15. Related Parties

In January 2017, the Company loaned $0.7 million to the chairman of its board of directors to purchase shares of common stock pursuant to a promissory note and a restricted stock agreement (see Note 10). In May 2017, the Company loaned $1.8 million to the chairman of its board of directors to purchase shares of common stock pursuant to a promissory note and a restricted stock agreement (see Note 10). The January 2017 promissory note provided that the unpaid principal amount of the loan bore interest at 1.97% annually, and the May 2017 promissory note provided that the unpaid principal amount of the loan bore interest at 2.04% annually. Interest was payable annually or was converted to principal and payable at the maturity date. The maturity date of the promissory notes occurred on the earliest of (i) seven years from the issuance date of the notes, (ii) 60 days following the date of termination of services of the borrower, and (iii) immediately prior to an initial filing of a registration statement by the Company. The promissory notes were partial-recourse and secured by a pledge of the shares of common stock purchased with the promissory notes. As of December 31, 2017, no amounts were due to the Company and no amounts had been received by the Company as repayment of these promissory notes. On June 21, 2018, the aggregate principal balance of both promissory notes of $2.5 million and all interest that had accrued thereon, totaling $0.1 million, was forgiven by the Company and the promissory notes were terminated.

In April 2017, the Company loaned $0.2 million to an executive officer of the Company to purchase shares of common stock pursuant to two promissory notes and two restricted stock agreements (see Note 10). The promissory notes provided that the unpaid principal amount of the loans bore interest at 2.05% annually, and interest was payable annually or was converted to principal and payable at the maturity date. The maturity date of the promissory notes occurred on the earliest of (i) seven years from the issuance date of the notes, (ii) 60 days following the date of termination of employment of the borrower, and (iii) immediately prior to an initial filing of a registration statement by the Company. The promissory notes were partial-recourse and secured by a pledge of the shares of common stock purchased with the promissory notes. As of December 31, 2017, no amounts were due to the Company and no amounts had been received by the Company as repayment of these promissory notes. On June 21, 2018, the aggregate principal balance of both promissory notes of $0.2 million and all interest that had accrued thereon, totaling less than $0.1 million, was repaid in full by the executive officer and the promissory notes were terminated.

​