Condensed Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 57,068	$ 117,773
Short-term investments	170,857	150,892
Receivables from collaborators	182	309
Prepaid expenses and other current assets	5,009	3,733
Total current assets	233,116	272,707
Property and equipment, net	2,890	2,600
Long-term investments	58,002	50,371
Other assets	6	53
Total assets	294,014	325,731
Current liabilities:
Accounts payable	6,003	3,232
Accrued compensation and employee benefits	2,273	2,569
Accrued and other liabilities	19,315	17,796
Deferred revenue, current portion	7,719	1,958
Total current liabilities	35,310	25,555
Deferred revenue, long-term	15,706	3,253
Other long-term liabilities	1,102	588
Total liabilities	52,118	29,396
Stockholders’ equity:
Preferred stock, $0.001 par value, 5,000,000 shares authorized at June 30, 2014 and December 31, 2013; 0 shares issued and outstanding at June 30, 2014 and December 31, 2013
Common stock, $0.001 par value, 100,000,000 shares authorized at June 30, 2014 and December 31, 2013; 41,396,227 and 40,915,130 shares issued and outstanding at June 30, 2014 and December 31, 2013, respectively	41	41
Additional paid-in capital	589,581	581,911
Accumulated deficit	(347,748)	(285,672)
Accumulated other comprehensive income	22	55
Total stockholders’ equity	241,896	296,335
Total liabilities and stockholders’ equity	$ 294,014	$ 325,731