CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net loss	$ (74,865)	$ (94,176)	$ (27,255)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	594	655	171
Non-cash impairment charges	1,845
Lease incentive obligation	(34)	(34)	(34)
Stock-based compensation expense	7,945	5,787	2,209
Non cash interest expense			6
Changes in operating assets and liabilities:
Accounts receivable	(7,840)	(2,129)
Inventories	(497)	(1,316)
Prepaid expenses and other assets	(1,057)	(923)	(659)
Refundable PDUFA fee			2,335
Accounts payable	(3,422)	5,569	1,298
Accrued expenses	(527)	6,570	362
Accrued rebates, returns and discounts	15,784
Deferred revenue	(4,944)	4,944
Net cash used in operating activities	(67,018)	(75,053)	(21,567)
Investing activities
Purchase of intangible assets		(2,500)
Purchases of property and equipment	(990)	(477)	(362)
Net cash used in investing activities	(990)	(2,977)	(362)
Financing activities
Proceeds from issuances of common stock from public offerings, net of issuance costs of $1,198, $845 and $2,408, respectively	34,338	137,340	72,029
Proceeds from issuances of common stock from employee stock purchase plans	1,141	442
Proceeds from issuance of Series D convertible redeemable preferred stock, net of issuance costs of $193			44,807
Repayment of term note	(2,667)	(2,667)	(1,286)
Repayment of lease note payable			(59)
Restricted cash			(16)
Proceeds from the exercise of stock options	736	443	517
Payments made for employee restricted stock tax withholdings	(68)
Net cash provided by financing activities	33,480	135,558	115,992
Net (decrease) increase in cash and cash equivalents	(34,528)	57,528	94,063
Cash and cash equivalents at beginning of period	153,225	95,697	1,634
Cash and cash equivalents at end of period	118,697	153,225	95,697
Supplemental disclosure of cash flow information
Cash paid for offering costs	1,228
Cash paid for interest	139	284	353
Supplemental disclosure of non-cash activities
Offering costs in accrued expenses	55
Acquisition of property and equipment in accrued expenses	$ 216	$ 81
Preferred stock conversion to common stock			120,302
Extinguishment of preferred stock			31,184
Accruals of dividends and accretion to redemption value			24,572
Conversion of bridge note to preferred stock			$ 5,000