Thein Swee Lay

Kuantan-born physician-scientist Dr Swee Lay Thein is recognised internationally for pioneering discoveries that fundamentally transformed the treatment of sickle cell disease—one of humanity’s oldest known genetic conditions. Her landmark research identified the BCL11A gene as the crucial genetic switch controlling fetal hemoglobin production. Previously known for its role in blood cancers, BCL11A’s newly discovered function reoriented the entire field and provided the scientific foundation for revolutionary therapies like Casgevy—the first CRISPR gene-editing therapy for sickle cell disease, approved by the FDA in 2023.

Thein’s decades-long research journey began at Oxford under the mentorship of Sir David Weatherall, exploring why some patients with severe blood disorders remained remarkably healthy. Her pursuit led to insights now benefiting patients worldwide.

In recognition of these achievements, Thein and Professor Stuart Orkin were jointly awarded the 2024 Shaw Prize in Life Science & Medicine, sharing US$1.2 million for their discovery of the molecular mechanism underlying the fetal hemoglobin switch—laying the groundwork for new treatments reaching millions of patients globally.

Now leading the Sickle Cell Branch at the National Heart, Lung, and Blood Institute in Bethesda, Maryland, United States, Dr. Thein oversees major clinical and translational research programs focused on sickle cell disease. In 2025, she initiated an NIH-sponsored Phase I clinical trial of fostamatinib, an oral drug under investigation for its potential to ease the pain episodes characteristic of sickle cell disease.

Prior to joining NIH, Thein served for 15 years at King’s College Hospital, London, where she established and grew one of Britain’s most significant adult sickle cell cohorts, contributing substantially to patient care and research impact.

Thein’s commitment to improving lives is shaped by her family heritage, including a mother who instilled the value of education and service. Her dedication is evident in her global mentorship, work with researchers across Africa and Asia, and organizational leadership—such as hosting the annual Sickle Cell in Focus conference, which rotates among key international centers.