5. Other Balance Sheet Accounts

Property and equipment consisted of the following at December 31 (in thousands):

	2015			2014
Equipment	$	17,425		$	17,515
Leasehold improvements		8,048			8,048
		25,473			25,563
Less accumulated depreciation and amortization		(23,600	)		(22,924	)
	$	1,873		$	2,639

Depreciation and amortization of equipment and leasehold improvements for the years ended December 31, 2015, 2014 and 2013, was $0.9 million, $1.4 million and $1.6 million, respectively.

Intangible assets consisted of the following at December 31 (in thousands):

	2015			2014
Patent application costs		2,252			2,972
Accumulated amortization patent costs		(952	)		(1,312	)
	$	1,300		$	1,660

Amortization of licensed technology rights and patent application costs for the years ended December 31, 2015, 2014 and 2013, was $0.2 million, $0.2 million and $0.4 million, respectively. Estimated annual amortization for these assets is $0.2 million for the years ended 2016 and 2017, $0.1 million for each of the years in the period from 2018 to 2020, and $0.6 million being recognized thereafter.

Accounts payable and accrued expenses consisted of the following at December 31 (in thousands):

	2015		2014
Employee compensation	$	2,220	$	2,471
Clinical trial accruals		102		1,686
Accounts payable		733		227
Deferred rent		496		432
Other accrued liabilities		361		385
	$	3,912	$	5,201