The Company’s authorized common stock has a par value of $0.001 per share and consists of 100,000,000 shares as of March 31, 2021, and December 31, 2020; 20,625,637 and 19,663,698 shares were issued and outstanding at March 31, 2021, and December 31, 2020, respectively.

On July 16, 2020, the Company filed a Certificate of Amendment to its Amended and Restated Certificate of Incorporation (the “Amendment”), which became effective on Friday, July 17, 2020, (a) implementing a 1-for-10 reverse stock split of the Company’s common stock and (b) decreasing the number of authorized shares of the Company’s common stock from 250,000,000 shares to 100,000,000 shares.

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

	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

On April 10, 2020, the Company entered into the Common Stock Purchase Agreement with Aspire Capital pursuant to which the Company has the right to sell to Aspire Capital from time to time in its sole discretion up to $20.0 million in shares of the Company’s common stock over the next 30 months, subject to certain limitations and conditions set forth in the Common Stock Purchase Agreement. The aggregate number of shares that we can sell to Aspire Capital under the Common Stock Purchase Agreement may in no case exceed 1,956,547 shares of the Company’s common stock (which is equal to approximately 19.99% of the common stock outstanding on the date of the Common Stock Purchase Agreement), including the 70,910 commitment shares (the Exchange Cap), unless either (a) shareholder approval is obtained to issue more, in which case the Exchange Cap will not apply, or (b) the average purchase price of all shares sold under the Common Stock Purchase Agreement exceeds $8.461; provided that at no time shall Aspire Capital (together with its affiliates) beneficially own more than 19.99% of the Company’s common stock. During the three months ended March 31, 2021 and 2020, the Company did not sell any shares of its common stock under the Common Stock Purchase Agreement.

In connection with the Company’s issuances of its April 2020 Notes and March 2019 Notes, the Company bifurcated the embedded conversion options, inclusive of the interest make-whole provisions and make-whole fundamental change provisions, and recorded the embedded conversion options as long-term derivative liabilities in the Company’s balance sheet in accordance with ASC 815, Derivatives and Hedging. The convertible debt and derivative liability associated with the March 2019 Notes are presented in total on the accompanying unaudited condensed consolidated balance sheets as the convertible debt and derivative liability. The derivative liability will be remeasured at each reporting period using the binomial lattice model with changes in fair value recorded in the statements of operations in other (income) expense. For the three months ended March 31, 2021 and 2020, the Company recorded a loss of $0.1 million and a gain of $0.7 million, respectively, due to the change in fair value of the derivative liabilities.

Warrants Associated with June 2016, March 2018, December 2019, and December 2020 Public Offerings

The outstanding warrants associated with the June 2016, March 2018, December 2019, and December 2020 public offerings contain a provision where the warrant holder has the option to receive cash, equal to the Black-Scholes fair value of the remaining unexercised portion of the warrant, as cash settlement in the event that there is a fundamental transaction (contractually defined to include various merger, acquisition or stock transfer activities). Due to this provision, ASC 480, Distinguishing Liabilities from Equity, requires that these warrants be classified as liabilities. The fair values of these warrants have been determined using the Black-Scholes valuation model, and the changes in the fair value are recorded in the accompanying unaudited condensed consolidated statements of operations. During the three months ended March 31, 2021 and 2020, the Company recorded gains of $1.3 million and $4.8 million, respectively, in the warrant liabilities fair value adjustment. As of March 31, 2021 and 2020, the fair value of the warrant liabilities was $49.9 million and $51.2 million, respectively.

On the closing date of the Company’s previous loan agreement with Solar, pursuant to the loan agreement the Company issued to Solar the warrant to purchase an aggregate of up to 12,243 shares of the Company’s common stock at an exercise price of $36.754 per share. The warrant will expire five years from the date of the grant. The warrant was classified as equity and recorded at its relative fair value at issuance in the stockholders’ equity section of the balance sheet.