Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Schedule of Reconciliation of Statutory Federal Income Tax Rate to Company's Effective Tax Rate

The effective tax rate of the Company’s provision for income taxes differs from the federal statutory rate as follows:

	Year Ended December 31,
	2021			2020			2019
Statutory federal income tax rate		21.0	%		21.0	%		21.0	%
State tax, net of federal benefit		10.2			7.9			4.2
Permanent differences		(0.1	)		(0.6	)		(0.8	)
Research and development tax credits		1.9			2.8			2.6
Other		(1.8	)		(0.2	)		(0.8	)
Change in state tax apportionment		—			9.4			—
Non-taxable stock premium		2.5			—			—
Change in valuation allowance		(33.7	)		(40.3	)		(26.3	)
Total provision for income taxes		—	%		—	%		—	%

Schedule of Components of Net Deferred Tax Assets/Liabilities

The components of the net deferred tax assets/liabilities are as follows (in thousands):

	December 31,
	2021			2020
Deferred tax assets:
Federal and state net operating loss carryforwards	$	97,575		$	74,278
Research and development tax credits		12,271			9,247
Lease liabilities		7,684			7,327
Accruals and other		3,184			3,354
Amortization		10,633			11,155
Deferred revenue		2,537			3,414
Gross deferred tax assets		133,884			108,775
Valuation allowance		(127,007	)		(101,781	)
Net deferred tax assets		6,877			6,994
Deferred tax liabilities:
Other depreciation		(212	)		(763	)
Operating lease right-of-use assets		(6,665	)		(6,231	)
Deferred tax assets, net of allowance	$	—		$	—

Schedule of Net Operating Loss and Tax Credit Carryforwards

Net operating loss and tax credit carryforwards as of December 31, 2021 are as follows (in thousands):

	Amount		Expiration Years
Net operating losses, federal (post December 31, 2017)	$	303,229	Do not expire
Net operating losses, federal (pre January 1, 2018)		50,587	2035 - 2037
Net operating loss, state		347,184	2035 - 2040
Tax credits, federal		10,990	2035 - 2040
Tax credits, state		7,806	CA: credits do not expire MA: 2035 - 2040

Schedule of Unrecognized Tax Benefits

The following table summarizes the activity related to the Company’s unrecognized tax benefits (in thousands):

	December 31,
	2021		2020		2019
Beginning of year—unrecognized tax benefits	$	4,025	$	2,610	$	2,077
Decrease for tax positions taken during prior periods		—		—		(711	)
Increases for tax positions taken during current period		1,456		1,415		1,244
End of year—unrecognized tax benefits	$	5,481	$	4,025	$	2,610