Stockholders’ Equity (Tables)

3 Months Ended

Mar. 31, 2021

The following table summarizes common stock share activity for the three months ended March 31, 2021 and 2020 (dollars in thousands):

	Three Months Ended March 31, 2021
	Shares of Common Stock		Common Stock		Additional Paid-in Capital			Accumulated Deficit			Total Stockholders’ Equity
Balance, December 31, 2020		19,663,698	$	20	$	349,351		$	(326,613	)	$	22,758
Net loss		—		—		—			(4,676	)		(4,676	)
Stock-based compensation expense		—		—		398			—			398
Common stock issued for conversion of April 2020 Notes		959,080		1		7,452			—			7,453
Common stock issued through employee stock purchase plan		2,184		—		6			—			6
Common stock issued for vested restricted stock units		675		—		(15	)		—			(15	)
Balance, March 31, 2021		20,625,637	$	21	$	357,192		$	(331,289	)	$	25,924

	Three Months Ended March 31, 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		—		—		—			(7,002	)		(7,002	)
Stock-based compensation expense		—		—		410			—			410
Common stock issued through employee stock purchase plan		2,215		—		18			—			18
Common stock issued, net of expenses		28,527		—		207			—			207
Common stock issued for vested restricted stock units		15,490		—		(73	)		—			(73	)
Balance, March 31, 2020		9,787,604	$	10	$	284,875		$	(278,430	)	$	6,455

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

	March 31, 2021		December 31, 2020
Outstanding stock options		1,371,606		830,343
Outstanding restricted stock units		96,974		29,087
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
Warrants to purchase common stock associated with December 2020 Public Offering - Series 1		6,800,000		6,800,000
Warrants to purchase common stock associated with December 2020 Public Offering - Series 2		6,800,000		6,800,000
Prefunded warrants to purchase common stock associated with December 2020 Public Offering		5,260,000		5,260,000
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		—		1,299,790
For possible future issuance under 2014 Equity Incentive Plan (Note 9)		318,097		146,488
For possible future issuance under Employee Stock Purchase Plan		6,652		5,895
For possible future issuance under 2015 Inducement Award Plan (Note 9)		14,050		14,050
Total common shares reserved for future issuance		27,510,704		28,028,978