Loan and Security Agreements	9 Months Ended
Sep. 30, 2017
Loan and Security Agreements
Loan and Security Agreements	6. Loan and Security Agreements Oxford Finance LLC In December 2012, the Company entered into a Loan and Security Agreement (the “Oxford Loan”) with Oxford Finance LLC (“Oxford”) pursuant to which the Company borrowed a total of $15.0 million from Oxford. The Oxford Loan accrued interest at a fixed annual rate equal to 9.20% (Three-month U.S. Libor rate of 0.47% plus 8.73%). Interest on the Oxford Loan was payable monthly and principal was due in 30 equal consecutive monthly installments beginning on February 1, 2015 and ending on July 1, 2017. In addition, the Company was required to make a final payment of $675 on the maturity date of the Oxford Loan (July 1, 2017). In connection with the Oxford Loan, the Company issued Oxford warrants to purchase 62,505 shares of common stock at an exercise price of $6.00 per share. These warrants expire on December 14, 2019. In February 2015, the Company terminated and repaid all amounts outstanding under the Oxford Loan and recorded a loss on the extinguishment of the Oxford Loan (see further discussion below). Hercules Capital, Inc. In February 2015, the Company entered into a loan and security agreement (the “Hercules Loan”) with Hercules Capital, Inc. (“Hercules”) for a term loan of up to $25.0 million. In August 2016, the Company entered into the First Amendment to Loan and Security Agreement (the “First Amendment”) with Hercules which amended certain terms of the Hercules Loan. In May 2017, the Company entered into the Second Amendment to Loan and Security Agreement (the “Second Amendment”) with Hercules which further amended certain terms of the Hercules Loan. A first tranche of $16.5 million was funded upon execution of the Hercules Loan, approximately $15.5 million of which was used to repay the Company’s existing term loan with Oxford. The First Amendment extended the Company’s option to draw down the second tranche of $8.5 million (the “Second Term Loan Advance”) of the term loan facility provided under the Hercules Loan (the “Term Loan”) until March 31, 2017, and makes the Second Term Loan Advance subject to the consent of Hercules, among other customary conditions. The Second Amendment further extended the Company’s option to draw the Second Term Loan Advance until January 31, 2018, and continues to make the Second Term Loan Advance subject to the consent of Hercules, among other customary conditions. The First Amendment also extended the interest-only payments until January 31, 2017, in connection with the first tranche of $16.5 million (the “First Term Loan Advance” and together with the Second Term Loan Advance, the “Term Loan Advances”). The First Amendment provides the Term Loan will mature on December 1, 2018. As a result of the First Amendment, and in connection with the extension of the interest-only period from the First Term Loan Advance, Hercules returned to the Company the principal payments paid by the Company in July and August 2016, which such returned payments will once again constitute outstanding Term Loan advances under the Hercules Loan. In connection with the execution of the First Amendment, the Company paid Hercules a facility fee of $165. The facility fee represents a debt issue cost which is being reflected as a reduction to the carrying amount of loan payable in accordance with ASU 2015-03. Such issue costs are being amortized to interest expense over the life of the loan using the effective interest method. The Hercules Loan accrues interest at a rate of the greater of 9.0% or 9.0% plus Prime minus 4.25% and is payable monthly. Principal is due in 23 consecutive monthly installments beginning on February 1, 2017 and ending on December 1, 2018. In addition, the Company is required to make a final payment of $610.5 on the maturity date of the Hercules Loan (December 1, 2018). The amount of the end of term final payment is being accrued over the loan term as interest expense. The Company may prepay all, but not less than all, of the Hercules Loan subject to a prepayment premium of 1.0% of the outstanding principal. The obligations of the Company under the Hercules Loan are secured by a perfected first position lien on all of the assets of the Company, excluding intellectual property assets. In connection with the Hercules Loan, the Company issued Hercules a warrant to purchase 180,274 shares of the Company’s common stock at an exercise price of $5.89 per share which expires on February 24, 2020 and granted Hercules the right to participate in future equity financings in an amount up to $2.0 million while the loan and warrant are outstanding. The Company allocated the proceeds of $16.5 million in accordance with ASC 470 based on the relative fair values. The relative fair value of the warrants of approximately $1.2 million at the time of issuance, which was determined using the Black-Scholes option pricing model, was recorded as additional paid-in capital and reduced the carrying value of the debt. The significant assumptions used in preparing the option pricing model for valuing the Company’s warrant issued to Hercules include (i) volatility (75.0%), (ii) risk free interest rate of 1.22% (estimated using treasury bonds with a 4 year life), (iii) strike price ($5.89) for the common stock warrant, (iv) fair value of common stock ($9.82) and (v) expected life (four years). The discount on the debt is being amortized to interest expense over the term of the debt.

6. Loan and Security Agreements

Oxford Finance LLC

In December 2012, the Company entered into a Loan and Security Agreement (the “Oxford Loan”) with Oxford Finance LLC (“Oxford”) pursuant to which the Company borrowed a total of $15.0 million from Oxford. The Oxford Loan accrued interest at a fixed annual rate equal to 9.20% (Three-month U.S. Libor rate of 0.47% plus 8.73%).

Interest on the Oxford Loan was payable monthly and principal was due in 30 equal consecutive monthly installments beginning on February 1, 2015 and ending on July 1, 2017. In addition, the Company was required to make a final payment of $675 on the maturity date of the Oxford Loan (July 1, 2017).

In connection with the Oxford Loan, the Company issued Oxford warrants to purchase 62,505 shares of common stock at an exercise price of $6.00 per share. These warrants expire on December 14, 2019.

In February 2015, the Company terminated and repaid all amounts outstanding under the Oxford Loan and recorded a loss on the extinguishment of the Oxford Loan (see further discussion below).

Hercules Capital, Inc.

In February 2015, the Company entered into a loan and security agreement (the “Hercules Loan”) with Hercules Capital, Inc. (“Hercules”) for a term loan of up to $25.0 million. In August 2016, the Company entered into the First Amendment to Loan and Security Agreement (the “First Amendment”) with Hercules which amended certain terms of the Hercules Loan. In May 2017, the Company entered into the Second Amendment to Loan and Security Agreement (the “Second Amendment”) with Hercules which further amended certain terms of the Hercules Loan. A first tranche of $16.5 million was funded upon execution of the Hercules Loan, approximately $15.5 million of which was used to repay the Company’s existing term loan with Oxford.

The First Amendment extended the Company’s option to draw down the second tranche of $8.5 million (the “Second Term Loan Advance”) of the term loan facility provided under the Hercules Loan (the “Term Loan”) until March 31, 2017, and makes the Second Term Loan Advance subject to the consent of Hercules, among other customary conditions. The Second Amendment further extended the Company’s option to draw the Second Term Loan Advance until January 31, 2018, and continues to make the Second Term Loan Advance subject to the consent of Hercules, among other customary conditions. The First Amendment also extended the interest-only payments until January 31, 2017, in connection with the first tranche of $16.5 million (the “First Term Loan Advance” and together with the Second Term Loan Advance, the “Term Loan Advances”).

The First Amendment provides the Term Loan will mature on December 1, 2018. As a result of the First Amendment, and in connection with the extension of the interest-only period from the First Term Loan Advance, Hercules returned to the Company the principal payments paid by the Company in July and August 2016, which such returned payments will once again constitute outstanding Term Loan advances under the Hercules Loan. In connection with the execution of the First Amendment, the Company paid Hercules a facility fee of $165. The facility fee represents a debt issue cost which is being reflected as a reduction to the carrying amount of loan payable in accordance with ASU 2015-03. Such issue costs are being amortized to interest expense over the life of the loan using the effective interest method.

The Hercules Loan accrues interest at a rate of the greater of 9.0% or 9.0% plus Prime minus 4.25% and is payable monthly. Principal is due in 23 consecutive monthly installments beginning on February 1, 2017 and ending on December 1, 2018. In addition, the Company is required to make a final payment of $610.5 on the maturity date of the Hercules Loan (December 1, 2018). The amount of the end of term final payment is being accrued over the loan term as interest expense.

The Company may prepay all, but not less than all, of the Hercules Loan subject to a prepayment premium of 1.0% of the outstanding principal. The obligations of the Company under the Hercules Loan are secured by a perfected first position lien on all of the assets of the Company, excluding intellectual property assets.

In connection with the Hercules Loan, the Company issued Hercules a warrant to purchase 180,274 shares of the Company’s common stock at an exercise price of $5.89 per share which expires on February 24, 2020 and granted Hercules the right to participate in future equity financings in an amount up to $2.0 million while the loan and warrant are outstanding.

The Company allocated the proceeds of $16.5 million in accordance with ASC 470 based on the relative fair values. The relative fair value of the warrants of approximately $1.2 million at the time of issuance, which was determined using the Black-Scholes option pricing model, was recorded as additional paid-in capital and reduced the carrying value of the debt. The significant assumptions used in preparing the option pricing model for valuing the Company’s warrant issued to Hercules include (i) volatility (75.0%), (ii) risk free interest rate of 1.22% (estimated using treasury bonds with a 4 year life), (iii) strike price ($5.89) for the common stock warrant, (iv) fair value of common stock ($9.82) and (v) expected life (four years). The discount on the debt is being amortized to interest expense over the term of the debt.