COLLABORATION AGREEMENTS	9 Months Ended
COLLABORATION AGREEMENTS	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
COLLABORATION AGREEMENTS	COLLABORATION AGREEMENTS License Agreement with Zenas BioPharma In October 2020, the Company became party to a license agreement with Zenas BioPharma (Cayman) Limited (“Zenas BioPharma”) to license technology comprising certain materials, patent rights, and know-how to Zenas BioPharma. Since February 2021, the Company has entered into several letter agreements with Zenas BioPharma pursuant to which the Company agreed to provide assistance to Zenas BioPharma with certain development activities, including manufacturing. In May 2022, the Company entered into a Manufacturing Development and Supply Agreement with Zenas BioPharma (the “Supply Agreement”) to manufacture and supply, or to have manufactured and supplied, clinical drug product for developmental purposes. The license agreement and subsequent letter agreements and supply agreement (collectively, the “Zenas Agreements”) were negotiated with a single commercial objective and are treated as a combined contract for accounting purposes. Under the terms of the Zenas Agreements, the Company granted Zenas BioPharma an exclusive license to develop, manufacture, and commercialize certain IGF-1R directed antibody products for non-oncology indications in the greater area of China. As consideration for the Zenas Agreements, the transaction price included upfront non-cash consideration and variable consideration in the form of payment for the Company’s goods and services and milestone payments due upon the achievement of specified events. Under the Zenas Agreements, the Company can receive non-refundable milestone payments upon achieving specific milestone events during the contract term. Additionally, the Company may receive royalty payments based on a percentage of the annual net sales of any licensed products sold on a country-by-country basis in the greater area of China. The royalty percentage may vary based on different tiers of annual net sales of the licensed products made. Zenas BioPharma is obligated to make royalty payments to the Company for the royalty term in the Zenas Agreements. The Zenas Agreements would qualify as a collaborative arrangement under the scope of Accounting Standards Codification, Topic 808, Collaborative Arrangements (“ASC 808”). While this arrangement is in the scope of ASC 808, the Company applied ASC 606 to account for certain aspects of this arrangement. The Company applied ASC 606 for certain activities within the arrangement associated with the Company’s transfer of a good or service (i.e., a unit of account) that is part of the Company’s ongoing major or central operations. The Company allocated the transaction price based on the relative estimated standalone selling prices of each performance obligation or, in the case of certain variable consideration, to one or more performance obligations. Research and development activities are priced generally at cost. The Company’s license of goods and services to Zenas BioPharma during the contract term was determined to be a single performance obligation satisfied over time. The Company is recognizing the transaction price from the license agreement over the Company’s estimated period to complete its activities. At the inception of the arrangement, the Company evaluated whether the milestones were considered probable of being reached and estimated the amount to be included in the transaction price using the most likely amount method. As it was not probable that a significant revenue reversal would not occur, none of the associated milestone payments were included in the transaction price at contract inception. For the sales-based royalties included in the arrangement, the license was deemed to be the predominant item to which the royalties relate. The Company will recognize royalty revenues at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). During the three and nine months ended September 30, 2023 the Company recognized $0.1 million and $0.2 million, respectively, of collaboration revenue related to the Zenas Agreements. During the three and nine months ended September 30, 2022, the Company recognized $1.2 million and $1.7 million, respectively, of collaboration revenue related to the Zenas Agreements. As of September 30, 2023, the Zenas Agreements are considered related party transactions because Fairmount Funds Management LLC (“Fairmount”) beneficially owns more than 5% of the Company’s common stock and is also a 5% or greater stockholder of Zenas BioPharma and has a seat on Zenas BioPharma’s board of directors. Antibody and Discovery Option Agreement with Paragon Therapeutics, Inc. In January 2022, the Company and Paragon Therapeutics, Inc. (“Paragon”) entered into an antibody and discovery option agreement (the “Paragon Agreement”) under which the Company and Paragon will cooperate to develop one or more antibodies. Under the terms of the Paragon Agreement, Paragon will perform certain development activities in accordance with an agreed upon research plan, and the Company will pay Paragon agreed upon development fees in exchange for Paragon’s commitment of the necessary personnel and resources to perform these activities. The Paragon Agreement stipulates a final deliverable to the Company comprising of a report summarizing the experiments and processes performed under the research plan (the “Final Deliverable”). Additionally, Paragon agreed to grant the Company an option for an exclusive license to all of Paragon’s right, title and interest in and to certain antibody technology and the Final Deliverable, and a non-exclusive license to certain background intellectual property owned by Paragon solely to research, develop, make, use, sell, offer for sale and import of the licensed intellectual property and resulting products worldwide (each, an “Option” and together, the “Options”). Paragon also granted to the Company a limited, exclusive, royalty-free license, without the right to sublicense, to certain antibody technology and the Final Deliverable, and a non-exclusive, royalty-free license without the right to sublicense, under certain background intellectual property owned by Paragon, solely to evaluate the antibody technology and Option and for the purpose of allowing the Company to determine whether to exercise the Option with respect to certain programs. The Company may, at its sole discretion, exercise the Option with respect to specified programs at any time until the date that is 90 days after the Company’s receipt of the Final Deliverable the applicable program, or such longer period as agreed upon by the parties (“Option Period”) by delivering written notice of such exercise to Paragon. If the Company fails to exercise an Option prior to expiration of the applicable Option Period, such Option for such Program will terminate. In consideration for Paragon’s grant of the Options to the Company, the Company paid to Paragon a non-refundable, non-creditable one-time fee of $2.5 million, which was recorded as research and development expense during the three months ended March 31, 2022. In December 2022, the Company and Paragon entered into a first amendment to the Paragon Agreement, under which the Company obtained an additional limited license for the purpose of conducting certain activities. In consideration for the rights and licenses obtained under the first amendment, Viridian paid Paragon a non-refundable fee of $2.3 million (the “First Amendment Payment”), which was recorded as research and development expense during the three months ended December 31, 2022. The non-refundable upfront fee and the First Amendment Payment are separate from any development costs or cost advance paid or owing with respect to the specified program. During the three and nine months ended September 30, 2023, the Company recorded $1.1 million and $6.5 million, respectively, in research and development costs related to the Paragon Agreement. During the three and nine months ended September 30, 2022, the Company recorded $1.6 million and $4.5 million, respectively, in research and development costs related to the Paragon Agreement.As of September 30, 2023, the Paragon Agreement is considered a related party transaction because Fairmount beneficially owns more than 5% of the Company’s capital stock and has two seats on the Company’s board of directors, and beneficially owns more than 5% of Paragon, which is a joint venture between Fairmount and FairJourney Biologics, and has appointed the sole director on Paragon’s board of directors and has the contractual right to approve the appointment of any executive officers.