Nature of Operations [Text Block] | (1) Description of Business Enzon Pharmaceuticals, Inc. (together with its subsidiaries, “Enzon” or the “Company,” “we” or “us”), manages its sources of royalty revenues from existing licensing arrangements with other companies primarily related to sales of certain drug products that utilize Enzon’s proprietary technology. In 2017, the primary source of the Company’s royalty revenues was the revenue from Nektar Therapeutics, Inc. (“Nektar”) pursuant to the entrance into a Second Amendment (“Nektar Second Amendment”) to the Company’s Cross-License and Option Agreement (the “Nektar License Agreement”) with Nektar, which generated non-recurring royalty revenues of $7 million (see below). The receipt of this $7 million satisfied all future obligations of royalty payments pursuant to the Nektar License Agreement. Prior to 2017, the primary source of the Company’s royalty revenues was derived from sales of PegIntron, which is marketed by Merck &; Co., Inc. (“Merck”). Prior to 2013, the Company was dedicated to the research and development of innovative therapeutics for patients with high unmet medical needs. The Company currently has no clinical operations and limited corporate operations. The Company In April 2013, the Company announced that it intended to distribute excess cash, expected to arise from ongoing royalty revenues, in the form of periodic dividends to stockholders. On February 4, 2016, the Company’s Board adopted a Plan of Liquidation and Dissolution (the “Plan of Liquidation and Dissolution”), the implementation of which has been postponed. (See Note 10 Plan of Liquidation and Dissolution.) Under the Company’s existing agreements with certain third party licensees, the Company may be entitled to (i) potential future milestone payments contingent upon the achievement of certain milestones with respect to several other drug products in various stages of clinical and preclinical development and (ii) potential future royalty payments related to any future sales of these drug products. Due to the challenges associated with developing and obtaining approval for drug products, there is substantial uncertainty whether any of these milestones will be achieved. The Company also has no control over the time, resources and effort that these third party licensees may devote to their programs and limited access to information regarding or resulting from such programs. Accordingly, there can be no assurance that the Company will receive any of the milestone or royalty payments under these agreements. The Company may be entitled to certain potential future milestone payments contingent upon the achievement of certain regulatory approval-related milestones with respect to Oncaspar from Shire plc (“Shire”), which assumed the milestone payment obligations when it acquired the Oncaspar product portfolio previously owned by Sigma-Tau Finanziaria S.p.A. in July 2015. In February 2018, Shire indicated that it was in the registration stage and awaiting further regulatory action. any of the Company’s other third party licensees On June 26, 2017, the Company entered into the Nektar Second Amendment, wherein Nektar agreed to buy-out all remaining payment obligations to the Company under the Nektar License Agreement. In consideration for fully paid-up licenses under the Nektar License Agreement and for the dismissal with prejudice of all claims and counterclaims asserted in the litigation with Nektar, Nektar agreed to pay the Company the sum of $7.0 million, which satisfies all future obligations of royalty payments pursuant to the Nektar License Agreement, the first $3.5 million of which was to be paid within one business day of the effective date of the Nektar Second Amendment and the remaining $3.5 million was to be paid by January 6, 2018. Accordingly, the Company recorded revenue of $7.0 million and a receivable of $3.5 million in the second quarter of 2017. The $3.5 million receivable was paid in full in December 2017. |