Debt	3 Months Ended
Mar. 31, 2019
Debt
Debt	10. Debt Credit Line Agreement In September 2015, the Company entered into a credit line with UBS (the “Credit Line”) providing for a $50.0 million revolving line of credit that can be drawn down in increments at any time. The Credit Line bears interest at 30-day LIBOR plus 1.10%. The Credit Line is secured by a first priority lien and security interest in the Company’s money market and marketable securities held in its managed investment account with UBS. UBS has the right to demand full or partial payment of the Credit Line Obligations and terminate the Credit Line, in its discretion and without cause, at any time. For the three months ended March 31, 2019 and 2018, the Company recorded interest expense of $0.4 million and $0.3 million, respectively, which were paid within the same periods. As of March 31, 2019, remaining accrued interest was $1.2 million, and the total principal amount outstanding with accrued interest was $50.2 million. 2017 Term Loan In August 2017, the Company entered into the 2017 Term Loan with OrbiMed, which has a maximum borrowing capacity of $100.0 million. On the closing date of August 8, 2017, the Company borrowed $75.0 million, with the remaining $25.0 million available to borrow at the Company’s option at any time through December 31, 2018, subject to standard conditions. The amounts borrowed under 2017 Term Loan will primarily be used for general corporate purposes and to fund and support the Company’s business and operations. Interest is accrued on the outstanding balance of the loan at a rate equal to the sum of (i) 8.75% plus (ii) the higher of 1.00% or LIBOR. The 2017 Term Loan has an eighty-four month term and will mature in August 2024. The Company is required to make interest payments on a quarterly basis, with repayment of the full outstanding balance on the maturity date. The Company’s obligations under the 2017 Term Loan are secured by substantially all of its assets, including its intellectual property, subject to certain customary exceptions. On December 31, 2018, the Company amended certain terms in the 2017 Term Loan with OrbiMed. The amendment increased the existing unused borrowing capacity from $25.0 million to $50.0 million and extended the expiration date for the option to draw the unused capacity to March 31, 2019. If such option were exercised by the Company, the interest rate described above would instead decrease to the sum of (i) 8.50% plus (ii) the higher of 1.00% or LIBOR. As of March 31, 2019, the Company did not exercise such option. The 2017 Term Loan contains customary affirmative and negative covenants including financial information maintenance covenants, indebtedness limitation covenants, minimum net revenues covenants, and investment covenants. It also includes standard events of default such as payment defaults and nonperformance of obligations and covenants described above. Upon an event of default, an additional interest of 3.00% may be applied to the outstanding debt balance until such default is cured, and OrbiMed may declare all outstanding obligations immediately due and payable. As of March 31, 2019, the Company was in compliance with all of its covenants under the 2017 Term Loan. The Company is allowed to voluntarily make prepayments on its outstanding debt balance either partially or in full. When prepayments are made, an additional prepayment premium will be applied to the outstanding principal amount at the time. The prepayment premium will gradually reduce from 12.5% to 2.5% over the term of the loan. The Company paid OrbiMed a fee in consideration of providing the 2017 Term Loan by issuing 300,000 shares of its common stock. The fair value of the fee was $2.4 million, and with legal fees of $0.3 million paid in connection with this term loan, the total of $2.7 million is accounted for as a debt discount to be amortized on a straight-line basis over the term of the loan. The Company has classified $2.0 million of the debt discount as a direct reduction from the outstanding debt balance of $75.0 million, while the remainder is classified as noncurrent assets (as described in Note 6). For the three months ended March 31, 2019 and 2018, the Company recorded interest expense totaling $2.3 million and $2.0 million, respectively, which also included the amortization of debt discount. Debt discount amortized as interest expense in the statements of operations and comprehensive loss was $0.1 million in both periods. In addition, the Company made interest payments totaling $2.2 million and $1.9 million during the three months ended March 31, 2019 and 2018, respectively. As of March 31, 2019, the amount of the unamortized debt discount was $1.6 million, and the net carrying amount of the debt was $73.4 million.

10. Debt

Credit Line Agreement

In September 2015, the Company entered into a credit line with UBS (the “Credit Line”) providing for a $50.0 million revolving line of credit that can be drawn down in increments at any time. The Credit Line bears interest at 30-day LIBOR plus 1.10%. The Credit Line is secured by a first priority lien and security interest in the Company’s money market and marketable securities held in its managed investment account with UBS. UBS has the right to demand full or partial payment of the Credit Line Obligations and terminate the Credit Line, in its discretion and without cause, at any time.

For the three months ended March 31, 2019 and 2018, the Company recorded interest expense of $0.4 million and $0.3 million, respectively, which were paid within the same periods. As of March 31, 2019, remaining accrued interest was $1.2 million, and the total principal amount outstanding with accrued interest was $50.2 million.

2017 Term Loan

In August 2017, the Company entered into the 2017 Term Loan with OrbiMed, which has a maximum borrowing capacity of $100.0 million. On the closing date of August 8, 2017, the Company borrowed $75.0 million, with the remaining $25.0 million available to borrow at the Company’s option at any time through December 31, 2018, subject to standard conditions. The amounts borrowed under 2017 Term Loan will primarily be used for general corporate purposes and to fund and support the Company’s business and operations. Interest is accrued on the outstanding balance of the loan at a rate equal to the sum of (i) 8.75% plus (ii) the higher of 1.00% or LIBOR. The 2017 Term Loan has an eighty-four month term and will mature in August 2024. The Company is required to make interest payments on a quarterly basis, with repayment of the full outstanding balance on the maturity date. The Company’s obligations under the 2017 Term Loan are secured by substantially all of its assets, including its intellectual property, subject to certain customary exceptions.

On December 31, 2018, the Company amended certain terms in the 2017 Term Loan with OrbiMed. The amendment increased the existing unused borrowing capacity from $25.0 million to $50.0 million and extended the expiration date for the option to draw the unused capacity to March 31, 2019. If such option were exercised by the Company, the interest rate described above would instead decrease to the sum of (i) 8.50% plus (ii) the higher of 1.00% or LIBOR. As of March 31, 2019, the Company did not exercise such option.

The 2017 Term Loan contains customary affirmative and negative covenants including financial information maintenance covenants, indebtedness limitation covenants, minimum net revenues covenants, and investment covenants. It also includes standard events of default such as payment defaults and nonperformance of obligations and covenants described above. Upon an event of default, an additional interest of 3.00% may be applied to the outstanding debt balance until such default is cured, and OrbiMed may declare all outstanding obligations immediately due and payable. As of March 31, 2019, the Company was in compliance with all of its covenants under the 2017 Term Loan.

The Company is allowed to voluntarily make prepayments on its outstanding debt balance either partially or in full. When prepayments are made, an additional prepayment premium will be applied to the outstanding principal amount at the time. The prepayment premium will gradually reduce from 12.5% to 2.5% over the term of the loan.

The Company paid OrbiMed a fee in consideration of providing the 2017 Term Loan by issuing 300,000 shares of its common stock. The fair value of the fee was $2.4 million, and with legal fees of $0.3 million paid in connection with this term loan, the total of $2.7 million is accounted for as a debt discount to be amortized on a straight-line basis over the term of the loan. The Company has classified $2.0 million of the debt discount as a direct reduction from the outstanding debt balance of $75.0 million, while the remainder is classified as noncurrent assets (as described in Note 6).

For the three months ended March 31, 2019 and 2018, the Company recorded interest expense totaling $2.3 million and $2.0 million, respectively, which also included the amortization of debt discount. Debt discount amortized as interest expense in the statements of operations and comprehensive loss was $0.1 million in both periods. In addition, the Company made interest payments totaling $2.2 million and $1.9 million during the three months ended March 31, 2019 and 2018, respectively. As of March 31, 2019, the amount of the unamortized debt discount was $1.6 million, and the net carrying amount of the debt was $73.4 million.