Marketable Securities, Available-for-sale (in thousands):



	March 31, 2015
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. treasury securities	$	30,049	$	—	$	(23	)	$	30,026
Certificates of deposit	49		—		—			49
Mutual funds	277		266		—			543
Total marketable securities	$	30,375	$	266	$	(23	)	$	30,618



	December 31, 2014
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. treasury securities	$	30,049	$	—	$	(29	)	$	30,020
Certificates of deposit	48		—		—			48
Mutual funds	277		243		—			520
Total marketable securities	$	30,374	$	243	$	(29	)	$	30,588

As of March 31, 2015 and December 31, 2014, gross unrealized losses on marketable securities were insignificant. There were no impairments considered other-than-temporary for the periods presented, as the Company has the intent and ability to hold the securities for a period of time sufficient to allow for recovery in the market value. As of March 31, 2015 all marketable securities were due within one year.

Other Current Assets and Prepaid Expenses (in thousands):



	March 31, 2015		December 31, 2014
Pooled patents agreement receivable	$	—	$	6,000
Other	5,446		6,112
Total	$	5,446	$	12,112

Inventories (in thousands):



	March 31, 2015		December 31, 2014
Raw materials	$	4,433	$	6,165
Work in process	346		351
Total	$	4,779	$	6,516

Accrued Expenses (in thousands):



	March 31, 2015		December 31, 2014
Accrued royalties, licenses, and collaboration payments	$	5,772	$	7,223
Accrued compensation and related taxes	5,841		7,606
Accrued professional fees and consulting	2,017		1,872
Other	1,673		5,454
Total	$	15,303	$	22,155