CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenue	$ 4,865	$ 2,541	$ 15,716	$ 5,943
Operating expenses
Research and development	19,791	9,737	62,512	28,723
General and administrative	7,052	3,251	18,547	9,027
Total operating expenses	26,843	12,988	81,059	37,750
Loss from operations	(21,978)	(10,447)	(65,343)	(31,807)
Other income (expense), net:
Change in fair value of convertible note payable			(9,758)
Interest expense			(182)
Interest income	1,236	691	3,322	1,213
Total other income (expense), net	1,236	691	(6,618)	1,213
Net loss and net loss attributable to common stockholders	$ (20,742)	$ (9,756)	$ (71,961)	$ (30,594)
Net loss per share attributable to common stockholders- basic and diluted	$ (0.41)	$ (0.62)	$ (1.85)	$ (1.94)
Weighted average shares of common stock outstanding- basic and diluted	50,623,665	15,816,748	39,002,304	15,751,091

Change in fair value of convertible note payable.

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The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Amount of the cost of borrowed funds accounted for as interest expense.

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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