STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2015

STOCK BASED COMPENSATION

Summary of stock option activity

				Weighted-
		Weighted-		average
		average		remaining	Aggregate
		exercise price		contractual	Intrinsic
	Shares	per share		term (years)	Value
Outstanding at December 31, 2014	281,029	$	0.69	7.49	$	1,505
Granted	1,350,952		11.46
Exercised	(173,251)		2.99
Cancelled	(6,581)		14.54
Outstanding at December 31, 2015	1,452,149	$	10.37	10.36	$	24,887
Exercisable at December 31, 2015	205,891	$	3.75	7.9	$	4,890
Vested and expected to vest at December 31, 2015	1,436,582	$	10.46	9.1	$	26,061

Summary of restricted stock awards

		Weighted average
		purchase price
	Shares	per share
Unvested at December 31, 2014	15,387		0.69
Granted	194,694		5.73
Vested	(134,363)		5.15
Unvested at December 31, 2015	75,718	$	5.73

Schedule of stock-based compensation for all stock options and restricted stock awards

	Years Ended December 31,
		2015		2014		2013
Research and development	$	223	$	12	$	24
General and administrative		1,986		10		38
Total stock-based compensation expense	$	2,209	$	22	$	62

Schedule of weighted-average assumptions used in Black-Scholes option-pricing model

	Years Ended December 31,
	2015		2014		2013
Risk-free interest rate	1.70	%	1.8	%	1.09 - 1.22	%
Volatility	77.0	%	77.1	%	87.8	%
Expected term (years)	6.20		6.25		6.25
Expected dividend yield	—	%	—	%	—	%