Condensed Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Balance, beginning (in shares) at Dec. 31, 2019		37,996,849
Balance, beginning at Dec. 31, 2019	$ 141,687		$ 441,216	$ (299,529)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued upon exercises of stock options (in shares)		376,311
Shares issued upon exercises of stock options	3,392		3,392
Shares issued upon vesting of restricted stock units (in shares)		13,000
Stock-based compensation	683		683
Net loss	(8,642)			(8,642)
Balance, ending (in shares) at Mar. 31, 2020		38,386,160
Balance, ending at Mar. 31, 2020	137,120		445,291	(308,171)
Balance, beginning (in shares) at Dec. 31, 2019		37,996,849
Balance, beginning at Dec. 31, 2019	$ 141,687		441,216	(299,529)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued upon exercises of stock options (in shares)	581,270
Net loss	$ (20,637)
Balance, ending (in shares) at Sep. 30, 2020		41,876,590
Balance, ending at Sep. 30, 2020	200,340		520,506	(320,166)
Balance, beginning (in shares) at Mar. 31, 2020		38,386,160
Balance, beginning at Mar. 31, 2020	137,120		445,291	(308,171)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued upon exercises of stock options (in shares)		98,882
Shares issued upon exercises of stock options	303		303
Shares issued upon vesting of restricted stock units (in shares)		1,500
Stock-based compensation	1,022		1,022
Net loss	(9,746)			(9,746)
Balance, ending (in shares) at Jun. 30, 2020		38,486,542
Balance, ending at Jun. 30, 2020	128,699		446,616	(317,917)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock and pre-funded warrants, net of commissions and offering expenses (in shares)		3,262,471
Issuance of common stock and pre-funded warrants, net of commissions and offering expenses	71,320		71,320
Shares issued upon exercises of stock options (in shares)		106,077
Shares issued upon exercises of stock options	882		882
Shares issued upon vesting of restricted stock units (in shares)		21,500
Stock-based compensation	1,688		1,688
Net loss	(2,249)			(2,249)
Balance, ending (in shares) at Sep. 30, 2020		41,876,590
Balance, ending at Sep. 30, 2020	200,340		520,506	(320,166)
Balance, beginning (in shares) at Dec. 31, 2020		42,196,296
Balance, beginning at Dec. 31, 2020	191,216		524,022	(332,806)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued upon exercises of stock options (in shares)		91,737
Shares issued upon exercises of stock options	282		282
Shares issued upon vesting of restricted stock units (in shares)		38,000
Stock-based compensation	2,420		2,420
Net loss	(14,950)			(14,950)
Balance, ending (in shares) at Mar. 31, 2021		42,326,033
Balance, ending at Mar. 31, 2021	178,968		526,724	(347,756)
Balance, beginning (in shares) at Dec. 31, 2020		42,196,296
Balance, beginning at Dec. 31, 2020	$ 191,216		524,022	(332,806)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued upon exercises of stock options (in shares)	124,366
Net loss	$ (45,525)
Balance, ending (in shares) at Sep. 30, 2021		42,428,134
Balance, ending at Sep. 30, 2021	154,866		533,197	(378,331)
Balance, beginning (in shares) at Mar. 31, 2021		42,326,033
Balance, beginning at Mar. 31, 2021	178,968		526,724	(347,756)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued upon exercises of stock options (in shares)		25,124
Shares issued upon exercises of stock options	95		95
Issuance of shares under Employee Stock Purchase Plan (in shares)		22,972
Issuance of shares under Employee Stock Purchase Plan	219		219
Shares issued upon vesting of restricted stock units (in shares)		45,000
Stock-based compensation	2,918		2,918
Net loss	(15,129)			(15,129)
Balance, ending (in shares) at Jun. 30, 2021		42,419,129
Balance, ending at Jun. 30, 2021	167,071		529,956	(362,885)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued upon exercises of stock options (in shares)		7,505
Shares issued upon exercises of stock options	31		31
Shares issued upon vesting of restricted stock units (in shares)		1,500
Stock-based compensation	3,210		3,210
Net loss	(15,446)			(15,446)
Balance, ending (in shares) at Sep. 30, 2021		42,428,134
Balance, ending at Sep. 30, 2021	$ 154,866		$ 533,197	$ (378,331)