Discovering a Transformative Cancer Drug: The Case of Ibrutinib

Ibrutinib, originally developed as a tool compound for autoimmune research, was repurposed into a breakthrough cancer treatment. This analysis documents how despite relatively low development costs, ibrutinib’s success was shaped by flexible regulatory approaches, public funding, and the willingness to redefine clinical trial criteria, ultimately leading to over $50 billion in sales and transforming treatment for B-cell cancers while raising affordability and access concerns.