Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flow from operating activities:
Net loss	$ (6,167)	$ (6,637)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	495	503
Share-based compensation	272	214
Loss on disposal and write-offs of property and equipment	44	0
Changes in operating assets and liabilities:
Contracts and grants receivable	230	0
Prepaid expenses and other current assets	125	45
Accounts payable	(692)	242
Accrued compensation	670	615
Accrued outside research and development services	915	254
Accrued legal and professional fees	(508)	(199)
Other accrued expenses	(52)	(406)
Deferred revenue	(1,143)	3,360
Research and development service obligation liabilities	(1,513)	0
Other long-term assets and liabilities	(114)	(101)
Net cash used in operating activities	(7,438)	(2,110)
Cash flow from investing activities:
Purchases of property and equipment	(352)	(17)
Proceeds from the sale of property and equipment	15	0
Net cash used in investing activities	(337)	(17)
Cash flow from financing activities:
Proceeds from issuance of common stock and pre-funded warrants, net of underwriting fees and commissions	12,577	0
Proceeds from exercise of common stock warrants	2,880	0
Proceeds from issuance of common stock under common stock purchase agreement	442	0
Payments related to public offering costs	(26)	0
Payments of offering costs related to new registration statement	(25)	0
Proceeds from exercise of stock options	0	10
Net cash provided by financing activities	15,848	10
Net increase (decrease) in cash, cash equivalents and restricted cash	8,073	(2,117)
Cash, cash equivalents and restricted cash as of beginning of period	14,251	8,733
Cash, cash equivalents and restricted cash as of end of period	22,324	6,616
Supplemental disclosure of non-cash investing and financing activities:
Purchases of property and equipment with accounts payable and accrued expenses	6	69
Deferred offering costs in accounts payable and accrued expenses	152	0
Deferred offering costs reclassified to additional paid-in capital	16	0
Reconciliation to condensed consolidated balance sheets:
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 22,324	$ 6,616