Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Amounts for the years ended December 31 were as follows (in thousands):

Deferred Tax Assets	2017			2016
Net operating losses	$	59,756		$	86,071
Credit carryovers		10,527			9,952
Depreciation and amortization		10,893			15,278
Deferred revenue		634			—
Accruals and reserves		450			701
Capital loss carryover		—			85
Other		1,350			2,677
Total deferred tax assets		83,610			114,764
Less valuation allowance		(83,610	)		(114,764	)
Net deferred tax assets	$	—		$	—

Reconciliation Between Provision for Income Taxes and Income Taxes

As part of the revaluation of the amounts disclosed within the financial statements related to the deferred tax assets in 2017 resulting from the Tax Cuts and Jobs Act (the “Act”) and in preparing the 2017 financial statement footnote disclosures, the Company determined that the December 31, 2016 deferred tax asset for net operating losses did not reflect the impact of the uncertain tax position recorded related to the Company’s orphan drug credits and was understated by $2.02 million with the valuation allowance also understated by the same amount. Accordingly, the 2016 amounts have been changed for the purposes of presentation within the above table. These changes in the disclosed deferred tax assets and valuation allowance did not impact the balance sheets or the statements of stockholders' equity, operations, comprehensive loss or cash flows as the Company is in a net loss position with a full valuation allowance on its deferred tax assets and were not considered to be material to the previously issued financial statements.

The reconciliation between the provision for income taxes and income taxes computed using the U.S. federal statutory corporate tax rate were as follows for the years ended December 31 (in thousands):

	2017			2016			2015
Computed “expected” tax benefit	$	(4,425	)	$	(3,051	)	$	(3,152	)
State income taxes, net of federal benefit		(268	)		(534	)		—
Tax effect of:
Change in valuation allowance		(31,665	)		(6,030	)		(4,069	)
Impact of Tax Cuts and Jobs Act		34,439			—			—
Rate change		—			—			3,524
Expiration of prior year credits and net operating losses		1,256			692			786
Stock compensation		458			491			376
Uncertain tax positions		276			9,010			3,074
Other		(71	)		(578	)		(539	)
Provision for income taxes	$	—		$	—		$	—

Summary of Activity Related to Unrecognized Tax Benefits

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

	2017			2016		2015
Beginning balance	$	17,561		$	4,340	$	582
Increases (decreases) related to prior year tax positions		(140	)		12,348		3,758
Increases related to current year tax positions		415			873		—
Ending balance	$	17,836		$	17,561	$	4,340