6. Loan and Security Agreement

        On May 23, 2011, the Company entered into a loan and security agreement (the "Loan and Security Agreement") with Oxford Finance LLC and General Electric Capital Corporation (collectively, the "Lender") pursuant to which the Lender agreed to lend the Company up to $25.0 million. Upon entering into the Loan and Security Agreement, the Company borrowed $6.3 million from the Lender on May 23, 2011("Term Loan A"), $6.3 million on November 21, 2011 ("Term Loan B") and an additional $12.5 million on May 29, 2012 ("Term Loan C"). The Company's obligations under the Loan and Security Agreement are secured by a first priority security interest in substantially all of the assets of the Company.

        Interest on the outstanding Term Loan A was payable on a monthly basis through and including December 1, 2011. Principal and interest payments on Term Loan A was payable in 36 equal monthly installments beginning December 1, 2011 through November 1, 2014, with a final balloon payment of $0.6 million due upon maturity on November 22, 2014. Interest was payable on Term Loan A at an annual interest rate of 10.16%. Interest on the outstanding Term Loan B was payable on a monthly basis through and including June 1, 2012. Principal and interest payments on Term Loan B was payable in 30 equal monthly installments beginning June 1, 2012, through November 1, 2014, with a final balloon payment of $0.6 million due upon maturity on November 22, 2014. Interest was payable on Term Loan B at an annual interest rate of 10%. Interest on Term Loan C was payable on a monthly basis through, and including, November 1, 2012. Principal and interest payments on Term Loan C was payable in 24 monthly installments beginning December 1, 2012, through November 1, 2014 with a final balloon payment of $1.3 million upon maturity on November 22, 2014. Interest is payable on Term Loan C at an annual interest rate of 10%.

        Per the Loan and Security Agreement, upon the last payment date of the amounts borrowed under the Loan and Security Agreement, whether on the maturity date of one of the Term Loans, on the date of any prepayment or on the date of acceleration in the event of a default, the Company would be required to pay the Lender a final payment fee equal to 3.5% of any of the Term Loans borrowed. In addition, if the Company repaid all or a portion of the Term Loans prior to maturity, it would pay the Lender a prepayment fee of three percent of the total amount prepaid if the prepayment occurs prior to the first anniversary of the funding of the relevant Term Loan, two percent of the total amount prepaid if the prepayment occurs between the first and second anniversary of the funding of the relevant Term Loan, and one percent of the total amount prepaid if the prepayment occurs on or after the second anniversary of the funding of the relevant Term Loan.

        In connection with each Term Loan, the Company issued warrants to the Lender to purchase 12,280 shares of the Company's Series A-1 convertible preferred stock (the "Warrants") at an exercise price per share of $81.42. The Warrants were initially classified as liabilities in the Company's balance sheet and were re-measured at their estimated fair value through completion of the Company's initial public offering. The changes in fair value are recorded as other (expense) income in the statement of operations. Upon the closing of its initial public offering and the automatic conversion of the Series A-1 convertible preferred stock into common stock, the Warrants became exercisable for up to 58,918 shares of common stock. Subsequent to the initial public offering, the Company's warrant liability was reclassified to equity.

        The Warrants are immediately exercisable in whole, or in part, and will expire ten years from their issuance.

        The initial fair value of the Warrants issued in connection with Term Loan A was $182.6 thousand and was recorded as a discount to Term Loan A. The Company also paid the Lender a facility fee of $250.0 thousand and reimbursed the Lender certain costs associated with the Loan and Security Agreement of approximately $117.0 thousand, both of which were also recorded as a discount to Term Loan A.

        The initial fair value of the Warrants issued in connection with Term Loan B was $177.6 thousand and was recorded as a discount to Term Loan B. The Company also reimbursed the Lender for certain costs associated with Term Loan B of approximately $18.0 thousand, which was also recorded as a discount to Term Loan B.

        The initial fair value of the Warrants issued in connection with Term Loan C was $379.7 thousand and was recorded as a discount to Term Loan C. The Company also reimbursed the Lender for certain costs associated with the Loan and Security Agreement of approximately $31.0 thousand, which was also recorded as a discount to Term Loan C.

        On May 30, 2014, the Company entered into a Loan and Security Agreement (the "New Credit Facility), with Solar Capital Ltd. ("Solar"), as collateral agent and a lender, and Oxford Finance LLC ("Oxford"), as a lender (the "New Lenders"), pursuant to which Solar and Oxford agreed to make available to the Company $30.0 million in the aggregate subject to certain conditions to funding. An initial term loan was made on May 30, 2014 in an aggregate principal amount equal to $21.0 million ("Initial Term Loan"). The Company used approximately $9.3 million of the Initial Term Loan to repay all the amounts owed under its Loan and Security Agreement with General Electric Capital Corporation and Oxford.

        The Company was initially required to make interest-only payments through June 1, 2015, and beginning on July 1, 2015, it is required to make payments of principal and accrued interest in equal monthly installments over a term of 36 months. However, the Company consummated public stock offerings resulting in the receipt of at least $65.0 million in aggregate net cash proceeds prior to May 31, 2015. Therefore, it is permitted to make interest-only payments through December 1, 2015 rather than July 1, 2015, and beginning on January 1, 2016, the Company is required to make principal and accrued interest payments in equal monthly installments over a term of 30 months.

        In addition to the Initial Term Loan, the Company would have been able to request an additional term loan in an aggregate principal amount of $9.0 million (the "Original Term B Loan") after the completion of this initial public offering if the net cash proceeds were at least $65.0 million subject to certain customary conditions to funding. Given the net proceeds from the Company's initial public offering were less than $65.0 million, it was not able to request the Original Term B Loan. The Initial Term Loan and the Original Term B Loan bear interest per annum at 9.85% plus one-month LIBOR (customarily defined) and all principal and accrued interest is due on June 1, 2018.

        As security for its obligations under the New Credit Facility, the Company granted a security interest in substantially all of its existing and after-acquired assets except for our intellectual property and certain other customary exclusions.

        On July 10, 2014, the Company entered into a first amendment to the New Credit Facility ("First Amendment"). Pursuant to the terms of the First Amendment, a second term loan of $4.0 million was drawn on July 10, 2014. The terms of the First Amendment, among other things,

        Although the Company closed a public offering resulting in over $13.0 million in aggregate net proceeds after the closing of the First Amendment, it did not exercise our right to draw the Term C Loan prior to December 31, 2014.

        The future principal payments under the New Credit Facility, as amended, are as follows, as of December 31, 2014 (in thousands):

                                                                                                                                                                                    

        On May 30, 2014, pursuant to the Loan and Security Agreement with Solar and Oxford, the Company issued to Solar and Oxford warrants to purchase an aggregate of up to 10,258 shares of its series B-2 convertible preferred stock ("Series B-2") at an exercise price equal to $61.42 per share. The warrants were initially classified as liabilities in the Company's balance sheet and were re-measured at their estimated fair value through completion of the Company's initial public offering. The changes in fair value are recorded as other (expense) income in the statement of operations. Upon the closing of its initial public offering at a price of $8.00 per share and the automatic conversion of the Series B-2 into common stock, these warrants became exercisable for up to 78,760 shares of common stock. Subsequent to the initial public offering, the Company's warrant liability was reclassified to equity. On July 10, 2014, pursuant to the First Amendment and closing of the Modified Term B Loan, the Company issued both Solar and Oxford warrants to purchase up to 4,706 shares of common stock, each at a price per share equal to $12.75.

        These warrants are immediately exercisable for cash or by net exercise and will expire five years from their issuance.

        The initial fair value of the warrants issued in connection with the Initial Term Loan was $0.3 million and was recorded as a discount to the Initial Term Loan. The initial fair value of the warrants issued in connection with the First Amendment was $41 thousand and was recorded as a discount to the Modified Term B Loan. The Company also paid Solar and Oxford a facility fee of $0.3 million and reimbursed certain costs associated with the Loan and Security Agreement of approximately $0.1 million, both of which were also recorded as a discount to the Initial Term Loan. The discount is being amortized to interest expense over the 48 month period that the Initial Term Loan is expected to be outstanding using the effective interest method.