STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities
Net loss	$ (10,833)	$ (5,270)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	5	10
Stock-based compensation expense	698	236
Noncash interest on convertible notes payable		91
Change in fair value of warrant liability	(1,192)	(153)
Amortization of debt issuance costs	4
Changes in operating assets and liabilities:
Prepaid expenses and other assets	1,344	(1,731)
Accounts payable and accrued expenses	1,385	189
Net cash used in operating activities	(8,589)	(6,628)
Cash flows from investing activities
Purchases of property and equipment	(33)	(17)
Net cash used in investing activities	(33)	(17)
Cash flows from financing activities
Proceeds from exercise of stock options	128	18
Proceeds from initial public offering, net of offering costs	41,202
Proceeds from notes payable, net of issuance costs	6,975
Proceeds from investor deposit		500
Proceeds from issuance of convertible preferred stock, net of issuance costs		7,530
Net cash provided by financing activities	48,305	8,048
Net increase in cash and cash equivalents	39,683	1,403
Cash and cash equivalents-beginning of year	10,037	8,634
Cash and cash equivalents-end of year	49,720	10,037
Supplemental disclosure of cash flow information
Conversion of preferred stock to common stock	70,340
Conversion of notes principal and accrued interest to preferred stock		2,761
Cash paid for interest	89
Issuance of Series C Preferred Stock	$ 500