12. Stock-Based Compensation

2018 Equity Incentive Plan

In August 2018, the Company adopted the 2018 Equity Incentive Plan (“2018 Plan”), which became effective on the business day prior to the effectiveness of the registration statement relating to the IPO. The 2018 Plan initially reserved 4,300,000 shares of common stock for the issuance of incentive stock options ("ISOs"), nonstatutory stock options ("NSOs"), restricted stock, restricted stock units (“RSUs”), stock appreciation rights, performance units and performance shares to employees, directors and consultants of the Company. The number of shares available for issuance increases annually on the first day of each fiscal year equal to the least of (1) 4,300,000 shares, and (2) 4% of outstanding shares of common stock as of the last day of the immediately preceding year, and (3) such other amount as determined by the board of directors. The exercise price of options must be equal to at least the fair market value of the common stock on the grant date. For ISOs, the term may not exceed ten years, except in respect to any participant with more than 10% of voting power of all classes or stock then the term may not exceed five years and the exercise price must be equal to at least 110% of the fair market value of the common stock on the grant date. Options and RSUs granted generally vest over four years.

The number of shares available for issuance increased by 2,073,050 shares in 2022 and there were 1,934,606 shares available for grant under the 2018 Plan as of December 31, 2022.

2021 Long-Term Performance Incentive Plan

The 2021 Long-Term Performance Incentive Plan (“2021 LTPIP”) was designed to be a long-term, pay-for-performance, incentive plan that would further align the interests of management and other eligible employees with the creation of substantial long-term value for the Company's stockholders. During 2021, eligible employees were provided a one-time opportunity to "opt-in" and forgo a portion of their annual equity incentive awards in exchange for a one-time grant of performance-based stock options from the 2021 LTPIP and 2018 Plan, collectively referred to as the "LTPIP Program". There were no options granted under the LTPIP Program for the year ended December 31, 2022.

Shares underlying the options granted under the LTPIP Program may be earned based on the achievement of the performance-based requirement based on stock price goals and/or certain operational milestones based on approval by the U.S. Food and Drug Administration of a Biologics License Application in respect of a first, second, and third major indication and based on sales. The performance-based requirement and operational milestones were not achieved as of December 31, 2022.

The Company determined the exchange of the original award of annual equity incentive awards with the modified award of options granted under the LTPIP Program represented a change in the original terms and conditions. The modification resulted in additional compensation cost equal to the incremental value between the original and modified awards to be recognized. For the annual equity incentive awards, the Company continues to record the unrecognized compensation expense over the original vesting period. For the options granted under the LTPIP Program, the stock-based compensation expense recognized during the years ended December 31, 2022 and 2021 was $65.1 million and $15.7 million, respectively.

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.

Restricted Shares

Restricted share activity, including restricted stock units (“RSUs”), and performance-based restricted stock units (“PSUs”), under the 2018 Plan is summarized as follows:

 

 

 

Number of
Restricted
Shares

 

 

Weighted
Average
Grant Date
Fair Value

 

Unvested at December 31, 2021

 

 

363,930

 

 

$

72.75

 

Granted

 

 

67,750

 

 

 

20.71

 

Vested

 

 

(103,032

)

 

 

71.06

 

Canceled

 

 

(48,126

)

 

 

76.44

 

Unvested at December 31, 2022

 

 

280,522

 

 

$

60.17

 

 

Employee Restricted Stock Units

The Company granted 67,750 RSUs to employees in 2022. The total fair value of RSUs vested during the year ended December 31, 2022, 2021, and 2020 was $4.9 million, $3.2 million and $0.3 million, respectively. Stock-based compensation expense recognized during the years ended December 31, 2022, 2021 and 2020 for RSUs was $4.6 million, $4.4 million, and $1.9 million, respectively.

Non-Employee Awards

The Company granted no stock options or RSUs to non-employees during the year ended December 31, 2022. The fair value of non-employee stock options was estimated using the following weighted-average assumptions:

 

 

 

 

 

Year Ended
  December 31,

 

 

 

 

 

2021

 

 

2020

 

Expected volatility

 

 

 

 

60

%

 

 

67

%

Risk-free interest rate

 

 

 

 

0.97

%

 

 

0.36

%

Dividend yield

 

 

 

 

0

%

 

 

0

%

Expected term

 

 

 

 

5.69

 

 

 

5.56

 

 

Stock-based compensation expense recognized during the years ended December 31, 2022, 2021 and 2020 for equity awards granted to non-employees was $1.2 million, $1.2 million and $0.7 million, respectively.

Performance-Based Awards

In December 2019, the Company granted 170,150 performance-based stock options and 128,900 performance-based RSUs (collectively "2019 PSA"). These equity awards would vest 25% upon the achievement of specific clinical development milestones. The remaining awards would then vest in three equal annual installments after that date. The performance criteria for 2019 PSA was achieved in June 2021. 42,536 of the performance-based stock options and 25,907 of the performance-based restricted stock vested during 2022. The total fair value of the performance-based stock options and RSUs vested during the years ended December 31, 2022 was $3.9 million.

The Company estimated the fair value of the 2019 PSA using the Black-Scholes valuation model and significant assumptions included an expected volatility of 72%, a risk-free rate of 1.67%, expected dividend yield of 0%, and expected term of 6.31 years.

In February 2021, the Company granted 190,831 performance-based stock options ("2021 Feb PSO"). These stock options will vest 25% upon the achievement of specific clinical development milestones. The remaining awards would then vest in 36 successive equal monthly installments after the performance criteria is achieved. The performance criteria for 2021 PSOs was achieved in February 2022. 80,456 of the performance-based stock options vested during 2022. The total fair value of the performance-based stock options vested during the year ended December 31, 2022 was $6.2 million.

The Company estimated the fair value of the 2021 Feb PSO using the Black-Scholes valuation model. Significant assumptions utilized in estimating the fair value of 2021 Feb PSO include an expected volatility of 66%, a risk-free rate of 0.66%, expected dividend yield of 0%, and expected term of 5.94 years.

In August 2021, the Company granted 478,750 performance-based stock options ("2021 Aug PSO"). These stock options will vest upon the achievement of specific clinical development milestones with the percentage of shares earned being dependent on the relative total stockholder return over the performance period. The remaining shares will then vest in 12 successive equal monthly installments after the performance criteria is achieved. As of December 31, 2022, the requisite performance criteria for the 2021 Aug PSO was not achieved and not probable and no stock-based compensation expense was recognized during the year ended December 31, 2022.

The Company estimated the weighted-average fair value of the 2021 Aug PSO using the Monte Carlo simulation model. Significant assumptions utilized in estimating the fair value of 2021 Aug PSO include an expected volatility of 60%, a risk-free rate of 1.05%, expected dividend yield of 0%, and expected term of 6.49 years.

Performance-based awards are recorded as expense beginning when vesting events are determined to be probable. Stock-based compensation expense recognized during the years ended December 31, 2022, 2021 and 2020 for the performance-based equity awards was $6.3 million, $11.4 million and $7.2 million, respectively.

2018 Employee Share Purchase Plan

In August 2018, the Company adopted the 2018 Employee Share Purchase Plan (“ESPP”), which became effective on the business day prior to the effectiveness of the registration statement relating to the IPO. A total of 460,000 shares of common stock were initially reserved for issuance under the ESPP. The initial offering period of the ESPP was authorized by the Company’s board of directors and commenced on January 4, 2021. Each offering period is twelve months long, with two purchase periods. ESPP participants will purchase shares of common stock at a price per share equal to 85% of the lesser of (1) the fair market value per share of the common stock on the enrollment date or (2) the fair market value of the common stock on the exercise date.

The Company issued 27,863 shares under the ESPP during the year ended December 31, 2022. Stock-based compensation expense recognized during the year ended December 31, 2022 and 2021 for the ESPP was $0.2 million and $0.3 million, respectively.

Stock-Based Compensation Expense

Stock-based compensation is classified in the consolidated statements of operations and comprehensive loss as follows (in thousands):

 

 

 

Year Ended
  December 31,

 

 

 

2022

 

 

2021

 

 

2020

 

Research and development

 

$

59,288

 

 

$

33,237

 

 

$

16,957

 

General and administrative

 

 

46,745

 

 

 

28,148

 

 

 

13,711

 

Total stock-based compensation

 

$

106,033

 

 

$

61,385

 

 

$

30,668

 

 

As of December 31, 2022, the Company had $311.3 million of unrecognized compensation expense related to unvested share-based awards including options granted under the LTPIP Program and ESPP, which is expected to be recognized over a weighted-average period of 3.61 years.

Shares Subject to Repurchase

The Company has a right of repurchase with respect to unvested shares issued upon early exercise of options at an amount equal to the lower of (1) the exercise price of each restricted share being repurchased and (2) the fair market value of such restricted share at the time the Company’s right of repurchase is exercised. The Company’s right to repurchase these shares lapses as those shares vest over the requisite service period.

Shares purchased by employees pursuant to the early exercise of stock options are not deemed, for accounting purposes, to be issued until those shares vest according to their respective vesting schedules. Cash received for early exercised stock options is recorded as accrued liabilities and other current liabilities on the consolidated balance sheet and is reclassified to common stock and additional paid-in capital as such shares vest. At December 31, 2022, there were no early exercised stock options subject to the Company’s right of repurchase.

About Stock Compensation Disclosures

Stock-based compensation disclosures detail the equity awards granted to employees and executives — including stock options, restricted stock units (RSUs), and performance shares — along with the valuation methods and assumptions used to expense them. This section reveals the true cost of talent retention and the alignment between management incentives and shareholder interests.

Key signals: total unrecognized compensation expense and its expected recognition period signal future earnings headwinds from already-granted awards. For stock options, examine Black-Scholes assumptions — expected volatility, risk-free rate, and expected term — as understating any of these reduces reported compensation expense. Compare stock compensation expense as a percentage of revenue against peers to assess dilution cost. Watch vesting schedules for acceleration clauses tied to change-of-control events. Performance-based awards with undemanding targets may indicate weak governance. Add back stock compensation to operating cash flow to calculate a more conservative free cash flow figure.