Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity

Stockholders' Equity
6 Months Ended
Jun. 30, 2022
Equity [Abstract]  
Stockholders' Equity Stockholders’ Equity
We grant options and awards to employees and non-employee directors pursuant to a stockholder approved stock incentive plan, which is described in further detail in Note 9, Stockholders’ Equity, of the Notes to Consolidated Financial Statements in our 2021 Annual Report.

The following is a summary of our stock option and restricted stock activity and related information:
Stock Options Restricted Stock Awards
Shares Weighted-Average Exercise Price Shares Weighted-Average Grant Date Fair Value
Balance as of December 31, 2021
2,199,598  $ 106.00  264,143  $ 138.21 
Granted 734,218  $ 91.58  186,526  $ 87.32 
Options exercised/RSUs vested (25,798) $ 20.53  (133,173) $ 120.66 
Forfeited (30,417) $ 67.60  (1,378) $ 137.16 
Balance as of June 30, 2022
2,877,601  $ 103.50  316,118  $ 115.58 

As of June 30, 2022, outstanding options to purchase 1.6 million shares were exercisable with a weighted average exercise price per share of $102.10.

Employee Stock Purchase Plan

The price at which common stock is purchased under the Amended Employee Stock Purchase Plan, or ESPP, is equal to 85% of the fair market value of the common stock on the first or last day of the offering period, whichever is lower. As of June 30, 2022, 38,007 shares were available for future purchases under the ESPP.

Share Repurchases
On September 11, 2019, our Board of Directors approved a stock repurchase program authorizing, but not obligating, the repurchase of up to $500.0 million of our common stock from time to time over the next three years. We expect to acquire shares primarily through open-market transactions and may enter into Rule 10b5-1 trading plans, to facilitate open-market repurchases. The timing and amount of repurchase transactions will be determined by management based on our evaluation of market conditions, share price, legal requirements and other factors. We did not have any share repurchases during the three and six months ended June 30, 2022. Authorization to repurchase $248.8 million of our common stock remained available as of June 30, 2022.