Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 270,648	$ 197,569
Short-term investments	15,455	52,086
Accounts receivable, net	1,125	0
Inventory	5,747	0
Prepaid expenses and other current assets	2,503	4,487
Total current assets	295,478	254,142
Property, plant and equipment, net	54,879	31,932
Other assets	2,604	4,202
Total assets	352,961	290,276
Current liabilities
Accounts payable	8,757	6,245
Accrued expenses and other current liabilities	20,016	18,939
Total current liabilities	28,773	25,184
Convertible notes, net	123,999	123,845
Other non-current liabilities	5,309	5,648
Total liabilities	158,081	154,677
Commitments and contingencies (Note 12)
Stockholders’ equity
Preferred stock, $0.001 par value; 15,000,000 shares authorized as of June 30, 2018 and December 31, 2017; None issued and outstanding	0	0
Common stock, $0.001 par value; 150,000,000 shares authorized as of June 30, 2018 and December 31, 2017; 39,839,373 and 36,947,637 shares issued and outstanding as of June 30, 2018 and December 31, 2017, respectively	40	37
Additional paid-in capital	754,437	597,318
Accumulated other comprehensive loss	(9)	(28)
Accumulated deficit	(559,588)	(461,728)
Total stockholders’ equity	194,880	135,599
Total liabilities and stockholders’ equity	$ 352,961	$ 290,276