Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities:
Net loss	$ (166,037)	$ (164,997)
Adjustments to reconcile net loss to net cash used for operating activities:
Stock-based compensation expense	33,963	34,183
Depreciation and amortization	2,227	2,135
Amortization of debt discount	785	1,013
Amortization of debt issuance costs	69
Amortization of premium on short-term investments	223	39
Impairment of property and equipment	354	61
Change in operating assets and liabilities:
Accounts receivable	(1,236)	6,225
Inventory	403	(17,781)
Prepaid expenses and other assets	(5,694)	6,799
Accounts payable	5,360	9,309
Accrued clinical and manufacturing liabilities	(32,811)	6,104
Accrued payroll and employee liabilities	2,409	(2,013)
Other accrued liabilities	1,889	(13,343)
Net cash used for operating activities	(158,096)	(132,266)
Investing activities:
Purchases of short-term investments	(91,321)	(92,040)
Maturities and sales of short-term investments	150,940	248,525
Purchases of property and equipment	(2,632)	(4,319)
Net cash provided by investing activities	56,987	152,166
Financing activities:
Net proceeds from convertible note financing	148,963
Proceeds from issuance of common stock under equity incentive plan	5,049	1,833
Proceeds from purchases under the Employee Stock Purchase Plan	1,529	1,507
Proceeds from warrant exercises		3
Net cash provided by financing activities	155,541	3,343
Net increase in cash and cash equivalents	54,432	23,243
Cash and cash equivalents at beginning of year	105,138	71,898
Cash and cash equivalents at end of period	$ 159,570	$ 95,141