Warrants

6 Months Ended

Jun. 30, 2018

As of June 30, 2018, the following warrants for common stock were issued and outstanding:



Issue date	Expiration date	Exercise price		Number of warrants outstanding
January 11, 2017	None	$	0.001	7,258,263
November 20, 2017	None	$	0.001	4,137,999
June 11, 2018	None	$	0.001	421,650
				11,817,912

During the three and six months ended June 30, 2018 and 2017, no warrants were exercised.

Stockholders' Equity

Sale of Common Stock

In June 2018, the Company sold 3,162,500 shares of its common stock at a public offering price of $38.85 per share and sold warrants to purchase up to 421,650 shares of its common stock at a public offering price of $38.849 per warrant. After deducting underwriter discounts and offering expenses, the Company received net proceeds from the transaction of $130.7 million. The public offering price for the warrants was equal to the public offering price of the common stock, less the $0.001 per share exercise price of each warrant. The warrants were recorded as a component of stockholders’ equity within additional paid-in capital. Per their terms, the outstanding warrants to purchase shares of common stock may not be exercised if certain holders' ownership of the Company’s common stock would exceed 9.99% for certain holders, 15.0% for certain holders, and 19.99% for other holders, following such exercise. Pursuant to the terms of the financing, the Company has an effective resale registration statement on file with the SEC covering shares of common stock sold and shares of common stock issuable upon the exercise of the warrants.

Share-based Compensation

Total share-based compensation expense by statement of operations and comprehensive loss classification is presented below (in thousands):



	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Research and development expense	$	1,771	$	938	$	3,264	$	1,919
General and administrative expense	2,103		1,285		4,270		2,070
	$	3,874	$	2,223	$	7,534	$	3,989

During the three and six months ended June 30, 2018, 110,860 and 513,808 shares were issued pursuant to stock option exercises, generating net proceeds of $1.5 million and $7.4 million, respectively. During the three and six months ended June 30, 2017, no shares were issued pursuant to stock option exercises.