CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating activities
Net loss	$ (17,073,018)	$ (20,955,594)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	171,109	89,958
Stock-based compensation expense	2,262,098	3,506,482
Amortization and accretion on investments	(15,895)	78,751
Changes in operating assets and liabilities:
Accounts receivable	(22,554)	(11,595)
Inventory	207,063	(274,302)
Prepaid expenses and other current assets	(283,209)	(1,351,291)
Other assets	64,800	(64,800)
Accounts payable	601,646	508,066
Accrued expenses and other current liabilities	101,705	(78,918)
Deferred revenue	8,323	65,115
Deferred rent	62,385	2,363
Other long term liabilities	0	(15,442)
Net cash used in operating activities	(13,915,547)	(18,501,207)
Investing activities
Purchases of marketable securities	(9,607,390)	(22,074,850)
Proceeds from maturities and sales of marketable securities	40,282,017	13,112,760
Purchases of property and equipment	(53,741)	(290,202)
Proceeds from sales of property and equipment	3,375	0
Net cash provided by (used in) investing activities	30,624,261	(9,252,292)
Financing activities
Proceeds from exercise of common stock	2,047	8,043
Net cash provided by financing activities	2,047	8,043
Net increase (decrease) in cash and cash equivalents	16,710,761	(27,745,456)
Cash and cash equivalents at beginning of period	22,416,040	66,686,695
Cash and cash equivalents at end of period	39,126,801	38,941,239
Supplemental cash flow information
Inventory purchases included in accrued expenses at June 30, 2017	441,116	0
Property and equipment purchases included in accounts payable at June 30, 2017 and 2016	19,630	161,049
Property and equipment purchases included in accounts payable and accrued expenses at December 31, 2016 and 2015	$ 7,100	$ 106,680