Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 142,086	$ 205,912
Accounts receivable	1,789	4,151
Prepaid expenses and other current assets	6,582	3,705
Total current assets	150,457	213,768
Property and equipment, net	1,054	943
Restricted cash	199	199
Other assets		7
Total assets	151,710	214,917
Current liabilities:
Accounts payable	2,555	2,857
Accrued expenses	7,685	6,931
Deferred revenue	1,255	909
Total current liabilities	11,495	10,697
Other long term liabilities	162	165
Commitments and contingencies
Stockholders' equity:
Preferred stock, par value $0.001 per share; 5,000 shares authorized; no shares issued and outstanding
Common stock, par value $0.001 per share; 125,000 shares authorized; 36,942 and 36,585 shares issued and outstanding at December 31, 2016 and 2015, respectively	37	37
Additional paid-in capital	487,148	473,670
Accumulated deficit	(347,132)	(269,652)
Total stockholders’ equity	140,053	204,055
Total liabilities and stockholders’ equity	$ 151,710	$ 214,917

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

Name:	us-gaap_AccountsPayableCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.