Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities
Net loss	$ (19,620)	$ (12,074)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	231	181
Amortization of premiums (accretion of discounts) on investments	0	(47)
Non-cash lease expense	366	446
Loss on disposal of property and equipment	1	70
Stock‑based compensation expense	1,409	1,180
Non‑cash interest expense	123	189
Warrant liabilities revaluation	846	0
Changes in operating assets and liabilities:
Accounts receivable	5,000	0
Prepaid expenses, deposits and other assets	(61)	(6,158)
Accounts payable	836	(407)
Deferred revenue	0	(2)
Accrued expenses and other liabilities	(829)	(3,618)
Net cash used in operating activities	(11,698)	(20,240)
Cash flows from investing activities
Purchases of short-term investments	0	(18,188)
Sale of short term investments	0	1,992
Purchases of property and equipment	(135)	0
Proceeds from the sale of property and equipment	0	77
Net cash used in investing activities	(135)	(16,119)
Cash flows from financing activities
Repayments of principal on outstanding debt	(2,100)	0
Net proceeds from issuance of common stock	0	30,942
Issuance costs paid for December 2019 financing	(4,381)	0
Other financing fees	(147)	0
Proceeds from exercise of stock options	3	145
Proceeds from issuance of common stock under Employee Stock Purchase Plan	114	20
Net cash (used in) provided by financing activities	(5,370)	31,107
Effect of exchange rate changes on cash	(84)	22
Net change in cash, cash equivalents, and restricted cash	(17,287)	(5,230)
Cash, cash equivalents, and restricted cash at beginning of period	91,551	37,682
Cash, cash equivalents, and restricted cash at end of period	74,264	32,452
Supplement cash flow information
Cash paid for interest	232	312
Noncash investing and financing activities
Purchase of property and equipment not yet paid	10	0
Equity offering costs in accrued liabilities	42	10
Unrealized gain on marketable securities	0	2
At-The-Market Offering
Cash flows from financing activities
Net proceeds from issuance of common stock	$ 1,141	$ 0