Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive (Loss) Income	Total
Balance, Value at Dec. 31, 2018	$ 39	$ 428,059	$ (294,354)	$ (114)	$ 133,630
Balance, Shares at Dec. 31, 2018	39,547,558
Sale of common stock in a follow-on public offering, net of underwriting discounts and commissions and offering expenses, value	$ 7	136,491			136,498
Sale of common stock in a follow-on public offering, net of underwriting discounts and commissions and offering expenses, Shares	6,325,000
Issuance of common stock upon entry into License Agreement with Enterise Biopharma, Inc. ($34.42 per share)		4,000			4,000
Issuance of common stock upon entry into License Agreement with Enterise Biopharma, Inc. ($34.42 per share), shares	170,793
Stock-based compensation expense		10,587			10,587
Shares issued upon exercise of stock options, value	$ 1	6,105			6,106
Shares issued upon exercise of stock options, shares	555,847
Shares issued upon vesting of restricted stock units, value		1,784			1,784
Shares issued upon vesting of restricted stock units, shares	110,832
Shares issued for consulting services, value		197			197
Shares issued for consulting services, shares	10,195
Net (loss) income			(106,373)		(106,373)
Other comprehensive income (loss)				284	284
Balance, Value at Dec. 31, 2019	$ 47	587,223	(400,727)	170	186,713
Balance, Shares at Dec. 31, 2019	46,720,225
Sale of common stock under license agreement with Vifor, value	$ 3	38,446			38,449
Sale of common stock under license agreement with Vifor, shares	2,939,552
Stock-based compensation expense		12,486			12,486
Shares issued upon exercise of stock options, value		691			691
Shares issued upon exercise of stock options, shares	55,852
Shares issued upon vesting of restricted stock units, value		2,349			2,349
Shares issued upon vesting of restricted stock units, shares	156,584
Net (loss) income			8,410		8,410
Other comprehensive income (loss)				(97)	(97)
Balance, Value at Dec. 31, 2020	$ 50	641,195	(392,317)	73	249,001
Balance, Shares at Dec. 31, 2020	49,872,213
Sale of common stock under license agreement with Vifor, value	$ 3	44,966			44,969
Sale of common stock under license agreement with Vifor, shares	3,282,391
Stock-based compensation expense		17,850			17,850
Shares issued upon exercise of stock options, value		1,639			$ 1,639
Shares issued upon exercise of stock options, shares	136,787				136,787
Shares issued upon vesting of restricted stock units, value		2,935			$ 2,935
Shares issued upon vesting of restricted stock units, shares	189,421
Net (loss) income			(88,441)		(88,441)
Other comprehensive income (loss)				(431)	(431)
Balance, Value at Dec. 31, 2021	$ 53	$ 708,585	$ (480,758)	$ (358)	$ 227,522
Balance, Shares at Dec. 31, 2021	53,480,812