Ones to Watch Netherlands 2026: Barbara Mooij

Last Thursday, a few champagne corks popped at Brinkhof’s Amsterdam office. The firm’s client, Halozyme, secured a significant victory. The District Court The Hague handed Halozyme a win in its global dispute with MSD over the subcutaneous version of the blockbuster cancer drug Keytruda. The court upheld Halozyme’s European patent and issued a cross-border injunction covering eight countries, prohibiting MSD from marketing Keytruda. The judgment is not final, as MSD can appeal. Nevertheless, the ruling was cause for celebration for Barbara Mooij and her colleagues at Brinkhof. Keytruda, containing the active ingredient pembrolizumab, generated sales of approximately €25.8 billion for MSD in 2024, making it one of the world’s best-selling medicines.

A team from Brinkhof is representing Halozyme in the Dutch proceedings, led by partner Mark van Gardingen and Rien Broekstra, with associate Barbara Mooij playing a key role in the team. “The Halozyme case has all the aspects a lawyer could want in a case. International cooperation with the client and law firms in other countries, complex technology, and legally interesting issues,” says Mooij. The case is also truly international, with parallel proceedings in the Netherlands, Germany, the UK, and the US.

A dedicated pharmaceutical litigator

The 33-year-old lawyer has now been with Brinkhof for seven years and is therefore one of the most experienced associates in the market-leading Dutch patent litigation team. With this experience behind her, she is involved in almost all the major life sciences cases currently being handled by the firm. These include the Dutch national proceedings for Novo Nordisk against Ceban concerning the weight-loss drug semaglutide. Mooij also worked for Sandoz in a nullity case against Bayer’s blockbuster drug rivaroxaban, sold under the brand name Xarelto. Furthermore, she represented Celltrion against Roche in nullity cases concerning subcutaneous formulations of trastuzumab/Herceptin, as well as Synthon against Novartis in invalidity proceedings concerning valsartan/Entresto.

During her career to date, Mooij has had the good fortune to work alongside Brinkhof partners Mark van Gardingen, Daan de Lange, and Koen Bijvank. All three are among Europe’s leading patent litigators. Her mentor during her first two years of training was van Gardingen. After completing their degrees, young Dutch lawyers undertake their legal training at a law firm, during which an experienced partner guides and supervises them.

First Unilever, then Brinkhof

Her strong focus on pharmaceutical and life sciences litigation is no coincidence. Before joining Brinkhof, she studied cosmetic science at the University of the Arts London. At the same time, she worked at Unilever in Leeds. There, she took part in the GDC Industrial Placement R&D programme. This is a twelve-month work placement for students in research and development. Students work on projects such as the development of new product lines.

“After my almost two years in Unilever’s R&D department, I wanted to try something outside the lab that was more about communication and collaboration,” says Mooij. She had been exposed to the legal profession and patents early on. Her parents are a lawyer and a patent attorney, respectively. “I was looking for the combination of science and research with law.”

After completing her law degree, she joined Brinkhof directly in 2019. She came across the firm through a law clinic incubator. She has remained with the firm to this day. Together with its German partner firm Vossius, it is heavily involved in the UPC through a joint venture, Vossius & Brinkhof UPC Litigators. However, among the many UPC cases handled by both firms, there are only a few pharmaceutical cases. The pharma giants are still reluctant to have their crown jewel patents for blockbuster active ingredients such as rivaroxaban, semaglutide or pembrolizumab heard before the UPC. Litigation usually takes place in national courts. Consequently, Mooij is less frequently involved in UPC cases than younger litigators with a broader technical background. She is currently working behind the scenes on new UPC cases.

Committed to students

Looking to the future, Mooij intends to remain deeply involved with Leiden University. She gives lectures on patent law at this flagship Dutch university. Alongside her legal practice, she aims to expand this involvement, as well as her commitment to the international Chips Network that connects women in technology, law, and policy.

Mooij takes a calm approach to one of the greatest challenges in her professional life. At present, patent lawyers around the globe are intensively and passionately discussing how the use of AI tools will affect their work — as was recently the case at the AIIPI World Congress in Hamburg. Mooij, however, finds AI very useful in her work to provide support, ranging from summarising documents, researching prior art to stress-testing arguments. “AI helps to prepare cases better, but I do not think it will take over the role of litigators, who are ultimately the ones presenting a case to a judge,” says Mooij. 

For in-depth analysis on the Dutch patent market, read the JUVE Patent Netherlands ranking 2026.