Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 124,184	$ 67,005
Restricted cash		158
Short-term investments	79,932
Accounts receivable, net	4,994	4,218
Inventory	7,152	4,973
Prepaid expenses and other current assets	3,482	3,122
Total current assets	219,744	79,476
Property and equipment, net	36,612	25,867
Long-term investments	56,619
Other assets	8,186	3,265
Total assets	321,161	108,608
Current liabilities:
Accounts payable	6,956	5,582
Accrued expenses and other current liabilities	27,419	19,707
Financing liability — current	6,977
Paycheck Protection Program loan — current		4,061
Deferred revenue — current	827	33,275
Recognized loss on purchase commitments — current	6,170	11,080
Total current liabilities	48,349	73,705
Promissory notes	18,425	63,027
Accrued interest — promissory notes	404	4,150
Financing liability — long term	93,525
Long-term Midcap credit facility	38,833	49,335
Senior convertible notes	223,944
Recognized loss on purchase commitments — long term	76,659	84,208
Operating lease liability	1,040	1,202
Deferred revenue — long term	19,543	1,662
Milestone rights liability	4,838	5,926
2024 convertible notes		5,000
Paycheck Protection Program loan — long term		812
Deposits from customer	4,950
Total liabilities	530,510	289,027
Commitments and contingencies (Note 13)
Stockholders' deficit:
Undesignated preferred stock, $0.01 par value — 10,000,000 shares authorized; no shares issued or outstanding at December 31, 2021 and 2020
Common stock, $0.01 par value — 400,000,000 shares authorized, 251,477,562 and 242,117,089 shares issued and outstanding at December 31, 2021 and 2020, respectively	2,515	2,421
Additional paid-in capital	2,918,205	2,866,303
Accumulated deficit	(3,130,069)	(3,049,143)
Total stockholders' deficit	(209,349)	(180,419)
Total liabilities and stockholders' deficit	$ 321,161	$ 108,608