FIXED ASSETS

Fixed assets, summarized by major category, consist of the following (in thousands):



	September 30,			December 31,
	2016			2015
Machinery and laboratory equipment	$	32,920		$	29,864
Leasehold improvements	32,665			30,834
Computer equipment and software	5,787			4,007
Office furniture and equipment	1,606			1,439
Construction in progress	61,898			49,097
Total	134,876			115,241
Less: accumulated depreciation	(34,488		)	(24,917		)
Fixed assets, net	$	100,388		$	90,324

For the three months ended September 30, 2016 and 2015, depreciation expense was $3.3 million and $2.8 million, respectively. For the three months ended September 30, 2016 and 2015, capitalized interest on the construction of manufacturing sites was $0.5 million and $0.2 million, respectively.

For the nine months ended September 30, 2016 and 2015, depreciation expense was $9.6 million and $8.1 million, respectively. For the nine months ended September 30, 2016 and 2015, capitalized interest on the construction of manufacturing sites was $1.2 million and $0.6 million, respectively.

As of September 30, 2016 and December 31, 2015, total fixed assets, net, includes leasehold improvements and manufacturing process equipment located in England in the amount of $32.3 million and $25.9 million, respectively.