CONDENSED CONSOLIDATED STATEMENTS OF REDEEMABLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Series B1 Preferred	Series Z preferred stock	Total
Temporary equity, Beginning balance (in shares) at Dec. 31, 2020				24
Temporary equity, Ending balance (in shares) at Mar. 31, 2021				10
Increase (Decrease) in Temporary Equity
Conversion of Series B1 preferred stock (in shares)				(14)
Beginning balance at Dec. 31, 2020	$ 38	$ 742,342	$ (833,552)			$ (91,172)
Beginning balance (in shares) at Dec. 31, 2020	38,291
Ending balance (in shares) at Mar. 31, 2021	46,537
Increase (Decrease) in Stockholders' Equity
Conversion of Series B1 preferred stock	$ 1	(1)
Conversion of Series B1 preferred stock (in shares)	1,415
Sale of common stock, net of issuance costs	$ 3	16,258				16,261
Sale of common stock, net of issuance costs (in shares)	3,195
Issuance of common stock under employee stock purchase plan		28				28
Issuance of common stock under employee stock purchase plan (in shares)	8
Issuance of common stock under equity incentive plan (vesting of restricted stock units) (in shares)	237
Issuance of common stock upon exercise of common stock options and warrants	$ 4	267				271
Issuance of common stock upon exercise of common stock options and warrants (in shares)	3,375
Issuance of common stock for services rendered		67				67
Issuance of common stock for services rendered (in shares)	16
Stock-based compensation expense		1,111				1,111
Net (loss) income			115,738			115,738
Ending balance at Mar. 31, 2021	$ 46	760,072	(717,814)			42,304
Temporary equity, Beginning balance (in shares) at Dec. 31, 2020				24
Beginning balance at Dec. 31, 2020	$ 38	742,342	(833,552)			(91,172)
Beginning balance (in shares) at Dec. 31, 2020	38,291
Ending balance (in shares) at Sep. 30, 2021	52,777
Increase (Decrease) in Stockholders' Equity
Net (loss) income						102,210
Ending balance at Sep. 30, 2021	$ 53	764,300	(731,342)			33,011
Temporary equity, Beginning balance (in shares) at Mar. 31, 2021				10
Increase (Decrease) in Temporary Equity
Conversion of Series B1 preferred stock (in shares)				(10)
Beginning balance at Mar. 31, 2021	$ 46	760,072	(717,814)			42,304
Beginning balance (in shares) at Mar. 31, 2021	46,537
Ending balance (in shares) at Jun. 30, 2021	52,115
Increase (Decrease) in Stockholders' Equity
Conversion of Series B1 preferred stock	$ 1	(1)
Conversion of Series B1 preferred stock (in shares)	953
Sale of common stock, net of issuance costs	$ 2	2,510				2,512
Sale of common stock, net of issuance costs (in shares)	2,076
Issuance of common stock under employee stock purchase plan		6				6
Issuance of common stock under employee stock purchase plan (in shares)	6
Issuance of common stock upon exercise of common stock options and warrants	$ 3	(3)
Issuance of common stock upon exercise of common stock options and warrants (in shares)	2,496
Issuance of common stock for services rendered		63				63
Issuance of common stock for services rendered (in shares)	47
Stock-based compensation expense		404				404
Net (loss) income			(7,563)			(7,563)
Ending balance at Jun. 30, 2021	$ 52	763,051	(725,377)			37,726
Ending balance (in shares) at Sep. 30, 2021	52,777
Increase (Decrease) in Stockholders' Equity
Sale of common stock and prefunded warrants, net of issuance costs	$ 1	760				761
Sale of common stock and prefunded warrants, net of issuance costs (in shares)	647
Issuance of common stock under employee stock purchase plan		14				14
Issuance of common stock under employee stock purchase plan (in shares)	15
Stock-based compensation expense		475				475
Net (loss) income			(5,965)			(5,965)
Ending balance at Sep. 30, 2021	$ 53	764,300	(731,342)			33,011
Beginning balance at Dec. 31, 2021	$ 53	764,861	(735,461)			$ 29,453	[1]
Beginning balance (in shares) at Dec. 31, 2021	52,818					52,818
Ending balance (in shares) at Mar. 31, 2022	52,924
Increase (Decrease) in Stockholders' Equity
Sale of common stock, net of issuance costs		(15)				$ (15)
Issuance of common stock under employee stock purchase plan		16				16
Issuance of common stock under employee stock purchase plan (in shares)	42
Issuance of common stock under equity incentive plan (vesting of restricted stock units) (in shares)	27
Issuance of common stock for services rendered		22				22
Issuance of common stock for services rendered (in shares)	37
Stock-based compensation expense		545				545
Net (loss) income			(4,178)			(4,178)
Ending balance at Mar. 31, 2022	$ 53	765,429	(739,639)			25,843
Temporary equity, Ending balance (in shares) at Sep. 30, 2022					81
Temporary equity, Ending balance at Sep. 30, 2022					$ 29,175
Beginning balance at Dec. 31, 2021	$ 53	764,861	(735,461)			$ 29,453	[1]
Beginning balance (in shares) at Dec. 31, 2021	52,818					52,818
Ending balance (in shares) at Sep. 30, 2022	59,018					59,018
Increase (Decrease) in Stockholders' Equity
Net (loss) income						$ (12,584)
Ending balance at Sep. 30, 2022	$ 59	768,754	(748,045)			20,768
Beginning balance at Mar. 31, 2022	$ 53	765,429	(739,639)			25,843
Beginning balance (in shares) at Mar. 31, 2022	52,924
Ending balance (in shares) at Jun. 30, 2022	52,999
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under employee stock purchase plan		12				12
Issuance of common stock under employee stock purchase plan (in shares)	34
Issuance of common stock for services rendered		22				22
Issuance of common stock for services rendered (in shares)	41
Stock-based compensation expense		562				562
Net (loss) income			(5,307)			(5,307)
Ending balance at Jun. 30, 2022	$ 53	766,025	(744,946)			$ 21,132
Temporary equity, Ending balance (in shares) at Sep. 30, 2022					81
Increase (Decrease) in Temporary Equity
Issuance of preferred stock upon Acquisition of Aceragen					$ 29,175
Issuance of preferred stock upon Acquisition of Aceragen (in shares)					81
Temporary equity, Ending balance at Sep. 30, 2022					$ 29,175
Ending balance (in shares) at Sep. 30, 2022	59,018					59,018
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under employee stock purchase plan		15				$ 15
Issuance of common stock under employee stock purchase plan (in shares)	36
Issuance of common stock upon exercise of common stock options and warrants	$ 2	14				16
Issuance of common stock upon exercise of common stock options and warrants (in shares)	1,533
Issuance of common stock for services rendered		22				22
Issuance of common stock for services rendered (in shares)	50
Stock-based compensation expense		411				411
Issuance of common stock upon Acquisition of Aceragen	$ 4	2,267				2,271
Issuance of common stock upon Acquisition of Aceragen (in shares)	4,399
Net (loss) income			(3,099)			(3,099)
Ending balance at Sep. 30, 2022	$ 59	$ 768,754	$ (748,045)			$ 20,768

[1] The condensed consolidated balance sheet at December 31, 2021 has been derived from the audited financial statements at that date.