Darren J.Kassab Ph.D.

Of Counsel

Washington + 1.202.879.3889

Dr. Darren Kassab has more than a decade of experience in developing and managing global patent portfolios and providing strategic counsel to clients. His practice involves the areas of pharmaceuticals, biotechnology, agrochemicals, polymers, and material sciences. He advises emerging companies and established companies on strategies for maximizing and leveraging intellectual property protection, including patent portfolio development, product development, and patent life cycle management.

In addition to drafting and prosecuting patent applications, Darren's practice includes performing due diligence evaluations of patent portfolios and advising clients regarding patentability, validity, infringement, and freedom-to-operate issues in connection with potential mergers and acquisitions, investments, joint ventures, public and private financings, and licensing opportunities. He also has experience assisting pharmaceutical clients in the preparation of patent term extensions. He has obtained hundreds of patents for clients in numerous technologies, including pharmaceuticals, small molecule drugs, combination therapies, biotechnology, ophthalmology, medical devices, drug delivery, medical diagnostics, organic chemistry, polymers, protein therapies, coatings, agrochemicals, adjuvants, surfactants, petroleum products, formulations, and health care and personal care.

Before joining Jones Day, Darren conducted discovery research for nearly 10 years as a medicinal chemist at Pfizer (formerly Pharmacia Inc., formerly Searle, the pharmaceutical division of Monsanto Company), focusing on small molecule design and synthesis to develop therapeutic treatments for inflammation, cancer, and cardiovascular diseases. Notably, he was a member of a team that discovered a successful Phase-I clinical trial drug candidate.

Darren is coauthor of several peer-reviewed scientific publications and a co-inventor of multiple patents regarding small molecule drug discovery.


  • Royalty Pharma and PureTech Health enter into KarXT royalty agreementJones Day advised Royalty Pharma in the acquisition of an interest in PureTech’s royalty in Karuna Therapeutics’ KarXT for up to $500 million, with $100 million in cash up front and up to $400 million in additional payments contingent on the achievement of certain regulatory and commercial milestones.
  • Royalty Pharma agrees to acquire royalty interest in Trelegy Ellipta from Theravance and InnovivaJones Day advised Royalty Pharma in the acquisition of a royalty interest in TRELEGY ELLIPTA (Trelegy) from Theravance Biopharma, Inc. and Innoviva, Inc. for an upfront payment of $1.31 billion and additional payments of up to $300 million contingent on achieving certain sales milestones.
  • Milliken & Company acquires Encapsys, LLCJones Day advised Milliken & Company in its acquisition of Encapsys, LLC, a world leader in microencapsulation delivery systems for the building, construction, paper, bedding and personal care industries.
  • Royalty Pharma acquires Oxlumo™ royalty interest from DicernaJones Day advised Royalty Pharma in the acquisition of an interest in Dicerna’s royalty in Dicerna’s OXLUMO™ (lumasiran) for an upfront cash payment of $180 million and up to $60 million in contingent sales-based milestone payments.
  • Takeda trial win in Hatch-Waxman case involving diabetes products upheld by Federal CircuitJones Day successfully represented Takeda Pharmaceutical Company Ltd. in a Hatch-Waxman Act dispute against companies seeking to market generic versions of three diabetes products prior to the expiration of Takeda's patents.
  • Royalty Pharma and Biohaven Pharmaceutical enter into zavegepant funding agreement and Nurtec™ ODT royalty agreementJones Day advised Royalty Pharma in the acquisition of approximately 3% in Biohaven Pharmaceutical Holding Company Ltd.’s royalty rights in Biohaven’s zavegepant (formerly known as vazegepant), a 0.4% royalty of Nurtec™ ODT and success-based milestone payments, for an upfront payment of $150 million and a further payment of $100 million upon the start of the oral zavegepant Phase 3 program.
  • Ensyn Renewables establishes technology to convert biomass residue to biocrudeJones Day represents Ensyn Renewables, Inc. in strategically developing its international patent portfolio directed to diverse innovations including catalytically cracking renewable fuel oil and petroleum and thermally processing biomass residues for use in heating systems.
  • Royalty Pharma and Biohaven Pharmaceutical enter into rimegepant (BHV-3000) royalty agreementJones Day advised Royalty Pharma in the acquisition of Biohaven Pharmaceutical Holding Company Ltd.'s approximately 2% royalty rights in Biohaven’s rimegepant (BHV-3000) and BHV- 3500 (vazegepant) for an upfront cash payment of $100 million.
  • Puma Biotechnology defends European patent licensed from Wyeth covering Neratinib and Vinorelbine in opposition proceedingsJones Day represents Puma Biotechnology, Inc. in European opposition proceedings initiated by Mylan to defend a patent licensed from Wyeth covering Neratinib and Vinorelbine.