STOCKHOLDERS' (DEFICIT) EQUITY (Tables)

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Summary of Common Stock

In addition, the Company had reserved for issuance the following amounts of shares of its common stock for the purposes described below as of December 31, 2019 and 2018 (in thousands):

	December 31,
	2019	2018
Shares of common stock issued	106,801	77,456
Shares of common stock reserved for issuance for:
Warrants	22,895	9,258
Stock options	6,236	3,942
Shares available for grant under 2014 Stock Incentive Plan	8,753	2,001
Shares available for sale under 2014 Employee Stock Purchase Plan	28	38
Total shares of common stock issued and reserved for issuance	144,713	92,695

Summary of Warrants Outstanding and Warrant Activity

The following table sets forth the Company's warrant activity for the year ended December 31, 2019 (in thousands):

Issued	Exercise Price	Expiration	December 31, 2018	Issued	(Exercised)		December 31, 2019
Jun-2019	$1.47	Jun-2020	—	20,410	—		20,410
Mar-2018	$0.95*	Mar-2023	7,211	—	(5,268	)	1,943
Nov-2017	$0.55*	Nov-2022	1,992	—	(1,505	)	487
May-2015	$11.83	Nov-2024	28	—	—		28
Nov-2014	$11.04	Nov-2024	27	—	—		27
			9,258	20,410	(6,773	)	22,895

* Exercise price shown (i) reflects modification described below and (ii) subject to further adjustment based on down round provision added by amendment described below.