Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 72,454	$ 45,214
Short-term investments	68,653	62,041
Accounts receivable	647	517
Inventory	684	607
Prepaid expenses	1,571	2,546
Restricted cash	6,000	0
Other receivables	3,134	3,156
Total current assets	153,143	114,081
Property and equipment, net	491	414
Security deposit	200	0
Total assets	153,834	114,495
Current liabilities:
Accounts payable	2,334	4,559
Accrued liabilities	6,186	4,935
Accrued litigation-related settlement	6,000	7,250
Deferred revenue	0	2,519
Total current liabilities	14,520	19,263
Other noncurrent liabilities	102	56
Commitments and contingencies (Note 9)
Stockholders’ equity:
Common stock, $0.001 par value per share; 100,000,000 authorized at December 31, 2017 and 2016; 48,068,650 and 25,413,055 shares issued and outstanding at December 31, 2017 and 2016, respectively	48	25
Preferred stock, $0.001 par value; 10,000,000 shares authorized at December 31, 2017 and 2016; no shares issued or outstanding	0	0
Additional paid-in capital	374,970	278,913
Accumulated deficit	(235,757)	(183,738)
Accumulated other comprehensive loss	(49)	(24)
Total stockholders’ equity	139,212	95,176
Total liabilities and stockholders’ equity	$ 153,834	$ 114,495

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.