Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Activities
Net loss	$ (33,917)	$ (65,051)	$ (70,252)
Adjustments to reconcile net loss to net cash used in operating activities:
Gain from sale of priority review vouches	(46,493)
Income related to asset purchase agreement	(281)
Depreciation and amortization	276	167	68
Amortization of debt securities premiums and discounts	996	124	(467)
Stock-based compensation	7,901	5,973	5,679
Non-cash interest expense	776	804	723
Amortization of operating lease right-of-use assets	523	478	418
Common stock issued under Product Development Agreement	218	217	226
Changes in operating assets and liabilities:
Accounts receivable	(2,576)
Inventories	(2,424)
Prepaid expenses and other current assets	(701)	(3,563)	(3,698)
Other assets	(607)	(1,392)	(2,075)
Accounts payable	3,234	(1,899)	584
Accrued liabilities	2,309	1,491	5,610
Operating lease liabilities	(576)	(534)	(430)
Net cash used in operating activities	(71,342)	(63,185)	(63,614)
Investing Activities
Purchase of debt securities available-for-sale	(84,647)	(128,295)	(96,267)
Proceeds from maturities of debt securities available-for-sale	99,630	83,766	80,271
Proceeds related to asset purchase agreement	281
Proceeds from sale of priority review voucher	95,000
Payments related to priority review voucher	(48,507)
Purchase of property and equipment	(225)	(258)	(475)
Net cash provided by (used) in investing activities	61,532	(44,787)	(16,471)
Financing Activities
Issuance of common stock upon offering at-the-market, net of commissions	3,040	96,779
Proceeds from issuance of common stock upon stock option exercises	361	520	844
Proceeds from issuance of common stock upon ESPP purchase	257	186	130
Payment of debt issuance costs	(175)
Common stock offering costs	(316)	(22)	(19)
Proceeds from borrowings in connection with term loan, net of issuance costs			6,627
Repayment of accrued exit fee and second amendment fee			(913)
Repayment of term loan			(1,667)
Net cash provided by financing activities	3,167	97,463	58,196
Net decrease in cash and cash equivalents	(6,643)	(10,509)	(21,889)
Cash and cash equivalents at beginning of year	28,864	39,373	61,262
Cash and cash equivalents at end of year	22,221	28,864	39,373
Supplemental disclosure of cash flow information:
Interest paid	$ 2,783	$ 2,791	2,638
Public Offering [Member]
Financing Activities
Issuance of common stock upon offering at-the-market, net of commissions			$ 53,194