Stockholder's Equity (Tables)

6 Months Ended

Jun. 30, 2020

Equity [Abstract]

Summary of Common Stock Shares Activity

The following table summarizes common stock share activity for the three and six months ended June 30, 2020 and 2019 (dollars in thousands): 

	Three Months Ended June 30, 2020
	Shares of Common Stock		Common Stock		Additional Paid-in Capital			Accumulated Deficit			Total Stockholders’ Equity
Balance, March 31, 2020		9,787,604	$	10	$	284,875		$	(278,430	)	$	6,455
Net loss		—		—		—			(6,381	)		(6,381	)
Stock-based compensation expense		—		—		410			—			410
Common stock issued for exercise of stock options		151		—		—			—			—
Common stock issued, net of expenses		303,038		—		2,463			—			2,463
Common stock issued for conversion of April 2020 Notes		316,461		—		2,784			—			2,784
Common stock issued for Commitment Shares		70,910		—		602			—			602
Common stock issued for vested restricted stock units		762		—		—			—			—
Balance, June 30, 2020		10,478,927	$	10	$	291,134		$	(284,811	)	$	6,333
	Six Months Ended June 30, 2020
	Shares of Common Stock		Common Stock		Additional Paid-in Capital			Accumulated Deficit			Total Stockholders’ Equity
Balance, December 31, 2019		9,741,372	$	10	$	284,313		$	(271,428	)	$	12,895
Net loss		—		—		—			(13,383	)		(13,383	)
Stock-based compensation expense		—		—		821			—			821
Common stock issued through employee stock purchase and stock option plans		2,368		—		18			—			18
Common stock issued, net of expenses		331,565		—		2,669			—			2,669
Common stock issued for conversion of April 2020 Notes		316,461		—		2,784			—			2,784
Common stock issued for Commitment Shares		70,910		—		602			—			602
Common stock issued for vested restricted stock units		16,250		—		(73	)		—			(73	)
Balance, June 30, 2020		10,478,927	$	10	$	291,134		$	(284,811	)	$	6,333
	Three Months Ended June 30, 2019
	Shares of Common Stock		Common Stock		Additional Paid-in Capital			Accumulated Deficit			Total Stockholders’ Equity
Balance, March 31, 2019		5,023,242	$	5	$	251,951		$	(240,626	)	$	11,330
Net loss		—		—		—			(8,403	)		(8,403	)
Stock-based compensation expense		—		—		446			—			446
Common stock issued, net of expenses		266,090		—		4,046			—			4,046
Common stock issued for conversion of March 2019 Notes		162,600		—		2,984			—			2,984
Common stock issued for vested restricted stock units		79		—		(1	)		—			(1	)
Balance, June 30, 2019		5,452,011	$	5	$	259,426		$	(249,029	)	$	10,402
	Six Months Ended June 30, 2019
	Shares of Common Stock		Common Stock		Additional Paid-in Capital			Accumulated Deficit			Total Stockholders’ Equity
Balance, December 31, 2018		4,797,198	$	5	$	248,938		$	(217,718	)	$	31,225
Net loss		—		—		—			(31,311	)		(31,311	)
Stock-based compensation expense		—		—		938			—			938
Common stock issued through employee stock purchase plan		1,926		—		21			—			21
Common stock issued, net of expenses		488,747		—		6,556			—			6,556
Common stock issued for conversion of March 2019 Notes		162,600		—		2,984			—			2,984
Common stock issued for vested restricted stock units		1,540		—		(11	)		—			(11	)
Balance, June 30, 2019		5,452,011	$	5	$	259,426		$	(249,029	)	$	10,402

Common Stock Reserved For Future Issuances

The Company had reserved shares of common stock for future issuance as follows:

	June 30, 2020		December 31, 2019
Outstanding stock options		781,685		526,070
Outstanding restricted stock units		84,929		96,637
Warrants to purchase common stock associated with June 2016 Public Offering		421,867		421,867
Warrants to purchase common stock associated with March 2018 Public Offering – Series 2		798,810		798,810
Warrants to purchase common stock associated with December 2019 Public Offering		4,472,205		4,472,205
Option to purchase common stock associated with December 2019 Public Offering		—		583,333
Warrants to purchase common stock associated with Solar loan agreement		12,243		12,243
For possible future issuance for the conversion of the March 2019 Notes		1,138,200		1,138,200
For possible future issuance for the conversion of the April 2020 Notes		1,622,138		—
For possible future issuance under 2014 Equity Incentive Plan (Note 9)		194,629		55,478
For possible future issuance under Employee Stock Purchase Plan		8,179		7,423
For possible future issuance under 2015 Inducement Award Plan (Note 9)		14,050		31,550
Total common shares reserved for future issuance		9,548,935		8,143,816