CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue:
Revenue		$ 1,583	$ 22,378	$ 4,342
Revenue, Product and Service [Extensible List]			nxtc:RelatedPartyMember
Operating expenses:
Research and development	$ 12,740	8,663	$ 34,448	22,819
General and administrative	4,659	2,622	12,918	6,995
Total operating expenses	17,399	11,285	47,366	29,814
Loss from operations	(17,399)	(9,702)	(24,988)	(25,472)
Other income, net	1,032	1,268	3,846	2,662
Net loss	$ (16,367)	$ (8,434)	$ (21,142)	$ (22,810)
Loss per share
Net loss per common share—basic and diluted (in dollars per share)	$ (0.59)	$ (0.37)	$ (0.77)	$ (1.81)
Shares used in the calculation of loss per share
Weighted average number of common shares —basic and diluted (in shares)	27,547,737	22,715,567	27,524,350	12,609,219
Comprehensive loss:
Net loss	$ (16,367)	$ (8,434)	$ (21,142)	$ (22,810)
Unrealized gain (loss) on marketable securities	(637)	(58)	1,298	(58)
Total comprehensive loss	$ (17,004)	$ (8,492)	$ (19,844)	$ (22,868)