CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($)
$ in Thousands
Jun. 30, 2019
Dec. 31, 2018
Current assets:    
Cash and cash equivalents $ 141,084 $ 307,064
Investments 221,246 96,987
Prepaid expenses and other current assets 4,196 9,737
Restricted cash 122 622
Total current assets 366,648 414,410
Operating lease, right-of-use-asset 27,643  
Property, plant and equipment, net 41,898 62,796
Restricted cash 1,735 1,735
Other assets 108 168
Total assets 438,032 479,109
Current liabilities:    
Accounts payable 2,344 7,886
Accrued expenses and other current liabilities 13,805 7,616
Operating lease liabilities 5,076 4,502
Total current liabilities 21,225 20,004
Long-term debt, net of discount 49,422 24,347
Other long-term liabilities 604 309
Operating lease liabilities, net of current portion 23,137 41,441
Total liabilities 94,388 86,101
Commitments and contingencies (see Note 11)
Stockholders' equity:    
Preferred stock, $0.001 par value; 10,000,000 shares authorized at June 30, 2019 and December 31, 2018, no shares issued or outstanding at June 30, 2019 and December 31, 2018
Common stock, $0.001 par value; 150,000,000 shares authorized at June 30, 2019 and December 31, 2018; 80,077,679 and 79,234,853 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively 80 79
Additional paid-in capital 564,527 543,040
Accumulated other comprehensive income (loss) 290 (29)
Accumulated deficit (221,253) (150,082)
Total stockholders' equity 343,644 393,008
Total liabilities and stockholders' equity $ 438,032 $ 479,109