Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Costs and expenses
Research and development expenses	$ 49,274	$ 39,298	$ 106,226	$ 70,203
General and administrative expenses	14,353	10,867	28,211	19,948
Total costs and expenses	63,627	50,165	134,437	90,151
Loss from operations	(63,627)	(50,165)	(134,437)	(90,151)
Other income
Interest income, net	609	2,614	1,824	5,650
Net Loss	$ (63,018)	$ (47,551)	$ (132,613)	$ (84,501)
Net Loss Per Share of Common Stock, Basic and Diluted	$ (0.47)	$ (0.38)	$ (1.02)	$ (0.68)
Weighted Average Shares of Common Stock Outstanding, Basic and Diluted	133,162	123,567	129,848	123,491