Stockholders’ Equity

The following is a summary of the Company's authorized and issued common and preferred stock as of June 30, 2018 and December 31, 2017:



			Outstanding as of
	Authorized	Issued	June 30, 2018	December 31, 2017
Common Stock, par value $0.001 per share	600,000,000	91,474,395	91,474,395	90,357,644
Series C Preferred Stock, par value $0.001 per share	1,091	1,091	23	23

Common Stock

In May 2018, the Company entered into an At-the-Market Equity Offering Sales Agreement (the “Sales Agreement”) with an outside placement agent (the “Placement Agent”) to sell shares of its common stock with aggregate gross proceeds of up to $100.0 million, from time to time, through an “at-the-market” equity offering program under which the Placement Agent will act as sales agent. Under the Sales Agreement, the Company will set the parameters for the sale of shares, including the number of shares to be issued, the time period during which sales are requested to be made, limitation on the number of shares that may be sold in any one trading day and any minimum price below which sales may not be made. The Sales Agreement provides that the Placement Agent will be entitled to compensation for its services in an amount equal to up to 3.0% of the gross proceeds from the sales of shares sold through the Placement Agent under the Sales Agreement. The Company has no obligation to sell any shares under the Sales Agreement, and may at any time suspend solicitation and offers under the Sales Agreement.

During the three and six months ended June 30, 2018, the Company sold a total of 92,479 shares of common stock under the Sales Agreement. The sales were made at a weighted average price of $4.52 per share resulting in aggregate net proceeds of $410,000. The Company may sell up to an additional $99.6 million in shares of its common stock under the Sales Agreement. The registration statement that registered with the SEC the shares that may be sold under the Sales Agreement expires on June 8, 2021.

In June 2016, the Company entered into an At-the-Market Equity Offering Sales Agreement (the “Prior Sales Agreement”) with the same placement agent. During the six months ended June 30, 2018, the Company sold a total of 314,950 shares of common stock under the Prior Sales Agreement. The sales were made at a weighted average price of $5.07 per share resulting in aggregate net proceeds of $1.6 million. During the six months ended June 30, 2017, the Company sold a total of 2,917,725 shares of common stock under the Prior Sales Agreement. The sales were made at a weighted average price of $8.41 per share resulting in aggregate net proceeds of $24.1 million. The registration statement that registered with the SEC the shares sold under the Prior Sales Agreement expired on June 5, 2018, and no further sales will be made under the Prior Sales Agreement. The Company sold an aggregate of 3,911,104 shares of common stock under the Prior Sales Agreement resulting in aggregate net proceeds of $32.1 million.

On July 25, 2017, the Company closed an underwritten public offering of 12,500,000 shares of common stock at a public offering price of $6.00 per share. The net proceeds to the Company, after deducting the underwriters' discounts and commissions and other offering expenses, were $70.1 million.

Warrants

The Company accounts for registered common stock warrants issued in March 2013 under the authoritative guidance on accounting for derivative financial instruments indexed to, and potentially settled in, a company’s own stock, on the understanding that in compliance with applicable securities laws, the registered warrants require the issuance of registered securities upon exercise and do not sufficiently preclude an implied right to net cash settlement. The Company classifies registered warrants on the condensed consolidated balance sheet as a current liability which is revalued at each balance sheet date subsequent to the initial issuance. Determining the appropriate fair-value model and calculating the fair value of registered warrants requires considerable judgment, including estimating stock price volatility and expected warrant life. The Company uses the Black-Scholes pricing model to value the registered warrants. The Company develops its estimates based on historical data. A small change in the estimates used may have a relatively large change in the estimated valuation. Changes in the fair market value of the warrants are reflected in the condensed consolidated statement of operations as change in fair value of common stock warrants.

The following table summarizes the warrants outstanding as of June 30, 2018 and December 31, 2017:



				As of June 30, 2018			As of December 31, 2017
Issued in Connection With:	Exercise Price		Expiration Date	Number of Warrants Outstanding	Common Stock Warrant Liability		Number of Warrants Outstanding	Common Stock Warrant Liability
March 2013 financing	$	3.17	September 12, 2018	284,091	$	228,665	284,091	$	360,795
Total				284,091	$	228,665	284,091	$	360,795

Stock Options

The Company has a stock-based incentive plan, the 2016 Omnibus Incentive Plan (the "2016 Incentive Plan"), pursuant to which the Company may grant stock options, restricted stock awards, restricted stock units and other stock-based awards or short-term cash incentive awards to employees, directors and consultants.

The 2016 Incentive Plan was approved by the Company's stockholders on May 13, 2016. The maximum number of shares of the Company’s common stock available for issuance over the term of the 2016 Incentive Plan may not exceed 6,000,000 shares, provided that commencing with the first business day of each calendar year beginning January 1, 2018, such maximum number of shares shall be increased by 2,000,000 shares of common stock unless the Board determines, prior to January 1 for any such calendar year, to increase such maximum amount by a fewer number of shares or not to increase the maximum amount at all for such year. On January 1, 2018, the maximum number of shares to be issued was increased by 2,000,000. At June 30, 2018, there were 8,000,000 shares of common stock reserved for issuance upon exercise of incentive awards granted and to be granted at future dates under the 2016 Incentive Plan. At June 30, 2018, the Company had 2,914,316 shares of common stock available for future grant under the 2016 Incentive Plan, 1,568,381 shares underlying outstanding but unvested restricted stock units and options outstanding to purchase 3,159,706 shares of common stock under the 2016 Incentive Plan. The awards granted and available for future grant under the 2016 Incentive Plan generally vest over three years and have a maximum contractual term of ten years. The 2016 Incentive Plan terminates by its terms on March 9, 2026.

The Amended and Restated 2007 Omnibus Incentive Plan (the "2007 Incentive Plan") was adopted on March 31, 2007 and terminated by its terms on March 31, 2017. At June 30, 2018, the Company had 192,329 shares underlying outstanding but unvested restricted stock units and options outstanding to purchase 5,894,837 shares of common stock under the 2007 Incentive Plan. The awards granted under the 2007 Incentive Plan generally vest over three years and have a maximum contractual term of ten years.

At June 30, 2018, the Company had options outstanding to purchase 191,438 shares of common stock under the VGX Equity Compensation Plan. The options under this plan were assumed in connection with the acquisition of VGX. The terms and conditions of the options outstanding under this plan remain unchanged.