CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 109,611	$ 307,064
Investments	215,078	96,987
Prepaid expenses and other current assets	5,073	9,737
Restricted cash		622
Total current assets	329,762	414,410
Operating lease, right-of-use-asset	47,911
Property, plant and equipment, net	52,478	62,796
Restricted cash	1,735	1,735
Other assets	386	168
Total assets	432,272	479,109
Current liabilities:
Accounts payable	11,679	7,886
Accrued expenses and other current liabilities	14,866	7,616
Operating lease liabilities	6,998	4,502
Total current liabilities	33,543	20,004
Long-term debt, net of discount	49,509	24,347
Other long-term liabilities	438	309
Operating lease liabilities, net of current portion	41,439	41,441
Total liabilities	124,929	86,101
Commitments and contingencies (see Note 11)
Stockholders' equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized at September 30, 2019 and December 31, 2018; no shares issued or outstanding at September 30, 2019 and December 31, 2018
Common stock, $0.001 par value; 150,000,000 shares authorized at September 30, 2019 and December 31, 2018; 79,777,733 and 79,234,853 shares issued and outstanding at September 30, 2019 and December 31, 2018, respectively	80	79
Additional paid-in capital	575,365	543,040
Accumulated other comprehensive income (loss)	166	(29)
Accumulated deficit	(268,268)	(150,082)
Total stockholders' equity	307,343	393,008
Total liabilities and stockholders' equity	$ 432,272	$ 479,109