Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash Flows From Operating Activities:
Net loss	$ (51,673)	$ (25,786)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	183	33
Stock-based compensation expense	4,645	2,130
Amortization of debt discount and issuance costs	410
Change in fair value of derivative liability	(41)
Loss on disposal of asset	2	7
Changes in assets and liabilities:
Related party receivable	(69)	(163)
Prepaid expenses and other current assets	860	(2,139)
Other assets	81	(2,619)
Accounts payable	(911)	(114)
Accrued expenses and other liabilities	5,537	2,431
Related party payable	43	88
Net cash used in operating activities	(40,933)	(26,132)
Cash Flows From Investing Activities:
Purchases of property and equipment	(243)	(35)
Net cash used in investing activities	(243)	(35)
Cash Flows From Financing Activities:
Proceeds from issuance of common stock under employee stock plan	350	308
Proceeds from issuance of common stock upon exercise of stock options	396	112
Net cash provided by financing activities	24,840	420
Net decrease in cash and cash equivalents	(16,336)	(25,747)
Cash and cash equivalents, beginning of period	191,157	157,147
Cash and cash equivalents, end of period	174,821	131,400
Other supplemental information
Interest paid	752
Supplemental disclosure of non-cash activities:
Lease liability arising from the right of use asset		1,058
Vesting of restricted stock and early exercised options	72	$ 75
Open Market Sale Agreement
Cash Flows From Financing Activities:
Proceeds from the issuance of common stock in at-the-market offering	$ 24,094