INCOME TAXES (Tables)

12 Months Ended

Dec. 31, 2019

Schedule of significant components of the entity's deferred tax assets

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of our deferred tax assets are as follows:

	December 31,
	2019			2018
	(In thousands)
Net operating loss carryforwards	$	204,600		$	192,100
Research credits		38,400			35,500
Capitalized research and development		5,900			2,500
Stock-based compensation		7,700			6,400
Operating lease liabilities		700			—
Other		1,200			600
Total deferred tax assets		258,500			237,100
Less: valuation allowance		(257,900	)		(237,100	)
Net deferred tax assets		600			—

Operating leases, right-of-use assets		(600	)		—
Total deferred tax liabilities		(600	)		—
Total net deferred tax assets	$	—		$	—

Schedule of reconciliation of the beginning and ending amounts of unrecognized tax benefits

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

Balance as of December 31, 2018	$	16,400
Decrease related to prior year tax positions		(40	)
Increase related to current year tax positions		1,340
Balance as of December 31, 2019	$	17,700