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Equity Incentive Plans - Graphite Bio, Inc. (Tables)
 12 Months Ended
Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]  
Summary of Assumptions under Employee Stock Purchase Plan
Effective January 1, 2022 and 2023, the number of shares of common stock available under the 2021 ESPP increased by 564,000 shares pursuant to the evergreen provision of the 2021 ESPP.
Year Ended December 31,
20232022
Expected volatility
75.00% - 79.00%
73.00% - 75.00%
Expected dividend yield0%0%
Expected term (in years)0.50.5
Risk-free interest rate
4.65% - 5.44%
0.10% - 4.65%
Schedule of Valuation Assumptions
The Company used the Black-Scholes option pricing model to estimate stock-based compensation expense for stock option awards granted during the periods presented, with the following assumptions.
Year Ended December 31,
20232022
Expected volatility
77.00% - 79.00%
74.00% - 75.00%
Expected dividend yield0%0%
Expected term (in years)6.04
5.97- 6.01
Risk-free interest rate
3.50% - 4.12%
1.91% - 4.23%
The assumptions used in the Black-Scholes option pricing model for stock options granted were as follows:
December 31
20222023
Expected term6.0 years6.0 years
Expected volatility
92.8% - 96.6%
92.0% - 92.7%
Risk free interest rate
1.9% - 4.2%
3.9% - 4.6%
Expected dividend yield0.0%0.0%
Schedule of Stock Option Activity
A summary of option activity under the 2020 Plan and the 2021 Plan during the year ended December 31, 2023 is as follows:
Number of
Options 		Weighted-
Average
Exercise
Price Per
Share		Weighted-
Average
Remaining
Contractual
Term
(in years)		Aggregate
Intrinsic
Value
(in thousands)
Outstanding as of December 31, 20227,755,303 $8.47 8.7$794 
Options granted - 2021 Plan3,223,400 $2.22 
Options exercised(101,900)$0.98 
Options cancelled(5,500,430)$6.79 
Outstanding as of December 31, 20235,376,373 $6.58 6.1$847 
Exercisable3,812,992 $6.42 5.2$664 
Vested and expected to vest as of December 31, 20235,376,373 $6.58 6.1$847 
A summary of stock option activity for awards under the 2020 Plan is presented below:
Number of SharesWeighted Average Exercise PriceWeighted Average Remaining Contractual Lives (years)Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2022
5,271,961$0.38 6.8$12,585 
Granted
4,045,329$1.26 — 
Outstanding as of December 31, 2023
9,317,290$0.76 7.4$18,691 
Exercisable as of December 31, 2023
7,261,957$0.63 6.9$15,536 
Vested and expected to vest
9,492,482$0.76 7.4$19,054 
Components of Stock-based Compensation Expense
The following table presents the components of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands):
Year Ended
December 31,
20232022
Restricted stock awards and founders’ common stock awards$7 $11 
ESPP96 391 
Stock options10,471 13,132 
Total stock-based compensation expense$10,574 $13,534 
Classification of Stock-based Compensation Expense
The following table presents the classification of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands):
Year Ended
December 31,
20232022
Research and development expenses$1,904 $5,317 
General and administrative expenses8,670 8,217 
Total stock-based compensation expense$10,574 $13,534