81 The fair value of options is estimated on the grant date using the Black-Scholes option valuation model or Monte Carlo simulation model. The calculation of stock-based compensation expense requires that we make certain assumptions and judgments about a number of complex and subjective variables used in the valuation model, including the expected term, expected volatility of the underlying common stock and risk-free interest rate. Our stock-based awards are subject to either service, performance-based or market-based vesting conditions. We evaluate whether achievement of the performance conditions is probable and record expense over the appropriate service period based on this assessment. Changes in these assumptions can materially affect the fair value and ultimately how much stock-based compensation expense is recognized. These inputs are subjective and generally require significant analysis and judgment to develop. Impairment of Long-Lived Assets We review long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amounts of the assets may not be recoverable. Recoverability is measured by comparing the carrying amount of the assets to the estimated undiscounted net cash flows which the assets are expected to generate. If such assets are deemed not recoverable, an impairment loss is recognized in the amount by which the carrying amount of the assets exceeds the estimated fair value of the assets. We applied significant judgment in determining we have one asset group and that there is no lower level to group assets for impairment testing. The determination of the asset group primarily considers the interdependencies of our assets, shared cost structure, and the interrelated future cash flow generation. We assessed the recoverability of our asset group during the year ended December 31, 2023 based on our decision to wind-down the tarcocimab program following the topline results from the Phase 3 GLEAM and GLIMMER studies. We determined that the estimated undiscounted net cash flows which the asset group was forecasted to generate exceeded the carrying amount of the asset group and therefore, no impairment loss was recognized in 2023. There was no such impairment of long-lived assets in the year ended December 31, 2024. Recent Accounting Pronouncements A description of recently issued accounting pronouncements that may potentially impact our financial position and results of operations is discussed under Note 2 to our consolidated financial statements included in “Part II, Item 8 — Financial Statements and Supplementary Data” of this Annual Report on Form 10-K.