Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($)	Common Stock IPO	Common Stock	Additional Paid-in capital IPO	Additional Paid-in capital	Accumulated other comprehensive loss	Accumulated deficit	Series A convertible preferred stock	Series B convertible preferred stock	Series C convertible preferred stock	IPO	Total
Temporary equity, beginning balance at Dec. 31, 2018							$ 6,483,044	$ 49,742,942	$ 56,364,645
Temporary Equity, Beginning Balance (in shares) at Dec. 31, 2018							612,446	7,235,969	4,712,698
Increase (Decrease) in Temporary Equity
Issuance of convertible preferred stock, net of issuance costs									$ 5,598,362
Issuance of convertible preferred stock (in shares)									467,179
Conversion of preferred stock into common stock							$ (6,483,044)	$ (49,742,942)	$ (61,963,007)
Conversion of preferred stock into common stock (in shares)							(612,446)	(7,235,969)	(5,179,877)
Equity, beginning balance at Dec. 31, 2018		$ 127,091		$ 19,666,588	$ (8,761,325)	$ (62,468,456)					$ (51,436,102)
Equity, beginning balance (in shares) at Dec. 31, 2018		1,155,366
Increase (Decrease) in Stockholders' Equity
Issuance of common stock	$ 6,517		$ 86,899,563	100						$ 86,906,080	100
Issuance of common stock (in shares)	6,516,667	160
Exercise of stock options		$ 3,179		67,818							70,997
Exercise of stock options (in shares)		322,267
Stockbased compensation				1,345,722							1,345,722
Foreign currency translation					(2,772,453)						(2,772,453)
Exchange of preferred and common stock of Aprea Therapeutics AB into stock of Aprea Therapeutics, Inc.		$ (128,792)		128,792
Conversion of preferred stock into common stock		$ 13,028		118,175,965							118,188,993
Conversion of preferred stock into common stock (in shares)		13,028,292
Net loss						(28,059,807)					(28,059,807)
Equity, ending balance at Dec. 31, 2019		$ 21,023		226,284,548	(11,533,778)	(90,528,263)					124,243,530
Equity, ending balance (in shares) at Dec. 31, 2019		21,022,752
Increase (Decrease) in Stockholders' Equity
Exercise of stock options		$ 164		150,785							150,949
Exercise of stock options (in shares)		164,075
Stockbased compensation				4,983,023							4,983,023
Foreign currency translation					1,496,517						1,496,517
Net loss						(53,478,812)					(53,478,812)
Equity, ending balance at Dec. 31, 2020		$ 21,187		231,418,356	(10,037,261)	(144,007,075)					77,395,207
Equity, ending balance (in shares) at Dec. 31, 2020		21,186,827
Increase (Decrease) in Stockholders' Equity
Issuance of common stock		$ 367		1,538,278							1,538,645
Issuance of common stock (in shares)		366,773
Exercise of stock options		$ 226		208,141							208,367
Exercise of stock options (in shares)		226,394
Stockbased compensation				7,813,743							7,813,743
Foreign currency translation					(321,695)						(321,695)
Vesting of restricted stock units		$ 79		(79)
Vesting of restricted stock units (in shares)		79,419
Net loss						(37,127,303)					(37,127,303)
Equity, ending balance at Dec. 31, 2021		$ 21,859		$ 240,978,439	$ (10,358,956)	$ (181,134,378)					$ 49,506,964
Equity, ending balance (in shares) at Dec. 31, 2021		21,859,413