SHARE-BASED COMPENSATION (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Compensation Expenses Related to Share Based Compensation

The compensation expense related to the Company’s share-based compensation arrangements has been included in the condensed consolidated statements of comprehensive loss as follows (in thousands):

	Three Months Ended March 31,
	2018		2017
General and administrative	$	7,256	$	5,453
Research and development		12,623		3,523
Total share-based compensation expense	$	19,879	$	8,976

Weighted-Average Assumptions for Stock Option Grants using Black-Scholes Option-Pricing Model

The estimated fair value of each stock option granted was determined on the date of grant using the Black-Scholes option-pricing model with the following weighted-average assumptions for the stock option grants:

	Three Months Ended March 31,
	2018	2017
Risk-free interest rate	2.4%	2.0%
Expected volatility of common stock	60.6%	58.1%
Dividend yield	0.0%	0.0%
Expected option term	4.7 years	5.8 years