Balance Sheet Components

Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets, as of December 31, 2019 and 2018 consists of the following (in thousands):



	December 31,
	2019		2018
Prepaid expenses	$	8,475	$	10,401
Tenant incentives receivables	4,093		10,089
Interest receivable on marketable securities	6,835		7,909
Prepaid expenses and other current assets	$	19,403	$	28,399

Property and Equipment, Net

Property and equipment, net as of December 31, 2019 and 2018 consists of the following (in thousands):



	December 31,
	2019			2018
Building ⁽¹⁾	$	—		$	140,442
Laboratory equipment	108,257			96,907
Leasehold improvements ⁽¹⁾	152,426			13,741
Furniture, fixtures and other	3,316			2,122
Computer equipment and software	11,985			11,513
Internally developed software	7,020			7,020
Right-of-use asset, financing	9,853			—
Construction in progress	3,222			4,688
	296,079			276,433
Less: Accumulated depreciation	(94,584		)	(64,456		)
Property and equipment, net	$	201,495		$	211,977

_________

⁽¹⁾Leasehold improvements related to our Moderna Technology Center manufacturing facility were previously capitalized as building under ASC 840 and are now included in leasehold improvements under ASC 842 (Note 2).

Depreciation and amortization expense for the years ended December 31, 2019, 2018 and 2017 was $31.0 million, $24.9 million, $20.5 million, respectively.

Accrued Liabilities

Accrued liabilities, as of December 31, 2019 and 2018 consists of the following (in thousands):



	December 31,
	2019		2018
In-licenses	$	—	$	22,000
Property and equipment	4,029		12,089
Compensation-related	27,428		23,406
External goods and services	36,195		21,578
Accrued liabilities	$	67,652	$	79,073