CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 193,617	$ 180,895
Marketable securities	424,185	848,217
Investment in equity securities of Regulus Therapeutics Inc.	8,997	51,419
Billed and unbilled collaboration receivables	23,334	8,298
Prepaid expenses and other current assets	21,744	16,559
Total current assets	671,877	1,105,388
Marketable securities	324,799	251,839
Property, plant and equipment, net	114,572	27,812
Restricted investments	150,000
Other assets	1,562	1,471
Total assets	1,262,810	1,386,510
Current liabilities:
Accounts payable	54,465	16,787
Accrued expenses	42,118	28,798
Deferred rent	1,576	1,162
Deferred revenue	33,540	15,352
Total current liabilities	131,699	62,099
Deferred rent, net of current portion	8,431	5,431
Deferred revenue, net of current portion	49,392	52,965
Long-term debt	150,000
Other liabilities	3,067	1,301
Total liabilities	342,589	121,796
Commitments and contingencies (Note 7)
Stockholders’ equity:
Preferred stock, $0.01 par value per share, 5,000,000 shares authorized and no shares issued and outstanding at December 31, 2016 and 2015
Common stock, $0.01 par value per share, 125,000,000 shares authorized; 85,941,344 shares issued and outstanding at December 31, 2016; 85,090,968 shares issued and outstanding at December 31, 2015	859	851
Additional paid-in capital	2,609,614	2,506,197
Accumulated other comprehensive (loss) income	(33,441)	4,369
Accumulated deficit	(1,656,811)	(1,246,703)
Total stockholders’ equity	920,221	1,264,714
Total liabilities and stockholders’ equity	$ 1,262,810	$ 1,386,510