Willem Hoorneman

Willem Hoorneman

Managing Partner

Newtonlaan 203
3584 BH Utrecht
PO Box 85250
3508 AG Utrecht
Languages English, Dutch

Willem Hoorneman is a partner with CMS Netherlands and a member of the IP/TMC Practice Group. With more than 25 years of experience in IP and author of the patent chapters in the leading handbook on software protection in the Netherlands, Willem is considered a pre-eminent IP lawyer, and one of the very best in the field of patent law. 

Willem has earned an excellent reputation both as a litigator and a legal advisor on the marketing of inventions, whether those under patent or not, with extensive experience in the areas of contracting and licensing. As a specialist with a general civil law background, Willem is able to see the big picture and he focuses his efforts on coming up with creative, yet pragmatic solutions. 

Willem heads the IP team – as well as the Life Sciences Group – with the drive, energy and commitment which made clients recognise him in Chambers as “bringing to the table not only accurate and professional legal advice, but also a clear sense of strategy” (2010) and as being “responsive and plain-speaking” (2011).

IAM Patent 1000 2013: "Experienced life sciences expert Willem Hoorneman heads the IP team at CMS Derks Star Busmann, and is highly valued as a patent litigator and all-round counsellor. A broad civil law background gives him a fresh, commercial perspective on IP matters".  

Chambers 2014: Willem Hoorneman has wide-reaching IP expertise and wins praise from clients: “he is a very experienced lawyer with good business sense”.

Chambers Global 2015: “Department head Willem Hoorneman wins warm plaudits from sources for his patent work. Commentators agree he is ‘easy-going, highly knowledgeable and fast to act’.”

In addition to running his private practice, Willem is a domain name dispute resolution panellist with the World Intellectual Property Organization. For many years he has served as editor-in-chief of the BMM Bulletin (the Benelux Trademark and Design Journal).

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CMS’ clients include Medtronic, Bayer and Johnson & Johnson Healthcare. Practice head Willem Hoorneman assisted Amgen with negotiating a licence agreement with DSM that gave Amgen access to DSM’s patented XD technology.

Legal 500 2016

Willem Hoorneman has wide-ranging expertise, encompassing patent, copyright and trade mark issues, with a particular focus on infringement matters. Clients describe him as "an excellent lawyer in this field, with good knowledge; an expert."

Chambers Global 2016

Department head Willem Hoorneman wins warm plaudits from sources for his patent work. Commentators agree he is "easy-going, highly knowledgeable and fast to act.

Chambers Global 2015

Notable practitioners: Willem Hoorneman heads the global life sciences group from the Netherlands and is a key contact at the firm.

Chambers Global 2015


  • Dutch Law, University of Amsterdam
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  • Head of CMS Lifesciences Sector Group
  • Managing Partner
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