Stockholders' Equity

9 Months Ended

Sep. 30, 2019

Share-based Payment Arrangement [Abstract]

Warrants

As of September 30, 2019, 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	5,133,230
November 20, 2017	None	$	0.001	4,137,999
June 11, 2018	None	$	0.001	421,650
				9,692,879

During the three months ended September 30, 2019, 725,008 warrants for shares of the Company's common stock were exercised via cashless exercise, resulting in the issuance of 725,000 shares of common stock. During the nine months ended September 30, 2019, 2,125,033 warrants for shares of the Company's common stock were exercised via cashless exercise, resulting in the issuance of 2,125,000 shares of common stock. During the three and nine months ended September 30, 2018, no warrants were exercised.Stockholders' Equity

Sale of Common Stock

In June 2019, the Company sold 2,415,000 shares of its common stock at a public offering price of $97.00 per share. After deducting underwriter discounts, commissions and offering expenses, the Company received net cash proceeds from the transaction of $219.9 million.

In January 2019, the Company sold 1,854,838 shares of its common stock at a public offering price of $62.00 per share. After deducting underwriter discounts, commissions and offering expenses, the Company received net cash proceeds from the transaction of $107.9 million.

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 or 4.99% for other holders, following such exercise.

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,
	2019		2018		2019		2018
Research and development expense	$	8,648	$	1,849	$	20,416	$	5,113
General and administrative expense	6,458		2,209		18,410		6,479
	$	15,106	$	4,058	$	38,826	$	11,592

During the three and nine months ended September 30, 2019, 91,257 and 424,144 shares were issued pursuant to stock option exercises, generating net proceeds of $1.1 million and $5.4 million, respectively. 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.

Disgorgement Proceeds

In January 2019, the Company received a payment of $1.1 million representing a disgorgement of short-swing profits from the sale of common stock by a beneficial owner pursuant to Section 16(b) of the Securities Exchange Act of 1934, as amended. The Company recognized these proceeds as a capital contribution from stockholders and reflected a corresponding increase to additional paid-in capital.