Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (24,431)	$ (24,095)
Adjustments to reconcile loss to net cash used in operating activities:
Depreciation and amortization	6	8
Stock-based compensation	6,883	3,762
Amortization of debt discount and debt issuance costs	446	573
Amortization of intangible asset	161	162
Changes in assets and liabilities:
Accounts receivable, net	(12,962)	6,138
Inventory	(107)	(4,844)
Prepaid and other current assets	(2,389)	(163)
Other long-term assets	(469)
Accrued interest payable	(73)	(327)
Deferred revenue	(547)	(142)
Accounts payable and other current liabilities	(2,238)	9,123
Other long-term liabilities	(2,369)
Net cash used in operating activities	(38,089)	(9,805)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net of transaction costs		70,007
Proceeds from exercise of stock options, net of transaction costs	15,456	1,548
Payment on long-term debt from royalty-bearing instrument	(6,423)	(3,785)
Taxes paid related to stock-based awards	(9,080)	(2,553)
Net cash (used in) provided by financing activities	(47)	65,217
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS AND RESTRICTED CASH	(38,136)	55,412
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH, BEGINNING OF PERIOD	250,727	74,237	$ 74,237
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH, END OF PERIOD	212,591	129,649	$ 250,727
Cash paid during the year for:
Interest	7,709	5,873
Income taxes		$ 23
Supplemental disclosure of non-cash transactions:
Initial recognition of operating lease right-of-use asset	$ 8,995

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