Grant Medal awardee Harry Büller looks back on a lifetime of science and serendipity

The International Society on Thrombosis and Haemostasis (ISTH) announces Harry R. Büller, M.D., Ph.D., as the recipient of the prestigious 2025 Robert P. Grant Medal. As the highest award of the ISTH, the Grant Medal honors an individual who has made significant lifetime contributions to the field of thrombosis and hemostasis. In this article, read more about Büller's early life, professional highlights and his proudest accomplishments.

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The early years: “I was a Sunday’s Child”

For Harry Büller, M.D., Ph.D., the 2025 recipient of the prestigious ISTH Grant Medal, both his life and career have unfolded as a blend of hard work and serendipitous opportunities.

Born in 1952 in Indonesia, then a Dutch colony, Büller spent the first nine years of his life in southeast Asia before returning with his family to the Netherlands.

It was in Amsterdam that he would later study medicine and find his way, somewhat unexpectedly, into the field of thrombosis and hemostasis.

“I’ve always considered myself a ‘Sunday’s child’—meaning someone who’s been lucky far more than he deserves,” he said with a smile.

While in medical school at the University of Amsterdam in 1978, Büller and his wife welcomed the birth of their first child, a daughter named Birre.

Shortly thereafter, Büller’s wife developed a postpartum deep vein thrombosis (DVT). At that time, it was commonly referred to as “milk leg,” due to the long hours that a mother would sit while breastfeeding a baby, which could lead to a blood clot in the leg. His wife was treated by thrombosis specialist Professor Jan Wouter (J.W.) ten Cate, and Büller showed up to the appointment with a long list of questions.

“I went to ten Cate’s office with all my questions, and he simply said, ‘You can start tomorrow,’” Büller recalled.

What started as a medical appointment for his wife turned into a fortuitous moment that would pivot the direction of Büller’s career, and he soon began work in the hematology department.

“That was the start of a great friendship and a very long collaboration. Jan Wouter ten Cate was my very first great role model.”

Taking the next step at McMaster University

In 1980, with a young family and a growing curiosity, Büller set out for a research fellowship at McMaster University in Canada, a global leader in thrombosis and hemostasis research at that time.

“I remember one Monday morning, I walked into the lab. Ten Cate just had dinner with Jack Hirsh the evening before, and he said to me, ‘We agreed that you should go to McMaster for a fellowship.’”

He and his wife had just welcomed their second child, a son named Peer, so the young family of four packed up and moved to Canada that fall. At McMaster University, he completed an exciting fellowship under the guidance of three leaders in the field: Jack Hirsh, David Sackett and Mike Gent.

“To have the opportunity to work with those three, including Jan Wouter as my mentor back home, it was like standing on the shoulders of four giants,” said Büller.

“They taught me how to become a real clinical scientist. The exposure to David Sackett gave me the tools to frame a study question, design a protocol and understand methodology in a way that makes research successful," he continued.

It was at McMaster University that Büller also discovered the joy of intellectual community.

“We were all in the same bubble,” he said, fondly remembering the weekly meetings at McMaster. There were ‘Big Gun Meetings’ with senior leaders and ‘Small Gun Meetings’ with peers. Beer and pizza were often part of the ‘Small Gun’ gatherings. Researchers from all five hospitals came together to share their findings and mentor younger investigators.
“That experience shaped everything I brought back to the Netherlands,” Büller said.

Transforming the diagnosis and treatment of VTE

When Büller began his career, the landscape for diagnosing and treating venous thromboembolism (VTE) was rudimentary at best. Diagnosis was largely based on clinical signs, such as a painful swollen leg, and often inaccurate. Treatment meant lengthy hospital stays and complicated regimens involving intravenous heparin and frequent blood monitoring.

“It was a unique time with enormous amounts of low-hanging fruit, so I decided to first focus on the diagnosis of DVT and PE,” he said.

Collaborating with teams across the globe, he developed studies to improve blood clot diagnosis, including the use of contrast dye in venography. What they discovered was startling: only 30% of patients clinically diagnosed with DVT actually had a blood clot.

“That meant 70% of patients were receiving anticoagulation unnecessarily,” he said. “Our goal became clear—create a patient-friendly and accurate way to diagnose.”

Over the span of just a few years, Büller and colleagues helped usher in non-invasive diagnostic methods for DVT and PE, transforming clinical practice.

Alongside this work, he was part of the global momentum behind low-molecular-weight heparin (LMWH) and later, direct oral anticoagulants (DOACs), which revolutionized treatment and “freed patients” from the hospital. In the early 1980s, it was common practice for a patient with thrombosis to be bed-ridden in the hospital for up to 3 weeks.

Putting thrombosis on the global map

Büller became an instrumental voice to global recognition of thrombosis as a founding member of the ISTH World Thrombosis Day (WTD) Steering Committee.

He remembered the early frustrations of trying to raise awareness for a disease that, despite its global burden, remained under-recognized.

“People were not as interested in thrombosis as they were in other diseases, which were actually even more rare anyway,” he said. “I remember from some of our first meetings as part of the Steering Committee that there was the spirit of frustration that no one would care or would want to learn about thrombosis. As thrombosis specialists, we needed to advocate for this condition.”

WTD launched in 2014 with resounding success, marking a turning point in global awareness of thrombosis. For the first time, patients had a dedicated platform to share their personal experiences, while the condition gained widespread attention among the public, healthcare providers, and policymakers alike.

The campaign united voices across sectors and continents, sparking conversations that had long been absent from the global health agenda.

“One of the best successes was finally being able to say: one in four deaths is due to thrombosis-related conditions,” he said. “It is a powerful data point, and it changed everything.”

The campaign’s first publication in The Lancet was a “big win” and helped put thrombosis on the international stage as an urgent health condition. Today, the WTD campaign is recognized in 123 countries around the world with an estimated 25,000 annual events and activities by countless partners and individuals.

“Hearing from these hundreds of thousands of patients around the world who felt recognition for the first time ever was phenomenal,” he shared.

Mentorship and looking forward

While Büller’s contributions to science are vast, he mentioned that he is most proud of his role as a mentor. Over the course of his career, he has supervised more than 50 Ph.D. students, many of whom have gone on to become leaders in the field.

“They come in smart but shy, and they leave as confident clinical scientists,” he said. “The greatest joy of my job has been helping others grow.”

Though he has stepped back from clinical work, Büller doesn’t call himself retired just yet. He meets weekly with high-potential staff at the hospital to advise them on decision-making in their careers.

When he’s not mentoring, he’s often traveling—recently boating around Japan with his wife, spending time at his vacation home in Italy or planning an upcoming trip to Egypt with his children and four grandchildren.

He also enjoys Chinese antiques and African art. In fact, his home office is surrounded by ancient art pieces and mementos from his global travels.

Honoring a lifelong commitment to advancement

Receiving the ISTH Grant Medal has given Büller a moment to pause and reflect.

“I have had a lot of good fortune with many great colleagues,” he reflected. “But the Grant Medal, its weight and its meaning, shows that the work over the past four decades has not gone unnoticed.”

For Büller, the legacy he hopes to leave is simple: a spirit of global collaboration rooted in honesty, generosity and curiosity.

“I would have been nobody without the collaboration of many great people around the world. This is what I hope people will remember about me. If you want to get good answers to good clinical questions, the likelihood you can do it by yourself is minimal. Collaboration is key," he shared.

He emphasized the importance of giving credit to early career professionals as an ingredient to successful scientific collaboration.

“Give the first authorship to someone who is young in their career. Encourage a young investigator to lead the presentation. It is a balance of collaborating and awarding to give people room to grow. With that, I have never regretted anything,” he remarked.

Looking back on his life, he thinks back to the early days of “serendipity” when his mentors and colleagues helped propel his career forward.

“My whole career has been a result of people being generous with their time, their knowledge and their trust,” he said. “I only hope I’ve given back as much as I received.”

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Photo descriptions:

1. Büller, age 3, in a passport photo.

2. Büller with his young children, Birre and Peer, in the early 1980s enjoying Canada during his fellowship at McMaster University

3. Büller (center) at his thesis defense. His twin brother is pictured left.

4. Büller (L) and his lifelong mentor J.W. ten Cate (R) serving on a panel discussion.

5. Büller gives a presentation.

6. Menno Huisman (L) and Büller (R).

7. Büller (R) and ten Cate (L) in later years.

8. Büller gives a presentation in recent years.