| Significant Components of Deferred Tax Assets |
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December 31,
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2015
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2014
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Deferred tax assets:
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(in thousands)
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Federal and state net operating losses
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$
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68,552
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$
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65,012
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Capitalized research and patent costs
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24,876
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25,567
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Research credits
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19,208
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22,789
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Biopharma Financing Agreement
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10,423
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13,296
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Stock-based compensation costs
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6,246
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6,410
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Other
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4,345
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2,995
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Total deferred tax assets
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133,650
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136,069
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Valuation allowance
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(133,650)
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(136,069)
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Net deferred tax assets
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$
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—
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$
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—
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| Reconciliation of Statutory Federal Income Tax Rate to Effective Rate |
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Year ended December 31,
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2015
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2014
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2013
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(in thousands)
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U.S. federal taxes (benefit) at statutory rate
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$
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(2,178)
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$
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(10,670)
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$
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(15,644)
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Unutilized net operating loss
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2,495
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11,002
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16,181
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Unutilized research credits
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(445)
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(1,308)
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(1,515)
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Non-deductible offset of Orphan Drug Credit
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—
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249
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383
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Non-deductible stock based compensation
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6
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673
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567
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Other
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122
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54
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28
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Total
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$
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—
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$
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—
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$
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—
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