Enzon, Inc.

Enzon Pharmaceuticals, Inc. (formerly Enzon, Inc.) is a U.S. biopharmaceutical company founded in 1981 and headquartered in Cranford, New Jersey (earlier addresses included Piscataway and Bridgewater, NJ). It is publicly traded under the ticker ENZN, now quoted over-the-counter. Enzon changed its name from Enzon, Inc. to Enzon Pharmaceuticals, Inc. in December 2002. Per its most recent 10-K, the company has no employees — its executive officer serves on a consulting basis — and it operates as a public acquisition vehicle seeking to deploy roughly $102.5 million in net operating loss carryforwards.

Products / operations. Enzon's historical business was PEGylation: chemically attaching polyethylene glycol (PEG) to protein and small-molecule drugs to extend circulation time and reduce immunogenicity. Its in-house products included Oncaspar (pegaspargase, for acute lymphoblastic leukemia) and Adagen (pegademase bovine), and it licensed its PEG platform to partners whose products generated royalties, notably PegIntron (Merck), Macugen (OSI/Pfizer), Pegasys (Roche) and CIMZIA (UCB). In 2010 Enzon sold its specialty pharmaceutical business — Oncaspar, Adagen, DepoCyt, Abelcet and an Indianapolis manufacturing facility — to Italy's sigma-tau Group for about $300 million plus milestones. It now holds legacy royalty/licensing interests, including a licensing agreement tied to Vicineum, and reports no significant ongoing operations.

Patent-litigation posture. The tracked data show one case, with Enzon as plaintiff and zero as defendant — it is not a patent assertion entity in the classic sense but a technology holder enforcing patents it developed and practiced. Enzon, Inc. v. Shearwater Polymers, Inc. (N.D. Ala.) asserted U.S. Patent 5,643,575, covering Enzon's branched-PEG technology, against Shearwater's supply of branched PEG reagents to Roche. The venue reflects Shearwater's Alabama home base, not a plaintiff-friendly Texas forum.

Context. Shearwater was acquired by Inhale Therapeutic Systems (later Nektar Therapeutics) in June 2001. In January 2002 Enzon and Nektar settled the suit as part of a broader alliance in which Enzon invested $40 million in Nektar convertible preferred stock and Nektar took responsibility for licensing Enzon's PEG patents. Enzon separately sued Roche in 2000 over Pegasys; that action was dismissed under a 2001 Schering-Plough–Roche cross-license. The single tracked case is a small sample and does not by itself characterize the company's current posture.