Asset Purchase and License Agreements	12 Months Ended
Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Asset Purchase and License Agreements	9. Asset Purchase and License Agreements *Antengene License Agreement* Effective May 23, 2018 (the “Antengene Effective Date”), the Company entered into a License Agreement (“Antengene License 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 the Company granted Antengene exclusive rights to develop and commercialize, at its own cost, (i) selinexor, the Company’s lead, novel, oral Selective Inhibitor of Nuclear Export (“SINE”) compound, (ii) eltanexor, the Company’s second-generation oral SINE compound, and (iii) KPT-9274, the Company’s first-in-class orally bioavailable small molecule that is a non-competitive dual modulator of PAK4 and NAMPT, each for the diagnosis, treatment and/or prevention of all human oncology indications (the “Oncology Field”), as well as (iv) verdinexor, the Company’s lead compound in development for the treatment of viral indications for the diagnosis, treatment and/or prevention of certain human non-oncology indications (the “Non-Oncology Field”) (the “Antengene Licensed Compounds”). The Company licensed the development and commercial rights to Antengene for selinexor and eltanexor in the Oncology Field in mainland China and Macau and licensed the development and commercial rights to Antengene for KPT-9274 in the Oncology Field and verdinexor in the Non-Oncology Field in mainland China, Taiwan, Hong Kong, Macau, South Korea, Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, Philippines, Singapore, Thailand, and Vietnam (the “Antengene Territory”). Pursuant to the terms of the Antengene License Agreement, the Company received an upfront payment of $11,703, and could receive up to $105,000 in milestone payments if certain development goals are achieved and up to $45,000 in milestone payments if certain sales milestones are achieved, as well as a high single-digit to low double-digit royalty based on future net sales of the Antengene Licensed Compounds in the Antengene Territory. In addition, upon Antengene’s election and the parties’ full execution of a manufacturing technology transfer plan and satisfaction of other specified conditions (the “Antengene Manufacturing Election”), the Company will grant to Antengene non-exclusive rights to manufacture the Antengene Licensed Compounds and products containing such compounds in or outside of the Antengene Territory solely for development and commercialization in the fields in the Antengene Territory. As part of the Antengene License Agreement, Antengene will also have the right to participate in global clinical studies of the Antengene Licensed Compounds and will bear the cost and expense for patients enrolled in 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 specifically necessary to obtain such approvals. Antengene is also responsible for the commercialization of the Antengene Licensed Compounds in the Oncology Field and Non-Oncology Field, as applicable, in the Antengene Territory at its own cost and expense. Until such time as Antengene elects to manufacture its own drug substance, the Company will furnish clinical supplies of drug substance to Antengene for use in Antengene’s development efforts pursuant to a clinical supply agreement to be entered into by the Company and Antengene, and Antengene may elect to have the Company provide commercial supplies of drug product to Antengene pursuant to a commercial supply agreement to be entered into by the Company and Antengene, in each case the costs of which will be borne by Antengene. The Antengene License 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 Antengene License Agreement may be terminated earlier by (i) either party for breach of the Antengene License 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) the Company in the event Antengene challenges or assists with a challenge to certain of the Company’s patent rights. The Company assessed the Antengene arrangement in accordance with ASC 606 and concluded that the contract counterparty, Antengene, is a customer. The Company identified the following material promises under the contract: (i) exclusive licenses for each Antengene Licensed Compound, (ii) initial data transfers for each Antengene Licensed Compound, which consisted of regulatory data compiled by the Company for the Antengene Licensed Compounds as of the Antengene Effective Date, and (iii) obligations to stand-ready to provide an initial clinical supply for each Antengene Licensed Compound. The Company also identified immaterial promises under the contract relating to information exchanges and participation on operating committees and other working groups. Separately, the Company also identified certain customer options that would create an obligation for the Company if exercised by Antengene, including (i) additional data transfers for each Antengene Licensed Compound, which would consist of the transfer of additional regulatory data compiled by the Company for each Antengene Licensed Compound after the Antengene Effective Date, (ii) obligations to provide additional clinical supply and related substance supply for each Antengene Licensed Compound upon request by Antengene, (iii) manufacturing technology transfers and licenses for each Antengene Licensed Compound under the Antengene Manufacturing Election, as detailed above, and (iv) options 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 (the “Antengene Transfer Options”). The Antengene Transfer Options individually represent material rights, as they were offered at a significant and incremental discount. Therefore, they were further assessed as performance obligations under the Antengene License Agreement. Finally, the Company also identified certain other customer options that would create a manufacturing obligation for the Company if exercised by Antengene, including for commercial supply. These options do not represent a material right, as they are not offered at a significant and incremental discount. In further evaluating the promises detailed above, the Company determined that the exclusive licenses, initial data transfers, and stand-ready obligation to provide initial clinical supply for each Antengene Licensed Compound were not distinct from one another, and must be combined as four separate performance obligations (the “Antengene Combined License Obligation for selinexor”, “Antengene Combined License Obligation for eltanexor”, “Antengene Combined License Obligation for KPT-9274” and “Antengene Combined License Obligation for verdinexor”). This is because, for each Antengene Licensed Compound, Antengene requires the initial data transfer and initial clinical supply to derive benefit from the exclusive licenses, since the Company did not grant manufacturing licenses to any of the Antengene Licensed Compounds at contract inception. The Company also determined that each of the Antengene Transfer Options represents a distinct performance obligation. Based on these determinations, the Company identified eight performance obligations at the inception of the Antengene License Agreement, including (i) the Combined License Obligation for selinexor, (ii) the Antengene Combined License Obligation for eltanexor, (iii) the Antengene Combined License Obligation for KPT-9274, (iv) the Antengene Combined License Obligation for verdinexor, and the four components of the Antengene Transfer Options, including (v) the material right for additional data transfer, (vi) the material right for additional clinical supply and related substance supply, (vii) the material right for manufacturing technology transfer and license, and (viii) the material right for the option for a backup compound. The Company further determined that the up-front payment of $11,703 constituted the entirety of the consideration included in the transaction price at contract inception, which was allocated to the performance obligations based on their relative stand-alone selling prices. The Company determined that substantially all of the total standalone selling price in the arrangement is derived from the four Antengene Combined License Obligations for selinexor, eltanexor, KPT-9274 and verdinexor. In connection therewith, the Company also estimated the standalone selling price for each of the material rights within the Antengene Transfer Options, and determined that such amounts were insignificant, and, therefore, immaterial for purposes of allocation. Accordingly, the Company allocated the $11,703 transaction price amongst the Antengene Combined License Obligations as follows: $9,363 for selinexor, $1,053 for eltanexor, $1,053 for KPT-9274, and $234 for verdinexor. The Company believes that a change in the assumptions used to determine its best estimate of the stand-alone selling prices for any of the identified performance obligations would not have a significant effect on the allocation of the underlying transaction price to the performance obligations. Upon execution of the Antengene License Agreement, the only fixed component of the transaction price included the $11,703 up-front payment owed to the Company. As referenced above, the Company is eligible to receive additional payments of up to $105,000 in milestone payments if certain development goals are achieved and up to $45,000 in milestone payments if certain sales milestones are achieved, as well as a high single-digit to low double-digit royalty on future net sales of the Antengene Licensed Compounds in the Antengene Territory. In addition, the Company would receive cost reimbursement in connection with Antengene’s election to receive additional clinical supply for the Antengene Licensed Compounds in the future. The future regulatory milestones and cost reimbursement for providing additional clinical supply of the Antengene Licensed Compounds, both of which represent variable consideration, were evaluated under the most likely amount method, and were not included in the transaction price at contract inception and/or through December 31, 2018, because the amounts were fully constrained as of December 31, 2018. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of such amounts is outside the control of the Company. Separately, any consideration related to sales-based milestones, as well as royalties on net sales upon commercialization by Antengene, will be recognized when the related sales occur, as they were determined to relate predominantly to the intellectual property licenses granted to Antengene and, therefore, have also been excluded from the transaction price in accordance with the sales-based royalty exception, as well as the Company’s accounting policy. The Company will re-evaluate the transaction price in each reporting period, as uncertain events are resolved, or as other changes in circumstances occur. Through December 31, 2018, the Company has recognized no revenue under the Antengene License Agreement. Revenue will be recognized for (i) the Antengene Combined License Obligation for selinexor once the initial clinical supply of selinexor is delivered, which is currently expected to occur before March 31, 2019. Revenue will be recognized for (ii) the Antengene Combined License Obligation for eltanexor, (iii) the Antengene Combined License Obligation for KPT-9274, and (iv) the Antengene Combined License Obligation for verdinexor once the Company’s completes both initial data transfer and the promise to stand-ready to provide initial clinical supply of the Antengene Licensed Compound in the future is fulfilled. The Company currently expects such promises will be fulfilled more than 12 months from the balance sheet date of December 31, 2018. Accordingly, and as of December 31, 2018, the entire $11,703 upfront payment represents a contract liability, (i) $9,363 of which was included in deferred revenue and is classified as a current liability in the consolidated balance sheet and (ii) $2,340 of which was included in deferred revenue and is classified as a non-current liability in the consolidated balance sheet. *Biogen Asset Purchase Agreement* On January 24, 2018, the Company entered into an Asset Purchase Agreement (the “APA”) and Letter Agreement with Biogen MA Inc., a Massachusetts corporation and subsidiary of Biogen, Inc. (“Biogen”). Under the terms of the APA and Letter Agreement, the Company sold to Biogen exclusive worldwide rights to develop and commercialize the Company’s oral SINE compound KPT-350 and certain related assets with an initial focus in amyotrophic lateral sclerosis (“ALS”) (the “Transfer of IP”), and also granted Biogen: (i) an exclusive worldwide license under certain of the Company’s intellectual property to manufacture or have manufactured KPT-350 (the “Manufacturing License”), (ii) a technology transfer package, consisting of information and the Company’s know-how regarding the manufacture of KPT-350 (the “Manufacturing Technology Transfer”), (iii) a right, at Biogen’s request, to have the Company provide transition assistance regarding manufacturing and other matters (the “Transition Assistance”), (iv) existing inventory of KPT-350 (the “Inventory”), (v) an initial supply of KPT-350 (the “Initial Supply”), and (vi) a right, at Biogen’s request, to have the Company manufacture and supply the active pharmaceutical ingredient for an additional supply of KPT-350 (the “Additional Supply”). In consideration for these rights, the Company received an upfront payment of $10,000, and is eligible to receive additional payments of up to $142,000 based on the achievement by Biogen of future specified development milestones, and up to $65,000 based on the achievement by Biogen of future specified commercial milestones. The Company will also be eligible to receive tiered royalty payments that reach low double-digits based on future net sales until the later of the tenth anniversary of the first commercial sale of the applicable product and the expiration of specified patent protection for the applicable product, determined on a country-by-country basis. The Company and Biogen have made customary representations and warranties and agreed to customary covenants in the APA, including covenants requiring Biogen to use commercially reasonable efforts to develop KPT-350 in specified neurological indications, including ALS, in any of the United States, United Kingdom, France, Spain, Germany or Italy. The APA will continue in effect until the expiration of all royalty obligations, provided that the APA may be terminated earlier by Biogen, subject to the requirements that Biogen (i) negotiate in good faith with the Company regarding an assignment or license back to the Company of the purchased assets and (ii) not transfer or license the purchased assets to a third party unless such third party assumes Biogen’s obligations to the Company under the APA. The Company assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Biogen, is a customer. The Company identified the following material promises in the arrangement: the Transfer of IP and the Manufacturing License. The Company also identified immaterial promises under the contract that were not deemed performance obligations. The Company further determined that other promises for Additional Supply and Transition Assistance represented customer options, which would create an obligation for the Company if exercised by Biogen. Since no additional or material consideration is owed to the Company by Biogen upon exercise of the customer options for Additional Supply and Transition Assistance, the Company determined that both are offered at significant and incremental discounts. Accordingly, they were assessed as material rights and, therefore, separate performance obligations in the arrangement. The Company then determined that the Transfer of IP and the Manufacturing License were not distinct from one another and must be combined as a performance obligation (the “Combined Performance Obligation”). This is because Biogen requires the Manufacturing License to derive benefit from the Transfer of IP. Based on these determinations, as well as the considerations noted above with respect to the material rights for Additional Supply and Transition Assistance, the Company identified three distinct performance obligations at the inception of the contract: (i) the Combined Performance Obligation, (ii) the material right for Additional Supply, and (iii) the material right for Transition Assistance. The Company further determined that the up-front payment of $10,000 constituted the entirety of the consideration included in the transaction price at contract inception, which was allocated to the performance obligations based on their relative stand-alone selling prices. In connection therewith, the Company estimated the stand-alone selling price of the (i) Combined Performance Obligation, (ii) material right for Additional Supply, and (iii) material right for Transition Assistance, and determined that the stand-alone selling price of the material rights for Additional Supply and Transition Assistance were insignificant based on various quantitative and qualitative considerations. Accordingly, the Company further determined that the allocation of the transaction price to the material rights for Additional Supply and Transition Assistance was insignificant. Based on the estimates of the stand-alone selling prices for each of the performance obligations, the Company determined that substantially all the $10,000 transaction price should be allocated to the Combined Performance Obligation. The Company believes that a change in the assumptions used to determine its best estimate of the stand-alone selling prices for the identified performance obligations would not have a significant effect on the allocation of the underlying transaction price to the performance obligations. Upon execution of the APA, the transaction price included only the $10,000 up-front payment owed to the Company. The Company may receive further payments upon the achievement of certain regulatory and sales milestones, as detailed above, as well as tiered royalty payments that reach low double-digits based on future net sales. The future regulatory milestones, which represent variable consideration, were evaluated under the most likely amount method, and were not included in the transaction price, because the amounts were fully constrained as of December 31, 2018. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of such milestones is outside the control of the Company. Separately, any consideration related to sales-based milestones, as well as royalties on net sales upon commercialization by Biogen, will be recognized when the related sales occur, as they were determined to relate predominantly to the intellectual property and, therefore, have also been excluded from the transaction price in accordance with the sales-based royalty exception, as well as the Company’s accounting policy. The Company will re-evaluate the transaction price in each reporting period, as uncertain events are resolved, or as other changes in circumstances occur. During the year ended December 31, 2018, the Company recognized $10,000 of revenue, as it had satisfied its promises under the Combined Performance Obligation by transferring the underlying promised goods during the first quarter of 2018. *Ono License Agreement* Effective October 11, 2017 (the “Ono Effective Date”), the Company entered into a license agreement (the “Ono License Agreement”) with Ono Pharmaceutical Co., Ltd., a corporation organized and existing under the laws of Japan (“Ono”), pursuant to which the Company granted Ono exclusive rights to develop and commercialize, at its own cost, selinexor and eltanexor, for the diagnosis, treatment and/or prevention of all human oncology indications (the “Ono Field”) in Japan, Republic of Korea, Republic of China (Taiwan) and Hong Kong, as well as in the ten Southeast Asian countries currently comprising the Association of Southeast Asian Nations (the “Ono Territory”) (the “Ono Exclusive License”). Pursuant to the terms of the Ono License Agreement, the Company received an upfront payment of ¥2.5 billion (US$21,916 on the date received), and could receive up to ¥10.15 billion (approximately US$90,500 at the exchange rate as of the Ono Effective Date) in milestone payments if certain development goals are achieved and up to ¥9.0 billion (approximately US$80,200 at the exchange rate as of the Ono Effective Date) in milestone payments if certain sales milestones are achieved, as well as a low double-digit royalty based on future net sales of selinexor and eltanexor in the Ono Territory. In addition, upon Ono’s election and the parties’ full execution of a manufacturing technology transfer plan and satisfaction of other specified conditions (the “Ono Manufacturing Election”), the Company will grant to Ono non-exclusive rights to manufacture selinexor, eltanexor and products containing such compounds in or outside of the Ono Territory solely for development and commercialization in the Ono Field in the Ono Territory. As part of the Ono License Agreement, Ono will also have the right to participate in global clinical studies of selinexor and eltanexor and will bear the cost and expense for patients enrolled in clinical studies in the Ono Territory. Ono is responsible for seeking regulatory and marketing approvals for selinexor and eltanexor in the Ono Territory, as well as any development of the products specifically necessary to obtain such approvals. Ono is also responsible for the commercialization of products containing selinexor or eltanexor in the Ono Field in the Ono Territory at its own cost and expense. Subject to the Ono Manufacturing Election, the Company will furnish clinical supplies of drug substance to Ono for use in Ono’s development efforts pursuant to a clinical supply agreement to be entered into by the Company and Ono, and Ono may elect to have the Company provide commercial supplies of drug product to Ono pursuant to a commercial supply agreement to be entered into by the Company and Ono, in each case the costs of which will be borne by Ono. The Ono License 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 Ono License Agreement may be terminated earlier by (i) either party for breach of the Ono License Agreement by the other party or in the event of the insolvency or bankruptcy of the other party, (ii) Ono 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) the Company in the event Ono challenges or assists with a challenge to certain of the Company’s patent rights. The Company assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Ono, is a customer. The Company identified the following material promises under the contract: (i) the Ono Exclusive License for selinexor and eltanexor, (ii) initial data transfer for selinexor and eltanexor, which consisted of regulatory data compiled by the Company for the licensed compounds and products as of the Ono Effective Date, (iii) initial clinical supply for selinexor, which consisted of units of clinical supply for Ono to conduct its Phase I Trial, and (iv) an obligation to stand-ready to provide initial clinical supply for eltanexor. The Company also identified immaterial promises under the contract relating to information exchanges, and participation on operating committees and other working groups. Separately, the Company also identified certain customer options that would create an obligation for the Company if exercised by Ono, including the (i) additional data transfer for selinexor and eltanexor, which would consist of the transfer of additional regulatory data compiled by the Company for the licensed compounds and products after the Ono Effective Date, (ii) additional clinical supply and related substance supply for selinexor and eltanexor, which would consist of supplying Ono with units and substance of selinexor and eltanexor incremental to the initial clinical supply for selinexor and the obligation to stand-ready to provide initial clinical supply for eltanexor, as noted above, (iii) manufacturing technology transfer and license for selinexor and eltanexor under the Ono Manufacturing Election, as detailed above, and (iv) options for a backup compound, which represents Ono’s option to select a replacement compound in the event it elects to discontinue the development of either of the licensed compounds (the “Ono Transfer Options”). The Ono Transfer Options individually represent material rights, as they were offered at a significant and incremental discount. Therefore, they were further assessed as performance obligations under the Ono License Agreement. The Company also identified certain other customer options that would create a manufacturing obligation for the Company if exercised by Ono, including commercial supply. This option is referred to herein as the “Ono Manufacturing Option.” The Ono Manufacturing Option does not represent a material right, as it is not offered at a significant and incremental discount. In further evaluating the promises detailed above, the Company determined that the (i) Ono Exclusive License, initial data transfer, and initial clinical supply for selinexor and (ii) Ono Exclusive License, initial data transfer, and obligation to stand-ready to provide initial clinical supply of eltanexor were not distinct from one another, and must be combined as two separate performance obligations (the “Ono Combined License Obligation for selinexor” and the “Ono Combined License Obligation for eltanexor”). This is because, for both selinexor and eltanexor, Ono requires the initial data transfer and clinical supply to derive benefit from the Ono Exclusive License since the Company did not grant manufacturing licenses for selinexor and eltanexor at contract inception. The Company also determined that each of the Ono Transfer Options represents a distinct performance obligation. Based on these determinations, the Company identified six distinct performance obligations at the inception of the Ono License Agreement, including (i) the Ono Combined License Obligation for selinexor, (ii) the Ono Combined License Obligation for eltanexor, and the four components of the Ono Transfer Options, including (iii) the material right for additional data transfer, (iv) the material right for additional clinical supply and related substance supply, (iv) the material right for manufacturing technology transfer and license, and (vi) the material right for the option for a backup compound. The Company further determined that the up-front payment of ¥2.5 billion (US$21,916 on the date received) constituted the entirety of the consideration included in the transaction price at contract inception, which was allocated to the performance obligations based on the Company’s best estimate of their relative stand-alone selling prices. The Company determined that substantially all of the total standalone selling price in the arrangement is derived from the Ono Combined License Obligation for selinexor and the Ono Combined License Obligation for eltanexor. In connection therewith, the Company estimated the standalone selling price for each of the material rights within the Ono Transfer Options, and determined that such amounts were insignificant, and, therefore, immaterial for purposes of allocation. Accordingly, the Company allocated the ¥2.5 billion (US$21,916 on the date received) upfront transaction price between the Ono Combined License Obligations as follows: $19,724 for selinexor and $2,192 for eltanexor. The Company believes that a change in the assumptions used to determine its best estimate of the stand-alone selling prices for any of the identified performance obligations would not have a significant effect on the allocation of the underlying transaction price to the performance obligations. Upon execution of the Ono License Agreement, the transaction price included only the ¥2.5 billion (US$21,916 on the date received) up-front payment owed to the Company. As referenced above, the Company is eligible to receive additional payments of up to ¥10.15 billion based on the achievement by Ono of future specified development milestones and up to ¥9.0 billion based on the achievement by Ono of future specified commercial milestones, as well as a low double-digit royalty based on future net sales of selinexor and eltanexor in the Ono Territory. In addition, the Company could receive cost reimbursement in connection with its promise to stand-ready to provide initial clinical supply for eltanexor in the future. The future regulatory milestones and cost reimbursement for providing initial clinical supply of eltanexor, both of which represent variable consideration, were evaluated under the most likely amount method, and were not included in the transaction price, because the amounts were fully constrained as of December 31, 2018. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of such amounts is outside the control of the Company. Separately, any consideration related to sales-based milestones, as well as royalties on net sales upon commercialization by Ono, will be recognized when the related sales occur, as they were determined to relate predominantly to the intellectual property granted to Ono and, therefore, have also been excluded from the transaction price in accordance with the sales-based royalty exception, as well as the Company’s accounting policy. The Company will re-evaluate the transaction price in each reporting period, as uncertain events are resolved, or as other changes in circumstances occur. As the initial clinical supply of selinexor was delivered in April 2018, the Ono Combined License Obligation for selinexor was determined to be fulfilled and revenue of $19,724 was recognized during the quarter ended June 30, 2018. The transaction price allocated to the Ono Combined License Obligation for eltanexor will be recognized as revenue once the Company’s stand-ready promise to provide initial clinical supply of eltanexor in the future is fulfilled, which is the last remaining undelivered promise associated with the Ono Combined License Obligation for eltanexor. As of December 31, 2018, $2,192 of the Ono License Agreement upfront payment is included in deferred revenue and is classified as a non-current liability in the consolidated balance sheet. Given the determination that the license rights conveyed to Ono lacked standalone value from the initial clinical supply of product required for Ono to obtain benefit from the rights granted and the fact that no initial clinical supply had been provided to Ono as of December 31, 2017, the Company concluded that no revenue should be recognized under ASC 605. Arrangement consideration at the inception of the arrangement included the ¥2.5 billion (US$21,916 on the date received) upfront payment. All other forms of consideration such as milestones and royalties, were considered contingent consideration, with no amount allocable to deliverables at the inception of the arrangement. The Company concluded that the contingent consideration would be recognized when the underlying contingencies have been resolved, assuming all other revenue recognition criteria are met. As the accounting treatment for this agreement did not materially differ under ASC 605 and ASC 606, and no revenue was recognized under the Company’s previous accounting policy through December 31, 2017, no transition adjustment was recorded to the opening balance of accumulated deficit as of January 1, 2018. Accordingly, the upfront payment of ¥2.5 billion (US$21,916 on the date received), which represents a contract liability, was also included in deferred revenue as of December 31, 2017. *MMRF Research Agreement* The Company is a party to a research agreement with the Multiple Myeloma Research Foundation (“MMRF”). Under this research agreement, the Company is obligated to make certain payments to MMRF, including if the Company out-licenses selinexor. The terms of this research agreement do not apply to eltanexor, KPT-9274 or verdinexor. During the year ended December 31, 2018, the Company paid approximately $278 to MMRF, which reflects the amount owed to MMRF under the Antengene License Agreement transaction. In connection with the transaction pursuant to the Ono License Agreement, the Company paid to MMRF $1,972 of the upfront cash payment from Ono in the year ended December 31, 2017. The Company will be obligated to pay a percentage of any milestone payments from Antengene and Ono and a mid-single-digit percentage of any royalty payments from Antengene and Ono. Such payments are recorded within research and development expense in the Company’s consolidated statement of operations. As of December 31, 2018, a maximum of $3,750 in potential future obligations to MMRF are remaining under the MMRF research agreement. *Anivive License Agreement* On April 28, 2017 (the “Anivive Effective Date”), the Company entered into a license agreement (the “Anivive Agreement”) with Anivive Lifesciences, Inc. (“Anivive”), a biopharmaceutical company engaged in the research, development and commercialization of animal health medicines, pursuant to which the Company has granted Anivive an exclusive, worldwide license to develop and commercialize verdinexor (KPT-335) for the treatment of cancer in companion animals (the “Anivive Exclusive License”). Pursuant to the terms of the Anivive Agreement, the Company received an upfront payment of $1,000 and a payment of $250 upon the completion of the technology transfer, which occurred during the year ended December 31, 2017. In addition, the Company is eligible to receive potential clinical, regulatory and commercial development milestone payments totaling up to $43,250, as well as a low double-digit royalty based on Anivive’s future net sales of verdinexor following commercialization. The potential future milestone payments are composed of $5,750 based on achievement of clinical and regulatory milestone events and $37,500 based on achievement of sales milestone events. The Company assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Anivive, is a customer. The Company identified the following material promises under the contract, the Anivive Exclusive License and the technology transfer, which consisted of regulatory data compiled by the Company for the licensed compound and product as of the Anivive Effective Date. The Company also identified immaterial promises under the contract that were not deemed performance obligations, including participating on a product advisory committee and sharing regulatory matter information. The Company further determined that other promises for (i) transfer of additional technology in the future, if developed by the Company, and (ii) facilitating manufacturing and supply relationships with the Company’s third-party contract manufacturers represented customer options, would create an obligation for the Company if exercised by Anivive. Since no additional or immaterial consideration is owed to the Company by Anivive upon exercise of the customer options noted, the Company determined that both are offered at significant and incremental discounts. Accordingly, they were assessed as material rights and, therefore, separate performance obligations in the arrangement. In further evaluating the promises detailed above, the Company determined that the Anivive Exclusive License and the technology transfer were not distinct from one another and must be combined as a performance obligation (the “Anivive Combined License Obligation”). This is because Anivive requires the technology transfer to derive benefit from the Anivive Exclusive License. Based on these determinations, the Company identified three distinct performance obligations at the inception of the contract: (i) the Anivive Combined License Obligation, (ii) the material right for transfer of additional technology in the future, if developed by the Company, and (iii) the material right for facilitating manufacturing and supply relationships with the Company’s third-party contract manufacturers. The Company further determined that the up-front payment of $1,000 upon contract execution, as well as the $250 upon completion of the technology transfer, constituted the entirety of the consideration included in the transaction price as of the transition date, January 1, 2018, which was allocated to the performance obligations based on their relative stand-alone selling prices. In connection therewith, the Company estimated the stand-alone selling price of the (i) Anivive Combined License Obligation, (ii) material right for transfer of additional technology in the future, if developed by the Company, and (iii) the material right for facilitating manufacturing and supply relationships with the Company’s third-party contract manufacturers, and determined that the stand-alone selling price of the material rights noted were insignificant based on various qualitative considerations. Accordingly, the Company further determined that the allocation of the upfront payment to the material rights noted was insignificant. Based on the estimates of the stand-alone selling prices for each of the performance obligations, the Company determined that substantially all the $1,250 transaction price should be allocated to the Anivive Combined License Obligation. The Company believes that a change in the assumptions used to determine its best estimate of the stand-alone selling prices for the identified performance obligations would not have a significant effect on the allocation of the underlying transaction price to the performance obligations. As referenced above, the up-front payment of $1,000 upon contract execution, as well as the $250 upon completion of the technology transfer, constituted the entirety of the consideration included in the transaction price as of the transition date, January 1, 2018. The Company is also eligible to receive additional payments up to $5,750 based on achievement of clinical and regulatory milestone events and up to $37,500 based on achievement of sales milestone events, as well as a low double-digit royalty based on Anivive’s future net sales of verdinexor following commercialization. The future regulatory milestones, which represent variable consideration, were evaluated under the most likely amount method, and were not included in the transaction price, because the amounts were fully constrained as of December 31, 2018. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of such milestones is outside the control of the Company. Separately, any consideration related to sales-based milestones, as well as royalties on net sales upon commercialization by Anivive, will be recognized when the related sales occur, as they were determined to relate predominantly to the intellectual property granted to Anivive and, therefore, have also been excluded from the transaction price in accordance with the sales-based royalty exception, as well as the Company’s policy. The Company will re-evaluate the transaction price in each reporting period, as uncertain events are resolved, or as other changes in circumstances occur. To date, the Company recognized $1,250 of revenue associated with the Anivive Agreement. Revenue for the upfront payment and technology transfer milestone was recognized upon completion of the technology transfer in October 2017, as all promises under the Anivive Combined License Obligation had been fulfilled. The Company reached similar conclusions when evaluating this agreement under its previous accounting policy, which was based on legacy guidance within ASC 605. When evaluating this agreement under ASC 605, the Company concluded that the licenses to verdinexor and technology transfer concerning the licensed product are essential to Anivive’s intended use of the license to develop and commercialize the licensed compound and represented a single unit of accounting. Other potential contractual obligations were evaluated and determined not to be deliverables at inception of the arrangement or were evaluated and determined to be immaterial to the arrangement and, therefore, not evaluated further in the Company’s analysis. Arrangement consideration at the inception of the arrangement included the $1,250 in upfront payments, which includes the milestone fee upon completion of the technology transfer. All other forms of consideration, such as milestones and royalties, were considered contingent consideration, with no amount allocable to deliverables at the inception of the arrangement. The Company concluded that the contingent consideration would be recognized when the underlying contingencies have been resolved, assuming all other revenue recognition criteria are met. Given the single unit of accounting and that the technology transfer would be the last item to be delivered within the unit of accounting, the Company concluded that revenue would be recognized upon the completion of delivery of the technology transfer assuming all other general revenue recognition criteria would be met as of that date. As the accounting treatment for this agreement did not materially differ under ASC 605 and ASC 606, and the upfront payment and technology transfer fee, totaling $1,250, was recognized as revenue during the year ended December 31, 2017 in accordance with the Company’s previous accounting policy, and would have also been recognized during the year ended December 31, 2017 in accordance with the Company’s accounting policy under ASC 606, no transition adjustment was recorded to the opening balance of accumulated deficit as of January 1, 2018.

9. Asset Purchase and License Agreements

Antengene License Agreement

Effective May 23, 2018 (the “Antengene Effective Date”), the Company entered into a License Agreement (“Antengene License 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 the Company granted Antengene exclusive rights to develop and commercialize, at its own cost, (i) selinexor, the Company’s lead, novel, oral Selective Inhibitor of Nuclear Export (“SINE”) compound, (ii) eltanexor, the Company’s second-generation oral SINE compound, and (iii) KPT-9274, the Company’s first-in-class orally bioavailable small molecule that is a non-competitive dual modulator of PAK4 and NAMPT, each for the diagnosis, treatment and/or prevention of all human oncology indications (the “Oncology Field”), as well as (iv) verdinexor, the Company’s lead compound in development for the treatment of viral indications for the diagnosis, treatment and/or prevention of certain human non-oncology indications (the “Non-Oncology Field”) (the “Antengene Licensed Compounds”). The Company licensed the development and commercial rights to Antengene for selinexor and eltanexor in the Oncology Field in mainland China and Macau and licensed the development and commercial rights to Antengene for KPT-9274 in the Oncology Field and verdinexor in the Non-Oncology Field in mainland China, Taiwan, Hong Kong, Macau, South Korea, Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, Philippines, Singapore, Thailand, and Vietnam (the “Antengene Territory”).

Pursuant to the terms of the Antengene License Agreement, the Company received an upfront payment of $11,703, and could receive up to $105,000 in milestone payments if certain development goals are achieved and up to $45,000 in milestone payments if certain sales milestones are achieved, as well as a high single-digit to low double-digit royalty based on future net sales of the Antengene Licensed Compounds in the Antengene Territory. In addition, upon Antengene’s election and the parties’ full execution of a manufacturing technology transfer plan and satisfaction of other specified conditions (the “Antengene Manufacturing Election”), the Company will grant to Antengene non-exclusive rights to manufacture the Antengene Licensed Compounds and products containing such compounds in or outside of the Antengene Territory solely for development and commercialization in the fields in the Antengene Territory.

As part of the Antengene License Agreement, Antengene will also have the right to participate in global clinical studies of the Antengene Licensed Compounds and will bear the cost and expense for patients enrolled in 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 specifically necessary to obtain such approvals. Antengene is also responsible for the commercialization of the Antengene Licensed Compounds in the Oncology Field and Non-Oncology Field, as applicable, in the Antengene Territory at its own cost and expense.

Until such time as Antengene elects to manufacture its own drug substance, the Company will furnish clinical supplies of drug substance to Antengene for use in Antengene’s development efforts pursuant to a clinical supply agreement to be entered into by the Company and Antengene, and Antengene may elect to have the Company provide commercial supplies of drug product to Antengene pursuant to a commercial supply agreement to be entered into by the Company and Antengene, in each case the costs of which will be borne by Antengene.

The Antengene License 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 Antengene License Agreement may be terminated earlier by (i) either party for breach of the Antengene License 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) the Company in the event Antengene challenges or assists with a challenge to certain of the Company’s patent rights.

The Company assessed the Antengene arrangement in accordance with ASC 606 and concluded that the contract counterparty, Antengene, is a customer. The Company identified the following material promises under the contract: (i) exclusive licenses for each Antengene Licensed Compound, (ii) initial data transfers for each Antengene Licensed Compound, which consisted of regulatory data compiled by the Company for the Antengene Licensed Compounds as of the Antengene Effective Date, and (iii) obligations to stand-ready to provide an initial clinical supply for each Antengene Licensed Compound. The Company also identified immaterial promises under the contract relating to information exchanges and participation on operating committees and other working groups. Separately, the Company also identified certain customer options that would create an obligation for the Company if exercised by Antengene, including (i) additional data transfers for each Antengene Licensed Compound, which would consist of the transfer of additional regulatory data compiled by the Company for each Antengene Licensed Compound after the Antengene Effective Date, (ii) obligations to provide additional clinical supply and related substance supply for each Antengene Licensed Compound upon request by Antengene, (iii) manufacturing technology transfers and licenses for each Antengene Licensed Compound under the Antengene Manufacturing Election, as detailed above, and (iv) options 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 (the “Antengene Transfer Options”). The Antengene Transfer Options individually represent material rights, as they were offered at a significant and incremental discount. Therefore, they were further assessed as performance obligations under the Antengene License Agreement. Finally, the Company also identified certain other customer options that would create a manufacturing obligation for the Company if exercised by Antengene, including for commercial supply. These options do not represent a material right, as they are not offered at a significant and incremental discount.

In further evaluating the promises detailed above, the Company determined that the exclusive licenses, initial data transfers, and stand-ready obligation to provide initial clinical supply for each Antengene Licensed Compound were not distinct from one another, and must be combined as four separate performance obligations (the “Antengene Combined License Obligation for selinexor”, “Antengene Combined License Obligation for eltanexor”, “Antengene Combined License Obligation for KPT-9274” and “Antengene Combined License Obligation for verdinexor”). This is because, for each Antengene Licensed Compound, Antengene requires the initial data transfer and initial clinical supply to derive benefit from the exclusive licenses, since the Company did not grant manufacturing licenses to any of the Antengene Licensed Compounds at contract inception. The Company also determined that each of the Antengene Transfer Options represents a distinct performance obligation. Based on these determinations, the Company identified eight performance obligations at the inception of the Antengene License Agreement, including (i) the Combined License Obligation for selinexor, (ii) the Antengene Combined License Obligation for eltanexor, (iii) the Antengene Combined License Obligation for KPT-9274, (iv) the Antengene Combined License Obligation for verdinexor, and the four components of the Antengene Transfer Options, including (v) the material right for additional data transfer, (vi) the material right for additional clinical supply and related substance supply, (vii) the material right for manufacturing technology transfer and license, and (viii) the material right for the option for a backup compound.

The Company further determined that the up-front payment of $11,703 constituted the entirety of the consideration included in the transaction price at contract inception, which was allocated to the performance obligations based on their relative stand-alone selling prices. The Company determined that substantially all of the total standalone selling price in the arrangement is derived from the four Antengene Combined License Obligations for selinexor, eltanexor, KPT-9274 and verdinexor. In connection therewith, the Company also estimated the standalone selling price for each of the material rights within the Antengene Transfer Options, and determined that such amounts were insignificant, and, therefore, immaterial for purposes of allocation. Accordingly, the Company allocated the $11,703 transaction price amongst the Antengene Combined License Obligations as follows: $9,363 for selinexor, $1,053 for eltanexor, $1,053 for KPT-9274, and $234 for verdinexor. The Company believes that a change in the assumptions used to determine its best estimate of the stand-alone selling prices for any of the identified performance obligations would not have a significant effect on the allocation of the underlying transaction price to the performance obligations.

Upon execution of the Antengene License Agreement, the only fixed component of the transaction price included the $11,703 up-front payment owed to the Company. As referenced above, the Company is eligible to receive additional payments of up to $105,000 in milestone payments if certain development goals are achieved and up to $45,000 in milestone payments if certain sales milestones are achieved, as well as a high single-digit to low double-digit royalty on future net sales of the Antengene Licensed Compounds in the Antengene Territory. In addition, the Company would receive cost reimbursement in connection with Antengene’s election to receive additional clinical supply for the Antengene Licensed Compounds in the future. The future regulatory milestones and cost reimbursement for providing additional clinical supply of the Antengene Licensed Compounds, both of which represent variable consideration, were evaluated under the most likely amount method, and were not included in the transaction price at contract inception and/or through December 31, 2018, because the amounts were fully constrained as of December 31, 2018. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of such amounts is outside the control of the Company. Separately, any consideration related to sales-based milestones, as well as royalties on net sales upon commercialization by Antengene, will be recognized when the related sales occur, as they were determined to relate predominantly to the intellectual property licenses granted to Antengene and, therefore, have also been excluded from the transaction price in accordance with the sales-based royalty exception, as well as the Company’s accounting policy. The Company will re-evaluate the transaction price in each reporting period, as uncertain events are resolved, or as other changes in circumstances occur.

Through December 31, 2018, the Company has recognized no revenue under the Antengene License Agreement. Revenue will be recognized for (i) the Antengene Combined License Obligation for selinexor once the initial clinical supply of selinexor is delivered, which is currently expected to occur before March 31, 2019. Revenue will be recognized for (ii) the Antengene Combined License Obligation for eltanexor, (iii) the Antengene Combined License Obligation for KPT-9274, and (iv) the Antengene Combined License Obligation for verdinexor once the Company’s completes both initial data transfer and the promise to stand-ready to provide initial clinical supply of the Antengene Licensed Compound in the future is fulfilled. The Company currently expects such promises will be fulfilled more than 12 months from the balance sheet date of December 31, 2018. Accordingly, and as of December 31, 2018, the entire $11,703 upfront payment represents a contract liability, (i) $9,363 of which was included in deferred revenue and is classified as a current liability in the consolidated balance sheet and (ii) $2,340 of which was included in deferred revenue and is classified as a non-current liability in the consolidated balance sheet.

Biogen Asset Purchase Agreement

On January 24, 2018, the Company entered into an Asset Purchase Agreement (the “APA”) and Letter Agreement with Biogen MA Inc., a Massachusetts corporation and subsidiary of Biogen, Inc. (“Biogen”).

Under the terms of the APA and Letter Agreement, the Company sold to Biogen exclusive worldwide rights to develop and commercialize the Company’s oral SINE compound KPT-350 and certain related assets with an initial focus in amyotrophic lateral sclerosis (“ALS”) (the “Transfer of IP”), and also granted Biogen: (i) an exclusive worldwide license under certain of the Company’s intellectual property to manufacture or have manufactured KPT-350 (the “Manufacturing License”), (ii) a technology transfer package, consisting of information and the Company’s know-how regarding the manufacture of KPT-350 (the “Manufacturing Technology Transfer”), (iii) a right, at Biogen’s request, to have the Company provide transition assistance regarding manufacturing and other matters (the “Transition Assistance”), (iv) existing inventory of KPT-350 (the “Inventory”), (v) an initial supply of KPT-350 (the “Initial Supply”), and (vi) a right, at Biogen’s request, to have the Company manufacture and supply the active pharmaceutical ingredient for an additional supply of KPT-350 (the “Additional Supply”). In consideration for these rights, the Company received an upfront payment of $10,000, and is eligible to receive additional payments of up to $142,000 based on the achievement by Biogen of future specified development milestones, and up to $65,000 based on the achievement by Biogen of future specified commercial milestones. The Company will also be eligible to receive tiered royalty payments that reach low double-digits based on future net sales until the later of the tenth anniversary of the first commercial sale of the applicable product and the expiration of specified patent protection for the applicable product, determined on a country-by-country basis.

The Company and Biogen have made customary representations and warranties and agreed to customary covenants in the APA, including covenants requiring Biogen to use commercially reasonable efforts to develop KPT-350 in specified neurological indications, including ALS, in any of the United States, United Kingdom, France, Spain, Germany or Italy. The APA will continue in effect until the expiration of all royalty obligations, provided that the APA may be terminated earlier by Biogen, subject to the requirements that Biogen (i) negotiate in good faith with the Company regarding an assignment or license back to the Company of the purchased assets and (ii) not transfer or license the purchased assets to a third party unless such third party assumes Biogen’s obligations to the Company under the APA.

The Company assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Biogen, is a customer. The Company identified the following material promises in the arrangement: the Transfer of IP and the Manufacturing License. The Company also identified immaterial promises under the contract that were not deemed performance obligations. The Company further determined that other promises for Additional Supply and Transition Assistance represented customer options, which would create an obligation for the Company if exercised by Biogen. Since no additional or material consideration is owed to the Company by Biogen upon exercise of the customer options for Additional Supply and Transition Assistance, the Company determined that both are offered at significant and incremental discounts. Accordingly, they were assessed as material rights and, therefore, separate performance obligations in the arrangement. The Company then determined that the Transfer of IP and the Manufacturing License were not distinct from one another and must be combined as a performance obligation (the “Combined Performance Obligation”). This is because Biogen requires the Manufacturing License to derive benefit from the Transfer of IP. Based on these determinations, as well as the considerations noted above with respect to the material rights for Additional Supply and Transition Assistance, the Company identified three distinct performance obligations at the inception of the contract: (i) the Combined Performance Obligation, (ii) the material right for Additional Supply, and (iii) the material right for Transition Assistance.

The Company further determined that the up-front payment of $10,000 constituted the entirety of the consideration included in the transaction price at contract inception, which was allocated to the performance obligations based on their relative stand-alone selling prices. In connection therewith, the Company estimated the stand-alone selling price of the (i) Combined Performance Obligation, (ii) material right for Additional Supply, and (iii) material right for Transition Assistance, and determined that the stand-alone selling price of the material rights for Additional Supply and Transition Assistance were insignificant based on various quantitative and qualitative considerations. Accordingly, the Company further determined that the allocation of the transaction price to the material rights for Additional Supply and Transition Assistance was insignificant. Based on the estimates of the stand-alone selling prices for each of the performance obligations, the Company determined that substantially all the $10,000 transaction price should be allocated to the Combined Performance Obligation. The Company believes that a change in the assumptions used to determine its best estimate of the stand-alone selling prices for the identified performance obligations would not have a significant effect on the allocation of the underlying transaction price to the performance obligations.

Upon execution of the APA, the transaction price included only the $10,000 up-front payment owed to the Company. The Company may receive further payments upon the achievement of certain regulatory and sales milestones, as detailed above, as well as tiered royalty payments that reach low double-digits based on future net sales. The future regulatory milestones, which represent variable consideration, were evaluated under the most likely amount method, and were not included in the transaction price, because the amounts were fully constrained as of December 31, 2018. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of such milestones is outside the control of the Company. Separately, any consideration related to sales-based milestones, as well as royalties on net sales upon commercialization by Biogen, will be recognized when the related sales occur, as they were determined to relate predominantly to the intellectual property and, therefore, have also been excluded from the transaction price in accordance with the sales-based royalty exception, as well as the Company’s accounting policy. The Company will re-evaluate the transaction price in each reporting period, as uncertain events are resolved, or as other changes in circumstances occur.

During the year ended December 31, 2018, the Company recognized $10,000 of revenue, as it had satisfied its promises under the Combined Performance Obligation by transferring the underlying promised goods during the first quarter of 2018.

Ono License Agreement

Effective October 11, 2017 (the “Ono Effective Date”), the Company entered into a license agreement (the “Ono License Agreement”) with Ono Pharmaceutical Co., Ltd., a corporation organized and existing under the laws of Japan (“Ono”), pursuant to which the Company granted Ono exclusive rights to develop and commercialize, at its own cost, selinexor and eltanexor, for the diagnosis, treatment and/or prevention of all human oncology indications (the “Ono Field”) in Japan, Republic of Korea, Republic of China (Taiwan) and Hong Kong, as well as in the ten Southeast Asian countries currently comprising the Association of Southeast Asian Nations (the “Ono Territory”) (the “Ono Exclusive License”). Pursuant to the terms of the Ono License Agreement, the Company received an upfront payment of ¥2.5 billion (US$21,916 on the date received), and could receive up to ¥10.15 billion (approximately US$90,500 at the exchange rate as of the Ono Effective Date) in milestone payments if certain development goals are achieved and up to ¥9.0 billion (approximately US$80,200 at the exchange rate as of the Ono Effective Date) in milestone payments if certain sales milestones are achieved, as well as a low double-digit royalty based on future net sales of selinexor and eltanexor in the Ono Territory. In addition, upon Ono’s election and the parties’ full execution of a manufacturing technology transfer plan and satisfaction of other specified conditions (the “Ono Manufacturing Election”), the Company will grant to Ono non-exclusive rights to manufacture selinexor, eltanexor and products containing such compounds in or outside of the Ono Territory solely for development and commercialization in the Ono Field in the Ono Territory.

As part of the Ono License Agreement, Ono will also have the right to participate in global clinical studies of selinexor and eltanexor and will bear the cost and expense for patients enrolled in clinical studies in the Ono Territory. Ono is responsible for seeking regulatory and marketing approvals for selinexor and eltanexor in the Ono Territory, as well as any development of the products specifically necessary to obtain such approvals. Ono is also responsible for the commercialization of products containing selinexor or eltanexor in the Ono Field in the Ono Territory at its own cost and expense.

Subject to the Ono Manufacturing Election, the Company will furnish clinical supplies of drug substance to Ono for use in Ono’s development efforts pursuant to a clinical supply agreement to be entered into by the Company and Ono, and Ono may elect to have the Company provide commercial supplies of drug product to Ono pursuant to a commercial supply agreement to be entered into by the Company and Ono, in each case the costs of which will be borne by Ono.

The Ono License 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 Ono License Agreement may be terminated earlier by (i) either party for breach of the Ono License Agreement by the other party or in the event of the insolvency or bankruptcy of the other party, (ii) Ono 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) the Company in the event Ono challenges or assists with a challenge to certain of the Company’s patent rights.

The Company assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Ono, is a customer. The Company identified the following material promises under the contract: (i) the Ono Exclusive License for selinexor and eltanexor, (ii) initial data transfer for selinexor and eltanexor, which consisted of regulatory data compiled by the Company for the licensed compounds and products as of the Ono Effective Date, (iii) initial clinical supply for selinexor, which consisted of units of clinical supply for Ono to conduct its Phase I Trial, and (iv) an obligation to stand-ready to provide initial clinical supply for eltanexor. The Company also identified immaterial promises under the contract relating to information exchanges, and participation on operating committees and other working groups. Separately, the Company also identified certain customer options that would create an obligation for the Company if exercised by Ono, including the (i) additional data transfer for selinexor and eltanexor, which would consist of the transfer of additional regulatory data compiled by the Company for the licensed compounds and products after the Ono Effective Date, (ii) additional clinical supply and related substance supply for selinexor and eltanexor, which would consist of supplying Ono with units and substance of selinexor and eltanexor incremental to the initial clinical supply for selinexor and the obligation to stand-ready to provide initial clinical supply for eltanexor, as noted above, (iii) manufacturing technology transfer and license for selinexor and eltanexor under the Ono Manufacturing Election, as detailed above, and (iv) options for a backup compound, which represents Ono’s option to select a replacement compound in the event it elects to discontinue the development of either of the licensed compounds (the “Ono Transfer Options”). The Ono Transfer Options individually represent material rights, as they were offered at a significant and incremental discount. Therefore, they were further assessed as performance obligations under the Ono License Agreement. The Company also identified certain other customer options that would create a manufacturing obligation for the Company if exercised by Ono, including commercial supply. This option is referred to herein as the “Ono Manufacturing Option.” The Ono Manufacturing Option does not represent a material right, as it is not offered at a significant and incremental discount.

In further evaluating the promises detailed above, the Company determined that the (i) Ono Exclusive License, initial data transfer, and initial clinical supply for selinexor and (ii) Ono Exclusive License, initial data transfer, and obligation to stand-ready to provide initial clinical supply of eltanexor were not distinct from one another, and must be combined as two separate performance obligations (the “Ono Combined License Obligation for selinexor” and the “Ono Combined License Obligation for eltanexor”). This is because, for both selinexor and eltanexor, Ono requires the initial data transfer and clinical supply to derive benefit from the Ono Exclusive License since the Company did not grant manufacturing licenses for selinexor and eltanexor at contract inception. The Company also determined that each of the Ono Transfer Options represents a distinct performance obligation. Based on these determinations, the Company identified six distinct performance obligations at the inception of the Ono License Agreement, including (i) the Ono Combined License Obligation for selinexor, (ii) the Ono Combined License Obligation for eltanexor, and the four components of the Ono Transfer Options, including (iii) the material right for additional data transfer, (iv) the material right for additional clinical supply and related substance supply, (iv) the material right for manufacturing technology transfer and license, and (vi) the material right for the option for a backup compound.

The Company further determined that the up-front payment of ¥2.5 billion (US$21,916 on the date received) constituted the entirety of the consideration included in the transaction price at contract inception, which was allocated to the performance obligations based on the Company’s best estimate of their relative stand-alone selling prices. The Company determined that substantially all of the total standalone selling price in the arrangement is derived from the Ono Combined License Obligation for selinexor and the Ono Combined License Obligation for eltanexor. In connection therewith, the Company estimated the standalone selling price for each of the material rights within the Ono Transfer Options, and determined that such amounts were insignificant, and, therefore, immaterial for purposes of allocation. Accordingly, the Company allocated the ¥2.5 billion (US$21,916 on the date received) upfront transaction price between the Ono Combined License Obligations as follows: $19,724 for selinexor and $2,192 for eltanexor. The Company believes that a change in the assumptions used to determine its best estimate of the stand-alone selling prices for any of the identified performance obligations would not have a significant effect on the allocation of the underlying transaction price to the performance obligations.

Upon execution of the Ono License Agreement, the transaction price included only the ¥2.5 billion (US$21,916 on the date received) up-front payment owed to the Company. As referenced above, the Company is eligible to receive additional payments of up to ¥10.15 billion based on the achievement by Ono of future specified development milestones and up to ¥9.0 billion based on the achievement by Ono of future specified commercial milestones, as well as a low double-digit royalty based on future net sales of selinexor and eltanexor in the Ono Territory. In addition, the Company could receive cost reimbursement in connection with its promise to stand-ready to provide initial clinical supply for eltanexor in the future. The future regulatory milestones and cost reimbursement for providing initial clinical supply of eltanexor, both of which represent variable consideration, were evaluated under the most likely amount method, and were not included in the transaction price, because the amounts were fully constrained as of December 31, 2018. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of such amounts is outside the control of the Company. Separately, any consideration related to sales-based milestones, as well as royalties on net sales upon commercialization by Ono, will be recognized when the related sales occur, as they were determined to relate predominantly to the intellectual property granted to Ono and, therefore, have also been excluded from the transaction price in accordance with the sales-based royalty exception, as well as the Company’s accounting policy. The Company will re-evaluate the transaction price in each reporting period, as uncertain events are resolved, or as other changes in circumstances occur.

As the initial clinical supply of selinexor was delivered in April 2018, the Ono Combined License Obligation for selinexor was determined to be fulfilled and revenue of $19,724 was recognized during the quarter ended June 30, 2018. The transaction price allocated to the Ono Combined License Obligation for eltanexor will be recognized as revenue once the Company’s stand-ready promise to provide initial clinical supply of eltanexor in the future is fulfilled, which is the last remaining undelivered promise associated with the Ono Combined License Obligation for eltanexor. As of December 31, 2018, $2,192 of the Ono License Agreement upfront payment is included in deferred revenue and is classified as a non-current liability in the consolidated balance sheet.

Given the determination that the license rights conveyed to Ono lacked standalone value from the initial clinical supply of product required for Ono to obtain benefit from the rights granted and the fact that no initial clinical supply had been provided to Ono as of December 31, 2017, the Company concluded that no revenue should be recognized under ASC 605. Arrangement consideration at the inception of the arrangement included the ¥2.5 billion (US$21,916 on the date received) upfront payment. All other forms of consideration such as milestones and royalties, were considered contingent consideration, with no amount allocable to deliverables at the inception of the arrangement. The Company concluded that the contingent consideration would be recognized when the underlying contingencies have been resolved, assuming all other revenue recognition criteria are met. As the accounting treatment for this agreement did not materially differ under ASC 605 and ASC 606, and no revenue was recognized under the Company’s previous accounting policy through December 31, 2017, no transition adjustment was recorded to the opening balance of accumulated deficit as of January 1, 2018. Accordingly, the upfront payment of ¥2.5 billion (US$21,916 on the date received), which represents a contract liability, was also included in deferred revenue as of December 31, 2017.

MMRF Research Agreement

The Company is a party to a research agreement with the Multiple Myeloma Research Foundation (“MMRF”). Under this research agreement, the Company is obligated to make certain payments to MMRF, including if the Company out-licenses selinexor. The terms of this research agreement do not apply to eltanexor, KPT-9274 or verdinexor. During the year ended December 31, 2018, the Company paid approximately $278 to MMRF, which reflects the amount owed to MMRF under the Antengene License Agreement transaction. In connection with the transaction pursuant to the Ono License Agreement, the Company paid to MMRF $1,972 of the upfront cash payment from Ono in the year ended December 31, 2017. The Company will be obligated to pay a percentage of any milestone payments from Antengene and Ono and a mid-single-digit percentage of any royalty payments from Antengene and Ono. Such payments are recorded within research and development expense in the Company’s consolidated statement of operations. As of December 31, 2018, a maximum of $3,750 in potential future obligations to MMRF are remaining under the MMRF research agreement.

Anivive License Agreement

On April 28, 2017 (the “Anivive Effective Date”), the Company entered into a license agreement (the “Anivive Agreement”) with Anivive Lifesciences, Inc. (“Anivive”), a biopharmaceutical company engaged in the research, development and commercialization of animal health medicines, pursuant to which the Company has granted Anivive an exclusive, worldwide license to develop and commercialize verdinexor (KPT-335) for the treatment of cancer in companion animals (the “Anivive Exclusive License”). Pursuant to the terms of the Anivive Agreement, the Company received an upfront payment of $1,000 and a payment of $250 upon the completion of the technology transfer, which occurred during the year ended December 31, 2017. In addition, the Company is eligible to receive potential clinical, regulatory and commercial development milestone payments totaling up to $43,250, as well as a low double-digit royalty based on Anivive’s future net sales of verdinexor following commercialization. The potential future milestone payments are composed of $5,750 based on achievement of clinical and regulatory milestone events and $37,500 based on achievement of sales milestone events.

The Company assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Anivive, is a customer. The Company identified the following material promises under the contract, the Anivive Exclusive License and the technology transfer, which consisted of regulatory data compiled by the Company for the licensed compound and product as of the Anivive Effective Date. The Company also identified immaterial promises under the contract that were not deemed performance obligations, including participating on a product advisory committee and sharing regulatory matter information. The Company further determined that other promises for (i) transfer of additional technology in the future, if developed by the Company, and (ii) facilitating manufacturing and supply relationships with the Company’s third-party contract manufacturers represented customer options, would create an obligation for the Company if exercised by Anivive. Since no additional or immaterial consideration is owed to the Company by Anivive upon exercise of the customer options noted, the Company determined that both are offered at significant and incremental discounts. Accordingly, they were assessed as material rights and, therefore, separate performance obligations in the arrangement.

In further evaluating the promises detailed above, the Company determined that the Anivive Exclusive License and the technology transfer were not distinct from one another and must be combined as a performance obligation (the “Anivive Combined License Obligation”). This is because Anivive requires the technology transfer to derive benefit from the Anivive Exclusive License. Based on these determinations, the Company identified three distinct performance obligations at the inception of the contract: (i) the Anivive Combined License Obligation, (ii) the material right for transfer of additional technology in the future, if developed by the Company, and (iii) the material right for facilitating manufacturing and supply relationships with the Company’s third-party contract manufacturers.

The Company further determined that the up-front payment of $1,000 upon contract execution, as well as the $250 upon completion of the technology transfer, constituted the entirety of the consideration included in the transaction price as of the transition date, January 1, 2018, which was allocated to the performance obligations based on their relative stand-alone selling prices. In connection therewith, the Company estimated the stand-alone selling price of the (i) Anivive Combined License Obligation, (ii) material right for transfer of additional technology in the future, if developed by the Company, and (iii) the material right for facilitating manufacturing and supply relationships with the Company’s third-party contract manufacturers, and determined that the stand-alone selling price of the material rights noted were insignificant based on various qualitative considerations. Accordingly, the Company further determined that the allocation of the upfront payment to the material rights noted was insignificant. Based on the estimates of the stand-alone selling prices for each of the performance obligations, the Company determined that substantially all the $1,250 transaction price should be allocated to the Anivive Combined License Obligation. The Company believes that a change in the assumptions used to determine its best estimate of the stand-alone selling prices for the identified performance obligations would not have a significant effect on the allocation of the underlying transaction price to the performance obligations.

As referenced above, the up-front payment of $1,000 upon contract execution, as well as the $250 upon completion of the technology transfer, constituted the entirety of the consideration included in the transaction price as of the transition date, January 1, 2018. The Company is also eligible to receive additional payments up to $5,750 based on achievement of clinical and regulatory milestone events and up to $37,500 based on achievement of sales milestone events, as well as a low double-digit royalty based on Anivive’s future net sales of verdinexor following commercialization. The future regulatory milestones, which represent variable consideration, were evaluated under the most likely amount method, and were not included in the transaction price, because the amounts were fully constrained as of December 31, 2018. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of such milestones is outside the control of the Company. Separately, any consideration related to sales-based milestones, as well as royalties on net sales upon commercialization by Anivive, will be recognized when the related sales occur, as they were determined to relate predominantly to the intellectual property granted to Anivive and, therefore, have also been excluded from the transaction price in accordance with the sales-based royalty exception, as well as the Company’s policy. The Company will re-evaluate the transaction price in each reporting period, as uncertain events are resolved, or as other changes in circumstances occur.

To date, the Company recognized $1,250 of revenue associated with the Anivive Agreement. Revenue for the upfront payment and technology transfer milestone was recognized upon completion of the technology transfer in October 2017, as all promises under the Anivive Combined License Obligation had been fulfilled.

The Company reached similar conclusions when evaluating this agreement under its previous accounting policy, which was based on legacy guidance within ASC 605. When evaluating this agreement under ASC 605, the Company concluded that the licenses to verdinexor and technology transfer concerning the licensed product are essential to Anivive’s intended use of the license to develop and commercialize the licensed compound and represented a single unit of accounting. Other potential contractual obligations were evaluated and determined not to be deliverables at inception of the arrangement or were evaluated and determined to be immaterial to the arrangement and, therefore, not evaluated further in the Company’s analysis. Arrangement consideration at the inception of the arrangement included the $1,250 in upfront payments, which includes the milestone fee upon completion of the technology transfer. All other forms of consideration, such as milestones and royalties, were considered contingent consideration, with no amount allocable to deliverables at the inception of the arrangement. The Company concluded that the contingent consideration would be recognized when the underlying contingencies have been resolved, assuming all other revenue recognition criteria are met. Given the single unit of accounting and that the technology transfer would be the last item to be delivered within the unit of accounting, the Company concluded that revenue would be recognized upon the completion of delivery of the technology transfer assuming all other general revenue recognition criteria would be met as of that date. As the accounting treatment for this agreement did not materially differ under ASC 605 and ASC 606, and the upfront payment and technology transfer fee, totaling $1,250, was recognized as revenue during the year ended December 31, 2017 in accordance with the Company’s previous accounting policy, and would have also been recognized during the year ended December 31, 2017 in accordance with the Company’s accounting policy under ASC 606, no transition adjustment was recorded to the opening balance of accumulated deficit as of January 1, 2018.