Balance Sheet Components

12 Months Ended

Dec. 31, 2019

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Components

5. Balance Sheet Components

Property and Equipment

Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the assets, ranging from two to five years. Leasehold improvements are amortized over the shorter of their estimated useful lives or the related lease term. Upon retirement or sale, the cost and related accumulated depreciation are removed from the consolidated balance sheet and the resulting gain or loss is reflected in the consolidated statement of operations and comprehensive loss.

Property and equipment consists of the following (in thousands):

	December 31,
	2019			2018
Scientific equipment	$	10,642		$	9,126
Furniture and equipment		2,572			1,248
Capitalized software		389			302
Leasehold improvements		509			451
Construction in progress		9,568			—
Total		23,680			11,127
Less: Accumulated depreciation		(7,937	)		(5,989	)
Property and equipment, net	$	15,743		$	5,138

Depreciation expense was $1.9 million, $1.6 million and $1.3 million for the years ended December 31, 2019, 2018 and 2017, respectively.  Construction in progress consists of leasehold improvements made to the Company’s Brisbane, California facility in preparation for occupancy in January 2020.  

The Company reviews long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. An impairment charge would be recorded when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount. Impairment, if any, is assessed using discounted cash flows or other appropriate measures of fair value. Through December 31, 2019, there have been no such impairment charges.

Accrued Liabilities

Accrued liabilities consist of the following (in thousands):

	December 31,
	2019		2018
Clinical trials accrued liabilities	$	11,494	$	6,272
Outside services		6,592		4,631
Payroll-related liabilities		11,724		8,151
Construction in progress		9,139		—
Other		2,343		1,704
Total accrued liabilities	$	41,292	$	20,758

Construction in progress consists of leasehold improvements made to the Company’s Brisbane, California facility in preparation for occupancy in January 2020.