CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue:
Revenue	$ 1,583		$ 4,342
Type of Revenue [Extensible List]			nxtc:RelatedPartyMember
Operating expenses:
Research and development	8,663	$ 4,895	$ 22,819	$ 13,539
General and administrative	2,622	925	6,995	2,590
Total operating expenses	11,285	5,820	29,814	16,129
Loss from operations	(9,702)	(5,820)	(25,472)	(16,129)
Other income, net	1,268	110	2,662	192
Net loss	$ (8,434)	$ (5,710)	$ (22,810)	$ (15,937)
Net loss per common share—basic and diluted (in dollars per share)	$ (0.37)	$ (4.17)	$ (1.81)	$ (11.64)
Weighted average number of common shares —basic and diluted (in shares)	22,715,567	1,369,212	12,609,219	1,369,212
Comprehensive loss:
Unrealized loss on marketable securities	$ (58)		$ (58)
Total comprehensive loss	$ (8,492)	$ (5,710)	$ (22,868)	$ (15,937)