Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 139,682	$ 238,183
Marketable securities	262,428	218,957
Accounts receivable	6,048	418
Prepaid expenses and other current assets	10,929	6,286
Total current assets	419,087	463,844
Marketable securities	109,664
Property and equipment, net	14,020	10,887
Right-of-use assets	25,128	28,761
Restricted cash and other non-current assets	4,703	5,393
Total assets	572,602	508,885
Current liabilities:
Accounts payable	6,408	5,843
Accrued expenses	24,046	22,120
Deferred revenue, current	20,943	23,514
Operating lease liabilities	6,811	5,804
Other current liabilities		2,682
Total current liabilities	58,208	59,963
Operating lease liabilities, net of current portion	19,324	23,277
Deferred revenue, net of current portion	73,984	163,207
Other non-current liabilities	27,500	1
Total liabilities	179,016	246,448
Stockholders' equity
Preferred stock, $0.0001 par value per share: 5,000,000 shares authorized; no shares issued or outstanding
Common stock, $0.0001 par value per share: 195,000,000 shares authorized; 62,689,457 and 54,533,798 shares issued, and 62,563,457 and 54,355,798 shares outstanding at December 31, 2020 and December 31, 2019, respectively	6	5
Additional paid-in capital	1,058,823	811,546
Accumulated other comprehensive (loss) income	(46)	107
Accumulated deficit	(665,197)	(549,221)
Total stockholders' equity	393,586	262,437
Total liabilities and stockholders' equity	$ 572,602	$ 508,885

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).