CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 72,564	$ 107,511
Short-term investments	171,108	196,421
Prepaid expenses and other current assets	6,859	8,687
Total current assets	250,531	312,619
Long-term investments	6,584
Property and equipment, net	29,414	26,328
Operating lease right-of-use assets	11,736
Prepaid expenses and other assets	511	608
Total assets	298,776	339,555
Current liabilities:
Accounts payable	14,086	8,833
Accrued liabilities	27,083	29,144
Operating lease liabilities, current	2,022
Other current liabilities	20	35
Total current liabilities	43,211	38,012
Long term debt, net of discount	38,526
Operating lease liabilities, non-current	11,036
Other liabilities	1,029	2,596
Total liabilities	93,802	40,608
Stockholders’ equity:
Preferred stock, par value $0.0001 per share— 10,000 shares authorized at June 30, 2019 and December 31, 2018; 0 shares issued and outstanding at June 30, 2019 and December 31, 2018
Common stock, par value $0.0001 per share—290,000 shares authorized as of June 30, 2019, and December 31, 2018; 62,660 and 62,142 shares issued and outstanding as of June 30, 2019, and December 31, 2018, respectively	6	6
Additional paid-in capital	798,058	775,283
Accumulated other comprehensive gain(loss)	236	(108)
Accumulated deficit	(593,326)	(476,234)
Total stockholders’ equity	204,974	298,947
Total liabilities and stockholders’ equity	$ 298,776	$ 339,555