9. Share-Based Compensation

The Company’s Board of Directors adopted and approved the 2015 Equity Incentive Plan in November 2015 (“the 2015 Plan”). The 2015 Plan was amended most recently in May 2017. The 2015 Plan provides for the grant of incentive stock options, nonstatutory stock options, restricted stock awards, restricted stock units, stock appreciation rights, and other stock awards to our employees, directors and consultants. On March 14, 2018, the Company’s Board of Directors adopted and approved the 2018 Equity Incentive Plan (the “2018 Plan”), which became effective on the execution and delivery of the underwriting agreement related to the IPO. The 2018 Plan authorizes the Company to grant up to 1,018,459 ordinary shares in the form of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock units, performance stock awards, performance cash awards and other stock awards. The types of share-based awards, including share purchase rights amount, terms, and exercisability provisions of grants are determined by the Company’s Board of Directors. Since the effectiveness of the 2018 Plan, the Company no longer grants awards under the 2015 Plan. However, any outstanding awards granted under the 2015 Plan will remain outstanding, subject to the terms of the 2015 Plan and stock option agreements, until such outstanding options are exercised or until they terminate or expire by their terms.

Restricted Ordinary Shares

In connection with the Company’s formation, 413,110 restricted ordinary shares were issued on October 14, 2015 to the Company’s founders at par value. These ordinary shares are subject to various restrictions pursuant to ordinary share purchase agreements between the Company and each founder, including restrictions on transfer and a Company right of repurchase. The restricted ordinary shares were 25% vested as of October 14, 2016 and 1/36th of the remaining restricted ordinary shares vest on a monthly basis thereafter (subject to acceleration of vesting in connection with certain change of control transactions). A change in status occurred on November 18, 2015 when the founders became employees of the Company. The grant date of these shares is now considered to be November 18, 2015 when the fair value was $3.14 per share.

The Company recorded an expense of $165 and $165 for the restricted ordinary shares for the six month periods ended June 30, 2018 and June 30, 2017, respectively. Total unamortized compensation expense related to restricted ordinary shares was $428 and $761 as of June 30, 2018 and June 30, 2017, respectively, expected to be recognized over a weighted average period of 1.38 years and 2.38 years as of June 30, 2018 and June 30, 2017, respectively.

The following table summarizes restricted ordinary shares activity for the six months ended June 30, 2018:

Stock Options

The Company awarded 447,984 stock options to employees and directors for the six month period ended June 30, 2018 under the 2018 Plan. The Company awarded 17,502 stock options to employees and directors during the six month period ended June 30, 2017 under the 2015 Plan. There were 663,916 and 56,596 unvested employee options outstanding as of June 30, 2018 and June 30, 2017, respectively. Total expense recognized related to the employee stock options was $189 and $15 for the six month periods ended June 30, 2018 and June 30, 2017, respectively. Total unamortized compensation expense related to employee stock options was $3,549 and $95 as of June 30, 2018 and June 30, 2017, respectively, which is expected to be recognized over a remaining average vesting period of 3.71 years and 3.28 years as of June 30, 2018 and June 30, 2017, respectively.

The assumptions that the Company used to determine the grant date fair value of employee and director options granted were as follows, presented on a weighted average basis:

The following table summarizes the number of options outstanding and the weighted-average exercise price:

Restricted stock units (RSUs)

The Company granted 36,924 RSUs to directors for the six month period ended June 30, 2018. No RSUs were awarded for the six month period ended June 30, 2017.

The table below shows the number of RSUs granted covering an equal number of our ordinary shares and the weighted-average grant date fair value of the RSUs granted:

The fair value of the RSUs is determined on the date of grant based on the market price of our ordinary shares on that date. The fair value of RSUs is expensed ratably over the vesting period, which is generally one year for directors. Total expense recognized related to the RSUs was $50 for the period ended June 30, 2018. Total unamortized compensation expense related to RSUs was $431 as of June 30, 2018, which is expected to be recognized over a remaining average vesting period of 0.9 years as of June 30, 2018.

The Company’s share-based compensation expense was classified in the consolidated statements of operations and comprehensive loss as follows:

There was a total of $4,408 and $856 unamortized share-based compensation expense for restricted ordinary shares, options and restricted stock units as of June 30, 2018 and June 30, 2017, respectively, which is expected to be recognized over a remaining average vesting period of 3.21 years and 2.48 years as of June 30, 2018 and June 30, 2017, respectively.