12. Notes payable

Loan agreement

On April 14, 2014, the Company executed a Loan Agreement with a lender, as subsequently amended. As of March 31, 2020, there were no additional amounts available to borrow under the debt facility. The interest rate on this term loan is variable based on a calculation of the prime rate less 5.25% with a minimum interest rate of 8%. Interest is paid monthly beginning the month following the borrowing date. At loan inception and in connection with the amendments, the Company issued the lender warrants to purchase shares of stock. The Loan Agreement also contains prepayment penalties and an end of term charge. Fees incurred upon execution of the agreements, and the fair value of warrants on the date of grant were accounted for as a reduction in the book value of debt and accreted through interest expense, using the effective interest rate method, over the term of the debt.

Amendment 5 to loan agreement

In August 2018, the Company signed Amendment 5 to the Loan Agreement (Amendment 5). Amendment 5 instituted a 2018 End of Term Charge of $0.1 million. Additionally, the Term Loan Maturity Date extended until March 1, 2020. Amendment 5 additionally, changed the due date of the End of Term Charge to, the earlier of (i) the Term Loan Maturity Date, (ii) the date that Borrower prepays the outstanding Secured Obligations or (iii) the date that the Secured Obligations become due and payable. The Company incurred a cost of $0.05 million in relation to the execution of Amendment 5. In connection with the extension of the due date of the Loan, the deferral of principal payments (Amendment 3) was further deferred until the new Term Loan Maturity Date.

On March 2, 2020, the Company paid $0.1 million in end of term fees related to Amendment 5 of the Loan Agreement.

Amendment 6 to loan agreement

In October 2018, the Company signed Amendment 6 to the Loan Agreement, which amended the Loan Agreement’s collateral clause to exclude the $1 million certificate of deposit associated with the lease on the Company’s new headquarters in Billerica, MA.

Amendment 7 to loan agreement

On April 15, 2019, the Company signed Amendment 7 to the Loan Agreement, which extends the interest only payment period through July 1, 2021 and also extends the maturity date until October 1, 2021. As part of this Amendment 7, a “2019 End of Term Charge” for $50,000 was added to the Loan Agreement due on the earliest to occur of (i) the Term Loan Maturity Date, (ii) the date that the Company prepays the outstanding Secured Obligations and (iii) the date that the Secured Obligations become due and payable. In addition, the Company is required to pay the loan principal in five equal installments starting July 1, 2021 with the final principal payment to be made on October 1, 2021. As of March 31, 2020, the remaining loan balance is classified as a long term liability since all principal payments are due greater than twelve months after the balance sheet date.

As of March 31, 2020, debt payment obligations due based on principal payments are as follows (in thousands):


Remainder 2020	$	—
2021		7,688
	$	7,688

Non‑cash interest expense related to debt discount amortization and accretion of end of term fees was $0.1 million or less for each of the three months ended March 31, 2020 and 2019.