Daniel Zeilberger

Daniel Zeilberger is a Partner in the Litigation Department at Paul Hastings LLP, based in the firm's Washington, D.C. office. His practice focuses on intellectual property matters, including patent office proceedings, district court litigation, and appeals to the U.S. Court of Appeals for the Federal Circuit. Zeilberger handles a broad range of technologies, including internet-related technologies, mobile devices, semiconductor devices, telecommunications, business methods, medical devices, and pharmaceuticals. He previously served as a patent examiner at the USPTO.

Zeilberger's litigation experience reflects a balanced approach, with a slight lean toward defending operating companies, having handled four defendant-side appearances and three plaintiff-side matters. Notable defendant representations include Apple Inc. against VirnetX Inc. in disputes over secure internet communication technology, where a $502.8 million jury verdict against Apple was later vacated following successful PTAB unpatentability rulings affirmed on appeal. He also defended Xencor, Inc. against Merus N.V. in a pharmaceutical patent case where the district court dismissed the infringement suit, ruling that the accused use of antibody technology was protected by the Hatch-Waxman safe harbor. On the plaintiff side, he represented Hyundai Motor Company against Optimum Vector Dynamics LLC, a case linked to patent monetization firms in e-commerce and software, and Google LLC in an IPR against Telcom Ventures LLC concerning NFC technology.

His significant involvement in post-grant proceedings is evident. Zeilberger is a recognized authority on Patent Trial and Appeal Board (PTAB) practice, serving as the Treasurer of the PTAB Bar Association (2025-Present) and having been a Board of Directors member. His PTAB experience includes successfully representing Chevron Oronite in an IPR where all challenged claims were found unpatentable and affirmed on appeal, and securing denials of institution or affirmance of claims for patent owner Acorda Therapeutics in multiple IPRs. He has also represented Google and Samsung in numerous IPRs, achieving favorable outcomes such as adverse judgments against patent owners and affirmed unpatentability decisions on appeal. He was also involved in appeals related to Centripetal Networks v. Palo Alto Networks, including one Federal Circuit affirmance of unpatentability for a cyberanalysis patent and a remand of another PTAB decision over a motivation-to-combine prior art issue.

Zeilberger earned his J.D. cum laude from Georgetown University Law Center in 2013 and a B.S. in Electrical Engineering with honors from Johns Hopkins University in 2007. He is admitted to practice in the District of Columbia and Virginia, and before the United States Patent & Trademark Office.