6. Stockholder’s Equity

Stock Option Plans

We have two stock option plans – the 2004 Equity Incentive Plan (the “2004 Plan”) and the 2012 Incentive Award Plan (the “2012 Plan”). In February 2018, our Board of Directors authorized a 4.6 million increase in the shares available for grant under the 2012 Plan pursuant to the annual increase provisions of the 2012 Plan.

During the nine months ended September 30, 2018, we issued 1,408,000 shares of our common stock upon the exercise of stock options.

The following table summarizes our stock-based compensation:

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2018		2017		2018		2017
	(in thousands)				(in thousands)
Research and development	$	1,961	$	1,049	$	5,388	$	2,552
Selling, general and administrative		4,549		2,574		12,093		6,977
Total stock-based compensation	$	6,510	$	3,623	$	17,481	$	9,529

Stock Repurchase Program

On August 9, 2018, we announced that our Board of Directors had approved a program to repurchase up to $100 million of our common stock (the “Stock Repurchase Program”). Unless it is terminated or suspended prior to its expiration, the Stock Repurchase Program will remain in effect until June 30, 2019. The timing and amount of any repurchases pursuant to the Stock Repurchase Program will be determined based on market conditions, our stock price and other factors. The Stock Repurchase Program does not require us to acquire any specific number of shares and it may be modified, suspended or discontinued at any time without notice. Repurchases pursuant to the Stock Repurchase Program may be made through a variety of methods, including open market purchases, privately negotiated transactions, block trades, accelerated share repurchase transactions or any combination of such methods.

During the three months ended September 30, 2018, we repurchased 674,000 shares of common stock under the Stock Repurchase Program in open market transactions at an average price of $13.21 per share, for an aggregate purchase price of $8.9 million. Shares repurchased are recorded as treasury stock at cost on our consolidated balance sheet. At September 30, 2018, $91.1 million of the current authorization remained available for the repurchase of shares of our common stock.