Castle Creek and Agenus Transactions	6 Months Ended
Castle Creek and Agenus Transactions	Jun. 30, 2025
Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract]
Castle Creek and Agenus Transactions	Castle Creek and Agenus Transactions Castle Creek Transaction On February 24, 2025, we entered into a Purchase and Sale Agreement (the “Castle Creek Investment” transaction) with Castle Creek Biosciences, Inc., Castle Creek Biosciences, LLC (collectively, “Castle Creek”) and a syndicate of co-investors for which Ligand acted as representative (collectively, including Ligand, the “Purchasers”), to support Castle Creek’s autologous human fibroblast cell-based gene therapy genetically modified to express COL7, also known as FCX-007 (dabocemagene autoficel) (“D-Fi”) Phase 3 clinical study, its lead candidate for patients with dystrophic epidermolysis bullosa (“DEB”). Pursuant to the Castle Creek Investment transaction, Ligand and the other Purchasers obtained, for an aggregate purchase price of $75 million ($50 million of which was paid by Ligand and $25 million of which was paid by the other Purchasers collectively) on a proportional basis: (a) high single digit royalty on worldwide sales of D-Fi; and (b) the Warrant to purchase shares of Castle Creek's Series D-1 Preferred Stock, exercisable until February 24, 2035 (“Castle Creek Warrant”). As part of the Agreement, Castle Creek granted the Purchasers a security interest in certain assets related to the programs included in the Agreement, subject to certain customary exceptions. In connection with the Castle Creek Investment transaction, on February 24, 2025, we acquired a portion of unsecured subordinated promissory notes (with an aggregate principal amount of $8.3 million payable upon FDA approval of D-Fi) from a Castle Creek related party for $1.8 million (“Milestone Buyout”). Management concluded that individual prices of these two transactions (Castle Creek Investment and Milestone Buyout) reflect the fair value of the related assets acquired on a standalone basis. We accounted for the Milestone Buyout transaction as a derivative asset. We further identified two units of account in the Castle Creek Investment transaction: (1) the Castle Creek Warrant, accounted for as a derivative asset; (2) D-Fi royalty rights accounted for as a research and development funding arrangement under ASC 730-20, Research and Development Arrangements, because (a) Castle Creek is contractually required to use Ligand’s capital for the execution of the Phase 3 clinical study for D-Fi and (b) the repayment of Ligand funding solely depends on the research and development results having future economic benefits. Out of the $50.1 million Castle Creek Investment transaction price, including transaction costs, $5.8 million was allocated to the Castle Creek Warrant (based on their estimated fair value as of the effective date), with the remaining amount of $44.3 million being allocated to D-Fi royalty rights, and recognized in research and development expenses for the period (as Ligand will not be controlling or actively involved in the ongoing research and development efforts). Both the Castle Creek Warrant and Milestone Buyout derivatives were presented in noncurrent derivative assets line in our condensed consolidated balance sheets. The derivative assets were recorded at fair value as of February 24, 2025, and are marked to fair value at each subsequent reporting period. The fair value of the Castle Creek Warrant as of February 24, 2025 was determined using a Black-Scholes model using a volatility of 110% and risk-free rate of 4.2%. Agenus Transaction On May 29, 2024, we closed the transactions pursuant to the $75 million purchase and sale agreement (the “Agenus Agreement”), dated May 6, 2024, among us and Agenus Inc., Agenus Royalty Fund, LLC, and Agenus Holdings 2024, LLC (collectively, “Agenus”). Under the terms of the Agenus Agreement, we received (i) 18.75% of the licensed royalties and 31.875% of the future licensed milestones paid to Agenus on six-partnered oncology programs, including BMS-986442 (Bristol Myers Squibb), AGEN2373 (Gilead Sciences), INCAGN2385 and INCAGN2390 (Incyte), MK-4830 (Merck), and UGN-301 (UroGen Pharma) (collectively referred as “Agenus Partnered Programs”), and (ii) a synthetic 2.625% royalty on future global net sales of Agenus’ novel immuno-oncology botensilimab in combination with balstilimab (“BOT/BAL”) program, collectively subject to certain events which may adjust the royalty and milestone percentages paid to us. In addition, we received the option to commit an additional $25 million in the same assets on a pro rata basis which expired on June 30, 2025 (“Upsize Option”). We have also agreed to allow Agenus to raise up to an additional $100 million bringing the total syndicated purchase price up to an aggregate of $200 million. As part of the Agenus Agreement, Agenus will grant us security over certain assets related to the programs included in the Agenus Agreement, subject to certain customary exceptions. In connection with entry into the Agenus Agreement, Agenus issued us a 5-year warrant (“Agenus Warrant”) to purchase 867,052 shares of its common stock, at an exercise price equal to $17.30. We accounted for all Agenus Partnered Programs, Agenus Warrant and Upsize Option as derivative assets. All derivatives, except for the Upsize Option, were presented in noncurrent derivative assets line in our condensed consolidated balance sheets. Agenus Partnered Programs were recognized as derivative assets under ASC 815, Derivatives and Hedging, as they have different underlyings (milestone payments and royalties). The commercial milestones and royalties are dependent on the development milestones and the commercial milestone and royalties underlyings are not determined to be predominant. The derivative assets were recorded at fair value as of May 29, 2024, and are marked to fair value at each subsequent reporting period. The fair value of Agenus Partnered Programs derivative assets is determined as a present value of expected future cash flows adjusted for the level of risk appropriate for a respective program stage. Certain Agenus partners discontinued development of their partnered programs in 2024. These programs may be relicensed at a later date, and Ligand would retain its economic interest upon any relicense activity. The fair value of the Upsize Option was determined using the binomial option pricing model under which we assessed and considered the possible upwards and downwards scenarios through the expiration date of the Upsize Option. The fair value of the Upsize Option was written down to zero as of December 31, 2024. For additional information on the Agenus Partnered Program derivative assets, Agenus Warrant, and Upsize Option, see Note 6, Fair Value Measurement. We accounted for the acquired BOT/BAL rights as a financial royalty asset, which is currently put under the non-accrual method as management cannot reliably estimate future cash flows from this program. The amount of BOT/BAL financial royalty asset was determined as the residual value from the $75 million aggregate investment amount, less fair value of all acquired derivative assets as of May 29, 2024. For additional information on the Agenus BOT/BAL rights, see Note 5, Financial Royalty Assets, net.