Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2019
Accounting Policies [Abstract]
Use of Estimates, Policy [Policy Text Block]	Use of Estimates The preparation of financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. On an ongoing basis, the Company evaluates its estimates, including those related to the useful lives of property and equipment, and assumptions used for purposes of determining stock-based compensation, income taxes, and the fair value of the derivative and warrant liability, among others. The Company bases its estimates on historical experience and on various other assumptions that it believes to be reasonable, the results of which form the basis for making judgments about the carrying value of assets and liabilities.
New Accounting Pronouncements, Policy [Policy Text Block]	Application of New or Revised Accounting Standards—Adopted From time to time, the Financial Accounting Standards Board (the “FASB”) or other standard-setting bodies issue accounting standards that are adopted by the Company as of the specified effective date. In April 2012, President Obama signed the Jump-Start Our Business Startups Act (the “JOBS Act”) into law. The JOBS Act contains provisions that, among other things, reduce certain reporting requirements for an emerging growth company. As an emerging growth company, the Company could have elected to adopt new or revised accounting standards when they become effective for non-public companies, which typically is later than public companies must adopt the standards. The Company has irrevocably elected not to take advantage of the extended transition period afforded by the JOBS Act and, as a result, will comply with new or revised accounting standards on the relevant dates on which adoption of such standards is required for non-emerging growth companies. In February 2016, the FASB issued ASU 2016 - 02, Leases (Topic 842 ) (“ASU 2016 - 02” ), which requires lessees to recognize operating and finance lease liabilities and corresponding right-of-use assets on the balance sheet and to provide enhanced disclosures surrounding the amount, timing and uncertainty of cash flows arising from leases. The Company leases office space and laboratory facilities under non-cancelable operating leases. In addition, the Company leases various laboratory equipment, furniture and office equipment and leasehold improvements that are accounted for as capital leases. The Company adopted the new standard effective January 1, 2019 on a modified retrospective basis and did not restate comparative periods. The Company elected the package of practical expedients permitted under the transition guidance, which allowed the Company to carryforward its historical lease classification and its assessment on whether a contract is or contains a lease for any leases that existed prior to adoption of the new standard. The Company also elected to combine lease and non-lease components and to keep leases with an initial term of 12 months or less off the balance sheet and recognize the associated lease payments in the condensed statements of operations on a straight-line basis over the lease term. The Company did not elect the hindsight practical expedient, which would have allowed the Company to use hindsight in determining the lease term and in assessing any impairment of right-of-use assets during the lookback period. The adoption of ASU 2016 - 02 resulted in the recognition of total right-of-use assets and total lease liabilities of approximately $2.6 million on the condensed balance sheets as of January 1, 2019. In July 2017, the FASB issued ASU 2017 - 11, Earnings Per Share (Topic 260 ), Distinguishing Liabilities from Equity (Topic 480 ), Derivatives and Hedging (Topic 815 ) – I. Accounting for Certain Financial Instruments with Down Round Features and II. Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception ("ASU 2017 - 11" ), which addresses the complexity of accounting for certain financial instruments with down round features and addresses the difficulty of navigating Topic 480 because of the existence of extensive pending content in the ASC as a result of the indefinite deferral of accounting requirements about mandatorily redeemable financial instruments of certain nonpublic entities and certain mandatorily redeemable noncontrolling interests. This update applies to all entities that issue financial instruments that include down round features and entities that present earnings per share in accordance with Topic 260. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. The adoption of ASU 2017 - 11 did not have a material impact on the Company's financial statements and disclosures. In June 2018, the FASB issued ASU 2018 - 07, Compensation – Stock Compensation (Topic 820 ) – Improvements to Nonemployee Share-Based Payment Accounting ("ASU 2018 - 07" ), which simplifies several aspects of the accounting for nonemployee share-based payment transactions resulting from expanding the scope of Topic 718, Compensation—Stock Compensation, to include share-based payment transactions for acquiring goods and services from nonemployees. This update applies to all entities that enter into share-based payment transactions for acquiring goods and services from nonemployees. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. The amendments in this ASU expand the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. An entity should apply the requirements of Topic 718 to nonemployee awards except for specific guidance on inputs to an option pricing model and the attribution of cost (that is, the period of time over which share-based payment awards vest and the pattern of cost recognition over that period). The amendments specify that Topic 718 applies to all share-based payment transactions in which a grantor acquires goods or services to be used or consumed in a grantor’s own operations by issuing share-based payment awards. The adoption of ASU 2018 - 07 did not have a material impact on the Company's financial statements and disclosures. Application of New or Revised Accounting Standards —Not Yet Adopted In August 2018, the FASB issued ASU 2018 - 13, Fair Value Measurement (Topic 820 ) – Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement ("ASU 2018 - 13" ), which modifies the disclosure requirements on fair value measurements in Topic 820, Fair Value Measurement, based on the concepts in the FASB Concepts Statement, Conceptual Framework for Financial Reporting—Chapter 8: Notes to Financial Statements, which the FASB finalized on August 28, 2018, including the consideration of costs and benefits. This update applies to all entities that are required, under existing GAAP, to make disclosures about recurring or nonrecurring fair value measurements. This guidance is effective for financial statements issued for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. Early adoption is permitted. An entity is permitted to early adopt any removed or modified disclosures and delay adoption of the additional disclosures until their effective date. The Company is currently evaluating the impact of the adoption of ASU 2018 - 13 on the Company's financial statements and disclosures.

Application of New or Revised Accounting Standards—Adopted

From time to time, the Financial Accounting Standards Board (the “FASB”) or other standard-setting bodies issue accounting standards that are adopted by the Company as of the specified effective date.

April 2012,

President Obama signed the Jump-Start Our Business Startups Act (the “JOBS Act”) into law. The JOBS Act contains provisions that, among other things, reduce certain reporting requirements for an emerging growth company. As an emerging growth company, the Company could have elected to adopt new or revised accounting standards when they become effective for non-public companies, which typically is later than public companies must adopt the standards. The Company has irrevocably elected

not

to take advantage of the extended transition period afforded by the JOBS Act and, as a result, will comply with new or revised accounting standards on the relevant dates on which adoption of such standards is required for non-emerging growth companies.

February 2016,

the FASB issued ASU

2016

02,

Leases (Topic

842

)

(“ASU

2016

02”

), which requires lessees to recognize operating and finance lease liabilities and corresponding right-of-use assets on the balance sheet and to provide enhanced disclosures surrounding the amount, timing and uncertainty of cash flows arising from leases. The Company leases office space and laboratory facilities under non-cancelable operating leases. In addition, the Company leases various laboratory equipment, furniture and office equipment and leasehold improvements that are accounted for as capital leases. The Company adopted the new standard effective

January 1, 2019

on a modified retrospective basis and did

not

restate comparative periods. The Company elected the package of practical expedients permitted under the transition guidance, which allowed the Company to carryforward its historical lease classification and its assessment on whether a contract is or contains a lease for any leases that existed prior to adoption of the new standard. The Company also elected to combine lease and non-lease components and to keep leases with an initial term of

months or less off the balance sheet and recognize the associated lease payments in the condensed statements of operations on a straight-line basis over the lease term. The Company did

not

elect the hindsight practical expedient, which would have allowed the Company to use hindsight in determining the lease term and in assessing any impairment of right-of-use assets during the lookback period. The adoption of ASU

2016

resulted in the recognition of total right-of-use assets and total lease liabilities of approximately

$2.6

million on the condensed balance sheets as of

January 1, 2019.

July 2017,

the FASB issued ASU

2017

11,

Earnings Per Share (Topic

260

), Distinguishing Liabilities from Equity (Topic

480

), Derivatives and Hedging (Topic

815

) – I. Accounting for Certain Financial Instruments with Down Round Features and II. Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception

("ASU

2017

11"

), which addresses the complexity of accounting for certain financial instruments with down round features and addresses the difficulty of navigating Topic

480

because of the existence of extensive pending content in the ASC as a result of the indefinite deferral of accounting requirements about mandatorily redeemable financial instruments of certain nonpublic entities and certain mandatorily redeemable noncontrolling interests. This update applies to all entities that issue financial instruments that include down round features and entities that present earnings per share in accordance with Topic

260.

This guidance is effective for financial statements issued for fiscal years beginning after

December 15, 2018,

and interim periods within those fiscal years. The adoption of ASU

2017

did

not

have a material impact on the Company's financial statements and disclosures.

June 2018,

the FASB issued ASU

2018

07,

Compensation – Stock Compensation (Topic

820

) – Improvements to Nonemployee Share-Based Payment Accounting

("ASU

2018

07"

), which simplifies several aspects of the accounting for nonemployee share-based payment transactions resulting from expanding the scope of Topic

718,

Compensation—Stock Compensation, to include share-based payment transactions for acquiring goods and services from nonemployees. This update applies to all entities that enter into share-based payment transactions for acquiring goods and services from nonemployees. This guidance is effective for financial statements issued for fiscal years beginning after

December 15, 2018,

and interim periods within those fiscal years. The amendments in this ASU expand the scope of Topic

718

to include share-based payment transactions for acquiring goods and services from nonemployees. An entity should apply the requirements of Topic

718

to nonemployee awards except for specific guidance on inputs to an option pricing model and the attribution of cost (that is, the period of time over which share-based payment awards vest and the pattern of cost recognition over that period). The amendments specify that Topic

718

applies to all share-based payment transactions in which a grantor acquires goods or services to be used or consumed in a grantor’s own operations by issuing share-based payment awards. The adoption of ASU

2018

did

not

have a material impact on the Company's financial statements and disclosures.

Application of New or Revised Accounting Standards

—Not

Yet Adopted

August 2018,

the FASB issued ASU

2018

13,

Fair Value Measurement (Topic

820

) – Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement

("ASU

2018

13"

), which modifies the disclosure requirements on fair value measurements in Topic

820,

Fair Value Measurement, based on the concepts in the FASB Concepts Statement,

Conceptual Framework for Financial Reporting—Chapter

Notes to Financial Statements,

which the FASB finalized on

August 28, 2018,

including the consideration of costs and benefits. This update applies to all entities that are required, under existing GAAP, to make disclosures about recurring or nonrecurring fair value measurements. This guidance is effective for financial statements issued for fiscal years beginning after

December 15, 2019,

and interim periods within those fiscal years. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level

fair value measurements, and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. Early adoption is permitted. An entity is permitted to early adopt any removed or modified disclosures and delay adoption of the additional disclosures until their effective date. The Company is currently evaluating the impact of the adoption of ASU

2018

on the Company's financial statements and disclosures.