8. Stockholders' Equity (Deficit)

Common Stock

        On December 10, 2014, the Company issued and sold 11,250,000 shares of common stock in a public offering of shares as well as 1,598,000 shares of common stock pursuant to the partial exercise of the underwriters' over-allotment option for a total of 12,848,000 shares at a price of $4.00 per share, for aggregate gross proceeds of approximately $51.4 million.

        On February 5, 2014, the Company issued and sold 9,250,000 shares of common stock in an IPO at a price of $7.00 per share, for aggregate gross proceeds of approximately $64.8 million. On March 6, 2014, in connection with the partial exercise of the IPO underwriters' over-allotment option, the Company sold an additional 270,449 shares of common stock at a price of $7.00 per share, for aggregate gross proceeds of approximately $1.9 million.

        As of December 31, 2013, the Company had outstanding the following redeemable convertible preferred stock that converted into common shares on a one-for-6.2 basis upon consummation of the Company's IPO:

                                                                                                                                                                                    

        In connection with the issuance of the Company's Series B-1 preferred shares in 2011, the Company issued warrants to purchase 1,650,000 shares of the Company's Series B-1 Preferred Stock. Additionally, in connection with a banking facility entered into in 2011, the Company issued a warrant to purchase 125,000 shares of Series B preferred stock. As of December 31, 2013, the fair value of the warrants outstanding of $350,519 was recognized as a liability in the Company's balance sheet. Upon the Company's IPO, 1,100,000 of the outstanding Series B-1 warrants were net exercised into 20,273 shares of common stock and the remaining fair value of $145,256 associated with these particular warrants was reclassified to additional paid-in capital. The warrant to purchase 125,000 shares of Series B preferred stock was converted into a warrant to purchase up to 20,161 shares of the Company's common stock and remains outstanding with a fair value recorded as a liability of $82,851 at December 31, 2014 as it contains a cash settlement feature upon certain strategic transactions.

        Under its certificate of incorporation, the Company was authorized to issue up to 100,000,000 and 132,000,000 shares of common stock as of December 31, 2014 and December 31, 2013, respectively. The Company also was authorized to issue up to 5,000,000 shares of preferred stock as of December 31, 2014. The Company is required, at all times, to reserve and keep available out of its authorized but unissued shares of common stock sufficient shares to effect the conversion of the shares of the preferred stock and all outstanding stock options and warrants.

Preferred Stock

        As part of the IPO, on February 5, 2014, all of the Company's outstanding convertible preferred stock was converted and all but 22,580 of its outstanding warrants were net exercised into an aggregate of 15,728,286 shares of common stock.

        On January 4, 2008, the Company authorized the sale and issuance of up to 25,000,000 shares of Series A Convertible Preferred Stock (the Series A). On January 7, 2008, the Company completed the first closing of its sale of the Series A and issued 501,562 shares at $1.00 per share generating gross proceeds of $501,562. On January 31, 2008, the Company completed a second closing of its sale of the Series A and issued an additional 4,514,062 shares at $1.00 per share generating gross proceeds of $4,514,062. Costs associated with these offerings were $200,137. In September 2008, the Company completed a third closing of its sale of the Series A and issued an additional 8,025,000 shares at $1.00 per share generating gross proceeds of $8,025,000. Costs associated with this offering were $2,154. On June 30, 2009, the Company completed a fourth closing of its sale of the Series A and issued 11,034,375 shares at $1.00 per share generating gross proceeds of $11,034,375. Costs associated with this offering were $561. On November 16, 2009, the Company amended the stock purchase agreement associated with the Series A financing and issued an additional 1,000,000 shares at $1.00 per share generating gross proceeds of $1,000,000. Costs associated with this offering were $3,398. All offering costs associated with the Series A were being accreted into the carrying value of the Series A until its conversion upon IPO.

        On July 8, 2010, the Company authorized the sale and issuance of up to 35,000,000 shares of Series B Preferred Stock (the Series B) and up to 4,300,000 of Series B-1 Preferred Stock (the Series B-1). In connection with the authorization of the Series B and the Series B-1, the Company also authorized the sale and issuance of warrants to purchase up to 1,700,000 shares of the Series B-1 (the Series B-1 Warrants). On July 8, 2010, the Company completed the first closing of its sale of the Series B and issued 17,500,000 shares at $1.00 per share generating gross proceeds of $17,500,000. Costs associated with this offering were $38,568. On July 8, 2011, the Company completed its second closing, issuing 5,700,000 shares of its Series B at $1.00 per share and 1,800,000 shares of its Series B-1 at $1.00 per share. Costs associated with this offering were $8,229. On December 15, 2011, the Company completed its third closing issuing 7,600,000 shares of its Series B at $1.00 per share and 2,400,000 shares of its Series B-1 at $1.00 per share. Costs associated with this offering were $4,989. All offering costs associated with the Series B and Series B-1 were being accreted into the carrying value of the preferred stock until its conversion upon IPO.

        In connection with the issuance of the Series B-1 shares in the second and third closings, the Series B-1 shareholders received ten-year warrants to purchase a total of 1,650,000 shares of the Company's Series B-1 Preferred Stock at an exercise price of $1.00 per share. The estimated fair value of the preferred stock warrants on the dates of issuance of $1,347,428 was recorded as a reduction to the carrying value of the Series B-1 Preferred stock and was being accreted into the carrying value of the Series B-1 until its conversion upon IPO. The preferred stock warrants were recorded as a liability pursuant to the guidance for accounting for certain financial instruments with characteristics of both liabilities and equity and are revalued at each reporting period to reflect any changes in fair value. In November 2013, one of the Company's warrant holders exercised its warrants to purchase 550,000 shares of the Company's Series B preferred stock. Of the remaining 1,225,000 outstanding warrants to purchase preferred stock at December 31, 2013, 1,100,000 were net exercised immediately prior to the consummation of the Company's initial public offering in February 2014. Upon consummation of the Company's initial public offering, the remaining warrant to purchase up to 125,000 shares of the Company's Series B preferred stock was converted into a warrant to purchase up to 20,161 shares the Company's common stock, and the fair value of the warrant liability at that time was reclassified to additional paid-in capital.

        In May, 2013, the Company authorized the sale and issuance of up to 37,000,000 shares of Series C Preferred Stock (the Series C). On May 3, 2013, the Company completed the closing of its sale of the Series C and issued 36,764,704 shares at $1.632 per share generating gross proceeds of $59,999,997. Costs associated with this offering were $81,080. All offering costs associated with the Series C were recorded as a discount and were being accreted into the carrying value of the Series C until its conversion upon IPO.

        Each share of the Series A, the Series B, the Series B-1 and the Series C preferred stock was convertible into approximately 0.1613 shares of common stock at any time at the option of the holder. The preferred stock was automatically convertible in the event of (i) an initial public offering at a price of at least $4.00 per share of common stock (subject to adjustment to reflect stock splits, stock dividends, stock combinations, recapitalizations and like occurrences) and net proceeds to the Company of at least $40 million; or (ii) the affirmative vote or written consent of the holders of at least 60% of shares of the preferred stock then outstanding. Each share of Series A, B or B-1 preferred stock was also subject to a special mandatory conversion feature. In the event that any holder of shares of Series A, B or B-1 preferred stock did not participate in a Qualified Financing (as defined in the Company's Certificate of Incorporation) by purchasing, in the aggregate, in such Qualified Financing and within the time period specified by the Company, such holder's pro rata amount, then such holder's shares of preferred stock would automatically convert into common stock at the respective Conversion Price (as defined). The Company evaluated each series of its Preferred Stock and determined that each individual series was considered an equity host under ASC 815. As a result of the Company's conclusion that the Preferred Stock represented an equity host, the conversion feature of all series of Preferred Stock was considered to be clearly and closely related to the associated Preferred Stock host instrument. Accordingly, the conversion feature of all series of Preferred Stock was not considered an embedded derivative that required bifurcation. The Company accounted for potential beneficial conversion features under FASB ASC Topic 470-20, Debt with Conversion and Other Options. At the time of each of the issuances of Preferred Stock, the Company's common stock into which each series of the Company's Preferred Stock is convertible had an estimated fair value less than the effective conversion prices of the Preferred Stock. Therefore, there was no intrinsic value on the respective commitment dates.

        Holders of the preferred stock were entitled to receive non-cumulative dividends at the rate of 8% of the applicable purchase price per share per annum if and when declared by the board of directors. No dividends were declared through conversion upon IPO.

        Holders of the preferred stock, voting as a class, were entitled to elect five members of the board of directors.

        Holders of the Series A, the Series B, and the Series B-1 were entitled to a liquidation preference in an amount equal to $1.00 per share plus all declared and unpaid dividends in the event of a liquidation, dissolution, or winding-up of the Company, or in the event the Company merged with or was acquired by another entity. Holders of the Series C were entitled to a liquidation preference in an amount equal to $1.632 per share plus all declared and unpaid dividends in the event of a liquidation, dissolution, or winding-up of the Company, or in the event the Company merged with or ws acquired by another entity.

        At any time on or after July 8, 2016, the holders of at least 60% of the outstanding shares of the preferred stock may have required the Company to redeem, in three annual installments beginning on the date of the initial redemption, all of the outstanding shares of the preferred stock for an amount equal to the original issue price per share plus any declared and unpaid dividends.