Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash flow from operating activities:
Net loss	$ (30,377)	$ (29,239)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,033	1,664
Share-based compensation	1,838	2,204
Loss on disposal and write-offs of property and equipment	36	154
Changes in operating assets and liabilities:
Contracts and grants receivable	(419)	0
Prepaid expenses and other current assets	(438)	(224)
Accounts payable	352	777
Accrued compensation	(1,030)	(701)
Accrued outside research and development services	450	(829)
Accrued legal and professional fees	159	132
Other accrued expenses	(397)	(615)
Deferred revenue	4,537	(1,610)
Advanced payment for research and development service obligation	12,000	0
Research and development service obligation liabilities	(8,185)	0
Other long-term assets and liabilities	(435)	(338)
Net cash used in operating activities	(19,876)	(28,625)
Cash flow from investing activities:
Purchases of property and equipment	(422)	(1,107)
Proceeds from the sale of property and equipment	0	49
Net cash used in investing activities	(422)	(1,058)
Cash flow from financing activities:
Proceeds from research and development funding arrangement	25,000	0
Proceeds from issuance of common stock, net of underwriting fees and commissions	747	35,625
Payments related to public offering costs	0	(321)
Proceeds from exercise of stock options	69	60
Payments on capital lease obligation	0	(11)
Net cash provided by financing activities	25,816	35,353
Net increase in cash, cash equivalents and restricted cash	5,518	5,670
Cash, cash equivalents and restricted cash as of beginning of period	8,733	3,063
Cash, cash equivalents and restricted cash as of end of period	14,251	8,733
Supplemental disclosure of cash flow information:
Cash paid for interest	2	1,043
Supplemental disclosure of non-cash investing and financing activities:
Purchases of property and equipment with accounts payable and accrued expenses	79	0
Right of use assets obtained in exchange for lease liabilities	1,827	0
Liability-based awards reclassified to additional paid-in capital	366	0
Common stock issued for payment of commitment fee	750	0
Deferred offering costs reclassified to additional paid-in capital	0	431
Reconciliation to consolidated balance sheets:
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 14,251	$ 8,733