CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (20,804)	$ (24,904)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	26	37
Amortization of contract asset	101
Amortization on right-of-use asset	406	541
Stock-based compensation expense	1,857	2,796
Foreign currency (gain) loss	(189)	114
Change in fair value of restricted stock liability	(94)	159
Changes in operating assets and liabilities:
Prepaid expenses and other assets	727	280
Research and development incentive receivable	(20)	(128)
Contract acquisition costs	(270)
Accounts payable and accrued expenses	(3,206)	717
Deferred revenue	1,875
Lease liability	(378)	(506)
Net cash used in operating activities	(19,969)	(21,008)
Cash flows from investing activities:
Proceeds from the sale of property and equipment	25
Purchases of property and equipment		(100)
Net cash provided by (used) in investing activities	25	(100)
Cash flows from financing activities:
Proceeds from issuance of common stock - June 2020 Public Offering	48,518
Proceeds from issuance of common stock		12,331
Proceeds from issuance of common stock from ATM sales		1,923
Proceeds from issuance of common stock in connection with July 2019 Lincoln Park Capital Registered Offering Purchase Agreement, net of issuance costs		999
Proceeds from the exercise of common stock warrants	348
Proceeds from the exercise of stock options	51
Payment of deferred offering costs	(1,906)	(417)
Net cash provided by financing activities	73,997	14,836
Effect of exchange rate changes on cash and cash equivalents	31	46
Net increase (decrease) in cash and cash equivalents	54,084	(6,226)
Cash and cash equivalents at beginning of period	3,891	16,284
Cash and cash equivalents at end of period	57,975	10,058
Supplemental disclosure of non-cash financing activities:
Reclassification of 2017 Warrants from liability to equity		3,448
Dividend attributable to down round feature of warrants	303	359
Offering costs included in accounts payable and accrued expenses - February 2019 Public Offering		20
Right-of-use asset recorded upon adoption of ASU 2016-02		1,720
Lease liability recorded upon adoption of ASU 2016-02		1,720
Prepaid rent reclassified upon adoption of ASU 2016-02		$ 35
Conversion of Series A convertible preferred stock to prefunded warrants	(8,836)
Conversion of Series B convertible preferred stock to common stock	(7,087)
Series A & B Convertible Preferred Stock discount - beneficial conversion feature	(9,399)
Series A Convertible Preferred Stock
Cash flows from financing activities:
Proceeds from the issuance of Series convertible preferred stock	14,986
Supplemental disclosure of non-cash financing activities:
Conversion of Series A convertible preferred stock to prefunded warrants	8,836
Series A & B Convertible Preferred Stock discount - beneficial conversion feature	5,226
Series B Convertible Preferred Stock
Cash flows from financing activities:
Proceeds from the issuance of Series convertible preferred stock	12,000
Supplemental disclosure of non-cash financing activities:
Conversion of Series B convertible preferred stock to common stock	7,087
Series A & B Convertible Preferred Stock discount - beneficial conversion feature	$ 4,173