Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 41,142	$ 38,501
Marketable securities		501
Funds receivable from New Jersey net operating loss		1,090
Accounts receivable, net	28	34
Prepaid expenses and other current assets	155	184
Total current assets	41,325	40,310
Property and equipment, net	6,145	6,473
Right of use asset, net	157	179
Patent and trademark rights, net	1,783	1,498
Marketable securities, long term	16,135	15,376
Other assets	1,177	748
Total assets	66,722	64,584
Current liabilities:
Accounts payable	451	383
Accrued expenses	373	442
Current portion of operating lease liability	52	47
Current portion of financing obligation		230
Total current liabilities	876	1,102
Long-term liabilities:
Operating lease liability	105	132
Financing obligation arising from sale leaseback transaction (Note 13)		1,876
Redeemable warrants	209	180
Commitments and contingencies (Notes 11, 12, 13, and 14)
Stockholders’ equity:
Series B Convertible Preferred Stock, stated value $1,000 per share, 725 shares designated, 732 shares issued and outstanding	725	732
Common Stock, par value $0.001 per share, authorized 350,000,000 shares: issued and outstanding 47,832,997 and 42,154,371, respectively	48	42
Additional paid-in capital	416,435	402,541
Accumulated other comprehensive loss	(247)	(47)
Accumulated deficit	(351,429)	(341,974)
Total stockholders’ equity	65,532	61,294
Total liabilities and stockholders’ equity	$ 66,722	$ 64,584