The Company has two equity incentive plans: the 2006 Stock Plan (“2006 Plan”) and the 2015 Omnibus Equity Incentive Plan (“2015 Plan”).

In 2006, the Company adopted the 2006 Plan, which provided for the granting of stock options to executives, employees, and other service providers under terms and provisions established by the Board of Directors. The Company granted non-statutory stock options (“NSOs”) under the 2006 Plan until May 2015, when the 2006 Plan was terminated for future awards. The 2006 Plan continues to govern the terms of options that remain outstanding and were issued under the 2006 Plan. The 2015 Plan became effective in May 2015 and all shares that were reserved, but not issued, under the 2006 Plan were assumed by the 2015 Plan. Upon effectiveness, the 2015 Plan had 154,387 shares of common stock reserved for future issuance, which included 10,637 shares under the 2006 Plan that were transferred to and assumed by the 2015 Plan. The 2015 Plan provides for automatic annual increases in shares available for grant. In addition, shares subject to awards under the 2006 Plan that are forfeited or canceled will be added to the 2015 Plan. The 2015 Plan provides for the grant of incentive stock options (“ISOs”), NSOs, restricted stock awards, stock units, stock appreciation rights, and other forms of equity compensation, all of which may be granted to employees, officers, non-employee directors, and consultants. The ISOs and NSOs will be granted at a price per share not less than the fair value at the date of grant. Options granted generally vest over a four-year period; however, the options granted in the third quarter of 2018 vest over a two-year period, vesting monthly on a pro-rated basis. Options granted, once vested, are generally exercisable for up to 10 years after grant.

In June 2019, the shareholders approved an amendment to the Company’s 2015 Plan for a one-time increase to the number of shares of common stock that may be issued under the 2015 Plan by 120,000 shares. As of September 30, 2020, a total of 1,047,188 shares of common stock were reserved for issuance under the 2015 Plan, of which 85,532 shares of common stock are available for future grant. As of September 30, 2020, a total of 19,227 and 961,656 options are outstanding under the 2006 and 2015 Plans, respectively.

A summary of activity under the stock incentive plans is as follows (in thousands, except share data and price per share):

	Shares Subject to Outstanding Options			Weighted- Average Exercise Price Per Share		Aggregate Intrinsic Value
Outstanding — Balance at December 31, 2019		661,701		$	21.60	$	305
Options granted		491,494			4.32
Options exercised		—			—
Options forfeited		(131,849	)		6.39
Options expired		(40,463	)		48.57
Outstanding — Balance at September 30, 2020		980,883		$	13.87	$	1
Vested and expected to vest — September 30, 2020		965,445		$	14.03	$	1
Exercisable —September 30, 2020		540,267		$	21.51	$	—

As of September 30, 2020, there was $1.2 million of unrecognized compensation cost related to unvested stock-based compensation grants that will be recognized over the weighted-average remaining recognition period of 2.7 years.

The fair value of stock option awards to employees, executives, directors, and other service providers was estimated at the date of grant using the Black-Scholes Model with the following weighted-average assumption. There were 491,494 and 186,571 options granted during the nine months ended September 30, 2020 and 2019, respectively.

	Three Months Ended September 30,				Nine Months Ended September 30,
		2020		2019		2020		2019
Expected term (years)		6.01		6.24		6.50		7.13
Expected volatility	230%		99%		133%		99%
Risk-free interest rate	0.38%		1.84%		1.03%		2.05%
Dividend yield		—		—		—		—

The Company’s 2015 Employee Stock Purchase Plan (“ESPP”) became effective on May 14, 2015. The ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount of up to 15% of their eligible compensation through payroll deductions, subject to any plan limitations. The ESPP provides for six-month offering periods, and at the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the last trading day of the offering period. As of September 30, 2020, the number of shares of common stock reserved for future issuance under the ESPP is 105,036. The ESPP provides for automatic annual increases in the shares available for purchase on January 1 of each year. As of September 30, 2020, 35,056 shares had been issued under the ESPP. The Company recorded $12,200 and $4,300 of stock compensation expense for the three months ended September 30, 2020 and 2019, respectively, and $40,500 and $6,000 for the nine months ended September 30, 2020 and 2019, respectively.

As of September 30, 2020, the Company has 4,450,689 common stock warrants outstanding with a weighted average exercise price of $6.31. The expiration of the warrants ranges from July 2021 to December 2025.

In connection with the Series D preferred stock financing in the first half of 2014, the Company issued warrants, exercisable as of the issuance date, to the Series D preferred stock investors to purchase an aggregate of 61,397 shares of common stock at an exercise price of $363.20 per share and to the placement agents to purchase 1,674 shares of common stock at $268.80. Of the 63,071 warrants issued, 1,759 expired on March 28, 2019 and the remaining 61,312 expired in the second quarter of 2019, along with those issued to the placement agents.

As of September 30, 2020, 656,454 common stock warrants are outstanding that were issued in the March 2018 Private Placement. Of the total, 641,416 shares have a purchase price of $10.7258 and the remaining 15,038 common stock warrants have an exercise price of $41.5625. See Note 10.

As of September 30, 2020, 69,617 common stock warrants are outstanding in accordance with the June 2018 Offering, all of which have an exercise price of $12.568. See Note 10.

In connection with a professional services agreement with a non-affiliated third party, executed in April 2019, the Company issued 45,154 warrants (“Service Warrants”) at an exercise price of $6.18. The Service Warrants vest ratably over 12 months and expire in five years from the date of issuance. The Service Warrants are cancelable immediately prior to a change of control subsequent to the termination/expiration of the advisory agreement. The Company also issued 100,000 performance-based warrants (“Performance Warrants”) at an exercise price of $6.18 and vest in 1/6 increments upon the achievement of a qualifying milestone as defined within the agreement. The Performance Warrants expire in five years from the date of issuance and are cancelable immediately prior to a change of control subsequent to the sixth month anniversary of the termination/expiration of the advisory agreement.

The Service and Performance Warrants were determined to be equity instruments. Stock compensation expense associated with the Service Warrants is recognized ratably over the service period (i.e. one-year term). A performance acceleration event was deemed to have been achieved in August 2019, triggering the full vesting of the Performance Warrants. The Company recognized a portion of the Performance Warrants’ stock compensation expense during the third quarter of 2019 as a cumulative adjustment for the period during which services have already been provided. The remaining Performance Warrants expense is being recognized ratably over the remaining service period. For the Service Warrants, $145,000 of stock compensation expense was recognized during the three and nine months ended September 30, 2020 and $56,000 and $100,000 of stock compensation expense was recognized during the three and nine months ended September 30, 2019, respectively.

In June 2019, concurrent with the June 2019 Offering and pursuant to the June 2019 Purchase Agreement, the Company commenced a private placement whereby it issued and sold warrants exercisable for an aggregate of 1,489,575 shares of common stock, which equals 100% of the shares of common stock sold in the June 2019 Offering, with a purchase price of $0.125 per underlying warrant share and with an exercise price of $5.00 per share. The June 2019 Warrants are exercisable upon issuance and will expire five and a half years from the date of issuance. In August and September 2019, investors exercised a portion of the June 2019 Warrants and purchased 1,053,745 shares of common stock. The Company also issued warrants to the placement agents to purchase a total of 74,479 shares of common stock with an exercise price equal to $6.2938. The placement agent warrants are exercisable upon issuance and will expire five years from the date of issuance. As of September 30, 2020, the investors and placement agent hold outstanding warrants to purchase 510,309 shares of common stock warrants issued pursuant to the June 2019 Offering. See Note 10.

In July 2019, the Company issued warrants to purchase 10,000 shares of common stock to an independent contractor at an exercise price of $2.19 and in August 2019, the Company issued warrants to purchase 20,000 shares of common stock to two affiliated third-parties at an exercise price of $1.92. These warrants were determined to be equity instruments and were measured on the grant date using the Black Scholes Model. The warrants issued in July vest ratably over 12 months and expire two years from the date of issuance. As such, stock compensation expense associated with these warrants is recognized ratably over the 12-month service period. The August warrants vested on the issuance date of August 5, 2019 and expire two years from the date of issuance. As such, stock compensation expense associated with the August warrants was recognized as vested on the issuance date. For the warrants issued in July 2019, stock compensation expense of $2,000 and $10,000 was recognized during the three and nine months ended September 30, 2020.

In September 2019, concurrent with the September 2019 Offering and pursuant to the September 2019 Purchase Agreement, the Company commenced a private placement whereby it issued and sold warrants exercisable for an aggregate of 659,414 shares of common stock, which equals 50% of the shares of common stock sold in the September 2019 Offering, with a purchase price of $0.125 per underlying warrant share and with an exercise price of $7.52 per share. The September 2019 Warrants are exercisable upon issuance and will expire five and a half years from the date of issuance. The Company also issued warrants to the placement agents to purchase a total of 65,942 shares of common stock with an exercise price equal to $9.4781. The placement agent warrants are exercisable upon issuance and will expire five years from the date of issuance. As of September 30, 2020, all 725,356 common stock warrants are outstanding that were issued with the September 2019 Offering. See Note 10.

In February 2020, the Company issued warrants to purchase 10,000 shares of common stock to an independent contractor at an exercise price of $4.91. These warrants were determined to be equity instruments and were measured on the grant date using the Black Scholes Model. The warrants vest ratably over 12 months and expire two years from the date of issuance. As such, stock compensation expense associated with these warrants is recognized ratably over the 12-month service period. Stock compensation expense of $9,400 and $28,200 associated with these warrants was recognized during the three and nine months ended September 30, 2020, respectively.

In connection with an extension of the professional services agreement with a non-affiliated third party, executed in April 2019, the Company issued an additional 150,000 warrants to purchase shares of common stock in February 2020 at an exercise price of $4.71. These warrants were determined to be equity instruments and were measured on the grant date using the Black Scholes Model. The warrants vest ratably over 12 months and expire two years from the date of issuance. As such, stock compensation expense associated with these warrants is recognized ratably over the 12-month service period. Stock compensation expense of $135,400 and $406,200 associated with these warrants was recognized during the three and nine months ended September 30, 2020, respectively.

In connection with a professional services agreement with a non-affiliated third party, executed in March 2020, the Company issued warrants to purchase 18,350 shares of common stock at an exercise price of $2.50. The warrants vested on the issuance date and expire in three years from the date of issuance. The warrants are cancelable immediately prior to a change of control subsequent to the termination/expiration of the advisory agreement. These warrants were determined to be equity instruments and were measured on the grant date using the Black Scholes Model. As such, stock compensation expense associated with these warrants was recognized as vested on the issuance date. Stock compensation expense of $0 and $36,700 was recognized during the three and nine months ended September 30, 2020, respectively.

In May 2020, in consideration for the exercise of the June 2018 Warrants in the May 2020 Warrant Exercise Transaction, the Company issued warrants to purchase 1,392,345 shares of common stock at an exercise price of $4.775 per share with an exercise period of five years from the date of issuance. The Company also issued placement agent warrants to purchase a total of 69,617 shares of common stock that have an exercise price per share equal to $6.125 and a term of five years. As of September 30, 2020, all 1,461,962 common stock warrants are outstanding that were issued with the May 2020 Warrant Exercise Transaction. See Note 10.

In July 2020, in consideration for the exercise of the March 2018 Warrants in the July 2020 Warrant Exercise Transaction, the Company issued warrants to purchase 641,416 shares of common stock at an exercise price of $3.85 per share with an exercise period of five and one-half years from the date of issuance. The Company also issued placement agent warrants to purchase a total of 32,071 shares of common stock that have an exercise price per share equal to $4.969 and a term of five and one-half years. As of September 30, 2020, all 673,487 common stock warrants are outstanding that were issued with the July 2020 Warrant Exercise Transaction. See Note 10.