Balance Sheet Details (Tables)

12 Months Ended

Dec. 31, 2021

Balance Sheet Related Disclosures [Abstract]

Schedule of Cash and Cash Equivalents

Cash equivalents consisted of the following (in thousands): 

	December 31, 2021				December 31, 2020
	Adjusted Cost		Estimated Fair Value		Adjusted Cost		Estimated Fair Value
Money market funds (1)	$	86,095	$	86,095	$	127,567	$	127,567

(1) Money market funds are classified in cash and cash equivalents on our consolidated balance sheets. Average contractual maturities (in days) is not applicable.

Schedule of Inventory Components

Inventories consisted of the following (in thousands): 

	December 31,
	2021		2020
Raw materials	$	49	$	77
Work in process	65		82
Finished goods	1,046		805
Inventories	$	1,160	$	964

Property and Equipment, Net

Property, equipment and leasehold improvements are stated at cost less accumulated depreciation and amortization calculated using the straight-line method over their estimated useful lives as follows:

Asset classification	Estimated useful life
Laboratory equipment	5 years
Computer equipment and software	3 to 5 years
Office equipment and furniture	5 years
Leasehold improvements	Lesser of useful life or lease term

Property and equipment, net consisted of the following (in thousands): 

	December 31,
	2021		2020
Laboratory equipment (1)	$	33,101	$	25,468
Leasehold improvements	16,117		10,785
Computer equipment and software	3,481		3,192
Office equipment and furniture	1,297		1,246
Construction in progress (2)	3,231		2,357
Property and equipment	57,227		43,048
Less: accumulated depreciation and amortization	(35,882)		(33,373)
Property and equipment, net	$	21,345	$	9,675

(1) Fully depreciated property and equipment with a cost of $0.6 million and $1.8 million were retired during the years ended December 31, 2021 and 2020, respectively.

(2) Construction in progress includes equipment received but not yet placed into service pending installation.

Depreciation expense included in both research and development expenses and selling, general and administrative expenses in the consolidated statements of operations was as follows (in thousands):

	Year Ended December 31,
	2021		2020		2019
Depreciation expense	$	3,113	$	1,950	$	1,570

Schedule of Accrued Liabilities

Other accrued liabilities consisted of the following (in thousands): 

	December 31,
	2021		2020
Accrued purchases	$	6,755	$	7,170
Accrued professional and outside service fees	5,147		2,589
Other	676		513
Total	$	12,578	$	10,272