CONDENSED STATEMENTS OF CASH FLOWS - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (6,155,000)	$ (4,996,000)
Adjustments to reconcile net loss to net cash provided by (used) in operating activities:
Depreciation and amortization	563,000	376,000
Stock-based compensation	383,000	24,000
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(897,000)	(38,000)
Accounts payable	455,000	(71,000)
Accrued liabilities and other current liabilities	(572,000)	(98,000)
Deferred revenue from related party	(857,000)
Net cash used in operating activities	(7,080,000)	(4,803,000)
Cash flows from investing activities:
Purchase of property and equipment	(935,000)	(465,000)
Net cash used in investing activities	(935,000)	(465,000)
Cash flows from financing activities:
Proceeds from issuance of common stock	4,000
Proceeds from the term loan	4,649,000
Payments of the term loan	(109,000)	(100,000)
Deferred financing costs	(1,574,000)
Net cash provided by (used in) financing activities	2,970,000	(100,000)
Net decrease in cash, cash equivalents and restricted cash	(5,045,000)	(5,368,000)
Cash, cash equivalents and restricted cash—beginning of year	135,633,000	9,287,000
Cash, cash equivalents and restricted cash—end of year	130,588,000	3,919,000
Supplemental disclosures of cash flow information:
Cash paid for interest	23,000	$ 7,000
Supplemental disclosures of noncash investing and financing activities:
Purchase of property and equipment included in accrued liabilities	75,000
Deferred financing costs in accrued liabilities	$ 290,000