Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities:
Net income (loss)	$ 6,199	$ (15,561)
Adjustments to reconcile net income (loss) to net cash provided by (used in)    operating activities:
Depreciation and amortization expense	345	406
Stock-based compensation expense	1,865	2,380
Non-cash interest expense related to note payable	146	708
Net amortization of premiums and discounts on marketable securities	178	142
Non-cash operating lease cost	614	502
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(695)	(2,661)
Unbilled receivable	(30,000)	0
Other assets	(20)	21
Accounts payable	1,074	642
Accrued expenses and other current liabilities	(2,601)	(5,010)
Operating lease liability	(671)	(532)
Net cash used in operating activities	(23,566)	(18,963)
Cash flows from investing activities:
Purchases of property and equipment	(35)	0
Purchases of marketable securities	0	(70,634)
Proceeds from sales or maturities of marketable securities	12,500	0
Net cash provided by (used in) investing activities	12,465	(70,634)
Cash flows from financing activities:
Proceeds from issuance of common stock upon public offering, net	20,556	14,716
Proceeds from employee stock purchases	157	118
Proceeds from exercise of stock options	0	148
Net cash provided by financing activities	20,713	14,982
Net increase (decrease) in cash and cash equivalents and restricted cash	9,612	(74,615)
Cash and cash equivalents and restricted cash at beginning of period	57,640	176,736
Cash and cash equivalents and restricted cash at end of period	67,252	102,121
Supplemental disclosure of cash flow information:
Cash paid for interest	531	327
Supplemental disclosure of non-cash investing and financing activities:
Additional right-of-use asset and related lease liability	755	0
Purchases of property and equipment included in accounts payable and accrued expenses	43	0
Conversion of note payable into shares of common stock	$ 0	$ 1,500