Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Operating activities
Net loss	$ (27,330)	$ (21,031)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	177	177
Stock-based compensation expense	4,451	878
Revaluation of convertible preferred stock warrant liability	0	4,277
Changes in operating assets and liabilities:
Accounts receivable	(1,173)	37
Inventory	(282)	(464)
Prepaid expenses	(792)	(609)
Accounts payable	(4,224)	2,204
Accrued liabilities	(1,064)	1,763
Deferred rent	(21)	(16)
Net cash used in operating activities	(30,258)	(12,784)
Investing activities
Purchases of property and equipment	(308)	(191)
Net cash used in investing activities	(308)	(191)
Financing activities
Issuance of common stock in public offering, net of offering costs	75,359	57,807
Proceeds from exercise of preferred stock warrants	0	8,150
Proceeds from exercise of stock options and employee stock purchases	343	19
Net cash provided by financing activities	75,702	65,976
Net increase in cash and cash equivalents	45,136	53,001
Cash and cash equivalents, beginning of period	75,354	30,387
Cash and cash equivalents, end of period	120,490	83,388
Conversion of Preferred Stock Into Common Stock [Member]
Conversion of stock, amount issued	0	81,394
Conversion of Preferred Warrants Into Common Stock [Member]
Conversion of stock, amount issued	$ 0	$ 7,613