BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 115,069	$ 79,741
Receivables	4,665	3,330
Prepaid expenses and other current assets	10,855	22,421
Total current assets	130,589	105,492
Property and equipment, net	10,231	1,110
Deposits	130	130
Right-of-use asset	4,650	2,272
Other non-current assets	745	110
Total assets	146,345	109,114
Current liabilities:
Accounts payable	960	906
Accrued expenses	16,589	10,846
Lease liability - current portion	819	774
Total current liabilities	18,368	12,526
Lease liability - noncurrent portion	3,995	1,578
Total liabilities	22,363	14,104
Commitments and contingencies (Note 9)
Stockholders' equity:
Common stock, $0.001 par value; 250,000,000 shares authorized; 214,591,906 and 181,803,320 shares issued and outstanding at December 31, 2020 and 2019, respectively	215	182
Additional paid-in capital	887,868	778,953
Accumulated deficit	(764,101)	(684,125)
Total stockholders' equity	123,982	95,010
Total liabilities and stockholders' equity	146,345	$ 109,114
Series 1 Preferred Stock
Current liabilities:
Series 1 preferred stock, $1,200 stated value; 250,000 designated; 0 shares issued and outstanding at December 31, 2020 and 2019; liquidation value of $0 million at December 31, 2020 and 2019