Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities
Net loss	$ (72,579)	$ (77,125)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	1,754	1,676
Amortization of intangible assets	330	125
Stock-based compensation expense	9,272	2,174
Amortization of premiums/(accretion of discounts) on marketable securities, net	113	(100)
Amortization of debt issuance costs	518	17,438
Amortization of right-of-use assets	507	470
Research and development - license acquired		15,000
Gain on disposal of property and equipment		(1)
Loss on debt extinguishment		1,447
Change in fair value of warrant liability and embedded derivative	5,555	608
Change in fair value of contingent consideration	(1,466)	700
Changes in operating assets and liabilities, net of effect from business combination:
Accounts receivable	(1,630)	(697)
Inventory	(1,865)	(3,829)
Prepaid expenses and other current assets	(2,729)	(306)
Other assets	(387)	(8)
Accounts payable	753	2,873
Accrued liabilities	1,423	9,268
Operating lease liabilities	(615)	(536)
Other long-term liabilities	8
Net cash used in operating activities	(61,038)	(30,823)
Cash flows from investing activities
Purchases of available-for-sale marketable securities	(108,528)	(68,735)
Sales of available-for-sale marketable securities	17,095
Maturities of available-for-sale marketable securities	45,000	11,550
Purchases of property and equipment	(7,822)	(683)
Purchase of research and development license		(10,000)
Cash paid, net of cash acquired for the Rhythm Xience Acquisition		(3,000)
Net cash used in investing activities	(54,255)	(70,868)
Cash flows from financing activities
Proceeds from issuance of debt and warrants		77,000
Repayment of debt		(15,000)
Payment of issuance and extinguishment costs related to debt		(2,332)
Payment of contingent consideration	(2,636)
Proceeds from issuance of convertible preferred stock, net of issuance costs		66,567
Proceeds from issuance of common stock upon IPO, net of issuance costs	166,286
Proceeds from stock options exercises	350	76
Net cash provided by financing activities	164,000	126,311
Effect of exchange rate changes on cash, cash equivalents and restricted cash	143	(50)
Net change in cash, cash equivalents and restricted cash	48,850	24,570
Cash, cash equivalents and restricted cash, at the beginning of the period	9,602	9,775
Cash, cash equivalents and restricted cash, at the end of the period	58,452	34,345
Supplemental disclosure of cash flow information:
Cash paid for interest	3,526	4,647
Supplemental disclosure of noncash investing and financing activities:
Issuance of Series D convertible preferred stock for 2018 Convertible Notes and 2019 Convertible Notes		68,476
Issuance of Series D convertible preferred stock for Biotronik asset purchase	5,000
Issuance of Series D convertible preferred stock for Rhythm Xience Acquisition	2,197
Change in unrealized (gain) loss on marketable securities	50	(47)
Warrants issued in conjunction with OrbiMed debt		872
Right-of-use assets exchanged for operating lease liabilities		2,978
Accrued purchase of research and development-license		5,000
Unpaid purchases of property and equipment	88	$ 35
Conversion of convertible preferred stock into common stock upon IPO	260,555
Reclassification of warrant liability to stockholders' equity	$ 14,474