CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Current assets:    
Cash and cash equivalents $ 288,086 $ 91,165
Investments 42,564 85,122
Prepaid expenses and other current assets 5,608 5,224
Total current assets 336,258 181,511
Operating lease, right-of-use-asset 39,106 40,447
Property, plant and equipment, net 53,293 53,952
Restricted cash 1,573 1,573
Other assets   311
Total assets 430,230 277,794
Current liabilities:    
Accounts payable 4,810 5,478
Accrued expenses and other current liabilities 7,587 13,417
Current portion of long-term debt, net of discount 9,375  
Operating lease liabilities 8,897 8,945
Total current liabilities 30,669 27,840
Long-term debt, net of discount and current portion 66,262 74,944
Other long-term liabilities 654 688
Operating lease liabilities, net of current portion 31,662 32,762
Total liabilities 129,247 136,234
Commitments and contingencies (see Note 9)
Stockholders' equity:    
Preferred stock, $0.001 par value; 10,000,000 shares authorized at March 31, 2021 and December 31, 2020; no shares issued or outstanding at March 31, 2021 and December 31, 2020
Common stock, $0.001 par value; 150,000,000 shares authorized at March 31, 2021 and December 31, 2020; 89,187,527 and 81,053,651 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively 89 81
Additional paid-in capital 823,688 621,946
Accumulated other comprehensive income 7 4
Accumulated deficit (522,801) (480,471)
Total stockholders' equity 300,983 141,560
Total liabilities and stockholders' equity $ 430,230 $ 277,794