In November 2017, the Company filed a shelf registration with the SEC on Form S-3. The shelf registration statement included a prospectus for the at-the-market offering to sell up to an aggregate of $16.0 million of shares of the Company’s common stock through B. Riley FBR, Inc. (“FBR”) as a sales agent (the “FBR Sales Agreement”). Effective January 6, 2021, the Company terminated the FBR Sales Agreement. As a result, there were no shares sold under the FBR Sales Agreement during 2021.

In December 2020, the Company filed a new shelf registration statement with the SEC on Form S-3, or the replacement shelf registration statement. The replacement shelf registration statement replaced the registration statement on Form S-3 the Company originally filed with the SEC in November 2017, which registration statement expired in December 2020. The replacement shelf registration was declared effective by the SEC on January 6, 2021. In December 2020, the Company also entered into a new At Market Issuance Sales Agreement (the “ATM Sales Agreement”), with FBR and H.C. Wainwright & Co. (together with FBR, the “Sales Agents”), pursuant to which the Company may sell from time to time, at its option, up to an aggregate of $30 million worth of shares of the Company’s common stock through the Sales Agents. The ATM Sales Agreement provides, among other things, that sales under the ATM Sales Agreement will be made pursuant to the registration statement, including the base prospectus filed as part of such registration statement. During the six months ended June 30, 2022, the Company sold 621,697 shares of common stock at a weighted-average price per share of $11.97 pursuant to the ATM Sales Agreement and received proceeds of approximately $7.3M, net of commissions and fees. No shares were sold pursuant to the ATM Sales Agreement in the three and six months ended June 30, 2023.

Future sales under the ATM Sales Agreement will depend on a variety of factors including, but not limited to, market conditions, the trading price of the Company’s common stock and the Company’s capital needs. There can be no assurance that the Sales Agents will be successful in consummating future sales based on prevailing market conditions or in the quantities or at the prices that the Company deems appropriate.

In addition, the Company will not be able to make future sales of common stock pursuant to the ATM Sales Agreement unless certain conditions are met, which include the accuracy of representations and warranties made to the Sales Agents under the ATM Sales Agreement. Furthermore, each of the Sales Agents is permitted to terminate the ATM Sales Agreement with respect to itself in its sole discretion upon ten days’ notice, or at any time in certain circumstances, including the occurrence of an event that would be reasonably likely to have a material adverse effect on the Company’s assets, business, operations, earnings, properties, condition (financial or otherwise), prospects, stockholders’ equity or results of operations. The Company has no obligation to sell the shares available for sale pursuant to the ATM Sales Agreement.

The Company has issued warrants to purchase common stock to banks that have previously loaned funds to the Company, as well as to representatives of the underwriters of the Company’s public offerings and certain of their affiliates.

During the six months ended June 30, 2022, warrants to purchase 139,972 shares of common stock expired. At June 30, 2023, and December 31, 2022, there were no warrants outstanding.

Stock-based compensation expense includes charges related to stock option grants. The Company measures stock-based compensation expense based on the grant date fair value of any awards granted to its employees. Such expense is recognized over the period of time that employees provide service and earn rights to the awards.

During the six months ended June 30, 2023 and 2022, the Company granted stock options to purchase 153,750 and 78,247 shares of the Company’s common stock, respectively. The estimated fair value of each stock option award granted was determined on the date of grant using the Black-Scholes option-pricing valuation model with the following assumptions for option grants during the three and six months ended June 30, 2023 and 2022:


	Three Months Ended June 30,		Six Months Ended June 30,
Common Stock Options	2023	2022	2023	2022
Risk free interest rate	3.39%	2.82% - 3.55%	1.34%- 3.39%	1.67% - 3.55%
Expected term	5.5 years	5.5 - 6.0 years	5.5 - 6.0 years	5.5 - 6.0 years
Expected volatility of common stock	103.64%	97.04% - 113.23%	99.34%- 103.64%	97.04% - 113.23%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%

The Company recognized stock-based compensation expense to employees and directors in its research and development and its selling, general and administrative functions during the three and six months ended June 30, 2023 and 2022 as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
	2023		2022		2023		2022
Research and development		—	$	3,752	$	2,841	$	5,608
Selling, general and administrative		280,140		363,172		561,871		742,377
Total stock-based compensation expense	$	280,140	$	366,924	$	564,712	$	747,985

As of June 30, 2023, there was approximately $1.6 million of unrecognized compensation costs related to outstanding employee and board of director options, which are expected to be recognized over a weighted-average period of 0.9 years.