Stockholders' Equity

9 Months Ended

Sep. 30, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Warrants

As of September 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 nine months ended September 30, 2018, no warrants were exercised. During the three and nine months ended September 30, 2017, no warrants were exercised. During the quarter ended September 30, 2017, the Company received proceeds totaling $2.1 million related to a warrant exercise of November 21, 2012 warrants. The warrant exercise was effective in early October 2017 and resulted in the issuance of 267,966 shares of common stock.

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 September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Research and development expense	$	1,849	$	584	$	5,113	$	2,504
General and administrative expense	2,209		895		6,479		2,964
	$	4,058	$	1,479	$	11,592	$	5,468

During the three and nine months ended September 30, 2018, 202,601 and 716,409 shares were issued pursuant to stock option exercises, generating net proceeds of $2.2 million and $9.5 million, respectively. During the three and nine months ended September 30, 2017, 7,937 shares were issued pursuant to stock option exercises, generating net proceeds of $0.04 million.