Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of temporary differences that give rise to deferred tax assets and liabilities

Temporary differences that give rise to deferred tax assets and liabilities are as follows (in thousands):

	For the years ended December 31,
	2019		2018		2017
Deferred Tax Liabilities
Unrealized gains on investments	$	62	$	—	$	—
Total deferred tax liabilities	$	62	$	—	$	—
Deferred Tax Assets
Charitable contributions	$	15	$	13	$	4
Accrued expenses		759		498		421
Intangibles		983		477		579
Stock compensation		10,943		4,395		605
Property, plant & equipment		13		9		—
Unrealized loss on investment		—		92		9
Net operating losses		17,635		14,851		9,229
Capitalized R&D		29,364		15,108		8,671

	For the years ended December 31,
	2019			2018			2017
R&D credit	$	6,141		$	3,505		$	1,901
Total deferred tax assets before valuation allowance		65,853			38,948			21,419
Valuation allowance		(65,791	)		(38,948	)		(21,419	)
Total deferred tax assets		62			—			—
Net deferred tax assets	$	—		$	—		$	—

Schedule of differences between the effective income tax rate and the US statutory rate

Differences between the effective income tax rate and the US statutory rate were as follows (in thousands):

	For the years ended December 31,
	2019			2018			2017
Tax benefit at U.S. federal statutory rate	$	(17,629	)	$	(6,890	)	$	(10,592	)
Stock based compensation		(47	)		(3,415	)		138
Effect of tax reform, change in federal tax rate		—			—			9,260
Other nondeductible expenses		14			—			1
State income taxes benefit before valuation allowance, net of federal benefit		(6,613	)		(5,460	)		(704	)
Increase in domestic valuation allowance		26,843			17,529			2,880
Research and development credit		(2,636	)		(1,604	)		(825	)
Other adjustments		68			(160	)		(158	)
Income tax expense (benefit)	$	—		$	—		$	—