Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Consolidated net income (loss)	$ (7,155)	$ 1,752
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	121	157
Stock-based compensation	360	423
Debt discount accretion and non-cash interest expense		129
Amortization (accretion) of premium (discount) of available-for-sale investment securities	51	(24)
Amortization of right-of-use assets	176	201
Loss on disposal of property and equipment		6
Changes in operating assets and liabilities:
Other receivables	1,950	48
Prepaid expenses and other assets	395	188
Accounts payable and accrued expenses	(1,521)	(578)
Contract liability		(65)
Operating lease liability	(204)	(179)
Net cash provided by (used in) operating activities	(5,827)	2,058
Cash flows from investing activities:
Purchases of property and equipment	(17)	(166)
Purchases of available-for-sale investment securities	(25,678)	(3,081)
Maturities of available-for-sale investment securities	2,300	14,650
Proceeds from sale of property and equipment		3
Net cash provided by (used in) investing activities	(23,395)	11,406
Cash flows from financing activities:
Proceeds from issuance of common stock from at the market offerings, net of offering costs	9,621
Proceeds from issuance of common stock from committed purchase agreement, net of offering costs	15,236
Proceeds from issuance of common stock from underwritten follow-on offering, net of offering costs		18,779
Repayments on borrowings		(2,000)
Net cash provided by financing activities	24,857	16,779
Net change in cash and cash equivalents	(4,365)	30,243
Cash and cash equivalents at beginning of period	16,952	9,210
Cash and cash equivalents at the end of period	$ 12,587	$ 39,453