10. Share-Based Compensation

On November 18, 2015, the Company’s Board of Directors adopted and approved the 2015 Equity Incentive Plan (the “2015 Plan”), which authorized the Company to grant up to 223,424 ordinary shares in the form of incentive share options, nonstatutory share options, share appreciation rights, restricted share awards, restricted share units and other share awards. The types of share-based awards, including the rights, amount, terms, and exercisability provisions of grants are determined by the Company’s Board of Directors. The purpose of the 2015 Plan is to provide the Company with the flexibility to issue share-based awards as part of an overall compensation package to attract and retain qualified personnel. On May 18, 2017, the Company amended the 2015 Plan to increase the number of ordinary shares available for issuance under the 2015 Plan by 219,605 shares to 443,029 shares.

On March 14, 2018, the Company’s Board of Directors adopted and approved the 2018 Equity Incentive Plan (the “2018 Plan”), which became effective upon the execution and delivery of the underwriting agreement related to the Company’s IPO in May 2018. No further grants will be made under the 2015 Plan. The ordinary shares underlying any options that are forfeited, cancelled, repurchased or are otherwise terminated by the Company under the 2015 Plan will not be added back to the ordinary shares available for issuance.

The 2018 Plan, adopted and approved on March 14, 2018, authorized the Company to grant up to 1,018,459 ordinary shares in the form of incentive share options, nonstatutory share options, share appreciation rights, restricted share awards, restricted share units, performance share awards, performance cash awards and other share awards. The types of share-based awards, including the rights, amount, terms, and exercisability provisions of grants are determined by the Company’s Board of Directors. The ordinary shares underlying any options that are forfeited, cancelled, repurchased or are otherwise terminated by the Company under the 2018 Plan will be added back to the ordinary shares available for issuance under the 2018 Plan.

On December 5, 2018, pursuant to powers delegated to it by the Board of Directors of the Company, the Compensation Committee approved an increase in the number of ordinary shares available to be granted pursuant to the 2018 plan by 4% of the total number of shares of the Company’s issued share capital on December 31, 2018, being 574,081 ordinary shares.

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 records share-based compensation expense for the restricted ordinary shares based on the grant date fair value. The Company recorded an expense of $167 and $165 for the six months ended June 30, 2019 and 2018, respectively. Total unamortized compensation expense related to restricted ordinary shares was $93 and $428 as of June 30, 2019 and June 30, 2018, respectively, expected to be recognized over a weighted average period of 0.29 years and 1.29 years as of June 30, 2019 and June 30, 2018, respectively.

The following table summarizes restricted ordinary shares activity for the six months ended June 30, 2019:

Share Options

The Company awarded 512,178 and 447,984 share options to employees and directors during the six months ended June 30, 2019 and 2018, respectively, under the 2018 Plan. There were 925,549 and 663,916 unvested employee options outstanding as of June 30, 2019 and June 30, 2018, respectively. Total expense recognized related to employee share options was $655 and $189 for the six months ended June 30, 2019 and 2018, respectively. Total unamortized compensation expense related to employee share options was $4,107 and $3,549 as of June 30, 2019 and June 30, 2018, respectively, which is expected to be recognized over a remaining average vesting period of 3.07 years and 3.71 years as of June 30, 2019 and June 30, 2018, 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 share units (RSUs)

The Company granted 31,367 and 36,924 RSUs to directors during the six months ended June 30, 2019 and 2018, respectively.

The table below shows the number of RSUs granted covering an equal number of the Company’s 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 $201 and $50 for the six months ended June 30, 2019 and 2018, respectively. Total unamortized compensation expense related to RSUs was $210 and $431 as of June 30, 2019 and June 30, 2018, respectively, which is expected to be recognized over a remaining average vesting period of 0.96 years and 0.90 years as of June 30, 2019 and June 30, 2018, respectively.

The Company awarded 50,000 RSUs to certain employees during the six months ended June 30, 2019 which are subject to certain performance based vesting conditions (Performance RSUs). No Performance RSUs were awarded or outstanding during the six months ended June 30, 2018.

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

The weighted average grant date fair value of restricted share units with a market condition was determined using the Monte Carlo simulation model. The fair value of Performance RSUs is expensed ratably over the vesting period. Total expense recognized related to the Performance RSUs was $90 for the six months ended June 30, 2019. Total unamortized compensation expense related to Performance RSUs was $320 as of June 30, 2019, which is expected to be recognized over approximately the next 1.32 years as of June 30, 2019.

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

There was a total of $4,730 and $4,408 unamortized share-based compensation expense for restricted ordinary shares, options, restricted share units and performance restricted share units as of June 30, 2019 and June 30, 2018, respectively, which is expected to be recognized over a remaining average vesting period of 2.83 years and 3.21 years as of June 30, 2019 and June 30, 2018, respectively.