CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities
Net loss	$ (3,615,207)	$ (17,275,099)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	46,506	124,000
Stock-based compensation expense	433,522	1,419,933
Amortization and accretion on investments	0	11,537
Other non-cash items	0	22,274
Changes in operating assets and liabilities:
Accounts receivable	(18,339)	(184)
Inventory	56,000	139,206
Prepaid expenses and other current assets	(273,884)	(93,909)
Accounts payable	462,986	(859,107)
Accrued expenses and other current liabilities	(533,588)	(1,127,164)
Deferred rent	0	(29,410)
Net cash used in operating activities	(3,442,004)	(17,667,923)
Investing activities
Purchases of marketable securities	0	(1,997,751)
Proceeds from maturities and sales of marketable securities	0	16,117,184
Proceeds from sales of property and equipment	0	1,415
Net cash provided by investing activities	0	14,120,848
Financing activities
Proceeds from exercise of common stock	0	118,010
Net cash provided by financing activities	0	118,010
Net decrease in cash, cash equivalents and restricted cash	(3,442,004)	(3,429,065)
Cash, cash equivalents and restricted cash at beginning of period	9,956,219	19,312,631
Cash, cash equivalents and restricted cash at end of period	$ 6,514,215	$ 15,883,566