Significant Contract, License and Royalty Agreements	12 Months Ended
Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Significant Contract, License and Royalty Agreements	6. Significant Contract, License and Royalty Agreements Contracts Astellas In July 2011, the Company entered into license agreements with Astellas, granting Astellas exclusive, worldwide, royalty-bearing licenses under certain of the Company’s know-how and intellectual property to develop and commercialize certain products containing plasmids encoding certain forms of glycoprotein B and/or phosphoprotein 65. Under the terms of the license agreements, Astellas paid a nonrefundable upfront license fee of $25.0 million. In 2012, the Company received a $10.0 million milestone payment upon finalization of the trial design for a Phase 3 registration trial of ASP0113 in hematopoietic stem cell transplant recipients. The Company identified the deliverables at the inception of the agreements. The Company determined that the license and related know-how, the development and regulatory services and the drug product supply individually represent separate units of accounting, because each deliverable has standalone value. The best estimated selling prices for these units of accounting was determined based on market conditions, the terms of comparable collaborative arrangements for similar technology in the pharmaceutical and biotechnology industry and entity-specific factors, such as the terms of the Company’s previous collaborative agreements, the Company’s pricing practices and pricing objectives and the nature of the research and development services to be performed for the partner. The arrangement consideration was allocated to the deliverables based on the relative selling price method. The amount of allocable arrangement consideration is limited to amounts that are fixed or determinable; therefore, the amount allocated to the licenses was limited to the extent of cash received. As a result, during the years ended December 31, 2018, 2017 and 2016, the Company recognized $0.0 million, $0.3 million and $1.5 million, respectively, related to the license fee and know-how. The Company recognized the amounts allocated to research and development services as revenues under the agreements as the related services were delivered and as reimbursements were received. During the years ended December 31, 2018, 2017 and 2016, the Company recognized $1.2 million, $12.9 million and $10.1 million, respectively, of revenue related to contract services delivered. The Company recognized as revenue the amounts allocated to the sales of drug product when the sale of that drug product had met all required specifications and the related title and risk of loss and damages passed to Astellas. During the years ended December 31, 2018, 2017 and 2016, the Company recognized $0.0 million, $0.0 million and $2.4 million, respectively, of revenue related to drug product delivered. In January 2018, Astellas announced the results from a Phase 3 trial of ASP0113 in approximately 515 CMV seropositive subjects undergoing HCT procedures. Top-line results from the Phase 3 study demonstrated that the trial did not meet its primary endpoint in CMV end organ disease. Based on these results, Astellas determined to cease further clinical development of ASP0113 and has terminated the license agreement. In-licensing Agreements Astellas In March 2015, the Company entered into a license agreement with Astellas which grants to the Company exclusive worldwide license to develop and commercialize a novel antifungal, VL-2397. As consideration for the rights under the license, the Company issued 86,121 shares of our common stock to Astellas and made an up-front payment of $250,000 in cash. The License Agreement provides for potential development, regulatory and sales milestone payments totaling up to $99.0 million, the vast majority of which are payable upon achievement of commercial and sales milestones, and single-digit royalties on net sales of commercial products. The Company is responsible for the worldwide development, manufacturing and commercialization of licensed products, at the Company’s cost, and we are required to use commercially reasonable efforts with respect to such development and commercialization activities. The license agreement, unless terminated earlier, will continue until expiration of Vical’s royalty obligations with respect to licensed products. Either party may terminate the license agreement earlier if the other party materially breaches the agreement and does not cure the breach within a specified notice period, or upon the other party’s insolvency. Astellas may terminate the license agreement earlier if Vical or any of its affiliates or sublicensees oppose or challenge any of the licensed patents. Vical may terminate the license agreement on a country-by-country basis for reasonable scientific, regulatory, commercial, financial, ethical or other reasons. Milestone Payments The Company may be required to make future payments to its licensors based on the achievement of milestones set forth in various in-licensing agreements. In most cases, these milestone payments are based on the achievement of development or regulatory milestones, including the exercise of options to obtain licenses related to specific disease targets, commencement of various phases of clinical trials, filing of product license applications, approval of product licenses from the FDA or a foreign regulatory agency, and the first commercial sale of a related product. Payment for the achievement of milestones under the Company’s in-license agreements is highly speculative and subject to a number of contingencies. The aggregate amount of additional milestone payments that the Company could be required to pay under its active in-license agreements in place at December 31, 2018, is approximately $99.0 million. These amounts assume that all remaining milestones associated with the milestone payments are met. In the event that product license approval for any of the related products is obtained, the Company may be required to make royalty payments in addition to these milestone payments. Although the Company believes that some of the milestones contained in its in-license agreements may be achieved, it is highly unlikely that a significant number of them will be achieved. Because the milestones are contingent the Company is not in a position to reasonably estimate how much, if any, of the potential milestone payments will ultimately be paid. Additionally, under the in-license agreements, many of the milestone events are related to progress in clinical trials which the Company estimates will take several years to achieve.

Significant Contract, License and Royalty Agreements

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Significant Contract, License and Royalty Agreements

6. Significant Contract, License and Royalty Agreements

Contracts

Astellas

In July 2011, the Company entered into license agreements with Astellas, granting Astellas exclusive, worldwide, royalty-bearing licenses under certain of the Company’s know-how and intellectual property to develop and commercialize certain products containing plasmids encoding certain forms of glycoprotein B and/or phosphoprotein 65. Under the terms of the license agreements, Astellas paid a nonrefundable upfront license fee of $25.0 million. In 2012, the Company received a $10.0 million milestone payment upon finalization of the trial design for a Phase 3 registration trial of ASP0113 in hematopoietic stem cell transplant recipients.

The Company identified the deliverables at the inception of the agreements. The Company determined that the license and related know-how, the development and regulatory services and the drug product supply individually represent separate units of accounting, because each deliverable has standalone value. The best estimated selling prices for these units of accounting was determined based on market conditions, the terms of comparable collaborative arrangements for similar technology in the pharmaceutical and biotechnology industry and entity-specific factors, such as the terms of the Company’s previous collaborative agreements, the Company’s pricing practices and pricing objectives and the nature of the research and development services to be performed for the partner. The arrangement consideration was allocated to the deliverables based on the relative selling price method.

The amount of allocable arrangement consideration is limited to amounts that are fixed or determinable; therefore, the amount allocated to the licenses was limited to the extent of cash received. As a result, during the years ended December 31, 2018, 2017 and 2016, the Company recognized $0.0 million, $0.3 million and $1.5 million, respectively, related to the license fee and know-how. The Company recognized the amounts allocated to research and development services as revenues under the agreements as the related services were delivered and as reimbursements were received. During the years ended December 31, 2018, 2017 and 2016, the Company recognized $1.2 million, $12.9 million and $10.1 million, respectively, of revenue related to contract services delivered. The Company recognized as revenue the amounts allocated to the sales of drug product when the sale of that drug product had met all required specifications and the related title and risk of loss and damages passed to Astellas. During the years ended December 31, 2018, 2017 and 2016, the Company recognized $0.0 million, $0.0 million and $2.4 million, respectively, of revenue related to drug product delivered.

In January 2018, Astellas announced the results from a Phase 3 trial of ASP0113 in approximately 515 CMV seropositive subjects undergoing HCT procedures. Top-line results from the Phase 3 study demonstrated that the trial did not meet its primary endpoint in CMV end organ disease. Based on these results, Astellas determined to cease further clinical development of ASP0113 and has terminated the license agreement.

In-licensing Agreements

Astellas

In March 2015, the Company entered into a license agreement with Astellas which grants to the Company exclusive worldwide license to develop and commercialize a novel antifungal, VL-2397. As consideration for the rights under the license, the Company issued 86,121 shares of our common stock to Astellas and made an up-front payment of $250,000 in cash. The License Agreement provides for potential development, regulatory and sales milestone payments totaling up to $99.0 million, the vast majority of which are payable upon achievement of commercial and sales milestones, and single-digit royalties on net sales of commercial products. The Company is responsible for the worldwide development, manufacturing and commercialization of licensed products, at the Company’s cost, and we are required to use commercially reasonable efforts with respect to such development and commercialization activities.

The license agreement, unless terminated earlier, will continue until expiration of Vical’s royalty obligations with respect to licensed products. Either party may terminate the license agreement earlier if the other party materially breaches the agreement and does not cure the breach within a specified notice period, or upon the other party’s insolvency. Astellas may terminate the license agreement earlier if Vical or any of its affiliates or sublicensees oppose or challenge any of the licensed patents. Vical may terminate the license agreement on a country-by-country basis for reasonable scientific, regulatory, commercial, financial, ethical or other reasons.

Milestone Payments

The Company may be required to make future payments to its licensors based on the achievement of milestones set forth in various in-licensing agreements. In most cases, these milestone payments are based on the achievement of development or regulatory milestones, including the exercise of options to obtain licenses related to specific disease targets, commencement of various phases of clinical trials, filing of product license applications, approval of product licenses from the FDA or a foreign regulatory agency, and the first commercial sale of a related product. Payment for the achievement of milestones under the Company’s in-license agreements is highly speculative and subject to a number of contingencies.

The aggregate amount of additional milestone payments that the Company could be required to pay under its active in-license agreements in place at December 31, 2018, is approximately $99.0 million. These amounts assume that all remaining milestones associated with the milestone payments are met. In the event that product license approval for any of the related products is obtained, the Company may be required to make royalty payments in addition to these milestone payments. Although the Company believes that some of the milestones contained in its in-license agreements may be achieved, it is highly unlikely that a significant number of them will be achieved. Because the milestones are contingent the Company is not in a position to reasonably estimate how much, if any, of the potential milestone payments will ultimately be paid. Additionally, under the in-license agreements, many of the milestone events are related to progress in clinical trials which the Company estimates will take several years to achieve.