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 received from Nektar Therapeutics, Inc. (“Nektar”) pursuant to the execution of 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 has no intention of resuming any clinical development activities or acquiring new sources of royalty revenues. Royalty revenues from sales of PegIntron accounted for 100% 80% (exclusive of downward revenue adjustment of $280,000 in the third quarter of 2018) and 13% (before adjustment for Merck’s recoupment of previously overpaid royalties of approximately $ 564,000 In March 2018, Merck notified the Company that a downward adjustment of approximately $ 313,000 in royalties was necessary, resulting primarily from product returns. Accordingly, at December 31, 2017, the Company accrued a liability to Merck of approximately $ 313,000 and partially offset that amount by the $ 88,000 that was due to the Company from Merck. Thus, the Company recorded a net payable to Merck of approximately $ 225,000 at December 31, 2017. In January 2018, Merck paid the $ 88,000 to the Company, which increased the liability to $ 313,000 . During the second quarter of 2018, Enzon earned approximately $ 60 ,000 of royalties, which reduced the royalty payable to Merck to $ 253,000 . In the third quarter of 2018, Merck notified the Company of an additional downward adjustment of approximately $ 280,000 , the net effect of royalty income of $ 54,000 and chargebacks of $ 334,000 . Such chargebacks resulted, primarily, from product rebates and returns. Accordingly, the liability to Merck was $ 533,000 at September 30, 2018, as discussed in Note 11 to the Condensed Consolidated Financial Statements. 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 to the Condensed Consolidated Financial Statements.) 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. The milestone payment obligations were assumed by Shire plc (“Shire”), 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. If Food and Drug Administration (“FDA”) approval is obtained for SC Oncaspar, the Company would be entitled to a milestone payment of $7.0 million from Servier S.A.S. (Servier), which entered into an agreement to purchase the oncology business from Shire in 2018. According to Shire, the Prescription Drug User Fee Act (“PDUFA”) date for approval of the Biologics License Application (“BLA”) is December 22, 2018. There can be no assurance that the FDA will approve the BLA. Accordingly, there can be no assurance that the Company will receive any of the milestone payments related to SC Oncaspar or any other such milestone payments resulting from its agreements with any of the Company’s other third party licensees. The Company will not recognize revenue from Servier or any of the Company’s other third party licensees until all current revenue recognition requirements are met. 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 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, whether such third party licensees will contest their obligations to make milestone or royalty payments 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. Except for these potential milestone payments, the Company anticipates little or no future revenue. 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 paid within one business day of the effective date of the Nektar Second Amendment and the remaining $3.5 million was to be paid on 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. |