Description of Business and Basis of Financial Statements	6 Months Ended
Jun. 30, 2018
Accounting Policies [Abstract]
Description of Business and Basis of Financial Statements	Description of Business and Basis of Financial Statements Description of Business We are a clinical-stage biotechnology company focusing on the discovery, development and commercialization of cell-based therapies capable of transforming the management of life-threatening conditions. Our initial product candidate, the ELAD^® System, or ELAD, is a human-cell-based, bio-artificial liver which is being developed to improve rates of survival among patients with acute forms of liver failure. Since inception, we have devoted essentially all of our efforts to product development, clinical testing and pilot manufacturing and have not recognized revenues from our planned principal operations. In August 2015, we reported that our VTI-208 phase 3 clinical trial of ELAD in severe alcoholic hepatitis failed to reach its primary or secondary endpoints, although medically pertinent pre-specified subsets based on age and disease severity did show trends toward efficacy. Considering the results of the VTI-208 clinical trial and in an effort to focus our personnel and financial resources, we also discontinued our VTI-210 and VTI-212 clinical trials. In March 2018, we completed enrollment in our phase 3 clinical trial, VTL-308, of 151 subjects with severe alcoholic hepatitis. The trial design of VTL-308, was based on our analysis of the results of the VTI-208 clinical trial. Our business, operating results, financial condition and growth prospects are subject to significant risks and uncertainties including the failure of our clinical trial to meet its endpoint, failure to obtain regulatory approval to commercialize ELAD and failure to secure additional funding to complete the development and commercialization of ELAD. Liquidity We have a history of incurring losses and negative cash flows from operations and have an accumulated deficit of $323.0 million through June 30, 2018. Assuming limited activities related to the submission for a biologics license application, or BLA, and that we do not begin building any significant commercial infrastructure, we believe that our existing cash and cash equivalents of $31.1 million as of June 30, 2018 should be sufficient to fund our operations through the first quarter of 2019, past the expected announcement of topline data for the VTL-308 clinical trial, which we currently anticipate to be in the second half of September 2018. We have based this estimate on assumptions that may prove to be wrong, and we could utilize our available capital resources sooner than we currently expect. The timing and amount of our actual expenditures will be based on many factors, including, but not limited to, the completion of our VTL-308 clinical trial, the timing of any possible submission of a BLA, decisions with respect to building commercial operations, and any unforeseen cash needs which may deplete current cash and cash equivalents sooner than planned. In any case, we will need additional liquidity to fund operations prior to a year from the date of the issuance of our condensed consolidated financial statements for the six months ended June 30, 2018. Our capital requirements and our ability to fund such requirements are expected to be different based on the outcome of the VTL-308 clinical trial. With successful clinical data, we plan to substantially increase our BLA and commercialization activities and, therefore, our costs. In this event, we would seek to obtain funding through equity or debt financing, and possibly marketing and distribution arrangements or other collaborations, strategic alliances or licensing agreements. Should the VTL-308 clinical trial require additional clinical development or should the trial be unsuccessful, we would attempt to substantially restructure our operations to conserve funds and possibly sell assets or even liquidate the company, depending on the VTL-308 data. In this event, we may also seek funding through similar sources; however, funding in such circumstances would be expected to be more difficult to secure, if at all. We currently have an effective shelf registration statement on Form S-3 on file with the Securities and Exchange Commission, or SEC, which expires June 2021. The shelf registration statement currently permits the offering, issuance and sale by us of up to an aggregate offering price of $200.0 million of common stock, preferred stock, warrants, debt securities or units in one or more offerings and in any combination, of which $60.0 million may be offered, issued and sold under an “at-the-market” sales agreement with Cantor Fitzgerald & Co. In the event of positive topline results from VTL-308, we plan to raise additional capital. There is no assurance that we will be able to obtain additional funding on acceptable terms or at all. If we are not able to secure adequate additional funding, we will be required to make reductions in certain spending to extend current funds. If we are unable to raise adequate funds, we may have to liquidate some or all of our assets, or we may have to delay, reduce the scope of, or eliminate some or all of our development programs and further clinical development. We may also have to delay development or commercialization of our products or license to third parties the rights to commercialize products or technology that we would otherwise seek to commercialize. Any of these factors could harm our operating results and future prospects. Based on the above, substantial doubt exists over our ability to continue as a going concern for one year from the date of the issuance of our condensed consolidated financial statements for the six months ended June 30, 2018. Basis of Presentation and Consolidation The accompanying unaudited interim condensed consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles, or GAAP, and the rules and regulations of the SEC related to a quarterly report on Form 10-Q. Certain information and note disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to those rules and regulations. The condensed consolidated balance sheet as of December 31, 2017 included in this report has been derived from the audited consolidated financial statements included in our Annual Report on Form 10-K. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the annual audited consolidated financial statements and, in the opinion of management, reflect all adjustments that are necessary for a fair statement of the financial position, results of operations and cash flows for the periods presented. All such adjustments are of a normal and recurring nature. In addition, our condensed consolidated financial statements have been prepared assuming that we will continue as a going concern, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business. The condensed consolidated financial statements for the six months ended June 30, 2018 do not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or the amounts and classification of liabilities that could result from uncertainty related to our ability to continue as a going concern. Unaudited Interim Financial Information The results for the six months ended June 30, 2018 are not necessarily indicative of results to be expected for the year ending December 31, 2018 or any other future interim period or year. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2017, included in our Annual Report on Form 10-K filed with the SEC on March 13, 2018. The unaudited interim condensed consolidated financial statements include the accounts of Vital Therapies, Inc. and its wholly-owned subsidiaries located in the United Kingdom and China, both of which are currently inactive. All intercompany accounts and transactions have been eliminated in consolidation. We manage our operations as a single reportable segment for the purposes of assessing performance and making operating decisions.

Description of Business and Basis of Financial Statements

Description of Business

We are a clinical-stage biotechnology company focusing on the discovery, development and commercialization of cell-based therapies capable of transforming the management of life-threatening conditions. Our initial product candidate, the ELAD^® System, or ELAD, is a human-cell-based, bio-artificial liver which is being developed to improve rates of survival among patients with acute forms of liver failure. Since inception, we have devoted essentially all of our efforts to product development, clinical testing and pilot manufacturing and have not recognized revenues from our planned principal operations. In August 2015, we reported that our VTI-208 phase 3 clinical trial of ELAD in severe alcoholic hepatitis failed to reach its primary or secondary endpoints, although medically pertinent pre-specified subsets based on age and disease severity did show trends toward efficacy. Considering the results of the VTI-208 clinical trial and in an effort to focus our personnel and financial resources, we also discontinued our VTI-210 and VTI-212 clinical trials. In March 2018, we completed enrollment in our phase 3 clinical trial, VTL-308, of 151 subjects with severe alcoholic hepatitis. The trial design of VTL-308, was based on our analysis of the results of the VTI-208 clinical trial. Our business, operating results, financial condition and growth prospects are subject to significant risks and uncertainties including the failure of our clinical trial to meet its endpoint, failure to obtain regulatory approval to commercialize ELAD and failure to secure additional funding to complete the development and commercialization of ELAD.

Liquidity

We have a history of incurring losses and negative cash flows from operations and have an accumulated deficit of $323.0 million through June 30, 2018. Assuming limited activities related to the submission for a biologics license application, or BLA, and that we do not begin building any significant commercial infrastructure, we believe that our existing cash and cash equivalents of $31.1 million as of June 30, 2018 should be sufficient to fund our operations through the first quarter of 2019, past the expected announcement of topline data for the VTL-308 clinical trial, which we currently anticipate to be in the second half of September 2018. We have based this estimate on assumptions that may prove to be wrong, and we could utilize our available capital resources sooner than we currently expect. The timing and amount of our actual expenditures will be based on many factors, including, but not limited to, the completion of our VTL-308 clinical trial, the timing of any possible submission of a BLA, decisions with respect to building commercial operations, and any unforeseen cash needs which may deplete current cash and cash equivalents sooner than planned. In any case, we will need additional liquidity to fund operations prior to a year from the date of the issuance of our condensed consolidated financial statements for the six months ended June 30, 2018.

Our capital requirements and our ability to fund such requirements are expected to be different based on the outcome of the VTL-308 clinical trial. With successful clinical data, we plan to substantially increase our BLA and commercialization activities and, therefore, our costs. In this event, we would seek to obtain funding through equity or debt financing, and possibly marketing and distribution arrangements or other collaborations, strategic alliances or licensing agreements. Should the VTL-308 clinical trial require additional clinical development or should the trial be unsuccessful, we would attempt to substantially restructure our operations to conserve funds and possibly sell assets or even liquidate the company, depending on the VTL-308 data. In this event, we may also seek funding through similar sources; however, funding in such circumstances would be expected to be more difficult to secure, if at all.

We currently have an effective shelf registration statement on Form S-3 on file with the Securities and Exchange Commission, or SEC, which expires June 2021. The shelf registration statement currently permits the offering, issuance and sale by us of up to an aggregate offering price of $200.0 million of common stock, preferred stock, warrants, debt securities or units in one or more offerings and in any combination, of which $60.0 million may be offered, issued and sold under an “at-the-market” sales agreement with Cantor Fitzgerald & Co. In the event of positive topline results from VTL-308, we plan to raise additional capital.

There is no assurance that we will be able to obtain additional funding on acceptable terms or at all. If we are not able to secure adequate additional funding, we will be required to make reductions in certain spending to extend current funds. If we are unable to raise adequate funds, we may have to liquidate some or all of our assets, or we may have to delay, reduce the scope of, or eliminate some or all of our development programs and further clinical development. We may also have to delay development or commercialization of our products or license to third parties the rights to commercialize products or technology that we would otherwise seek to commercialize. Any of these factors could harm our operating results and future prospects. Based on the above, substantial doubt exists over our ability to continue as a going concern for one year from the date of the issuance of our condensed consolidated financial statements for the six months ended June 30, 2018.

Basis of Presentation and Consolidation

The accompanying unaudited interim condensed consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles, or GAAP, and the rules and regulations of the SEC related to a quarterly report on Form 10-Q. Certain information and note disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to those rules and regulations. The condensed consolidated balance sheet as of December 31, 2017 included in this report has been derived from the audited consolidated financial statements included in our Annual Report on Form 10-K. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the annual audited consolidated financial statements and, in the opinion of management, reflect all adjustments that are necessary for a fair statement of the financial position, results of operations and cash flows for the periods presented. All such adjustments are of a normal and recurring nature.

In addition, our condensed consolidated financial statements have been prepared assuming that we will continue as a going concern, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business. The condensed consolidated financial statements for the six months ended June 30, 2018 do not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or the amounts and classification of liabilities that could result from uncertainty related to our ability to continue as a going concern.

Unaudited Interim Financial Information

The results for the six months ended June 30, 2018 are not necessarily indicative of results to be expected for the year ending December 31, 2018 or any other future interim period or year. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2017, included in our Annual Report on Form 10-K filed with the SEC on March 13, 2018.

The unaudited interim condensed consolidated financial statements include the accounts of Vital Therapies, Inc. and its wholly-owned subsidiaries located in the United Kingdom and China, both of which are currently inactive. All intercompany accounts and transactions have been eliminated in consolidation. We manage our operations as a single reportable segment for the purposes of assessing performance and making operating decisions.