Income Taxes	6 Months Ended
Jun. 30, 2018
Income Taxes
Income Taxes	10. Income Taxes During the three and six months ended June 30, 2018 and 2017, we did not record an income tax benefit related to our loss before income taxes in the statement of operations and comprehensive loss because a valuation allowance has been required to be established for all deferred tax assets due to our cumulative net loss position. As of December 31, 2017, our gross federal net operating loss carryforwards of $110.9 million will expire at various dates beginning in 2028. In addition, net operating loss carryforwards for state income tax purposes of $65.9 million that include net operating losses that will begin to expire in 2028. We also have R&D credit carryforwards of $1.4 million as of December 31, 2017 of which will expire at various dates beginning in 2032. Utilization of the net operating loss carryforwards may be subject to an annual limitation due to the ownership change limitations provided by Section 382 of the Internal Revenue Code of 1986 and similar state provisions. The annual limitation may result in the expiration of the net operating loss before utilization. Realization of the deferred tax assets is dependent upon the generation of future taxable income, if any, the amount and timing of which are uncertain. Based on available objective evidence and cumulative losses, management believes it is more likely than not that the deferred tax assets are not recognizable and will not be recognizable until we have sufficient taxable income. Accordingly, the net deferred tax assets have been fully offset by a valuation allowance. We had no unrecognized tax benefits as of June 30, 2018 and December 31, 2017. We file income tax returns in the U.S. federal and various state jurisdictions. The 2014 to 2017 tax years remain open to examination by the major taxing authorities to which we are subject. We do not expect a significant change to our unrecognized tax benefits over the next 12 months. The Tax and Jobs Act ("the Act") was enacted on December 22, 2017. The Act reduces the U.S. federal corporate tax rate from 35% to 21%, requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax deferred and creates new taxes on certain foreign-sourced earnings. We have applied the guidance in ASU 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118, when accounting for the enactment-date effects of the Act. At June 30, 2018, we have not completed our accounting for the tax effects of the Act, as we are in the process of analyzing certain aspects of the Act, obtaining information, and refining our calculations of the Act's impact. There have been no material measurement period adjustments made during the six months ended June 30, 2018 related to the provisional amounts recorded and disclosed in our Registration Statement Form S-1 and Prospectus dated May 2, 2018. We expect to complete the accounting for the tax effects of the Act during 2018.

10. Income Taxes

During the three and six months ended June 30, 2018 and 2017, we did not record an income tax benefit related to our loss before income taxes in the statement of operations and comprehensive loss because a valuation allowance has been required to be established for all deferred tax assets due to our cumulative net loss position.

As of December 31, 2017, our gross federal net operating loss carryforwards of $110.9 million will expire at various dates beginning in 2028. In addition, net operating loss carryforwards for state income tax purposes of $65.9 million that include net operating losses that will begin to expire in 2028. We also have R&D credit carryforwards of $1.4 million as of December 31, 2017 of which will expire at various dates beginning in 2032.

Utilization of the net operating loss carryforwards may be subject to an annual limitation due to the ownership change limitations provided by Section 382 of the Internal Revenue Code of 1986 and similar state provisions. The annual limitation may result in the expiration of the net operating loss before utilization.

Realization of the deferred tax assets is dependent upon the generation of future taxable income, if any, the amount and timing of which are uncertain. Based on available objective evidence and cumulative losses, management believes it is more likely than not that the deferred tax assets are not recognizable and will not be recognizable until we have sufficient taxable income. Accordingly, the net deferred tax assets have been fully offset by a valuation allowance.

We had no unrecognized tax benefits as of June 30, 2018 and December 31, 2017. We file income tax returns in the U.S. federal and various state jurisdictions. The 2014 to 2017 tax years remain open to examination by the major taxing authorities to which we are subject. We do not expect a significant change to our unrecognized tax benefits over the next 12 months.

The Tax and Jobs Act ("the Act") was enacted on December 22, 2017. The Act reduces the U.S. federal corporate tax rate from 35% to 21%, requires companies to pay a one-time transition tax on earnings of certain foreign subsidiaries that were previously tax deferred and creates new taxes on certain foreign-sourced earnings.

We have applied the guidance in ASU 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118, when accounting for the enactment-date effects of the Act. At June 30, 2018, we have not completed our accounting for the tax effects of the Act, as we are in the process of analyzing certain aspects of the Act, obtaining information, and refining our calculations of the Act's impact. There have been no material measurement period adjustments made during the six months ended June 30, 2018 related to the provisional amounts recorded and disclosed in our Registration Statement Form S-1 and Prospectus dated May 2, 2018. We expect to complete the accounting for the tax effects of the Act during 2018.