CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Revenue from collaborations	$ 910
Operating expenses:
Research and development	22,869	$ 17,302
General and administrative	5,781	3,419
Total operating expenses	28,650	20,721
Loss from operations	(27,740)	(20,721)
Interest and other income, net	111	692
Loss before income tax expense	(27,629)	(20,029)
Income tax expense	(45)
Net loss	(27,674)	(20,029)
Other comprehensive gain (loss):
Unrealized gain (loss) on available-for-sale securities	(41)	401
Unrealized gain on pension plans	2	166
Other comprehensive income (loss)	(39)	567
Comprehensive loss	$ (27,713)	$ (19,462)
Net loss per share, basic and diluted	$ (0.74)	$ (7.56)
Weighted average shares of common stock, basic and diluted	37,434,261	2,648,885