CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net loss	$ (54,121)	$ (36,726)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	278	127
Stock-based compensation expense	5,672	4,788
Loss on disposal of fixed assets	42
Noncash lease expense	225
Noncash lease liability	(131)
Amortization of discount on investments	(8)	(79)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(1,480)	(237)
Accounts payable and accrued expenses	890	4,285
Net cash used in operating activities	(48,633)	(27,842)
Cash flows from investing activities
Maturities of short-term investments	6,994	20,000
Purchases of short-term investments	(2,725)
Purchases of property and equipment	(388)	(83)
Net cash provided by investing activities	3,881	19,917
Cash flows from financing activities
Proceeds from exercise of stock options	97	14
Proceeds from equity offerings, net of offering costs	67,871	42,300
Repayments of short-term bank borrowings		(193)
Net cash provided by/(used in) financing activities	67,968	42,121
Net decrease in cash and cash equivalents	23,216	34,196
Cash and cash equivalents—beginning of year	67,727	33,531
Cash and cash equivalents—end of year	90,943	67,727
Supplemental disclosure of cash flow information
Financing in accounts payable and accrued expenses	(195)	$ (153)
Operating lease liability	3,357
Operating right-of-use asset	$ 2,458