Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net Loss	$ (17,176)	$ (5,681)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash rent expense	92	92
Stock based compensation	1,955	190
Depreciation and amortization	83	19
Amortization of (discount) premium on available for sale investments	56	(171)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	49	(3,628)
Other assets		(250)
Accounts payable	1,879	1,451
Accrued expenses and other current liabilities	2,283	762
Net cash used in operating activities	(10,779)	(7,216)
Cash flow from investing activities:
Purchase of investments	(95,543)	(25,585)
Proceeds from maturities of investments	22,867	28,800
Purchase of property and equipment	(5)	(51)
Net cash (used in) provided by investing activities	(72,681)	3,164
Cash flows from financing activities:
Payments of finance leases	(29)
Proceeds from issuance of common stock upon exercise of stock options	191	64
Proceeds from private placement offering, net of issuance costs	117,690
Net cash provided by financing activities	117,852	64
Net change in cash and cash equivalents	34,392	(3,988)
Cash, cash equivalents and restricted cash at beginning of period	51,214	24,872
Cash, cash equivalents and restricted cash at end of period	85,606	20,884
Supplemental disclosures of non-cash information:
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 122	$ 815