Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 197,569	$ 197,945
Short-term investments	52,086	35,717
Prepaid expenses and other current assets	4,487	4,028
Total current assets	254,142	237,690
Property, plant and equipment, net	31,932	7,857
Other assets	4,202	2,707
Total assets	290,276	248,254
Current liabilities
Accounts payable	6,245	5,610
Accrued expenses and other current liabilities	18,939	13,761
Total current liabilities	25,184	19,371
Convertible notes, net	123,845	123,539
Other non-current liabilities	5,648	0
Total liabilities	154,677	142,910
Commitments and contingencies (Note 11)
Stockholders’ equity
Preferred stock, $0.001 par value; 15,000,000 shares authorized as of December 31, 2017 and December 31, 2016; None issued and outstanding	0	0
Common stock, $0.001 par value; 150,000,000 shares authorized as of December 31, 2017 and December 31, 2016; 36,947,637 and 33,458,607 shares issued and outstanding as of December 31, 2017 and December 31, 2016, respectively	37	33
Additional paid-in capital	597,318	422,002
Accumulated other comprehensive loss	(28)	(68)
Accumulated deficit	(461,728)	(316,623)
Total stockholders’ equity	135,599	105,344
Total liabilities and stockholders’ equity	$ 290,276	$ 248,254