CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
CURRENT ASSETS:
Cash and cash equivalents	$ 46,399	$ 68,789
Held-to-maturity investments	133,980	44,889
Withholding tax receivable		1,583
Prepaid expenses and other current assets	3,107	3,415
Total current assets	183,486	118,676
NONCURRENT ASSETS:
Property and equipment, net	1,212	1,512
Restricted cash equivalents	744	744
Other noncurrent assets	66	70
Total noncurrent assets	2,022	2,326
TOTAL ASSETS	185,508	121,002
CURRENT LIABILITIES:
Accounts payable	3,595	4,920
Accrued expenses and other current liabilities	8,101	5,726
Litigation settlement payable	12,797
Current portion of deferred revenue	4,635	6,180
Total current liabilities	29,128	16,826
NONCURRENT LIABILITIES:
Deferred revenue, net of current portion		3,090
Total noncurrent liabilities		3,090
TOTAL LIABILITIES	29,128	19,916
COMMITMENTS AND CONTINGENCIES
STOCKHOLDERS’ EQUITY:
Preferred stock, $0.0001 par value – 5,000,000 shares authorized; no shares issued or outstanding at September 30, 2018 or December 31, 2017
Common stock, $0.0001 par value – 150,000,000 shares authorized; 61,889,206 and 51,644,841 shares issued and outstanding at September 30, 2018 and December 31, 2017, respectively	6	5
Additional paid-in capital	542,572	417,037
Accumulated deficit	(386,198)	(315,956)
Total stockholders’ equity	156,380	101,086
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 185,508	$ 121,002