STOCKHOLDERS’ EQUITY AND EARNINGS PER SHARE

Common Stock

Pursuant to our amended and restated certificate of incorporation, we are authorized to issue 47,000,000 shares of common stock. Holders of our common stock are entitled to dividends as and when declared by the board of directors, subject to rights and holders of all classes of stock outstanding having priority rights to dividends. There have been no dividends declared to date. Each share of common stock is entitled to one vote.

On February 22, 2017, we completed the private placement sale of 1,626,898 units at a price of $4.61 per unit to one investor. Each unit consists of one share of our common stock and one warrant to purchase one share of our common stock at an exercise price of $8.25 for a period commencing 6 months and ending 30 months after the closing of the financing. Gross proceeds were $7.5 million. We incurred $29,000 of legal expenses in connection with the financing. We registered for resale by the investor the shares of common stock, and the shares of common stock issuable upon exercise of the warrants, purchased by the investor in the financing pursuant to a registration statement that was declared effective by the SEC in April 2017.

On October 2, 2017, we completed the private placement sale of 1,976,919 units. Each unit consisted of one share of our common stock and one warrant to purchase one share of our common stock at an exercise price of $4.85 per share for a period commencing 6 months and ending 36 months from September 28, 2017, the date of the first closing of the offering. The sale closed in two rounds with the first closing on September 28, 2017 which included the private placement sale of 1,745,581 units at a price of $4.70 per unit to institutional and individual investors. Gross proceeds in the first closing were $8.2 million with net proceeds of $7.5 million after deducting placement agent fees and offering expenses. The second closing, completed on October 2, 2017, was for 231,338 units and gross proceeds of $1.1 million with net proceeds of $1.0 million after deducting placement agent fees and offering expenses. We also issued to the placement agent, warrants to purchase an aggregate of 98,846 shares of our common stock at an exercise price of $4.85 per share for a period commencing 6 months and ending 36 months from September 28, 2017.

On March 27, 2018, we completed the sale of 5,714,286 shares of common stock at a price of $3.50 per share in an underwritten public offering. Gross proceeds were $20.0 million with net proceeds of $18.4 million after deducting underwriter fees and offering expenses. The shares were issued pursuant to a shelf registration statement that we filed with the SEC, which became effective in May 2016. On April 6, 2018, following exercise by the underwriter of its overallotment option, we sold an additional 857,142 shares at a price of $3.50, resulting in gross proceeds of $3.0 million and net proceeds of $2.8 million after deducting underwriter fees and offering expenses.

We have a Form S-3 universal shelf registration statement on file with the SEC. The universal shelf registration statement on Form S-3 permits us to sell, in one or more public offerings, shares of our common stock, shares of preferred stock or debt securities, or any combination of such securities and warrants to purchase securities, for proceeds in an aggregate amount of up to $50.0 million, subject to potential limitations on the amount of securities we may sell in any twelve-month period. The Form S-3 will expire in November 2021. No securities have been issued pursuant to the registration statement.

Preferred Stock

Pursuant to our amended and restated certificate of incorporation, we are authorized to issue 3,000,000 shares of preferred stock. The board of directors has the authority, without action by our stockholders, to designate and issue shares of preferred stock in one or more series and to fix the rights, preferences, privileges and restrictions thereof. To-date, no preferred shares have been issued.

Stock Repurchase Program

On November 26, 2018, we announced that our board of directors had authorized a program to repurchase up to $4.0 million of our common stock over a 12-month period, either in the open market or through privately negotiated transactions. During the year ended December 31, 2018, we repurchased and retired 80,100 shares of common stock, at an aggregate cost of approximately $152,000, including commissions, or an average price of $1.88 per share.

Earnings Per Share

The following table presents the number of shares excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods below:



	Year Ended December 31, 2017	Year Ended December 31, 2018
Common stock warrants	3,730,255	3,385,100
Common stock options	1,082,490	1,255,280
Non-vested restricted stock unit awards	1,476,858	1,921,594
Total shares excluded from net loss per share attributable to common stockholders	6,289,603	6,561,974