Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 58,288	$ 68,454
Marketable securities	422,407	445,733
Accounts receivable	15,500	0
Prepaid expenses	8,071	6,718
Other current assets	6,323	11,825
Total current assets	510,589	532,730
Property and equipment, net	10,632	2,870
Operating lease right-of-use assets	8,423	0
Intangible assets	102,500	102,500
Goodwill	6,234	6,234
Other noncurrent assets	2,154	3,997
Total assets	640,532	648,331
Current liabilities:
Accounts payable	8,167	7,989
Accrued and other current liabilities	18,594	18,086
Deferred revenue, current	5,000	0
Current portion of operating lease liabilities	1,412	0
Current portion of contingent consideration	22,800	32,300
Total current liabilities	55,973	58,375
Deferred revenue, noncurrent	10,500	0
Operating lease liabilities, net of current portion	11,355	0
Contingent consideration, net of current portion	48,400	45,900
Deferred income taxes	17,425	17,425
Other long-term liabilities	0	3,830
Total liabilities	143,653	125,530
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000 shares authorized; none issued and outstanding	0	0
Common stock, $0.001 par value; 50,000 shares authorized; 42,446 and 41,925 shares issued and outstanding at March 31, 2019 and December 31, 2018, respectively	42	42
Additional paid-in capital	1,227,620	1,218,710
Accumulated deficit	(731,156)	(695,954)
Accumulated other comprehensive income	373	3
Total stockholders’ equity	496,879	522,801
Total liabilities and stockholders’ equity	$ 640,532	$ 648,331