INCOME TAXES (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of Deferred Tax Assets

The significant components of the Company’s net deferred tax assets as of December 31, 2019 and 2018 are shown below.

	December 31,
(in thousands)	2019		2018
Deferred tax assets
Net operating loss carryforwards	$	82,252	$	45,215
Research and development credits	8,968		4,090
Capitalized assets	79		23
Accruals and reserves	651		390
Operating lease liabilities	2,070		806
Stock-based compensation	4,250		—
Gross deferred tax assets	98,270		50,524
Deferred tax liabilities
Operating lease right-of-use assets	(1,969)		—
Gross deferred tax liabilities	(1,969)		—
Total net deferred tax assets	96,301		50,524
Less: valuation allowance	(96,301)		(50,524)
Net deferred tax assets	$	—	$	—

Schedule of Effective Income Tax Rate Reconciliation

The following is a reconciliation between the U.S. federal income statutory tax rate and the Company’s effective tax rate for the years ended December 31, 2019, 2018 and 2017.

	Years Ended December 31,
	2019		2018		2017
U.S. federal statutory rate	21.0	%	21.0	%	34.0	%
State income taxes, net of federal benefit	—		—		5.8
Stock-based compensation	2.2		(0.2)		(0.7)
Permanent adjustments	(0.1)		(0.1)		4.2
Change to valuation allowance	(25.9)		(21.9)		(19.6)
Tax Cuts and Jobs Act Impact	—		—		(25.4)
Research and development credits	2.8		1.3		1.6
Net unrealized gain on available-for-sale investments	0.1		—		—
Other	—		(0.1)		—
Effective tax rate	0.1	%	—	%	—	%

Schedule of Unrecognized Tax Benefits

The beginning and ending gross unrecognized tax benefits amounts are as follows.

	Years Ended December 31,
(in thousands)	2019		2018		2017
Gross unrecognized tax benefits at beginning of year	$	1,297	$	819	$	574
Additions for tax positions related to prior year	—		—		2
Decrease related to prior year tax provisions	—		—		(92)
Additions for tax positions related to current year	1,246		478		335
Gross unrecognized tax benefits at end of year	$	2,543	$	1,297	$	819