Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 86,058	$ 117,763
Marketable securities	127,441	89,607
Accounts receivable, net of allowance of $171 at March 31, 2016 and December 31, 2015	8,201	7,362
Receivable due from Roche	2,368	403
Inventory	6,743	7,992
Prepaid expenses and other current assets	5,088	6,517
Total current assets	235,899	229,644
Marketable securities		24,939
Property and equipment, net	41,104	41,333
Restricted cash	1,395	1,395
Other assets	2,155	678
Total assets	280,553	297,989
Current liabilities:
Accounts payable	8,518	10,469
Accrued expenses and other current liabilities	14,290	12,822
Deferred revenue	1,797	717
Roche related-party deferred revenue	230	3,742
Current portion of deferred rent	2,184	2,146
Total current liabilities	27,019	29,896
Deferred rent, net of current portion and other non-current liabilities	$ 9,801	$ 10,404
Commitments and contingencies (Note 14)
Stockholders’ equity:
Preferred stock, $0.0001 par value, 5,000,000 shares authorized; no shares issued and outstanding at March 31, 2016 and December 31, 2015
Common stock, $0.0001 par value, 150,000,000 shares authorized; 34,592,610 and 34,513,845 shares issued and outstanding at March 31, 2016 and December 31, 2015, respectively	$ 3	$ 3
Additional paid-in capital	492,667	489,480
Accumulated other comprehensive loss	(14)	(178)
Accumulated deficit	(248,923)	(231,616)
Total stockholders’ equity	243,733	257,689
Total liabilities and stockholders’ equity	$ 280,553	$ 297,989