Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net loss	$ (25,973)	$ (17,103)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	283	190
Stock-based compensation expense	2,822	1,455
Deferred rent expense	(53)	(40)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	976	(1,485)
Other assets	319
Accounts payable	(1,443)	671
Accrued expenses and other current liabilities	635	(1,426)
Net cash used in operating activities	(22,434)	(17,738)
Cash flows from investing activities:
Purchases of property and equipment	(577)	(340)
Net cash used in investing activities	(577)	(340)
Cash flows from financing activities:
Proceeds from exercise of stock options	35	252
Proceeds from issuance of common shares upon completion of public offering, net of offering costs	93,628
Net cash provided by financing activities	93,663	252
Net increase (decrease) in cash, cash equivalents and restricted cash	70,652	(17,826)
Cash, cash equivalents and restricted cash at beginning of period	187,535	126,794
Cash, cash equivalents and restricted cash at end of period	258,187	108,968
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment held for sale		336
Offering costs included in accrued expenses and accounts payable	249
Reconciliation of cash, cash equivalents and restricted cash reported within the condensed consolidated balance sheets:
Cash and cash equivalents	257,695	108,476
Long-term restricted cash (included in other assets)	492	492
Cash, cash equivalents and restricted cash at end of period	$ 258,187	$ 108,968