini in 2022 (the “Supply Agreement”). We determined that the promise of the Supply Agreement was not a performance obligation at the outset of the arrangement as the rate charged for the Product was not at a significant and incremental discount and therefore did not represent a material right. We then determined that the granting of the license and the initial transfer of know-how were not distinct from one another and must be combined as a performance obligation (the “Combined Performance Obligation”). Based on these determinations, we identified one distinct performance obligation at the inception of the contract: the Combined Performance Obligation. We further determined that the up-front payment of $75.0 million constituted the entirety of the consideration included in the transaction price at contract inception, which was allocated to the Combined Performance Obligation. The Combined Performance Obligation was fully satisfied as of December 31, 2021.

All development and regulatory milestones, which represent variable consideration, will be evaluated each reporting period and included in the transaction price if the milestone is considered likely of achievement and if it is probable that a significant revenue reversal will not occur in future periods. Milestones included in the transaction price will be fully recognized in revenue in the same reporting period because the Combined Performance Obligation was fully satisfied as of December 31, 2021.

Any consideration related to sales-based milestones, as well as royalties on net sales upon commercialization by Menarini, are recognized when the related sales occur, as they were determined to relate predominantly to the intellectual property licenses granted to Menarini.

Neumedicines Asset Purchase Agreement and Libo License Agreement

In November 2020, we entered into an asset purchase agreement (the “Asset Purchase Agreement”) with Neumedicines Inc. (“Neumedicines”). Pursuant to the Asset Purchase Agreement, we agreed to acquire certain clinical-stage assets from Neumedicines, including a proprietary recombinant human interleukin 12 (“Il-12”). The acquisition closed in July 2021 (the “Closing”), having a total value of approximately $7.4 million. We paid $0.5 million in cash during the year ended December 31, 2020, and at the time of closing, paid $5.5 million in cash and issued 150,000 shares of our common stock to Neumedicines. Further, we will owe Neumedicines up to $65.0 million in royalty payments on net product sales of the acquired IL-12 asset (“KPT-1200”) and an additional 75,000 shares of our common stock as well as other contingent and variable cash payments upon the satisfaction of certain development and regulatory milestones. The $7.4 million of consideration was recorded as research and development expense for the year ended December 31, 2021. The $5.5 million cash portion of the consideration paid at the time of closing was recorded as an investing activity on the consolidated statement of cash flows for the year ended December 31, 2021.

Contemporaneously with the Closing, we entered into a license agreement with Libo Pharma Corp. (“Libo”) under which we granted to Libo an exclusive license to manufacture, develop and commercialize IL-12 products in certain countries in Asia, Africa and Oceania. In December 2023, we entered into an amended and restated license agreement with Libo (the "Amended Libo Agreement") under which we granted to Libo an exclusive license to manufacture, develop and commercialize IL-12 products worldwide for all indications except for acute radiation syndrome, which remains limited to certain countries in Asia, Africa and Oceania.

Summary of License and Other Revenue

The following table presents information about our license and other revenue (in thousands):

For the YearsEnded December 31,

During the year ended December 31, 2023, we recognized (i) $15.0 million of revenue for the reimbursement of development related expenses, $4.0 million of milestone-related revenue, $3.5 million of license-related revenue, $1.1 million of royalty revenue, and $0.8 million of other reimbursement revenue from Menarini; (ii) $1.5 million of royalty revenue, and $1.2 million of other reimbursement revenue from Antengene; and (iii) $3.4 million of license-related revenue, $2.5 million of milestone-related revenue, $0.5 million of royalty revenue, and $0.5 million of other reimbursement revenue from our other partners.

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During the year ended December 31, 2022, we recognized (i) $15.0 million of revenue for the reimbursement of development related expenses, $0.3 million of royalty revenue, and $0.4 million of other reimbursement revenue from Menarini; (ii) $7.8 million of milestone-related revenue, $3.8 million of royalty revenue, and $1.8 million of other reimbursement revenue from Antengene; and (iii) $5.2 million of royalty revenue and $2.3 million of milestone-related revenue from our other partners.

During the year ended December 31, 2021, we recognized (i) $75.0 million of revenue related to the upfront payment we received from Menarini; (ii) $29.3 million of milestone-related revenue, $0.8 million of royalty revenue, and $0.3 million of other revenue from Antengene; and (iii) $6.0 million of other revenue.

License and other revenue of $9.1 million and $22.5 million were included in accounts receivable, net at December 31, 2023 and 2022, respectively. License and other revenue of $1.0 million and $7.8 million were included in other current assets at December 31, 2023 and 2022, respectively.

6. Fair Value Measurements

Financial instruments, including cash, cash equivalents, accounts receivable, net, other current assets, other assets, restricted cash, accounts payable, and accrued expenses, are presented at amounts that approximate fair value at December 31, 2023 and 2022.

Items classified as Level 2 consist of corporate debt securities, commercial paper, and U.S. government and agency securities. We estimate the fair values of these marketable securities by taking into consideration valuations obtained from third-party pricing sources. These pricing sources utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include market pricing based on real-time trade data for the same or similar securities, issuer credit spreads, benchmark yields, and other observable inputs. We validate the prices provided by our third-party pricing sources by understanding the models used, obtaining market values from other pricing sources and analyzing pricing data in certain instances.

In certain cases where there is limited activity or less transparency around inputs to valuation, the related assets or liabilities are classified as Level 3. The embedded derivative liability associated with a Revenue Interest Financing Agreement we entered into with HCR in September 2019 and amended in June 2021 and August 2023, as discussed further in Note 10, “Long-Term Obligations”, is measured at fair value and is included as a component of the deferred royalty obligation on our consolidated balance sheets. The embedded derivative liability is subject to remeasurement at the end of each reporting period, with changes in fair value recognized as a component of other expense, net on the consolidated statements of operations. The valuation method incorporates certain unobservable Level 3 key inputs including: (i) the probability-weighted net sales of XPOVIO and any of our other future products, including worldwide net product sales, upfront payments, milestones and royalties; (ii) our risk-adjusted discount rate; and (iii) the probability of a change in control occurring during the term of the instrument.

The following tables present information about our financial assets and liability that have been measured at fair value and indicate the fair value hierarchy of the valuation inputs utilized to determine such fair value (in thousands):

Financial assets

Cash equivalents:

U.S. government and agency securities 1,998 — 1,998 —

Investments:

U.S. government and agency securities 47,507 — 47,507 —

Financial liability

Embedded derivative liability $ 2,800 $ — $ — $ 2,800

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Financial assets

Cash equivalents:

Investments:

U.S. government and agency securities 20,722 — 20,722 —

Financial liability

Embedded derivative liability $ 2,800 $ — $ — $ 2,800

7. Investments

The following tables summarize our investments in debt securities, classified as available-for-sale (in thousands):

AmortizedCost TotalUnrealizedGains TotalUnrealizedLoss Aggregate Fair Value

At December 31, 2023 and 2022, we held 41 and 60 debt securities, respectively, that were in an unrealized loss position. The unrealized losses at December 31, 2023 and 2022 were attributable to changes in interest rates and do not represent credit losses. We do not intend to sell the investments before recovery of their amortized cost bases, which may be at maturity. All our investments mature within two years from December 31, 2023. The following tables summarize our debt securities in an unrealized loss position for which an allowance for credit losses has not been recorded, aggregated by major security type and length of time in a continuous unrealized loss position (in thousands):

Less than 12 Months 12 Months or Longer Total

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Less than 12 Months 12 Months or Longer Total

8. Stockholders’ Equity

Authorized Common Shares

On May 24, 2023, our stockholders approved an amendment to our Restated Certificate of Incorporation, as amended, to increase the number of authorized shares of our common stock from 200,000,000 shares to 400,000,000 shares.

Private Placement Offering and Common Share Warrants

On August 1, 2023, in connection with the Second Amendment to the Revenue Interest Agreement, we issued warrants to HCR to purchase up to 250,000 shares of common stock at an exercise price of $2.25 per share. The warrants are exercisable through August 1, 2030. As of December 31, 2023, none of these warrants have been exercised.

Open Market Sale Agreement

Under the 2023 Open Market Sale Agreement, Jefferies may sell the Shares by methods deemed to be an “at the market offering” as defined in Rule 415(a)(4) promulgated under the Securities Act. We may sell the Shares in amounts and at times to be determined by us from time to time subject to the terms and conditions of the 2023 Open Market Sale Agreement, but we have no obligation to sell any of the Shares in the 2023 Open Market Offering.

We or Jefferies may suspend or terminate the offering of Shares upon notice to the other party and subject to other conditions. We have agreed to pay Jefferies commissions for its services in acting as agent in the sale of the Shares in the amount of up to 3.0% of gross proceeds from the sale of the Shares pursuant to the 2023 Open Market Sale Agreement. We have also agreed to provide Jefferies with customary indemnification and contribution rights.

During the years ended December 31, 2022 and 2021, we sold an aggregate of 3,991,652 and 638,341 Open Market Shares, respectively, under the 2018 Open Market Sale Agreement, for net proceeds of approximately $35.1 million and $9.9 million, respectively. We did not sell any Open Market Shares under the 2018 Open Market Sale Agreement nor any Shares under the 2023 Open Market Sale Agreement during the year ended December 31, 2023. As of December 30, 2023, $100.0 million of Shares was available for issuance and sale under the 2023 Open Market Sale Agreement.

9. Stock-based Compensation

On May 19, 2022, our stockholders approved the 2022 Equity Incentive Plan (the “2022 Plan”), succeeding our 2013 Stock Incentive Plan (the “2013 Plan”), which has expired and under which no further grants may be made. The 2022 Plan provides for the

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grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock awards, RSU awards and other stock-based awards. On May 24, 2023, our stockholders approved an amendment to the 2022 Plan to increase the number of shares of our common stock available for issuance under the 2022 Plan by 5,000,000 shares. As of December 31, 2023, there were 8,591,362 shares available for future grants under the 2022 Plan.

Under the terms of the 2022 Plan, 2013 Plan and the 2010 Stock Incentive Plan, which was replaced by the 2013 Plan, we granted stock options, RSUs, and PSUs to our employees, officers, directors, consultants and advisors. Stock options have a ten-year term and an exercise price equal to the fair market value of a share of our common stock on the grant date. Stock options vest over four years with 25% vesting on the one-year anniversary of the grant date and the remainder vesting in equal monthly installments thereafter. RSUs generally vest over a period of one to four years in annual installments beginning on the first anniversary of the grant date. PSUs will vest if certain performance goals are achieved over a certain performance period. Certain portions of certain PSU awards vest based on continuous service to the Company throughout the performance period even if the performance goal is not achieved.

During 2023, 2022, and 2021, we also granted stock options and RSUs through inducement grants outside of our stockholder approved equity compensation plans as permitted under the Nasdaq Stock Market listing rules to certain employees to induce them to accept employment with us (collectively, “Inducement Awards”). In February 2022, our Board approved the 2022 Inducement Stock Incentive Plan (the “2022 Inducement Plan”) under which 850,000 shares of common stock were initially reserved for issuance for inducement awards to be granted to newly hired full-time employees. In May 2022 and February 2023, the Board increased the number of shares reserved for issuance under the 2022 Inducement Plan by 850,000 and 1,200,000, respectively. We assessed the terms of these Inducement Awards and determined there was no possibility that we would have to settle these awards in cash and therefore, equity accounting was applied. As of December 31, 2023, there were 874,498 shares available for future grants under the 2022 Inducement Plan.

As of December 31, 2023, we had 25,753,096 shares reserved for issuance, which includes shares available for future grants and outstanding stock options, RSUs and PSUs under the 2010 Plan, 2013 Plan, 2022 Plan, and Inducement Awards (including the Inducement Awards granted under the 2022 Inducement Plan).

During the year ended December 31, 2022, we accelerated the vesting and extended the exercise date of certain stock-based awards granted to our former Chief Executive Officer and former Chief Scientific Officer in connection with their departure from the Company in May 2022. These modifications resulted in the recognition of incremental stock-based compensation expense of $7.4 million.

Stock-based Compensation Expense

In connection with all stock-based payment awards, total stock-based compensation expense recognized was as follows (in thousands):

For the Years Ended December 31,

The total stock-based compensation expense recognized by award type was as follows (in thousands):

For the Years Ended December 31,

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Stock Options

The following table summarizes stock option activity related to the 2010 Plan, 2013 Plan, 2022 Plan, and Inducement Awards (including the stock option Inducement Awards granted under the 2022 Inducement Plan):

The total intrinsic value of stock options exercised for the year ended December 31, 2023 was less than $0.1 million. The total intrinsic value of stock options exercised for the years ended December 31, 2022 and 2021 was $0.3 million and $1.0 million, respectively.

The fair value of each stock option granted is estimated on the date of grant using the Black-Scholes option-pricing model. The following table summarizes the assumptions used in calculating the fair value of the stock option awards:

For the Years Ended December 31,

Dividend —% —% —%

We use the simplified method to calculate the expected term as our historical exercise data does not provide a reasonable basis upon which to estimate the expected term. The expected term is applied to the stock option grant group as a whole, as we do not expect substantially different exercise or post-vesting termination behavior among our employee population. Our expected stock price volatility assumption is based on the historical volatility of our publicly traded stock. The risk-free interest rate is based on a treasury instrument whose term is consistent with the expected term of the stock options. We account for forfeitures as they occur.

Using the Black-Scholes option-pricing model, the weighted-average grant date fair values of options granted during the years ended December 31, 2023, 2022 and 2021 was $1.54, $5.83 and $7.57 per share, respectively.

At December 31, 2023, there was $9.7 million of unrecognized compensation related to unvested stock option awards, which are expected to be recognized over a weighted-average period of 1.7 years.

Restricted Stock Units and Performance-Based Restricted Stock Units

The following is a summary of RSU and PSU activity for the 2010 Plan, 2013 Plan, 2022 Plan, and Inducement Awards (including the RSU Inducement Awards granted under the 2022 Inducement Plan):

Number ofSharesUnderlyingRSUs and PSUs Weighted-AverageGrant DateFair Value

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As of December 31, 2023, there was $24.0 million of unrecognized compensation costs related to unvested RSUs and PSUs, which are expected to be recognized over a weighted-average period of 1.9 years.

Employee Stock Purchase Plan

We have an ESPP that permits eligible employees to enroll in six-month offering periods. Participants may purchase shares of our common stock, through payroll deductions, at a price equal to 85% of the fair market value of the common stock on the first or last day of the applicable six-month offering period, whichever is lower. Purchase dates under the ESPP occur on or about May 1 and November 1 each year. In 2013, our stockholders approved an increase in the number of shares of common stock authorized for issuance pursuant to the ESPP to 242,424 shares of common stock, plus an annual increase to be added on the first day of each fiscal year, commencing on January 1, 2015 and ending on December 31, 2023, equal to the lesser of 484,848 shares of our common stock, 1% of the number of outstanding shares on such date, or an amount determined by the Board (the "Evergreen Provision"). On May 24, 2023, our stockholders approved an amendment and restatement (the “Amended and Restated ESPP”) of our ESPP. The Amended and Restated ESPP (i) eliminated the Evergreen Provision and (ii) increased the number of shares of common stock authorized for issuance under the ESPP from 2,508,923 shares to 4,008,923 shares.

As of December 31, 2023, 1,632,818 shares of our common stock remained available for issuance under the Amended and Restated ESPP.

During the years ended December 31, 2023, 2022 and 2021, $1.1 million, $2.3 million and $2.0 million, respectively, was withheld from employees, on an after-tax basis, in order to purchase 638,182, 508,391 and 330,257 shares of our common stock, respectively. As of December 31, 2023, there was $0.2 million of total unrecognized stock-based compensation expense related to the Amended and Restated ESPP. The expense is expected to be recognized over a period of four months.

The fair value of the option component of the shares purchased under the Amended and Restated ESPP was estimated using the Black-Scholes option-pricing model with the following weighted-average assumptions:

For the Years Ended December 31,

Expected term (in years) 0.5 0.5 0.5

Dividend —% —% —%

10. Long-Term Obligations

3.00% Convertible Senior Notes due 2025

On October 16, 2018, we completed an offering of $150.0 million aggregate principal amount of our 3.00% convertible senior notes due 2025. In addition, on October 26, 2018, we issued an additional $22.5 million aggregate principal amount of the Notes pursuant to the full exercise of the option to purchase additional Notes granted to the initial purchasers in the offering. The Notes were sold in a private offering to qualified institutional buyers in reliance on Rule 144A under the Securities Act. In accordance with accounting guidance for debt with conversion and other options, we separately accounted for the liability component (“Liability Component”) and the embedded conversion option (“Equity Component”) of the Notes by allocating the proceeds between the Liability Component and the Equity Component, due to our ability to settle the Notes in cash, shares of our common stock or a combination of cash and shares of our common stock, at our option. In connection with the issuance of the Notes, we incurred approximately $5.6 million of debt issuance costs, which primarily consisted of underwriting, legal and other professional fees, and allocated these costs between the Liability Component and the Equity Component based on the allocation of the proceeds. Of the total debt issuance costs, $2.2 million was allocated to the Equity Component and recorded as a reduction to additional paid-in capital and $3.4 million was allocated to the Liability Component and recorded as a reduction of the Notes. The portion allocated to the Liability Component is amortized to interest expense using the effective interest method over seven years.

In 2021, upon adoption of ASU 2020-06, we reclassified the Equity Component as of January 1, 2021 and combined it with the Liability Component of the Notes, increasing the carrying value of our convertible debt by approximately $50.6 million, with a corresponding decrease to additional paid-in capital of $65.6 million and accumulated deficit of $15.0 million. Our deferred tax liability related to the Notes also decreased by approximately $11.8 million, with a corresponding increase in the income tax valuation allowance.

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The Notes are senior unsecured obligations and bear interest at a rate of 3.00% per year payable semiannually in arrears on April 15 and October 15 of each year, beginning on April 15, 2019. Upon conversion, the Notes will be converted into cash, shares of our common stock, or a combination of cash and shares of our common stock, at our election. As of October 15, 2022, the Notes are subject to redemption at our option in whole or in part, if the conditions described below are satisfied. Holders may require us to repurchase their Notes following a fundamental change (as defined within the indenture governing the Notes) at a cash repurchase price generally equal to the principal amount of the Notes to be repurchased, plus accrued and unpaid interest. The Notes will mature on October 15, 2025, unless earlier converted, redeemed or repurchased in accordance with their terms. Subject to satisfaction of certain conditions and during the periods described below, the Notes may be converted at an initial conversion rate of 63.0731 shares of common stock per $1,000 principal amount of the Notes (equivalent to an initial conversion price of approximately $15.85 per share of common stock).

Holders of the Notes may convert all or any portion of their Notes, in multiples of $1,000 principal amount, at their option at any time prior to the close of business on the business day immediately preceding June 15, 2025 only under the following circumstances:

(1)

during any calendar quarter commencing after the calendar quarter ending on December 31, 2018 (and only during such calendar quarter), if the last reported sale price of our common stock for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price for the Notes on each applicable trading day;

(2)

during the five-business day period immediately after any five consecutive trading day period (the “Measurement Period”) in which the trading price per $1,000 principal amount of Notes for each trading day of the Measurement Period was less than 98% of the product of the last reported sale price of our common stock and the conversion rate on each such trading day;

(3)

if we call the Notes for redemption, until the close of business on the business day immediately preceding the redemption date; or

(4)

upon the occurrence of specified corporate events as described within the indenture governing the Notes.

As of December 31, 2023, none of the above circumstances had occurred and as such, the Notes could not have been converted.

As of October 15, 2022, we may redeem for cash all or part of the Notes at our option if the last reported sale price of our common stock equals or exceeds 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period ending within five trading days prior to the date on which we send any notice of redemption. The redemption price will be 100% of the principal amount of the Notes to be redeemed, plus accrued and unpaid interest, if any. In addition, calling any convertible note for redemption will constitute a make-whole fundamental change with respect to that convertible note, in which case the conversion rate applicable to the conversion of that convertible note, if it is converted in connection with the redemption, will be increased in certain circumstances. We did not redeem any of the Notes as of December 31, 2023.

The outstanding balances of the Notes consisted of the following (in thousands):

As of December 31,

Less: debt issuance costs (1,581 ) (2,395 )

We determined the expected life of the Notes was equal to its seven-year term and the effective interest rate was 3.53%. As of December 31, 2023, the “if-converted value” did not exceed the remaining principal amount of the Notes. The fair value of the Notes was determined based on data points other than quoted prices that are observable, either directly or indirectly, and has been classified as Level 2 within the fair value hierarchy. The fair value of the Notes, which differs from their carrying value, is influenced by market

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interest rates, our stock price and stock price volatility. The estimated fair value of the Notes as of December 31, 2023 and 2022 was approximately $87.9 million and $133.1 million, respectively.

The following table sets forth total interest expense recognized related to the Notes (in thousands):

For the YearsEnded December 31,

Amortization of debt issuance costs 814 812 780

Future minimum payments on the Notes were as follows (in thousands):

Years ended December 31, Future MinimumPayments

Less: interest expense and issuance costs (11,931 )

Convertible senior notes $ 170,919

Deferred Royalty Obligation

In September 2019, we entered into a Revenue Interest Financing Agreement (“the Revenue Interest Agreement”) with HCR. In June 2021, we, and certain of our subsidiaries, entered into an amendment of the Revenue Interest Agreement (the “Amended Revenue Interest Agreement”) with, among others, HCR. We received $75.0 million, less certain transaction expenses, upon closing of the Revenue Interest Agreement (the “First Investment Amount”) and $60.0 million upon closing of the Amended Revenue Interest Agreement (the “Second Investment Amount” and, together with the First Investment Amount, the “Investment Amount”).

In exchange for the above payments, HCR receives payments from us at a tiered percentage (the “Applicable Tiered Percentage”) of net revenues of selinexor and any of our other future products, including worldwide net product sales and upfront payments, milestones, and royalties. The Applicable Tiered Percentage is subject to reduction in the future if a target based on cumulative U.S. net sales of selinexor is met. Prior to the Second Amendment (as defined below) in August 2023, total payments to HCR were capped at 185% of the Investment Amount (the "Payment Cap").

Under the terms of the Amended Revenue Interest Agreement, if HCR had not received 100% of the First Investment Amount and 65% of the Second Investment Amount by December 31, 2024 (the "First Minimum Aggregate Payment"), or 100% of both the First Investment Amount and the Second Investment Amount by September 30, 2026, we were required to make a cash payment sufficient to gross up the payments to such minimum amounts.

On August 1, 2023, we entered into a Second Amendment to the Amended Revenue Interest Agreement (the “Second Amendment”) with HCR. The Second Amendment (i) increased the Payment Cap from 185% to 195% of the Investment Amount; (ii) extended by six months the payment date of the First Minimum Aggregate Payment from December 31, 2024 to June 30, 2025; and (iii) issued warrants to HCR for the purchase of up to 250,000 shares of our common stock with a termination date of August 1, 2030 and an exercise price of $2.25 per share. Except as set forth in the Second Amendment, all other terms and conditions of the Amended Revenue Interest Agreement remain in full force and effect.

As the repayment of the funded amount is contingent upon worldwide net product sales and upfront payments, milestones, and royalties, the repayment term may be shortened or extended depending on actual worldwide net product sales and upfront payments, milestones, and royalties. The repayment period commenced on October 1, 2019 for the First Investment Amount and on July 1, 2021 for the Second Investment Amount, and expires on the earlier of (i) the date in which HCR has received cash payments totaling an aggregate of 195% of the Investment Amount or (ii) the legal maturity date of October 1, 2031. If HCR has not received payments equal to 195% of the Investment Amount by the twelve-year anniversary of the initial closing date, we will be required to pay an amount equal to the Investment Amount plus a specific annual rate of return less payments previously paid to HCR. In the event of a change of control, we are obligated to pay HCR an amount equal to 195% of the Investment Amount less payments previously paid to HCR. In addition, upon the occurrence of an event of default, including, among others, our failure to pay any amounts due to HCR, insolvency, our failure to pay indebtedness when due, the revocation of regulatory approval of XPOVIO in the U.S. or our breach of any covenant contained in the Amended Revenue Interest Agreement and our failure to cure the breach within the prescribed time

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frame, we are obligated to pay HCR an amount equal to 195% of the Investment Amount less payments previously paid to HCR. In addition, upon an event of default, HCR may exercise all other rights and remedies available under the Amended Revenue Interest Agreement, including foreclosing on the collateral that was pledged to HCR, which consists of all of our present and future assets. As of December 31, 2023, we have made $61.7 million in payments to HCR.

We have concluded that the features of both the First Investment Amount and Second Investment Amount are similar to those of a debt instrument. Accordingly, we have accounted for the transaction as long-term debt and presented it as a deferred royalty obligation on our consolidated balance sheets. We have also determined that the repayment of 195% of the Investment Amount, less any payments made to date, upon a change of control is an embedded derivative that requires bifurcation from the debt instrument and fair value recognition, as further described in Note 6, “Fair Value Measurements” to our consolidated financial statements.

The effective interest rate as of December 31, 2023 was 15%. In connection with the First Investment Amount, we incurred debt issuance costs totaling $1.4 million. Debt issuance costs have been netted against the debt and are being amortized over the estimated term of the debt using the effective interest method, adjusted on a prospective basis for changes in the underlying assumptions and inputs.

The carrying value of the deferred royalty obligation at December 31, 2023 and December 31, 2022 was $129.7 million and $129.9 million, respectively, based on $135.0 million of proceeds, net of the fair value of the bifurcated embedded derivative liability upon execution of the Revenue Interest Agreement and the Amended Revenue Interest Agreement, and debt issuance costs incurred. The carrying value of the deferred royalty obligation approximated fair value at December 31, 2023 and 2022 and is based on our current estimates of future payments to HCR over the life of the arrangement, which are considered Level 3 inputs.

11. Commitments and Contingencies

Operating Leases

We determine if an arrangement contains a lease at contract inception based on the facts and circumstances in the arrangement. Lease classification, recognition, and measurement are then determined at the lease commencement date. For arrangements that contain a lease we (i) identify lease and non-lease components, (ii) determine the consideration in the contract, (iii) determine whether the lease is an operating or financing lease; and (iv) recognize lease right-of-use assets and liabilities. Lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected lease term.

The interest rate implicit in lease contracts is typically not readily determinable and as such, we use our incremental borrowing rate based on the information available at the lease commencement date, which represents an internally developed rate that would be incurred to borrow, on a collateralized basis, over a similar term, an amount equal to the lease payments in a similar economic environment. In determining the incremental borrowing rate, we consider (i) our estimated public credit rating, (ii) our observable debt yields, as well as other bonds in the market issued by other companies with similar credit ratings as us, and (iii) adjustments necessary for collateral, lease term, and inflation or foreign currency.

Most leases include options to renew and/or terminate the lease, which can impact the lease term. The exercise of these options is at our discretion and we do not include any of these options within the expected lease term as we are not reasonably certain we will exercise these options. Leases that have a lease term of 12 months or less at commencement date are excluded from this treatment and are recognized on a straight-line basis over the term of the lease.

Fixed, or in substance fixed, lease payments on our operating lease are recognized over the expected term of the lease on a straight-line basis. Variable lease expenses that are not considered fixed, or in substance fixed, are recognized as incurred. Fixed and variable lease expense on our operating lease is recognized within operating expenses on our consolidated statements of operations.

We are party to an operating lease of 98,502 square feet of office and research space in Newton, Massachusetts with a term through September 30, 2025 (the “Newton, MA Lease”). The lease contains a renewal option for an additional five years which was not included in the lease term as its exercise is not reasonably certain. Pursuant to the Newton, MA Lease, we have provided a security deposit in the form of a cash-collateralized letter of credit in the amount of $0.3 million which is classified within long-term restricted cash on the consolidated balance sheets.

The Newton, MA Lease provides for increases in future minimum annual rental payments, as defined in the lease agreement. The operating lease expense for each of the years ended December 31, 2023, 2022 and 2021 were $2.8 million. Variable lease costs pertain to reimbursement of certain landlord expenses and were immaterial for each of the years ended December 31, 2023, 2022 and 2021.

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In addition, we are party to certain short-term leases having a term of twelve months or less at the commencement date. We recognize short-term lease expense on a straight-line basis and do not record a related right-of use asset or lease liability for such leases. These costs were immaterial for the years ended December 31, 2023, 2022 and 2021.

We review the carrying values of our lease assets for possible impairment whenever events or changes in circumstances indicate that the carrying amounts of the assets may not be recoverable. We have not recorded an impairment in any period since inception.

Lease Commitments

As of December 31, 2023, future minimum lease payments under non-cancellable operating lease agreements for which we have recognized operating lease right-of-use assets and liabilities are as follows (in thousands):

Years ending December 31, FutureMinimumPayments

Total minimum lease payments 6,735

Less: present value adjustment (638 )

Operating lease liabilities $ 6,097

As of December 31, 2023, the remaining lease term on the Newton, MA Lease was 1.8 years and the discount rate used to calculate the operating lease liability was 11%.

Litigation

From time to time we may face legal claims or actions in the normal course of business. There are no outstanding legal claims or actions as of December 31, 2023.

12. Accrued Expenses

KPTI US Equity

KPTI · 10-K · period ended 2023-12-31

Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations

Item 7A. Quantitative and Qualitative Disclosures about Market Risk

Item 8. Financial Statements and Supplementary Data

Item 9A. Controls and Procedures

Item 9B. Other Information

Item 9C. Disclosure Regarding Foreign Jurisdictions that Prevent Inspections

Item 10. Directors, Executive Officers and Corporate Governance

Item 11. Executive Compensation

Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters

Item 13. Certain Relationships and Related Transactions, and Director Independence

Item 14. Principal Accountant Fees and Services

Item 15. Exhibits and Financial Statement Schedules

Item 16. Form 10-K Summary

KPTI US Equity☆

KPTI · 10-K · period ended 2023-12-31

Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations

Item 7A. Quantitative and Qualitative Disclosures about Market Risk

Item 8. Financial Statements and Supplementary Data

Item 9A. Controls and Procedures

Item 9B. Other Information

Item 9C. Disclosure Regarding Foreign Jurisdictions that Prevent Inspections

Item 10. Directors, Executive Officers and Corporate Governance

Item 11. Executive Compensation

Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters

Item 13. Certain Relationships and Related Transactions, and Director Independence

Item 14. Principal Accountant Fees and Services

Item 15. Exhibits and Financial Statement Schedules

Item 16. Form 10-K Summary

KPTI US Equity