Collaboration and License Agreements	9 Months Ended
Collaboration and License Agreements	Sep. 30, 2020
Collaboration and License Agreements [Abstract]
Collaborative Arrangement Disclosure	Collaboration and License Agreements Lexicon has derived substantially all of its revenues from drug discovery and development alliances, target validation collaborations for the development and, in some cases, analysis of the physiological effects of genes altered in knockout mice, product sales, government grants and contracts, technology licenses, subscriptions to its databases and compound library sales. Ipsen. In October 2014, Lexicon entered into a License and Collaboration Agreement, which was subsequently amended in March 2015 (collectively, the “Ipsen Agreement”), with Ipsen for the development and commercialization of XERMELO outside of the United States and Japan (the “Licensed Territory”). The Ipsen Agreement was assigned to TerSera in September 2020 in connection with the XERMELO sale. Under the Ipsen Agreement, Lexicon granted Ipsen an exclusive, royalty-bearing right and license under its patent rights and know-how to commercialize XERMELO in the Licensed Territory. Ipsen was responsible for using diligent efforts to commercialize XERMELO in the Licensed Territory pursuant to a mutually approved commercialization plan. Subject to certain exceptions, Lexicon was responsible for conducting clinical trials required to obtain regulatory approval for XERMELO for carcinoid syndrome in the European Union, including those contemplated by a mutually approved initial development plan, and had the first right to conduct most other clinical trials of XERMELO. Lexicon was responsible for the costs of all clinical trials contemplated by the initial development plan. The costs of additional clinical trials were to be allocated between the parties based on the nature of such clinical trials. Under the Ipsen Agreement, Ipsen paid Lexicon an aggregate of $47.2 million through September 30, 2020, consisting of $24.5 million in upfront payments and a $6.4 million milestone payment upon the acceptance of the filing submitted by Ipsen to the European Medicines Agency for XERMELO as an adjunct to somatostatin analog therapy for the long-term treatment of carcinoid syndrome, a $5.1 million milestone upon Ipsen’s receipt of approval from the European Commission for the marketing of XERMELO in all member states of the European Union, Norway and Iceland, a $3.8 million milestone upon Ipsen’s first commercial sale in Germany, a $3.8 million milestone upon Ipsen’s first commercial sale in the United Kingdom, a $1.3 million milestone upon Ipsen’s receipt of approval from Health Canada and a $2.3 million milestone upon Ipsen’s first commercial sale in Canada. In addition, Lexicon was eligible to receive from Ipsen (a) up to an aggregate of approximately $9.6 million upon the achievement of specified regulatory and commercial launch milestones and (b) up to an aggregate of €72 million upon the achievement of specified sales milestones. Milestone payments that were contingent upon the achievement of a substantive milestone were deemed constrained. Lexicon was also entitled to tiered, escalating royalties ranging from low twenties to mid-thirties percentages of net sales of XERMELO in the Licensed Territory, subject to a credit for amounts previously paid to Lexicon by Ipsen for the manufacture and supply of such units of XERMELO. Lexicon and Ipsen had entered into a commercial supply agreement pursuant to which Lexicon supplied Ipsen’s commercial requirements of XERMELO, and Ipsen paid an agreed upon transfer price for such commercial supply. The Company considered the following as its performance obligations with respect to the revenue recognition of the $24.5 million upfront payments: •The exclusive license granted to Ipsen to develop and commercialize XERMELO in the Licensed Territory; •The development services Lexicon was performing for XERMELO; •The obligation to participate in committees which governed the development of XERMELO until commercialization; and •The obligation to supply commercial supply of XERMELO under a commercial supply agreement. The Company determined that the license had stand-alone value because it was an exclusive license that gave Ipsen the right to develop and commercialize XERMELO or to sublicense its rights. In addition, at the time of the agreement, it would have been possible for Ipsen or another third party to conduct clinical trials without assistance from Lexicon. As a result, the Company considered the license and the development services under the Ipsen Agreement to be separate performance obligations. The Company recognized the portion of the transaction price allocated to the license immediately because Lexicon delivered the license and earned the revenue at the inception of the arrangement. The Company recognized as revenue the amount allocated to the development services and the obligation to participate in committees over the period of time Lexicon performed the services, which was completed in 2018. The Company determined that the commercial supply agreement was a contingent deliverable at its onset. There was inherent uncertainty in obtaining regulatory approval at the time of entry into the commercial supply agreement, thus making the applicability of the commercial supply agreement outside the control of Lexicon and Ipsen. As a result, the Company determined the commercial supply agreement did not meet the definition of a performance obligation that needed to be accounted for at the inception of the arrangement. The Company also determined that there was no significant and incremental discount related to the commercial supply agreement that should have been accounted for at the inception of the arrangement. The Company determined that the initial transaction price was the $24.5 million in upfront payments because they were the only payments that were fixed and determinable at the inception of the arrangement. There was considerable uncertainty at the date of the agreement as to whether Lexicon would earn milestone payments, royalty payments or payments for finished drug product. As such, the Company did not include those payments in the transaction price. The Company allocated the transaction price based on the relative best estimate of selling price of each performance obligation. The Company estimated the selling price of the license deliverable by applying a probability-based income approach utilizing an appropriate discount rate. The significant inputs the Company used to determine the projected income of the license included: estimated future product sales, estimated cost of goods sold, estimated operating expenses, income taxes, and an appropriate discount rate. The Company estimated the selling price of the development services by using internal estimates of the cost to hire third parties to perform the services over the expected period to perform the development. The Company estimated the selling price of the obligation to participate in committees by using internal estimates of the number of internal hours and salary and benefits costs to perform these services. As a result of the allocation, the Company recognized $21.2 million of the $24.5 million in upfront payments for the license in 2014, and an additional $1.4 million in 2015 upon entering into the amendment. The Company recognized the $1.7 million allocated to the development services performance obligation over the period of performance as development occurred, and recognized the $0.1 million allocated to the committee participation performance obligation ratably over the period of performance. Milestone payments that were contingent upon the achievement of a substantive milestone were deemed constrained. If or when the constraint was determined to be resolved, the Company would re-evaluate the overall transaction price and recognize an adjustment on a cumulative catch-up basis in the period that the adjustment was evaluated. Revenue recognized under the Ipsen Agreement was $0.3 million and $3.5 million for the nine months ended September 30, 2020 and 2019, respectively. Royalty revenue of $0.3 million was recognized for each of the nine months ended September 30, 2020 and 2019, respectively. Sanofi. In November 2015, Lexicon entered into a Collaboration and License Agreement, which was subsequently amended in July 2017 (collectively, the “Sanofi Agreement”), with Sanofi for the worldwide development of Lexicon’s diabetes drug candidate sotagliflozin. In December 2016, Sanofi terminated its rights under the Sanofi Agreement with respect to Japan. Effective as of September 9, 2019 (the “Settlement Date”), Lexicon entered into the Termination Agreement with Sanofi, pursuant to which the Sanofi Agreement was terminated and certain associated disputes between Lexicon and Sanofi were settled. Under the terms of the Termination Agreement, Lexicon regained all rights to sotagliflozin and assumed full responsibility for the worldwide development and commercialization of sotagliflozin in all indications. Sanofi paid Lexicon $208 million in September 2019 and $26 million in each of March and September 2020 (less amounts withheld by Sanofi offsetting certain third party costs and internal costs incurred by Sanofi and asserted by Sanofi to be payable by Lexicon under the terms of the Termination Agreement), and neither party will owe any additional payments pursuant to the Sanofi Agreement. The parties have cooperated in the transition of responsibility for ongoing clinical studies and other activities, and each party is responsible for its own expenses associated with such transition, subject to certain exceptions. See Note 7, Commitments and Contingencies, for additional information. In March 2020, Lexicon announced its plan to close out the clinical studies related to the Phase 3 development program for sotagliflozin in type 2 diabetes, heart failure and chronic kidney disease. Revenue relating to the Termination Agreement was recognized in the third quarter of 2019. Revenue recognized under the Sanofi Agreement was $286.0 million for the nine months ended September 30, 2019.