Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net loss	$ (84,936,000)	$ (84,234,000)
Adjustments to reconcile net loss to cash used in operating activities:
Non-cash goodwill impairment charge	32,466,000
Non-cash licensed technology impairment charge		32,916,000
Non-cash gain on settlement with licensor	(6,743,000)
Depreciation and amortization	3,250,000	4,586,000
Stock option-based compensation expense	5,250,000	5,853,000
Restricted stock-based compensation expense	3,666,000	2,334,000
Non-cash PPP loan payable forgiveness income	(1,758,000)
Non-cash interest expense	67,000	600,000
Accretion and interest on short-term investments	122,000	(70,000)
Amortization of right-of-use lease assets	1,214,000	1,015,000
Other		347,000
Change in operating assets and liabilities:
Accounts receivable	(3,000,000)
Prepaid expenses, other current assets and restricted cash	331,000	424,000
Other assets and restricted cash	(7,000)	(127,000)
Accounts payable, accrued expenses, lease liabilities and other liabilities	825,000	(2,178,000)
Payable to licensor	(16,412,000)	3,515,000
Net cash used in operating activities	(65,665,000)	(35,019,000)
Cash flows from investing activities:
Capital expenditures	(4,151,000)	(1,336,000)
Purchases of short-term investments	(20,163,000)	(170,472,000)
Proceeds from maturities of short-term investments	90,376,000	88,094,000
Net cash provided by/(used in) investing activities	66,062,000	(83,714,000)
Cash flows from financing activities:
Proceeds from loan payable		1,758,000
Proceeds from issuance of common stock and warrants in public offering	17,433,000	1,000
Payment of offering costs in public offering	(1,454,000)
Proceeds from open market sales of common stock	8,051,000
Proceeds from exercise of stock options	831,000	177,000
Net cash provided by financing activities	24,861,000	1,936,000
Net increase/(decrease) in cash, cash equivalents and restricted cash	25,258,000	(116,797,000)
Cash, cash equivalents and restricted cash at beginning of year	13,571,000	130,368,000
Cash, cash equivalents and restricted cash at end of year	38,829,000	13,571,000
Supplemental cash flow information:
Cash and cash equivalents	32,938,000	12,596,000
Restricted cash	5,891,000	975,000
Total cash, cash equivalents and restricted cash	38,829,000	13,571,000
Cash paid for interest
Cash paid for taxes
Additions to right-of-use lease assets obtained from new operating lease liabilities resulting from modification of original lease arrangement	$ 3,585,000