Stockholders' Equity

12 Months Ended

Dec. 31, 2021

Stockholders’ Equity

Common Stock

As December 31, 2021, there were 200,000,000 shares of common stock authorized, and 74,980,546 and 72,234,303 shares issued and outstanding, respectively. As of December 31, 2020, there were 200,000,000 shares of common stock authorized, and 70,264,265 and 67,554,435 shares issued and outstanding, respectively. The par value for the common stock is $0.001 per share.

Preferred Stock

As of December 31, 2021 and 2020, there were 5,000,000 shares of preferred stock authorized, and zero shares issued and outstanding. The par value for the preferred stock is $0.001 per share.

Stock-Based Compensation

Stock Option Plans

The Company’s 2019 Stock Incentive Plan, as amended and restated (the “2019 Plan”), became effective on April 11, 2019. The 2019 Plan allows the Company to grant incentive stock options and restricted stock units to its employees and directors to participate in the Company’s future performance through stock-based awards at the discretion of the board of directors. On April 19, 2021, the Company’s board of directors amended the plan and authorized 5,000,000 new shares for issuance. The number of shares authorized for issuance is 40,067,744 shares in the aggregate. Options to acquire common stock granted thereunder have ten-year terms. As of December 31, 2021, approximately 5.0 million shares of common stock remained available for issuance (taking into account all option exercises and other equity award settlements through December 31, 2021).

Employee Stock Purchase Plan

There are 1,000,000 shares authorized and reserved for issuance under the 2019 Employee Stock Purchase Plan. As of December 31, 2021, approximately 0.7 million shares of common stock remain available for issuance under the 2019 Employee Stock Purchase Plan (taking into account all share purchases through December 31, 2021).

Inducement Plan

There are 3,368,048 shares of common stock authorized and reserved for issuance under the Inducement Plan. As of December 31, 2021, no more shares of common stock remained available for issuance under the Inducement Plan (taking into account all option exercises and other equity award settlements through December 31, 2021).

Stock Option Activity

A summary of the Company’s stock option activity and weighted average exercise prices follows:


	Stock Option Activity			Weighted Average Remaining Contractual Term (In years)	Aggregate Intrinsic Value (In thousands)
	Options (In thousands)	Weighted Average Exercise Price
Balance outstanding at December 31, 2018	6,266	$	12.13
Granted	1,425	29.76
Exercised	(1,523)	11.12
Cancelled or expired	(369)	14.76
Balance outstanding at December 31, 2019	5,799	$	16.57	6.79	$	119,064
Options vested and expected to vest	5,096	$	15.29	6.49	$	110,934
Options exercisable at December 31, 2019	2,901	$	12.03	4.95	$	72,424

Balance outstanding at December 31, 2019	5,799	$	16.57
Granted	737	31.21
Exercised	(1,683)	12.69
Cancelled or expired	(521)	23.27
Balance outstanding at December 31, 2020	4,332	$	19.78	6.79	$	183,825
Options vested and expected to vest	1,470	$	23.88	8.19	$	56,382
Options exercisable at December 31, 2020	2,280	$	14.80	5.40	$	108,128

Balance outstanding at December 31, 2020	4,332	$	19.78
Granted	1,705	48.24
Exercised	(863)	13.55
Cancelled or expired	(392)	32.94
Balance outstanding at December 31, 2021	4,782	$	27.52	6.77	$	62,300
Options vested and expected to vest	1,419	$	36.41	8.61	$	11,387
Options exercisable at December 31, 2021	2,564	$	17.87	5.05	$	46,932

The total fair value of stock options exercised during the years ended December 31, 2021 and 2020 was approximately $6.6 million and $10.0 million, respectively. As of December 31, 2021, there was approximately $44.8 million of total unrecognized compensation cost related to nonvested share-based compensation arrangements. That cost is expected to be recognized over a weighted average period of approximately 2.7 years.

Restricted Stock Unit Activity

A summary of the Company’s restricted stock units (“RSUs”) activity and weighted average exercise prices follows:


	Restricted Stock Unit Activity
	Number of Shares (In thousands)	Weighted Average Grant Date Fair Value (Per Share)		Aggregate Fair Value (In thousands)
Balance outstanding at December 31, 2018	2,690	$	15.81	$	50,756
Awarded	1,979	30.99
Released	(1,197)	14.24
Forfeited	(423)	20.28
Non-vested and outstanding at December 31, 2019	3,049	$	24.73	$	112,848

Balance outstanding at December 31, 2019	3,049	$	24.73	$	112,848
Awarded	2,530	26.51
Released	(1,906)	23.40
Forfeited	(723)	25.19
Non-vested and outstanding at December 31, 2020	2,950	$	27.00	$	183,781

Balance outstanding at December 31, 2020	2,950	$	27.00	$	183,781
Awarded	3,066
Released	(1,596)
Forfeited	(688)
Non-vested and outstanding at December 31, 2021	3,732	$	43.63	$	133,308
Expected to vest	2,246	$	41.86	$	80,242

RSUs granted to employees generally vest over a three to four-year period, or upon achievement of certain performance conditions. As of December 31, 2021, total unrecognized compensation cost, adjusted for estimated forfeitures, related to nonvested RSUs was approximately $141.9 million and the weighted-average remaining vesting period was 3.2 years.

For the year ended December 31, 2021, the Company accrued approximately $18.4 million for cash awards related to bonus to be settled in shares of the Company’s stock and recorded a corresponding expense, which is included as a component of stock-based compensation expense in the accompanying consolidated financial statements. For the year ended December 31, 2020, the Company accrued approximately $20.4 million and $8.9 million for cash awards related to bonus and for the achievement of long term incentive plan awards, respectively, to be settled in shares of the Company’s stock and recorded a corresponding expense, which is included as a component of stock-based compensation expense in the accompanying consolidated financial statements.

Stock-based compensation expense recognized in the Company’s consolidated statements of operations and cash flows was $69.7 million, $65.9 million, and $44.1 million for the years ended December 31, 2021, 2020, and 2019, respectively.

The per share weighted average fair value of stock options granted during the years ended December 31, 2021, 2020 and 2019 was $28.68, $13.84, and $12.12, respectively. The fair value of each option grant is estimated on the date of grant using the Black-Scholes option-pricing model with the following weighted average assumptions for the periods presented:


	Year Ended December 31,
	2021	2020	2019
Dividend yield	—%	—%	—%
Risk-free interest rate	0.46% – 1.33%	0.26% – 0.66%	1.66% – 3.05%
Expected life (in years)	5	5	5
Historical volatility	53.51% – 54.55%	46.50% – 53.91%	43.42% – 44.00%

A description of the methods used in the significant assumptions used to estimate the fair value of stock-based-based compensation awards follows:

•Dividend yield – The Company uses 0% as it has never issued dividends and does not anticipate issuing dividends in the near term.

•Risk-free interest rate – The Company uses the market yield on U.S. Treasury securities at five years with constant maturity, representing the current expected life of stock options in years.

•Expected life – The Company uses historical data to estimate the expected life of a stock option

•Historical volatility – The Company uses a trailing five year from grant date to determine volatility.