Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
OPERATING ACTIVITIES:
Net loss	$ (31,829,000)	$ (21,351,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,304,000	2,354,000
Amortization of right-of-use assets	1,496,000	802,000
Charge of in-process research and development costs with no alternative future use	8,500,000	0
Unrealized translation gains (loss) on obligation related to royalty	0	(144,000)
Re-valuation of contingent consideration	(190,000)	0
Non-cash stock-based compensation	6,338,000	3,182,000
Amortization of premium (discount) on marketable securities	580,000	(553,000)
Others	56,000	0
Changes in operating assets and liabilities:
Accounts receivable, net	(179,000)	11,608,000
Inventory	(9,967,000)	(1,120,000)
Prepaid expenses and other current assets	(2,598,000)	(947,000)
Other assets	161,000	(833,000)
Accounts payable	9,491,000	(2,610,000)
Accrued compensation	4,378,000	1,697,000
Accrued expenses	(660,000)	2,308,000
Operating lease liabilities	(1,858,000)	329,000
Deferred revenue	(341,000)	975,000
Other liabilities	36,000	0
Net cash used in operating activities	(13,282,000)	(4,303,000)
INVESTING ACTIVITIES:
Purchases of marketable securities	(55,760,000)	(45,966,000)
Maturity of marketable securities	104,048,000	64,000,000
Purchases of property and equipment	(9,598,000)	(2,705,000)
Purchase of intangible assets	(17,886,000)	0
Net cash provided by investing activities	20,804,000	15,329,000
FINANCING ACTIVITIES:
Payments made on royalty obligations	0	(73,000)
Payments made on capital lease obligations	(38,000)	(21,000)
Proceeds from issuance of common stock upon exercise of stock options	1,504,000	538,000
Proceeds from issuances of common stock under employee stock purchase plan	0	1,933,000
Payment of offering costs related to initial public offering and follow-on offering	0	(89,000)
Net cash provided by financing activities	1,466,000	2,288,000
Net effect of foreign exchange rate changes on cash and cash equivalents	23,000	(69,000)
Net increase in cash and cash equivalents	9,011,000	13,245,000
Cash and cash equivalents—Beginning of period	143,228,000	140,544,000
Cash and cash equivalents—End of period	152,239,000	153,789,000
Supplemental Disclosures of Cash Flow Information:
Operating lease liabilities arising from obtaining right-of-use assets	1,957,000	0
Supplemental Disclosures of Noncash Investing and Financing Activities:
Purchases of property and equipment included in accounts payable and accrued expenses	$ 1,365,000	$ 490,000