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Mark R. Leslie

Mark is a Partner in the firm’s Intellectual Property practice with extensive experience helping clients create, manage, protect, enforce, and extract value from intellectual property assets in the United States and internationally. His practice spans patent and trademark acquisition, prosecution, portfolio management, product clearance, IP policing and enforcement, technology transfer, trade secrets, and related opinions and agreements.

Mark regularly counsels companies on the development and management of worldwide patent and trademark portfolios, with a particular focus on aligning IP strategy with business objectives, competitive positioning, and product-development plans. He advises large and small companies across a wide range of industries, including highly technical and innovation-driven businesses, and assists clients with freedom-to-operate analyses, infringement and validity assessments, product clearance, and strategic protection of core technologies.

His experience includes patent and trademark infringement litigation in the federal district courts and appeals before the US Court of Appeals for the Federal Circuit, as well as US and European patent post-grant proceedings. Mark also advises on IP aspects of corporate transactions, including mergers, acquisitions, divestitures, and joint ventures, helping clients evaluate, protect, and maximize the value of intellectual property assets in business-critical transactions.

Mark’s technical background is particularly strong in chemical, materials science, and mechanical technologies. As examples, he has handled matters involving polymers, carbon and stainless steel alloy design and production, metal casting, cemented carbide production, high-performance aerospace alloys, powder metallurgy and atomization, ore beneficiation, cutting tool design, battery cell design, small molecule pharmaceuticals, aerospace fasteners, and synthetic fiber spinning.

Mark brings a distinctive combination of private-practice, judicial, and USPTO experience to his intellectual property practice. After law school, he served as a judicial clerk to the Honorable Glenn L. Archer, Jr., of the US Court of Appeals for the Federal Circuit, giving him direct exposure to appellate patent jurisprudence at the nation’s primary patent appeals court. Before law school, he worked as a patent examiner in the organic chemical section of the US Patent and Trademark Office (USPTO), providing him with practical insight into patent examination, prosecution strategy, and USPTO practice.

  • Listed in The Best Lawyers in America® in Pittsburgh:
    • Patent Law, 2024-2026
    • Trademark Law, 2025-2026
    • Litigation - Intellectual Property, 2026
  • Recognized as a Thomson Reuters Stand-Out Lawyer, 2025-2026
  • Pennsylvania Bar Association
  • DC Bar Association
  • AIPLA
  • Graduate work in Materials Science at the University of Pittsburgh
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