Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of Reconciliation between Statutory Federal Income Tax Rate and Effective Tax Rate

The following is the reconciliation between the statutory federal income tax rate and the Company’s effective tax rate:  

	Year Ended December 31,
	2019			2018			2017
Federal statutory income tax rate		21.0	%		21.0	%		34.0	%
State taxes (tax effected)		7.3			8.6			7.1
Non-deductible expenses and other		(0.5	)		2.5			2.0
Research and development reimbursements		3.2			5.9			6.0
Change in valuation allowance		(31.0	)		(38.0	)		(24.0	)
Tax Act – net deferred tax rate change		—			—			(25.1	)
Total		—	%		—	%		—	%

Components of Company's Deferred Tax Assets

As of December 31, 2019 and 2018, the components of the Company’s deferred tax assets are as follows (in thousands):

	As of December 31,
	2019			2018
Deferred tax assets:
Net operating loss carryforwards		98,445			49,689
Research and development reimbursement carryforwards		23,061			12,908
Stock-based compensation		8,861			4,349
Start-up costs		22,896			1,237
Depreciation		(1,027	)		(959	)
Other		2,646			1,858
Total deferred tax assets		154,882			69,082
Less: valuation allowance		(154,882	)		(69,082	)
Net deferred tax assets		—			—

Schedule of Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):

	For the Year Ended December 31,
	2019		2018		2017
Beginning balance	$	3,810	$	2,471	$	1,474
Increases (decreases) of unrecognized tax benefits related to prior year		380		289		(97	)
Increases of unrecognized tax benefits related to current year		3,314		1,050		1,094
Ending balance	$	7,504	$	3,810	$	2,471