Kodiak Sciences Inc. Notes to Consolidated Financial Statements (in thousands, except share and per share data) 102 As of December 31, 2022, there was $247.9 million of unrecognized stock-based compensation expense related to the 6,818,584 options granted under the LTPIP Program, but not yet earned or vested, to be recognized over a weighted-average period of 4.02 years. Stock Options Stock option activity, including stock options and PSOs under the 2021 LTPIP, 2018 Plan and 2015 Plan is summarized as follows: Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2021...................... 14,523,917 $ 61.68 8.60 $ 335,440 Granted................................................................. 3,079,120 $ 8.99 Exercised.............................................................. (126,999) $ 13.93 Forfeited or canceled ........................................... (933,931) $ 75.23 Outstanding at December 31, 2022...................... 16,542,107 $ 51.48 7.91 $ 5,410 Shares exercisable December 31, 2022 ............... 8,452,058 $ 41.84 7.03 $ 5,390 Vested and expected to vest December 31, 2022 16,542,107 $ 51.48 7.91 $ 5,410 The weighted-average grant date fair value of the time-vested stock options granted for 2022, 2021 and 2020 was $6.31, $51.55 and $32.44 per share, respectively. The total intrinsic value of stock options exercised during 2022, 2021 and 2020 was $6.1 million, $40.2 million, and $58.1 million, respectively. The intrinsic value represents the amount by which the market price of the underlying stock exceeds the exercise price of an option. Employee Stock Options The Company estimated the fair value of employee stock options using the Black-Scholes valuation model. The fair value of time-vested employee stock options was estimated using the following weighted-average assumptions: Year Ended December 31, 2022 2021 2020 Expected volatility........................................................ 83% 61% 66% Risk-free interest rate.................................................... 2.86% 1.03% 0.39% Dividend yield............................................................... 0% 0% 0% Expected term ............................................................... 5.98 6.25 6.00 The Company granted 3,079,120 options to employees in 2022. The total fair value of employee options vested during the years ended December 31, 2022, 2021 and 2020 was $28.9 million, $26.9 million and $19.7 million, respectively. Stock- based compensation expense recognized during the years ended December 31, 2022, 2021 and 2020 for options granted to employees, including the options granted under the LTPIP Program, was $93.8 million, $44.1 million and $20.8 million, respectively.