Areas of Practice
  • DePaul University College of Law, J.D., 1986
  • Michigan Technological University, M.S., Chemical Engineering, 1980
  • Loyola University Chicago, B.A., Chemistry, 1978
Bar & Court Admissions
  • Illinois
  • US Supreme Court
  • Northern District of Illinois Trial Bar
  • US Court of Appeals, Federal Circuit
  • US Court of Appeals, 9th Circuit
  • US Patent and Trademark Office

Thomas J. Filarski

115 South LaSalle Street
Suite 3100
Chicago IL 60603
TEL: +1 312 577 1252
FAX: +1 312 577 1370


Thomas J. Filarski is a recognized patent trial lawyer who represents prominent pharmaceutical, medical device, and electronics companies. According to clients, Mr. Filarski “has a gift for explaining technology and technological terms in a way that makes them understandable to a judge, a jury, or any decision maker.” Mr. Filarski frequently tries high-profile patent matters and Hatch-Waxman disputes in US district courts, the Court of Appeals for the Federal Circuit, and the US Patent Office and has been involved in a number of landmark patent cases. During his career, Mr. Filarski has been at the forefront of two major topics in patent law – claim construction and venue. He led the team that resolved the debate within the Federal Circuit over the interpretation of product-by process claim and more recently was involved in a case that resulted in the Federal Circuit’s groundbreaking venue decision that set forth the standard for determining what constitutes a “regular and established place of business.”

Mr. Filarski’s most recent experience includes the successful representation of a major drug manufacturer in multiple patent disputes, which ultimately paved the way for the company to sell generic drug products used to enhance eyelash growth and to treat upper respiratory infections.

Mr. Filarski is the past president of the Licensing Executives Society (USA and Canada), which promotes the development and transfer of technology and intellectual property. He also served on the board of the Richard Linn American Inn of Court. Mr. Filarski speaks and writes regularly to professional and industry groups in the United States and abroad on patent litigation and intellectual property topics. He authors the chapter “Patent Defenses” in BNA Books’ Patent Litigation Strategies Handbook.

Representative Matters

  • Representing Sandoz Inc. in patent litigation involving a drug used to grow eyelashes.
  • Representing Raytheon in a suit involving four patents on hardware architecture, fault tolerance, and job management for high performance computing (HPC) systems.
  • Representing Raytheon in asserting allegations of patent infringement involving a patent related to a process of manufacturing a microelectric device. 
  • Represented Sandoz Inc. in patent litigation and obtained temporary restraining order and preliminary injunction over patents relating to an antibiotic used to treat upper respiratory infections.


  • Managing Intellectual Property's "Stars" in IL, 2013-2017
  • "Life Science Star," LMG Life Sciences, 2012, 2014-2017
  • IAM Patent 1000, Litigation:  Illinois, 2012-2017
  • Highly Recommended, IAM Patent 1000, Transactions:  Illinois, 2012-2015
  • The Best Lawyers in America, Patent Law, 2010-2018
  • Highly Recommended,IAM 250 - The World's Leading Patent & Technology Licensing Lawyers, 2011-2012
  • Listed in IAM 250 - The World's Leading Patent & Technology Licensing Lawyers, Life Sciences, 2011-2012
  • IAM Patent Litigation 250 - The World's Leading Patent Litigators, 2011 
  • IAM Life Sciences 250 - The World's Leading Life Sciences Patent Litigators, 2010
  • Illinois Super Lawyers, Intellectual Property Litigation, 2005-2017
  • Leading Intellectual Property and Patent Lawyer, Leading Lawyers Network, Law Bulletin Publishing Company, 2004, 2005, 2007, 2009, 2010, 2014

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