Canakinumab is an anti-interleukin-1β monoclonal antibody approved for use in a range of immune-related disorders. During the clinical investigation (CANTOS trial) for prevention of cardiovascular complications, therapy was linked to a reduction in both the occurrence and mortality of lung cancer. This unexpected observation fuelled the rapid initiation of four large clinical trials to evaluate potential anticancer efficacy (in combination with chemotherapy and/or immunotherapy), before fully validating these observations in a dedicated study. The first two trials (CANOPY-1 and 2) have now been reported and have both have failed to meet their primary efficacy endpoints. In this article, we explore the scientific and clinical rationale behind the development of canakinumab in oncology, the repurposing approach utilised and implications this may have for the wider drug repurposing field in the development of new cancer medicines.