BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 171,002	$ 79,741
Receivables	782	3,330
Prepaid expenses and other current assets	19,836	22,421
Total current assets	191,620	105,492
Property and equipment, net	3,784	1,110
Right of use asset	2,079	2,272
Deposits	130	130
Other non-current assets	666	110
Total assets	198,279	109,114
Current liabilities:
Accounts payable	396	906
Accrued expenses	15,355	10,846
Lease liability - current portion	828	774
Total current liabilities	16,579	12,526
Lease liability - noncurrent portion	1,363	1,578
Total liabilities	17,942	14,104
Commitments and contingencies (Note 6)
Stockholders' equity:
Common stock, $0.001 par value; 250,000,000 shares authorized; 214,286,337 and 181,803,320 shares issued and outstanding at March 31, 2020 and December 31, 2019, respectively	214	182
Additional paid-in capital	882,541	778,953
Accumulated deficit	(702,418)	(684,125)
Total stockholders' equity	180,337	95,010
Total liabilities and stockholders' equity	$ 198,279	$ 109,114

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).