In September 2015, the Company adopted the 2015 Omnibus Incentive Plan (the “2015 Plan”). Under the 2015 Plan, the Company can issue various types of equity compensation awards such as share options, restricted shares, performance shares, restricted stock units (“RSUs”), performance units, long-term cash awards and other share-based awards.

Options granted under the 2015 Plan generally have a four-year vesting period and expire ten years after the date of grant. Options granted under the 2015 Plan that are cancelled or forfeited before expiration become available for future grants. RSUs granted under the 2015 Plan generally vest over a three-year period. RSUs granted under the 2015 Plan that are cancelled before expiration become available for future grants. As of March 31, 2019, 12,649,222 ordinary shares were available for grant under the 2015 Plan.

A summary of the status of the Company’s option plans as of March 31, 2019 and changes during the period then ended is presented below:

	Three months ended March 31, 2019
	Unaudited
	Number of options			Weighted average exercise price
Outstanding at beginning of year		14,438,215		$	13.56
Granted		751,471			47.04
Exercised		(2,047,421	)		8.38
Forfeited and cancelled		(40,258	)		14.47
Outstanding as of March 31, 2019		13,102,007		$	16.29

Exercisable options		5,852,344		$	12.79

For the three months, ended March 31, 2019, options to purchase 2,047,421 ordinary shares were exercised, resulting in the issuance of 2,047,421 ordinary shares.

A summary of the status of the Company’s RSUs as of March 31, 2019 and changes during the period then ended is presented below:

	Three months ended March 31, 2019
	Unaudited
	Number of RSUs			Weighted average grant date fair value price
Unvested at beginning of year		1,613,197		$	14.04
Granted		486,506			47.04
Vested		(391,191	)		12.09
Forfeited and cancelled		(3,837	)		21.15
Unvested as of March 31, 2019		1,704,675		$	23.89

In September 2015, the Company adopted an employee share purchase plan (“ESPP”) to encourage and enable eligible employees to acquire ownership of the Company’s ordinary shares purchased through accumulated payroll deductions on an after-tax basis. In the United States, the ESPP is intended to be an “employee stock purchase plan” within the meaning of Section 423 of the Internal Revenue Code and the provisions of the ESPP will be construed in a manner consistent with the requirements of such section. The Company began its offerings under the ESPP on August 1, 2016. As of March 31, 2019, 3,122,410 ordinary shares were available to be purchased by eligible employees under the ESPP and 347,193 shares had been issued under the ESPP.

The fair value of share-based awards was estimated using the Black-Scholes model for all equity grants. For market condition awards, the Company also applied the Monte-Carlo simulation model, with the following underlying assumptions:

	Three months ended March 31,		Year ended December 31,
	2019	2018	2018
	Unaudited		Audited
Stock Option Plans
Expected term (years)	6.23	6.25	5.50-6.25
Expected volatility	55%	55%	52%-55%
Risk-free interest rate	2.40%	2.77%	2.70%-2.99%
Dividend yield	0.00%	0.00%	0.00%
ESPP
Expected term (years)	0.50	0.50	0.50
Expected volatility	62%	53%	45%-53%
Risk-free interest rate	2.51%	1.61%	1.61%-2.14%
Dividend yield	0.00%	0.00%	0.00%

The total non-cash share-based compensation expense related to all of the Company’s equity-based awards recognized for the three months ended March 31, 2019 and 2018 and the year ended December 31, 2018 was:

	Three months ended March 31,				Year ended December 31,
	2019		2018		2018
	Unaudited				Audited
Cost of revenues	$	426	$	164	$	1,261
Research, development and clinical trials		1,188		906		4,709
Sales and marketing		1,962		1,436		7,393
General and administrative		6,073		6,014		26,483
Total share-based compensation expense	$	9,649	$	8,520	$	39,846